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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2014	Feb. 27, 2015	Jun. 30, 2014
Document and Entity Information [Abstract]
Entity Registrant Name	WHITE MOUNTAINS INSURANCE GROUP LTD
Entity Central Index Key	0000776867
Document Type	10-K
Document Period End Date	Dec. 31, 2014
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 3,502,863,310
Entity Common Stock, Shares Outstanding		5,991,549
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013
Assets
Fixed maturity investments, at fair value	$ 4,784.3	$ 5,030.5
Short-term investments, at amortized cost (which approximates fair value)	871.7	635.9
Common equity securities, at fair value	801.6	1,156.8
Convertible fixed maturity and preferred investments, at fair value	20.5	80.5
Other long-term investments	408.2	288.9
Total investments	6,886.3	7,192.6
Cash (restricted $23.7 and $56.1)	373.2	382.8
Reinsurance recoverable on unpaid losses	483.9	428.1
Reinsurance recoverable on paid losses	23.6	25.4
Insurance and reinsurance premiums receivable	547.7	518.9
Funds held by ceding entities	129.0	106.3
Investments in unconsolidated affiliates	414.4	321.4
Deferred acquisition costs	177.1	174.7
Deferred tax asset	456.1	512.1
Ceded unearned insurance and reinsurance premiums	94.0	92.4
Accrued investment income	34.5	39.3
Accounts receivable on unsettled investment sales	56.5	12.1
Goodwill and intangible assets	366.4	20.7
Other assets	356.1	437.4
Assets held for sale	58.1	1,880.1
Total assets	10,456.9	12,144.3
Liabilities
Loss and loss adjustment expense reserves	3,159.8	3,079.3
Unearned insurance and reinsurance premiums	955.3	901.4
Debt	746.6	676.4
Deferred tax liability	282.8	356.2
Accrued incentive compensation	184.6	218.3
Ceded reinsurance payable	105.7	71.9
Funds held under insurance and reinsurance contracts	138.9	127.1
Accounts payable on unsettled investment purchases	2.6	20.5
Other liabilities	341.0	415.7
Liabilities held for sale	0.0	1,880.1
Total liabilities	5,917.3	7,746.9
White Mountains’s common shareholders’ equity
White Mountains’s common shares at $1 par value per share—authorized 50,000,000 shares; issued and outstanding 5,986,214 and 6,176,739 shares	6.0	6.2
Paid-in surplus	1,028.7	1,044.9
Retained earnings	3,011.4	2,802.3
Accumulated other comprehensive income (loss), after-tax:
Equity in net unrealized (losses) gains from investments in Symetra common shares	34.9	(40.4)
Net unrealized foreign currency translation (losses) gains	(79.8)	88.4
Pension liability and other	(4.6)	4.1
Total White Mountains’s common shareholders’ equity	3,996.6	3,905.5
Non-controlling interests
Non-controlling interests	543.0	491.9
Total equity	4,539.6	4,397.4
Total liabilities and equity	$ 10,456.9	$ 12,144.3

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Restricted Cash and Cash Equivalents, Current	$ 23.7	$ 56.1
Common shares, par value per share (in dollars per share)	$ 1.00	$ 1.00
Common shares, authorized shares	50,000,000	50,000,000
Common shares, issued shares	5,986,214	6,176,739
Common shares, outstanding shares	5,986,214	6,176,739

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues
Earned insurance and reinsurance premiums	$ 2,058.9	$ 1,987.3	$ 2,063.6
Net investment income	105.0	110.9	153.6
Net realized and unrealized investment gains	283.9	161.7	118.2
Other revenue	62.4	57.5	100.3
Total revenues	2,510.2	2,317.4	2,435.7
Expenses
Loss and loss adjustment expenses	1,169.3	1,040.5	1,193.9
Insurance and reinsurance acquisition expenses	399.8	376.9	430.2
Other underwriting expenses	309.3	331.3	321.8
General and administrative expenses	288.2	181.3	182.2
Interest expense on debt	41.9	42.5	44.8
Total expenses	2,208.5	1,972.5	2,172.9
Pre-tax income	301.7	344.9	262.8
Income tax (expense) benefit	(53.3)	(76.6)	15.7
Net income from continuing operations	248.4	268.3	278.5
(Loss) gain on sale of discontinued operations, net of tax	(1.6)	46.6	(91.0)
Net loss from discontinued operations, net of tax	(1.8)	(42.1)	(24.0)
Income before equity in earnings of unconsolidated affiliates	245.0	272.8	163.5
Equity in earnings of unconsolidated affiliates, net of tax	45.6	36.6	29.9
Net income	290.6	309.4	193.4
Net loss attributable to non-controlling interests	22.1	12.4	14.0
Net income attributable to White Mountains’s common shareholders	312.7	321.8	207.4
Other comprehensive income, net of tax:
Change in equity in net unrealized gains (losses) from investments in Symetra common shares, net of tax	75.3	(98.1)	57.7
Change in foreign currency translation, net of tax	(168.5)	2.7	39.6
Net change in pension liability and other, net of tax	(11.7)	20.8	(2.9)
Comprehensive income	207.8	247.2	301.8
Comprehensive loss (income) attributable to non-controlling interests	3.3	(5.2)	0.8
Comprehensive income attributable to White Mountains’s common shareholders	$ 211.1	$ 242.0	$ 302.6
Basic earnings (loss) per share
Continuing operations	$ 51.77	$ 51.15	$ 47.41
Discontinued operations	(0.56)	0.74	(16.91)
Total consolidated operations	51.21	51.89	30.50
Diluted earnings (loss) per share
Continuing operations	51.77	51.15	47.41
Discontinued operations	(0.56)	0.74	(16.91)
Total consolidated operations	51.21	51.89	30.50
Dividends declared and paid per White Mountains’s common share	$ 1.00	$ 1.00	$ 1.00

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Total	Common shares and paid-in surplus	Retained earnings	AOCI, after-tax	Parent [Member]	Total	Non-controlling Interests	Total Equity includes Noncontrolling Interest [Member]
Beginning balance at Dec. 31, 2011		$ 1,261.3	$ 2,789.7	$ 36.7		$ 4,087.7	$ 580.2	$ 4,667.9
Increase (Decrease) in Shareholders' Equity
Net income	$ 193.4	0.0	207.4	0.0		207.4	(14.0)	193.4
Net change in unrealized gains (losses) on investments in unconsolidated affiliates, after tax	57.7	0.0	0.0	57.7		57.7	0.0	57.7
Change in foreign currency translation, net of tax	39.6	0.0	0.0	39.6		39.6	0.0	39.6
Net change in pension liability and other accumulated comprehensive items	(2.9)	0.0	0.0	(2.1)		(2.1)	(0.8)	(2.9)
Comprehensive income	301.8	0.0	207.4	95.2		302.6	(14.8)	287.8
Dividends declared on common shares		0.0	(6.6)	0.0		(6.6)	0.0	(6.6)
Dividends/distributions to non-controlling interests		0.0	0.0	0.0		0.0	(39.1)	(39.1)
Issuances of common shares		5.8	0.0	0.0		5.8	0.0	5.8
Repurchases and retirements of common shares	(669.1)	(221.3)	(447.8)	0.0		(669.1)	0.0	(669.1)
Contribution or Distribution to/ from Non-Controlling Interests		0.0	0.0	0.0		0.0	1.6	1.6
Amortization of restricted share and option awards		13.6	0.0	0.0		13.6	0.8	14.4
Allocation of fair value of net assets acquired to non-controlling interests		(2.2)	0.0	0.0		(2.2)		0.0
Deconsolidation of Hamer and Bri-Mar		0.0	0.0	0.0		0.0	(4.5)	(4.5)
Ending balance at Dec. 31, 2012		1,057.2	2,542.7	131.9		3,731.8	526.4	4,258.2
Increase (Decrease) in Shareholders' Equity
Net income	309.4	0.0	321.8	0.0	$ 321.8		(12.4)	309.4
Net change in unrealized gains (losses) on investments in unconsolidated affiliates, after tax	(98.1)	0.0	0.0	(98.1)	(98.1)		0.0	(98.1)
Accumulated Other Comprehensive Income (Loss) Foreign Currency Translation		0.0	0.0	2.7	2.7		0.0	2.7
Change in foreign currency translation, net of tax	2.7
Net change in pension liability and other accumulated comprehensive items	20.8	0.0	0.0	15.6	15.6		5.2	20.8
Comprehensive income	247.2	0.0	321.8	(79.8)		242.0	(7.2)	234.8
Dividends declared on common shares		0.0	(6.2)	0.0	(6.2)		0.0	(6.2)
Dividends/distributions to non-controlling interests		0.0	0.0	0.0	0.0		(39.7)	(39.7)
Issuances of common shares		1.0	0.0	0.0	1.0		0.0	1.0
Repurchases and retirements of common shares	(79.8)	(23.8)	(56.0)	0.0	(79.8)		0.0	(79.8)
Contribution or Distribution to/ from Non-Controlling Interests		0.0	0.0	0.0	0.0		11.5	11.5
Amortization of restricted share and option awards		16.7	0.0	0.0	16.7		0.9	17.6
Ending balance at Dec. 31, 2013	3,905.5	1,051.1	2,802.3	52.1		3,905.5	491.9	4,397.4
Increase (Decrease) in Shareholders' Equity
Net income	290.6	0.0	312.7	0.0	312.7		(22.1)	290.6
Net change in unrealized gains (losses) on investments in unconsolidated affiliates, after tax	75.3	0.0	0.0	75.3	75.3		0.0	75.3
Accumulated Other Comprehensive Income (Loss) Foreign Currency Translation		0.0	0.0	(168.2)	(168.2)		(0.3)	(168.5)
Change in foreign currency translation, net of tax	(168.5)
Net change in pension liability and other accumulated comprehensive items	(11.7)	0.0	0.0	(8.7)	(8.7)		(3.0)	(11.7)
Comprehensive income	207.8	0.0	312.7	(101.6)		211.1	(25.4)	185.7
Dividends declared on common shares		0.0	(6.2)	0.0	(6.2)		0.0	(6.2)
Dividends/distributions to non-controlling interests		0.0	0.0	0.0	0.0		(40.7)	(40.7)
Issuances of common shares		4.8	0.0	0.0	4.8		0.0	4.8
Repurchases and retirements of common shares	(134.5)	(37.1)	(97.4)	0.0	(134.5)		0.0	(134.5)
Contribution or Distribution to/ from Non-Controlling Interests		0.0	0.0	0.0	0.0		8.3	8.3
Noncontrolling Interest, Increase from Business Combination		0.0	0.0	0.0	0.0		122.1	122.1
Partners' Capital Account, Redemptions		0.0	0.0	0.0	0.0		(14.0)	(14.0)
Amortization of restricted share and option awards		15.9	0.0	0.0	$ 15.9		0.8	16.7
Ending balance at Dec. 31, 2014	$ 3,996.6	$ 1,034.7	$ 3,011.4	$ (49.5)		$ 3,996.6	$ 543.0	$ 4,539.6

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operations:
Net income	$ 290.6	$ 309.4	$ 193.4
Charges (credits) to reconcile net income to net cash (used for) provided from operations:
Net realized and unrealized investment gains	(283.9)	(161.7)	(118.2)
Net gain on sale of consolidated and unconsolidated affiliates	(0.7)	(21.3)	0.0
Amortization and depreciation	69.7	60.6	50.8
Excess of fair value of acquired net assets over cost	0.0	(15.2)	(34.2)
Deferred income tax (benefit) expense	(2.7)	39.7	(16.8)
Undistributed equity in earnings from unconsolidated affiliates, after-tax	(45.6)	(36.6)	(29.9)
Net loss from discontinued operations	1.8	42.1	24.0
Net loss (gain) on sale of other discontinued operations	1.6	(46.6)	91.0
Other operating items:
Net change in loss and loss adjustment expense reserves	189.6	(164.6)	(172.2)
Net change in reinsurance recoverable on paid and unpaid losses	(93.0)	25.0	42.4
Net change in unearned insurance and reinsurance premiums	(119.6)	12.5	(63.1)
Net change in ceded reinsurance premiums payable	46.1	(28.1)	3.8
Net change in ceded unearned insurance and reinsurance premiums	(21.2)	1.4	0.0
Net change in insurance and reinsurance premiums receivable	(88.0)	12.7	(79.2)
Net change in variable annuity benefit guarantee liabilities	(53.5)	(388.7)	(327.1)
Net change in variable annuity benefit derivative instruments	12.7	29.1	192.1
Net change in deferred acquisition costs	(12.6)	17.1	(5.7)
Net change in funds held by ceding companies	(35.5)	14.4	(17.7)
Net change in funds held under reinsurance treaties	22.4	98.8	10.6
Net change in restricted cash	32.4	193.7	203.7
Net change in other assets and liabilities, net	57.1	2.6	(103.5)
Net cash provided from (used for) continuing operations	206.9	(28.7)	(29.6)
Net cash used for discontinued operations	(88.1)	(72.3)	(196.2)
Net cash provided from (used for) operations	118.8	(101.0)	(225.8)
Cash flows from investing activities:
Net change in short-term investments	(351.5)	34.8	145.3
Sales of fixed maturity and convertible investments	4,845.1	3,879.8	6,040.0
Maturities, calls and paydowns of fixed maturity and convertible investments	629.2	465.8	678.4
Sales of common equity securities	660.9	521.1	192.4
Distributions and redemptions of other long-term investments	102.9	58.1	86.7
Sales of unconsolidated affiliates, net of cash sold and held in escrow	12.8	32.4	24.8
Contributions to other long-term investments	(137.0)	(36.3)	(96.7)
Funding of operational cash flows for discontinued operations	(88.1)	(72.3)	(196.2)
Purchases of common equity securities	(328.8)	(432.2)	(365.2)
Purchases of fixed maturity and convertible investments	(5,112.8)	(4,132.0)	(5,810.1)
Purchases of consolidated and unconsolidated affiliates (net of cash acquired)	(199.2)	15.9	(41.3)
Net change in unsettled investment purchases and sales	(62.1)	7.5	(22.4)
Net acquisitions of property and equipment	(11.6)	(13.1)	(2.3)
Net cash (used for) provided from investing activities — continuing operations	(40.2)	329.5	633.4
Net cash provided from investing activities — discontinued operations	88.1	72.3	196.2
Net cash provided from investing activities	47.9	401.8	829.6
Cash flows from financing activities:
Draw down of revolving line of credit	0.0	200.0	150.0
Repayment of revolving line of credit	(66.5)	(275.0)	(75.0)
Repurchase of debt	65.0	0.0	(275.9)
Issuance of debt, net of debt issuance costs	68.6	0.0	271.9
Change in capital lease obligation	(5.3)	(5.7)	(4.9)
Cash dividends paid to the Company’s common shareholders	(6.2)	(6.2)	(6.6)
Cash dividends paid to OneBeacon Ltd.’s non-controlling common shareholders	(19.8)	(19.9)	(19.8)
Cash dividends paid on SIG Preference Shares	(18.8)	(18.8)	(18.8)
Common shares repurchased	(128.2)	(79.8)	(669.1)
OneBeacon Ltd. common shares repurchased and retired	(1.7)	0.0	0.0
Capital contributions from non-controlling interest of consolidated LPs	4.9	1.6	0.0
Redemptions paid to non-controlling interest of consolidated LPs	(5.5)	(0.7)	0.0
Distribution to non-controlling interest shareholders of Tranzact	(25.8)	0.0	0.0
Purchase of interest rate cap	0.0	(9.9)	0.0
Collateral provided by interest rate cap counterparties	(6.5)	10.8	0.0
Capital contributions from BAM members	16.2	17.1	0.0
Net cash used for financing activities	(129.6)	(186.5)	(648.2)
Effect of exchange rate changes on cash	(14.3)	(0.2)	3.1
Net change in cash during the period	22.8	114.1	(41.3)
Cash reclassified to assets held for sale (net of cash sold of $0, $0, and $3.5)	0.0	0.0	2.0
Cash balance at beginning of year (excludes restricted cash balances of $56.1, $249.8 and $453.5)	326.7	212.6	251.9
Cash balance at end of year (excludes restricted cash balances of $23.7, $56.1, and $249.8)	$ 349.5	$ 326.7	$ 212.6

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Cash Flows [Abstract]
Cash restricted	$ 23.7	$ 56.1
Cash reclassified to assets held-for-sale	$ 0.0	$ 0.0	$ 3.5

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2014

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Basis of Presentation

The accompanying consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) and include the accounts of White Mountains Insurance Group, Ltd. (the “Company” or the “Registrant”), its subsidiaries (collectively with the Company, “White Mountains”) and other entities required to be consolidated under GAAP. The Company is an exempted Bermuda limited liability company whose principal businesses are conducted through its insurance, reinsurance and insurance services subsidiaries and affiliates. The Company’s headquarters is located at 14 Wesley Street, Hamilton, Bermuda HM 11, its principal executive office is located at 80 South Main Street, Hanover, New Hampshire 03755-2053 and its registered office is located at Clarendon House, 2 Church Street, Hamilton, Bermuda HM 11. White Mountains’s reportable segments are OneBeacon, Sirius Group, HG Global/BAM and Other Operations.

The OneBeacon segment consists of OneBeacon Insurance Group, Ltd. (“OneBeacon Ltd.”), an exempted Bermuda limited liability company that owns a family of property and casualty insurance companies (collectively “OneBeacon”). OneBeacon is a specialty property and casualty insurance writer that offers a wide range of insurance products in the United States primarily through independent agencies, regional and national brokers, wholesalers and managing general agencies. As of December 31, 2014 and 2013, White Mountains owned 75.3% and 75.2% of OneBeacon Ltd.’s outstanding common shares. As discussed further in Note 2, in December 2014, OneBeacon completed the sale of its runoff business (the “Runoff Transaction”) and in February 2012, OneBeacon sold its AutoOne Insurance business (“AutoOne”). Accordingly, OneBeacon’s runoff business and AutoOne are presented as discontinued operations. (See Note 22 for discontinued operations.) OneBeacon currently owns property in Canton, MA, with a carrying value of $58.1 million for which it has entered into an agreement to sell and which is presented as held for sale in the December 31, 2014 balance sheet.

The Sirius Group segment consists of Sirius International Insurance Group, Ltd., an exempted Bermuda limited liability company, and its subsidiaries (collectively, “Sirius Group”). Sirius Group provides insurance and reinsurance products for property, accident and health, aviation and space, trade credit, marine, agriculture and certain other exposures on a worldwide basis through its primary subsidiaries, Sirius International Insurance Corporation (“Sirius International”), Sirius America Insurance Company (“Sirius America”) and Lloyd’s Syndicate 1945 (“Syndicate 1945”). Sirius Group also specializes in the acquisition and management of runoff insurance and reinsurance companies both in the United States and internationally through its White Mountains Solutions division (“WM Solutions”).

The HG Global/BAM segment consists of White Mountains’s investment in HG Global Ltd. (“HG Global”) and the consolidated results of Build America Mutual Assurance Company (“BAM”). BAM is a municipal bond insurer domiciled in New York that was established in 2012 to provide insurance on bonds issued to support essential U.S. public purposes such as schools, utilities, core governmental functions and existing transportation facilities. HG Global, together with its subsidiaries, provided the initial capitalization of BAM through the purchase of $503 million of surplus notes issued by BAM (the “BAM Surplus Notes”). HG Global, through its wholly-owned subsidiary, HG Re Ltd. (“HG Re”), also provides 15%-of-par, first loss reinsurance protection for policies underwritten by BAM. As of December 31, 2014 and 2013, White Mountains owned 96.9% and 97.3% of HG Global's preferred equity and 88.4% and 88.7% of its common equity. White Mountains does not have an ownership interest in BAM, which is a mutual insurance company owned by its members. However, GAAP requires White Mountains to consolidate BAM’s results in its financial statements. BAM’s results are attributed to non-controlling interests.

White Mountains’s Other Operations segment consists of the Company and its intermediate holding companies, its wholly-owned investment management subsidiary, White Mountains Advisors LLC (“WM Advisors”), White Mountains’s variable annuity reinsurance business, White Mountains Life Reinsurance (Bermuda) Ltd. (“Life Re Bermuda”), which is in runoff with all of its contracts maturing by June 30, 2016, and Life Re Bermuda’s U.S.-based service provider, White Mountains Financial Services LLC (collectively, “WM Life Re”), White Mountains’s ownership positions in Tranzact Holdings, LLC, QL Holdings LLC (“QuoteLab”) and Wobi Insurance Agency Ltd. (“Wobi”), as well as various other entities and investments. The Other Operations segment also includes Star & Shield Services LLC, Star & Shield Risk Management LLC, and Star & Shield Claims Services LLC (collectively “Star & Shield”). Star & Shield provides management services for a fee to Star & Shield Insurance Exchange (“SSIE”), a reciprocal that is owned by its members, who are policyholders. As of December 31, 2014, White Mountains held $17.0 million of surplus notes issued by SSIE (the “SSIE Surplus Notes”) but does not have an ownership interest in SSIE. However, as a result of Star & Shield’s role as the attorney-in-fact to SSIE and the investment in SSIE Surplus Notes, White Mountains is required to consolidate SSIE in its GAAP financial statements. SSIE’s results do not affect White Mountains’s common shareholders’ equity as they are attributable to non-controlling interests. The consolidated results of Hamer and Bri-Mar are also included in the Other Operations segment from January 1, 2012 through September 30, 2012, from which point these companies are no longer consolidated by White Mountains.

All significant intercompany transactions have been eliminated in consolidation. Certain amounts in the prior period financial statements have been reclassified to conform to the current presentation. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Significant Accounting Policies

Investment Securities

As of December 31, 2014, White Mountains’s invested assets consisted of securities and other investments held for general investment purposes. White Mountains’s portfolio of fixed maturity investments and common equity securities held for general investment purposes are classified as trading and are reported at fair value as of the balance sheet date. Changes in unrealized gains and losses are reported pre-tax in revenues. Realized investment gains and losses are accounted for using the specific identification method and are reported pre-tax in revenues. Premiums and discounts on all fixed maturity investments are amortized and accreted to income over the anticipated life of the investment.

White Mountains’s invested assets that are measured at fair value include fixed maturity securities, common and preferred equity securities, convertible fixed maturity and preferred investments and other long-term investments, such as interests in hedge funds and private equities. In determining its estimates of fair value, White Mountains uses a variety of valuation approaches and inputs. Whenever possible, White Mountains estimates fair value using valuation methods that maximize the use of quoted prices and other observable inputs.

As of December 31, 2014 and 2013, approximately 93% and 95% of the investment portfolio recorded at fair value was priced based upon quoted market prices or other observable inputs. Investments valued using Level 1 inputs include fixed maturities, primarily investments in U.S. Treasuries, common equities and short-term investments, which include U.S. Treasury Bills. Investments valued using Level 2 inputs comprise fixed maturities including corporate debt, state and other governmental debt, convertible fixed maturity and preferred investments and mortgage and asset-backed securities. Fair value estimates for investments that trade infrequently and have few or no observable market prices are classified as Level 3 measurements. Level 3 fair value estimates based upon unobservable inputs include White Mountains’s investments in hedge funds and private equity funds, as well as investments in certain debt securities, including asset-backed securities, where quoted market prices are unavailable. White Mountains determines when transfers between levels have occurred as of the beginning of the period. White Mountains uses brokers and outside pricing services to assist in determining fair values. For investments in active markets, White Mountains uses the quoted market prices provided by outside pricing services to determine fair value. The outside pricing services used by White Mountains have indicated that if no observable inputs are available for a security, they will not provide a price. In those circumstances, White Mountains estimates the fair value using industry standard pricing models and observable inputs such as benchmark interest rates, market comparables, broker quotes, issuer spreads, bids, offers, credit rating prepayment speeds and other relevant inputs. White Mountains performs procedures to validate the market prices obtained from the outside pricing sources. Such procedures, which cover substantially all of its fixed maturity investments include, but are not limited to, evaluation of model pricing methodologies and a review of the pricing services’ quality control processes and procedures on at least an annual basis, comparison of market prices to prices obtained from different independent pricing vendors on at least a semi-annual basis, monthly analytical reviews of certain prices, and review of assumptions utilized by the pricing service for selected measurements on an ad hoc basis throughout the year. White Mountains also performs back-testing of selected sales activity to determine whether there are any significant differences between the market price used to value the security prior to sale and the actual sale price on an ad-hoc basis throughout the year. Prices provided by the pricing services that vary by more than 5% and $1.0 million from the expected price based on these procedures are considered outliers. Prices that have not changed from period to period and prices that have trended unusually compared to market conditions are also considered outliers.

In circumstances where the results of White Mountains’s review process do not appear to support the market price provided by the pricing services, White Mountains challenges the price. During the past year, approximately 21 securities fell outside White Mountains’s expected results, thereby triggering the challenge with the pricing service. If White Mountains cannot gain satisfactory evidence to support the challenged price, it relies upon its own pricing methodologies to estimate the fair value of the security in question. The fair values of such securities are considered to be Level 3 measurements.

White Mountains’s investments in debt securities, including asset-backed securities, are generally valued using matrix and other pricing models. Key inputs include benchmark yields, benchmark securities, reported trades, issuer spreads, bids, offers, credit ratings and prepayment speeds. Income on mortgage-backed and asset-backed securities is recognized using an effective yield based on anticipated prepayments and the estimated economic life of the securities. When actual prepayments differ significantly from anticipated prepayments, the estimated economic life is recalculated and the remaining unamortized premium or discount is amortized prospectively over the remaining economic life.

Short-term investments consist of money market funds, certificates of deposit and other securities which, at the time of purchase, mature or become available for use within one year. Short-term investments are carried at amortized cost, which approximated fair value as of December 31, 2014 and 2013.

Other Long-term Investments

Other long-term investments consist primarily of hedge funds, private equity funds, other investments in limited partnerships, private equity securities and surplus note investments (see Note 5). White Mountains has taken the fair value option for most of its investments in hedge funds, private equity funds and other limited partnership investments as well as for the OBIC surplus notes. For the investments for which White Mountains has taken the fair value option, changes in fair value are reported in revenues on a pre-tax basis. For those long-term investments for which White Mountains has not made the fair value election, White Mountains accounts for its interests under the equity method.

Derivative Financial Instruments

White Mountains holds a variety of derivative financial instruments for both risk management and investment purposes. White Mountains recognizes all derivatives as either assets or liabilities, measured at fair value, in the consolidated balance sheets. Changes in the fair value of derivative instruments are recognized in current period pre-tax income.

Warrants

As of December 31, 2012, White Mountains held warrants to purchase 9.49 million common shares of Symetra, which were included as investments in unconsolidated affiliates. The Symetra warrants held by White Mountains were entitled to dividends declared to common shareholders. On June 20, 2013, White Mountains exercised its warrants in a cashless transaction and received 2.65 million common shares of Symetra in exchange for the warrants.

White Mountains also holds warrants that it has received in the restructuring (e.g., securities received from bankruptcy proceedings) of certain of its common equity and/or fixed maturity investments. White Mountains accounts for its investments in warrants as derivatives.

Derivatives—Variable Annuity Reinsurance

White Mountains has entered into agreements to reinsure death and living benefit guarantees associated with certain variable annuities in Japan through its wholly owned subsidiary, WM Life Re. The accounting for benefit guarantees differs depending on whether or not the guarantee is classified as a derivative or an insurance liability.

Guaranteed minimum accumulation benefits (“GMABs”) are paid to an annuitant for any shortfall between accumulated account value at the end of the accumulation period and the annuitant’s total deposit, less any withdrawal payments made to the annuitant during the accumulation period. GMABs meet the definition of a derivative for accounting purposes. Therefore, GMABs are carried at fair value, with changes thereon recognized in income in the period of the change. The liability for the reinsured GMAB contracts has been determined using internal valuation models that use assumptions for interest rates, equity markets, foreign exchange rates and market volatilities at the valuation date, as well as annuitant-related actuarial assumptions, including surrender and mortality rates.

If an annuitant dies during the accumulation period of an annuity contract, guaranteed minimum death benefits (“GMDBs”) are paid to the annuitant’s beneficiary for shortfalls between accumulated account value at the time of an annuitant’s death and the annuitant’s total deposit, less any living benefit payments or withdrawal payments previously made to the annuitant. White Mountains has elected to measure its GMDB liabilities at fair value.

The valuation of these liabilities involves significant judgment and is subject to change based upon changes in capital market assumptions and emerging surrender and mortality experience of the underlying contracts in force.

WM Life Re has entered into derivative contracts that are designed to economically hedge against changes in the fair value of living and death benefit liabilities associated with its variable annuity reinsurance arrangements. The derivatives include futures and over-the-counter option contracts on interest rates, major bond and equity indices, and foreign currencies. All WM Life Re’s derivative instruments are recorded as assets or liabilities at fair value on the balance sheet within other assets. These derivative financial instruments do not meet the criteria for hedge accounting treatment, and accordingly, changes in fair value are recognized in the current period as gains or losses in the income statement within other revenues.

WM Life Re includes the effect of counterparty credit risk when determining the fair value of its derivative contracts and its GMAB and GMDB liabilities.

Cash

Cash includes amounts on hand and demand deposits with banks and other financial institutions. Amounts presented in the statement of cash flows are shown net of balances acquired and sold in the purchase or sale of the Company’s consolidated subsidiaries and exclude changes in amounts of restricted cash (See Note 9).

Insurance and Reinsurance Operations

White Mountains accounts for insurance and reinsurance policies that it writes in accordance with ASC 944. Premiums written are recognized as revenues and are earned ratably over the term of the related policy or reinsurance treaty. Unearned premiums represent the portion of premiums written that are applicable to future insurance or reinsurance coverage provided by policies or treaties in force. White Mountains charges fees on certain of its insurance policies. Refundable fees are classified with premiums and recognized in earnings over the policy term. Fees that represent a reimbursement of expenses, such as installment fees, are recorded as a reduction of underwriting expenses.

Deferred acquisition costs represent commissions, premium taxes, brokerage expenses and other costs which are directly attributable to and vary with the production of business. These costs are deferred and amortized to the extent they relate to successful contract acquisitions over the applicable premium recognition period as insurance and reinsurance acquisition expenses. Amortization of deferred acquisition costs are presented within insurance and reinsurance acquisition expenses. Deferred acquisition costs are limited to the amount expected to be recovered from future earned premiums and anticipated investment income. This limitation is referred to as a premium deficiency. A premium deficiency is recognized if the sum of expected loss and loss adjustment expenses (“LAE”), expected dividends to policyholders, unamortized acquisition costs, and maintenance costs exceeds related unearned premiums and anticipated investment income. A premium deficiency is recognized by charging any unamortized acquisition costs to expense to the extent required in order to eliminate the deficiency. If the premium deficiency exceeds unamortized acquisition costs then a liability is accrued for the excess deficiency.

Losses and LAE are charged against income as incurred. Unpaid insurance losses and LAE are based on estimates (generally determined by claims adjusters, legal counsel and actuarial staff) of the ultimate costs of settling claims, including the effects of inflation and other societal and economic factors. Unpaid reinsurance losses and LAE are based primarily on reports received from ceding companies and actuarial projections. Unpaid loss and LAE reserves represent management’s best estimate of ultimate losses and LAE, net of estimated salvage and subrogation recoveries, if applicable. Such estimates are regularly reviewed and updated and any resulting adjustments are reflected in current operations. The process of estimating loss and LAE involves a considerable degree of judgment by management and the ultimate amount of expense to be incurred could be considerably greater than or less than the amounts currently reflected in the financial statements.

OneBeacon discounts certain of its long-term workers compensation loss and LAE reserves when such liabilities constitute unpaid but settled claims under which the payment pattern and ultimate costs are fixed and determinable on an individual claim basis. OneBeacon discounts these reserves using an average discount rate which is determined based on the various assumptions including consideration of when the claims will be settled (2.5% and 3.5% as of December 31, 2014 and 2013). As of December 31, 2014 and 2013, the discount on OneBeacon’s workers compensation loss and LAE reserves amounted to $1.0 million and $3.0 million (excluding $61.7 million which relates to reserves classified as held for sale as of December 31, 2013).

White Mountains’s insurance and reinsurance subsidiaries enter into ceded reinsurance contracts from time to time to protect their businesses from losses due to concentration of risk, to manage their operating leverage ratios and to limit losses arising from catastrophic events. Such reinsurance contracts are executed through excess of loss treaties and catastrophe contracts under which the reinsurer indemnifies White Mountains for a specified part or all of certain types of losses over stipulated amounts arising from any one occurrence or event. White Mountains has also entered into quota share treaties with reinsurers under which all risks meeting prescribed criteria are covered on a pro-rata basis. The amount of each risk ceded by White Mountains is subject to maximum limits which vary by line of business and type of coverage.

Amounts recoverable from reinsurers are estimated in a manner consistent with the claim liability associated with the reinsured policies. The collectability of reinsurance recoverables is subject to the solvency of the reinsurers. White Mountains is selective in regard to its reinsurers, principally placing reinsurance with those reinsurers with a strong financial condition, industry ratings and underwriting ability. Management monitors the financial condition and ratings of its reinsurers on an ongoing basis.

Reinsurance premiums, commissions, expense reimbursements and reserves related to reinsured business are accounted for on a basis consistent with those used in accounting for the original policies issued and the terms of the reinsurance contracts. Premiums ceded to other companies are reported as a reduction of premiums written. Expense allowances received in connection with reinsurance ceded have been accounted for as a reduction of the related policy acquisition costs and are deferred and amortized accordingly. Funds held by ceding companies represent amounts due to White Mountains in connection with certain assumed reinsurance agreements in which the ceding company retains a portion of the premium to provide security against future loss payments. The funds held by ceding companies are generally invested by the ceding company and a contractually agreed interest amount is credited to the Company and recognized as investment income. Funds held under insurance and reinsurance contracts represent contractual payments due to White Mountains that have been retained to secure such obligations. Such amounts are recorded as liabilities in the consolidated financial statements.

Accruals for contingent commission liabilities are established for reinsurance contracts that provide for the stated commission percentage to increase or decrease based on the loss experience of the contract. Changes in the estimated liability for such arrangements are recorded as contingent commissions. Accruals for contingent commission liabilities are determined through the review of the contracts that have these adjustable features and are estimated based on expected loss and LAE.

Municipal Bond Insurance

All of the contracts issued by BAM are accounted for as insurance contracts under ASC 944-605, Financial Guarantee Insurance Contracts. Premiums are generally received upfront and an unearned premium revenue liability, equal to the amount of the premium received, is established at contract inception. Premium revenues are recognized in revenue over the period of the contracts in proportion to the amount of insurance protection provided using a constant rate. The constant rate is calculated based on the relationship between the par outstanding in a given reporting period compared with the sum of each of the par amounts outstanding for all periods.

Deferred acquisition costs represent commissions, premium taxes, excise taxes and other costs which are directly attributable to and vary with the production of business. These costs are deferred and amortized to the extent they relate to successful contract acquisitions over the applicable premium recognition period as acquisition expenses. Deferred acquisition costs are limited to the amount expected to be recovered from future earned premiums and anticipated investment income.

Funds Held

Funds held under reinsurance contracts primarily represent amounts due to White Mountains in connection with the Standard Reinsurance Agreement (“SRA”) with the Federal Crop Insurance Corporation (“FCIC”), which is managed by an agency of the U.S. Department of Agriculture. The SRA governs the relationship, including the exchange of funds, between private insurance companies, including White Mountains, and the FCIC relating to our MPCI crop insurance business. Funds held under insurance contracts represents unrestricted collateral held by White Mountains primarily relating to the surety business.

Mandatory Shared Market Mechanisms

As a condition to its licenses to do business in certain states, White Mountains’s insurance operations must participate in various mandatory shared market mechanisms commonly referred to as “residual” or “involuntary” markets. These markets generally consist of risks considered to be undesirable from a standard or routine underwriting perspective. Each state dictates the levels of insurance coverage that are mandatorily assigned to participating insurers within these markets. The total amount of such business an insurer must accept in a particular state is generally based on that insurer’s market share of voluntary business written within that state. In certain cases, White Mountains is obligated to write business from shared market mechanisms at a future date based on its historical market share of all voluntary policies written within that state. Involuntary business generated from mandatory shared market mechanisms is accounted for as direct insurance business or as assumed reinsurance depending upon the structure of the mechanism.

OneBeacon’s market assignments are typically required to be written in the current period, however, in certain cases OneBeacon is required to accept policy assignments at a future date. Anticipated losses associated with future market assignments are recognized when the amount of such anticipated losses is determined to be probable and can be reasonably estimated.

Insurance-related Assessments

Under existing guaranty fund laws in all states, insurers licensed to do business in those states can be assessed for certain obligations of insolvent insurance companies to policyholders and claimants. White Mountains records guaranty fund assessments when it is probable that an assessment will be made and the amount can be reasonably estimated.

Deferred Software Costs

White Mountains capitalizes costs related to computer software developed for internal use during the application development stage of software development projects. These costs generally consist of certain external, payroll and payroll-related costs. White Mountains begins amortization of these costs once the project is completed and ready for its intended use. Amortization is on a straight-line basis and over a useful life of three to five years. As of December 31, 2014 and 2013, White Mountains had unamortized deferred software costs of $26.0 million and $23.8 million.

Federal and Foreign Income Taxes

A significant portion of White Mountains’s subsidiaries file consolidated tax returns in the United States. Income earned or losses generated by companies outside the United States are generally subject to an overall effective tax rate lower than that imposed by the United States.

Deferred tax assets and liabilities are recorded when a difference between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts for tax purposes exists, and for other temporary differences. The deferred tax asset or liability is recorded based on tax rates expected to be in effect when the difference reverses. The deferred tax asset is recognized when it is more likely than not that it will be realized.

Foreign Currency Exchange

The U.S. dollar is the functional currency for all of White Mountains’s businesses except for Sirius International, the Canadian reinsurance operations of Sirius America and certain other smaller international activities. White Mountains also invests in securities denominated in foreign currencies. Assets and liabilities recorded in these foreign currencies are translated into U.S. dollars at exchange rates in effect at the balance sheet date, and revenues and expenses are converted using the average exchange rates for the period. Net foreign exchange gains and losses arising from the translation of functional currencies are generally reported in shareholders’ equity, in accumulated other comprehensive income or loss.

Assets and liabilities relating to foreign operations are translated into the functional currency using current exchange rates; revenues and expenses are translated into the functional currency using the weighted average exchange rate for the period. The resulting exchange gains and losses are reported as a component of net income in the period in which they arise. As of December 31, 2014 and 2013, White Mountains had unrealized foreign currency translation (losses) gains of $(79.8) million and $88.4 million recorded in accumulated other comprehensive income on its consolidated balance sheet.

The following rates of exchange for the U.S. dollar have been used for the most significant operations:



Currency	Opening Rate 2014	Closing Rate 2014	Opening Rate 2013	Closing Rate 2013
Swedish kronor	6.4339	7.7737	6.4973	6.4339
British pound	0.6044	0.6426	0.6154	0.6044
Euro	0.7259	0.8245	0.7564	0.7259

Goodwill and Other Intangible Assets

Goodwill represents the excess of the amount paid to acquire subsidiaries over the fair value of identifiable net assets at the date of acquisition. Other intangible assets consist primarily of trademarks, URL and online names, customer relationships, information technology and insurance licenses. Finite-life intangible assets are measured at their acquisition date fair values, are amortized over their economic lives and presented net of accumulated amortization on the balance sheet. Other intangible assets with indefinite lives consist primarily of insurance licenses.

Goodwill and other intangible assets with indefinite lives are not amortized, but rather are evaluated for impairment on at least an annual basis. Other intangible assets with finite lives are evaluated for impairment at least annually and when events or changes in circumstances indicate that it is more likely than not that the asset is impaired. White Mountains did not recognize any impairment losses for goodwill or other intangible assets for any of the years ended December 31, 2014, 2013 and 2012 (See Note 6).

Non-controlling Interest

Non-controlling interests consist of the ownership interests of non-controlling shareholders in consolidated subsidiaries, and are presented separately on the balance sheet. The portion of comprehensive income attributable to non-controlling interests is presented net of related income taxes in the statement of operations and comprehensive income (See Note 14).

Variable Interest Entities

White Mountains consolidates a variable interest entity (“VIE”) when it has both the power to direct the activities of the VIE that most significantly impact its economic performance and either the obligation to absorb losses or the right to receive returns from the VIE that could potentially be significant to the VIE (See Note 18).

Recently Adopted Changes in Accounting Principles

Unrecognized Tax Benefits

Effective January 1, 2014, White Mountains adopted ASU 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists (ASC 740). The new ASU requires balance sheet presentation of an unrecognized tax benefit as a reduction of a deferred tax asset for a net operating loss (“NOL”) carryforward or tax credit carryforward rather than as a liability. The exception is in circumstances where a carryforward is not available to settle the additional taxes that might arise upon disallowance of the tax position under the tax law of the applicable jurisdiction. Prior to the issuance of ASU 2013-11, the guidance for unrecognized tax benefits under ASC 740 did not provide explicit guidance on whether an entity should present an unrecognized tax benefit as a liability or as a reduction of NOL carryforwards or other tax credits. In circumstances where an NOL carryforward is not available to offset settlement of any additional taxes arising from a disallowed tax position, the unrecognized tax benefit should be presented as a liability. The new guidance became effective for White Mountains on January 1, 2014. Adoption did not have any impact on White Mountains's financial condition, results of operations, cash flows or financial statement presentation.

Recent Accounting Pronouncements

Pushdown Accounting

On November 18, 2014, the FASB issued ASU 2014-17, Pushdown Accounting, a consensus of the FASB Emerging Issues Task Force. The new guidance gives an acquired non-public company the option to apply pushdown accounting in its separate company financial statements in the period in which it is acquired in a change of control transaction. Once pushdown accounting has been applied, the election is irreversible. Acquired entities that chose not to apply pushdown accounting at the time of acquisition, may apply pushdown accounting in a subsequent period as a change in accounting principle under ASC 250, Accounting Changes and Error Corrections. ASU 2014-17 became effective at issuance and will apply prospectively. All of White Mountains’s acquisitions in 2014 were made before ASU 2014-17 became effective.

Share-Based Compensation Awards

On June 19, 2014, the FASB issued ASU 2014-12, Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period. The new guidance is intended to eliminate diversity in practice for employee share-based awards containing performance targets that could be achieved after the requisite service period. Some reporting entities account for performance targets that can be achieved after the requisite service period as performance conditions that affect the vesting of the award while other reporting entities treat those performance targets as non-vesting conditions that affect the grant-date fair value of the award. The updated guidance requires that a performance target that affects vesting and that can be achieved after the requisite service period be treated as a performance condition. Compensation cost should be recognized in the period it becomes probable that the performance target will be achieved and should represent the compensation cost attributable to the periods for which service has been rendered. White Mountains does not expect adoption to have a significant effect on its financial position, results of operations, or cash flows. The new guidance is effective for annual and interim reporting periods beginning after December 15, 2015.

Revenue Recognition

On May 28, 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (ASC 606), which modifies the guidance for revenue recognition. The scope of the new ASU excludes insurance contracts but is applicable to certain fee arrangements, such as third-party investment management fees charged by White Mountains Advisors, which were $18.4 million, $16.6 million and $15.9 million for the years ended December 31, 2014, 2013 and 2012, respectively. White Mountains is in the process of evaluating the new guidance and has not yet determined the potential effect of adoption on its financial position, results of operations, or cash flows. ASU 2014-09 is effective for annual and interim reporting periods beginning after December 15, 2016.

Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity

On April 10, 2014, the FASB issued ASU 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity to reduce diversity in practice for reporting discontinued operations. Under the previous guidance, any component of an entity that was a reportable segment, an operating segment, a reporting unit, a subsidiary, or an asset group was eligible for discontinued operations presentation. The revised guidance only allows disposals of components of an entity that represent a strategic shift (e.g., disposal of a major geographical area, a major line of business, a major equity method investment, or other major parts of an entity) and that have a major effect on a reporting entity’s operations and financial results to be reported as discontinued operations. The revised guidance also requires expanded disclosure in the financial statements for discontinued operations as well as for disposals of significant components of an entity that do not qualify for discontinued operations presentation. The updated guidance is effective for transactions entered into after December 15, 2014.

Qualified Affordable Housing Projects

On January 15, 2014, the FASB issued ASU 2014-01, Accounting for Investments in Qualified Affordable Housing Projects ("QAHP") (ASC 323). The new guidance eases the requirements for an investor to elect to account for its investment in a QAHP using the effective yield method. Prior to the issuance of the new guidance, investors had to have a letter of credit guaranteeing the availability of the tax credit allocable to the investor, had to demonstrate that the projected yield based solely on the cash flows from the guaranteed tax credits was positive and had to be a limited partner in the QAHP for both legal and tax purposes. Under the new guidance, the letter of credit requirement has been eliminated and instead, the investor must simply be able to demonstrate that the tax credit allocable to the investor will be available. Investments in QAHP not meeting the criteria in the new guidance would be accounted for under the equity method or the cost method. The election to use the effective yield method is considered an accounting policy decision that should be applied consistently to all QAHP investments. The new guidance is effective for annual and interim reporting periods beginning after December 15, 2014.White Mountains holds an investment in a QAHP which is accounted for under the equity method and intends to adopt ASU 2014-01 during the first quarter of 2015, with retrospective application. White Mountains does not expect adoption to have a material effect on its consolidated financial statements.

Significant Transactions	12 Months Ended
Significant Transactions	Dec. 31, 2014
Significant Transactions [Abstract]
Significant Transactions	Significant Transactions Acquisitions The following acquisitions are included in White Mountains’s consolidated financial statements from the date of acquisition. The total assets acquired and liabilities assumed have been measured at their acquisition date fair values. Olympus In December 2014, Sirius Group acquired 100% of Olympus Reinsurance Company, Ltd. (“Olympus Re”) for $11.5 million. Olympus Re is a Bermuda-domiciled insurance and reinsurance company that assumed property and marine business from Sirius Group from 2001 to 2007 and has been in runoff since then. At acquisition, Sirius Group recognized total assets acquired of $24.6 million and total liabilities assumed of $13.1 million at their estimated fair values. Tranzact On October 10, 2014, White Mountains acquired majority ownership of Tranzact, a leading provider of end-to-end, performance-driven customer acquisition solutions to the insurance sector. White Mountains acquired 63.2% of Tranzact for a purchase price of $177.7 million, representing an enterprise value of $281.2 million. Immediately following the closing, Tranzact completed a recapitalization that allowed for the return of $44.2 million in capital to White Mountains. As of the acquisition date, White Mountains recognized total assets acquired related to Tranzact of $332.8 million, including $41.4 million of tangible assets, $145.1 million of goodwill, and $146.3 million of other intangible assets; and total liabilities assumed of $108.7 million at their estimated fair values. The liabilities assumed include a contingent consideration liability of $7.4 million associated with a prior acquisition by Tranzact. The contingent consideration is payable if earnings before interest expense, taxes, depreciation and amortization (“EBITDA”) of the acquiree exceed amounts defined in the purchase agreement. QuoteLab On March 14, 2014, White Mountains acquired 60.0% of the outstanding Class A common units of QuoteLab. QuoteLab is a California-based advertising technology company offering a transparent online exchange and sophisticated analytical tools that facilitate transactions between buyers (advertisers) and sellers (publishers) of insurance media (clicks and calls), including its own media inventory generated by owned and operated websites. Its exchange operates in four verticles: auto, home, health and life. White Mountains paid an initial purchase price of $28.1 million. The purchase price is subject to adjustment equal to 62.5% of the 2015 gross profit in excess of the 2013 gross profit. As of December 31, 2014, White Mountains has recognized a $7.9 million liability for the contingent purchase price adjustment. After adjustment for the estimated contingent purchase price adjustment, White Mountains recognized total assets acquired related to QuoteLab of $70.1 million, including $18.3 million of goodwill and $38.5 million of other intangible assets; and total liabilities assumed of $10.0 million, reflecting acquisition date fair values. Wobi On February 19, 2014, White Mountains acquired 54.0% of the outstanding common shares of Wobi for NIS 14.4 million (approximately $4.1 million based upon the foreign exchange spot rate at the date of acquisition). During 2014, in addition to the common shares, White Mountains also purchased NIS 31.5 million (approximately $9.0 million based upon the foreign exchange spot rate at the dates of acquisition) of newly-issued convertible preferred shares of Wobi. As of December 31, 2014 White Mountains’s ownership share was 63.3% on a fully converted basis. Wobi is the only insurance price comparison/aggregation business in Israel, with a carrier panel that represents 85% of the premiums written in the Israeli insurance market. Wobi sells four lines of business, primarily personal auto, and operates as an agency, charging upfront commissions on all policy sales. As of the acquisition date, White Mountains recognized total assets acquired related to Wobi of $13.4 million, including $5.5 million of goodwill and $2.9 million of other intangible assets; and total liabilities assumed of $0.7 million at their estimated fair values. WM Solutions In the first quarter of 2013, WM Solutions acquired Ashmere Insurance Company (“Ashmere”, formerly known as American Fuji Fire and Marine Insurance Company), an American International Group, Inc. (“AIG”) runoff subsidiary. The transaction resulted in a gain of $6.9 million recorded in other revenue. On October 15, 2013, WM Solutions acquired Empire Insurance Company (“Empire”), a runoff insurance subsidiary of Leucadia National Corporation. The transaction resulted in a gain of $7.3 million recorded in other revenue. On December 3, 2012, WM Solutions acquired four runoff entities including Physicians Insurance Company of Ohio (“PICO”) and Citation Insurance Company (“Citation”) from PICO Holdings and two AIG runoff subsidiaries, Woodridge Insurance Company (“Woodridge”, formerly known as American General Indemnity Company) and Oakwood Insurance Company (“Oakwood”, formerly known as American General Property Insurance Company). The transactions resulted in a gain of $14.5 million recorded in other revenue. Star & Shield On January 31, 2014, White Mountains acquired certain assets and liabilities of Star & Shield Holdings LLC, including SSRM, the attorney-in-fact for SSIE, for a purchase price of $1.8 million. During 2014, White Mountains also purchased $17.0 million of surplus notes issued by SSIE. Principal and interest on the surplus notes are payable to White Mountains only with approval from the Florida Office of Insurance Regulation. SSIE is a Florida-domiciled reciprocal insurance exchange providing private passenger auto insurance to the public safety community and their families. SSIE is a VIE. As a result of SSRM’s role as the attorney-in-fact to SSIE and the investment in SSIE’s surplus notes, White Mountains is required to consolidate SSIE. As of December 31, 2014, consolidated amounts included total assets of $13.5 million and total liabilities of $25.9 million of SSIE. For the twelve months ended December 31, 2014, SSIE had pre-tax losses of $12.4 million that were recorded in net loss attributable to non-controlling interests. Formation of HG Global and BAM In 2012, White Mountains capitalized HG Global with $594.5 million to fund BAM, a newly formed mutual municipal bond insurer. HG Global, together with its subsidiaries, provided the initial capitalization of BAM through the purchase of $503.0 million of BAM Surplus Notes. (See Note 10 and Note 18) Dispositions Sale of OneBeacon Runoff Business On December 23, 2014, OneBeacon completed the sale of its Runoff Business to Trebuchet US Holdings, Inc., a wholly-owned subsidiary of Armour Group Holdings Limited (“Armour”). Financing was provided in the form of surplus notes of $101.0 million that had a fair value of $64.9 million. These surplus notes are presented within other investments (see Note 5). The difference of $36.1 million between the par value and the fair value of the surplus notes at the date of sale is included in the loss from sale of discontinued operations (see Note 22). WM Solutions In October 2014, White Mountains Solutions entered into an agreement to sell Ashmere to Agency Bonding Captives, Inc. as a “shell company” for $6.0 million in excess of statutory surplus, which is expected to result in a GAAP pre-tax gain of under $1.0 million. The liabilities of Ashmere were transferred to a Sirius Group affiliate during the fourth quarter of 2014 and the transaction is expected to close during the first quarter of 2015 subject to receipt of all necessary regulatory approvals. In the first quarter of 2014, WM Solutions completed the shell sale of Citation Insurance Company, which resulted in a gain of $0.7 million recorded in other revenue. Sale of Essentia Insurance Company Effective January 1, 2013, OneBeacon completed the sale of Essentia Insurance Company (“Essentia”), an indirect wholly-owned subsidiary which wrote the collector cars and boats business, to Markel Corporation. Concurrently therewith, OneBeacon and Hagerty Insurance Agency (“Hagerty”) terminated their underwriting arrangement with respect to the collector cars and boats business. OneBeacon recognized a pre-tax gain on sale of $23.0 million ($15.0 million after tax) in the first quarter of 2013. The business associated with this agreement generated net written premiums of $179.7 million or 8.0% of White Mountains’s net written premiums for December 31, 2012. Sale of AutoOne On August 30, 2011, OneBeacon entered into a definitive agreement (the “Purchase Agreement”) to sell the AutoOne business to Interboro Holdings, Inc. (“Interboro”). On February 22, 2012, OneBeacon completed the sale of AutoOne to Interboro Holdings, Inc. (“Interboro”). OneBeacon formed AutoOne in 2001 to provide products and services to automobile assigned risk markets primarily in New York and New Jersey. OneBeacon transferred to the buyer AutoOne Insurance Company (“AOIC”) and AutoOne Select Insurance Company (“AOSIC”), which contained the assets, liabilities (including loss reserves and unearned premiums), and the capital of the AutoOne business, and transferred substantially all of the AutoOne infrastructure including systems and office space as well as certain staff. As a result of the sale, AutoOne is reported as discontinued operations (see Note 22).

Reserves for Unpaid Losses and Loss Adjustment Expenses

12 Months Ended

Dec. 31, 2014

Insurance Loss Reserves [Abstract]

Reserves for Unpaid Losses and Loss Adjustment Expenses

Insurance Operations

White Mountains establishes loss and LAE reserves that are estimates of amounts needed to pay claims and related expenses in the future for insured events that have already occurred. The process of estimating reserves involves a considerable degree of judgment by management and, as of any given date, is inherently uncertain.

Loss and LAE reserves are typically comprised of (1) case reserves for claims reported and (2) reserves for losses that have occurred but for which claims have not yet been reported, referred to as incurred but not reported (“IBNR”) reserves, which include a provision for expected future development on case reserves. Case reserves are estimated based on the experience and knowledge of claims staff regarding the nature and potential cost of each claim and are adjusted as additional information becomes known or payments are made. IBNR reserves are typically derived by subtracting paid loss and LAE and case reserves from estimates of ultimate loss and LAE. Actuaries estimate ultimate loss and LAE using various generally accepted actuarial methods applied to known losses and other relevant information. Like case reserves, IBNR reserves are adjusted as additional information becomes known or payments are made.

Ultimate loss and LAE are generally determined by extrapolation of claim emergence and settlement patterns observed in the past that can reasonably be expected to persist into the future. In forecasting ultimate loss and LAE with respect to any line of business, past experience with respect to that line of business is the primary resource, but cannot be relied upon in isolation. White Mountains’s own experience, particularly claims development experience, such as trends in case reserves, payments on and closings of claims, as well as changes in business mix and coverage limits, is the most important information for estimating its reserves. External data, available from organizations such as statistical bureaus, consulting firms and reinsurance companies, is sometimes used to supplement or corroborate White Mountains’s own experience. External data can be especially useful for estimating costs on new lines of business. Ultimate loss and LAE for major losses and catastrophes are estimated based on the known and expected exposures to the loss event, rather than simply relying on the extrapolation of reported and settled claims.

For some lines of business, such as “long-tail” coverages discussed below, claims data reported in the most recent accident or report year is often too limited to provide a meaningful basis for analysis due to the typical delay in reporting and settling of claims. For this type of business, White Mountains uses an expected loss ratio method for the initial accident year or years. This is a standard and accepted actuarial reserve estimation method in these circumstances in which the loss ratio is selected based upon information used in pricing policies for that line of business, as well as any publicly available industry data, such as industry pricing, experience and trends, for that line of business.

Uncertainties in estimating ultimate loss and LAE are magnified by the time lag between when a claim actually occurs and when it is reported and eventually settled. This time lag is sometimes referred to as the “claim-tail”. The claim-tail for most property coverages is typically short (usually a few days up to a few months). The claim-tail for liability/casualty coverages, such as automobile liability, general liability, products liability, multiple peril coverage, and workers compensation, can be especially long as claims are often reported and ultimately paid or settled years, even decades, after the related loss events occur. During the long claims reporting and settlement period, additional facts regarding coverages written in prior accident years, as well as about actual claims and trends may become known and, as a result, White Mountains may adjust its reserves. If management determines that an adjustment is appropriate, the adjustment is booked in the accounting period in which such determination is made in accordance with GAAP. Accordingly, should reserves need to be increased or decreased in the future from amounts currently established, future results of operations would be negatively or positively impacted, respectively.

In determining ultimate loss and LAE, the cost to indemnify claimants, provide needed legal defense and other services for insureds and administer the investigation and adjustment of claims are considered. These claim costs are influenced by many factors that change over time, such as expanded coverage definitions as a result of new court decisions, inflation in costs to repair or replace damaged property, inflation in the cost of medical services and legislated changes in statutory benefits, as well as by the particular, unique facts that pertain to each claim. As a result, the rate at which claims arose in the past and the costs to settle them may not always be representative of what will occur in the future. The factors influencing changes in claim costs are often difficult to isolate or quantify and developments in paid and incurred losses from historical trends are frequently subject to multiple and conflicting interpretations. Changes in coverage terms or claims handling practices may also cause future experience and/or development patterns to vary from the past. A key objective of actuaries in developing estimates of ultimate loss and LAE, and resulting IBNR reserves, is to identify aberrations and systemic changes occurring within historical experience and accurately adjust for them so that the future can be projected reliably. Because of the factors previously discussed, this process requires the use of informed judgment and is inherently uncertain.

White Mountains’s actuaries use several generally accepted actuarial methods to evaluate its loss reserves, each of which has its own strengths and weaknesses. Management places more or less reliance on a particular method based on the facts and circumstances at the time the reserve estimates are made. These methods generally fall into one of the following categories or are hybrids of one or more of the following categories:

•

Historical paid loss development methods: These methods use historical loss payments over discrete periods of time to estimate future losses. Historical paid loss development methods assume that the ratio of losses paid in one period to losses paid in an earlier period will remain constant. These methods necessarily assume that factors that have affected paid losses in the past, such as inflation or the effects of litigation, will remain constant in the future. Because historical paid loss development methods do not use case reserves to estimate ultimate losses, they can be more reliable than the other methods discussed below that look to case reserves (such as actuarial methods that use incurred losses) in situations where there are significant changes in how case reserves are established by a company’s claims adjusters. However, historical paid loss development methods are more leveraged, meaning that small changes in payments have a larger impact on estimates of ultimate losses, than actuarial methods that use incurred losses because cumulative loss payments take much longer to equal the expected ultimate losses than cumulative incurred amounts. In addition, and for similar reasons, historical paid loss development methods are often slow to react to situations when new or different factors arise than those that have affected paid losses in the past.

•

Historical incurred loss development methods: These methods, like historical paid loss development methods, assume that the ratio of losses in one period to losses in an earlier period will remain constant in the future. However, instead of using paid losses, these methods use incurred losses (i.e., the sum of cumulative historical loss payments plus outstanding case reserves) over discrete periods of time to estimate future losses. Historical incurred loss development methods can be preferable to historical paid loss development methods because they explicitly take into account open cases and the claims adjusters’ evaluations of the cost to settle all known claims. However, historical incurred loss development methods necessarily assume that case reserving practices are consistently applied over time. Therefore, when there have been significant changes in how case reserves are established, using incurred loss data to project ultimate losses can be less reliable than other methods.

•

Expected loss ratio methods: These methods are based on the assumption that ultimate losses vary proportionately with premiums. Expected loss ratios are typically developed based upon the information used in pricing, and are multiplied by the total amount of premiums earned to calculate ultimate losses. Expected loss ratio methods are useful for estimating ultimate losses in the early years of long-tailed lines of business, when little or no paid or incurred loss information is available.

•

Adjusted historical paid and incurred loss development methods: These methods take traditional historical paid and incurred loss development methods and adjust them for the estimated impact of changes from the past in factors such as inflation, the speed of claim payments or the adequacy of case reserves. Adjusted historical paid and incurred loss development methods are often more reliable methods of predicting ultimate losses in periods of significant change, provided the actuaries can develop methods to reasonably quantify the impact of changes.

White Mountains performs an actuarial review of its recorded reserves each quarter. White Mountains’s actuaries compare the previous quarter’s estimates of paid loss and LAE, case reserves and IBNR to amounts indicated by actual experience. Differences between previous estimates and actual experience are evaluated to determine whether a given actuarial method for estimating loss and LAE should be relied upon to a greater or lesser extent than it had been in the past. While some variance is expected each quarter due to the inherent uncertainty in loss and LAE, persistent or large variances would indicate that prior assumptions and/or reliance on certain reserving methods may need to be revised going forward.

Upon completion of each quarterly review, White Mountains’s actuaries select indicated reserve levels based on the results of the actuarial methods described previously, which are the primary consideration in determining management's best estimate of required reserves. However, in making its best estimate, management also considers other qualitative factors that may lead to a difference between held reserves and actuarially indicated reserves levels in the future. Typically, these factors exist when management and our actuaries conclude that there is insufficient historical incurred and paid loss information or that trends included in the historical incurred and paid loss information are unlikely to repeat in the future. Such factors include, among others, recent entry into new markets or new products, improvements in the claims department that are expected to lessen future ultimate loss costs, legal and regulatory developments, or other volatilities that may arise.

Reinsurance Operations

Sirius Group establishes loss and LAE reserves that are estimates of future amounts needed to pay claims and related expenses for events that have already occurred. Sirius Group also obtains reinsurance whereby another reinsurer contractually agrees to indemnify White Mountains for all or a portion of the reinsurance risks underwritten by White Mountains. Such arrangements, where one reinsurer provides reinsurance to another reinsurer, are usually referred to as “retrocessional reinsurance” arrangements. White Mountains establishes estimates of amounts recoverable from retrocessional reinsurance in a manner consistent with the loss and LAE liability associated with reinsurance contracts offered to its customers (the “ceding companies”), net of an allowance for uncollectible amounts. Net reinsurance loss reserves represent loss and LAE reserves reduced by retrocessional reinsurance recoverable on unpaid losses.

The estimation of net reinsurance loss and LAE reserves is subject to the same risk as the estimation of insurance loss and LAE reserves. In addition to those risk factors which give rise to inherent uncertainties in establishing insurance loss and LAE reserves, the inherent uncertainties of estimating such reserves are even greater for the reinsurer, due primarily to: (1) the claim-tail for reinsurers and insurers working through MGUs being further extended because claims are first reported to either the original primary insurance company or the MGU and then through one or more intermediaries or reinsurers, (2) the diversity of loss development patterns among different types of reinsurance treaties, facultative contracts or direct insurance contracts, (3) the necessary reliance on the ceding companies, intermediaries and MGUs for information regarding reported claims and (4) the differing reserving practices among ceding companies and MGUs.

As with insurance reserves, the process of estimating reinsurance reserves involves a considerable degree of judgment by management and, as of any given date, is inherently uncertain. Based on the above, such uncertainty may be larger relative to the reserves for a company that principally writes reinsurance compared to an insurance company, and certainty may take a longer time to emerge.

Upon notification of a loss from an insured (typically a ceding company), Sirius Group establishes case reserves, including LAE reserves, based upon Sirius Group’s share of the amount of reserves established by the insured and Sirius Group’s independent evaluation of the loss. In cases where available information indicates that reserves established by a ceding company are inadequate, Sirius Group establishes case reserves or IBNR in excess of its share of the reserves established by the ceding company. Also, in certain instances, Sirius Group may decide not to establish case reserves or IBNR, when the information available indicates that reserves established by ceding companies are not adequately supported. In addition, specific claim information reported by insureds or obtained through claim audits can alert management to emerging trends such as changing legal interpretations of coverage and liability, claims from unexpected sources or classes of business, and significant changes in the frequency or severity of individual claims where customary. Generally, ceding company audits are not customary outside the United States. This information is often used to supplement estimates of IBNR.

Although loss and LAE reserves are initially determined based on underwriting and pricing analyses, Sirius Group regularly reviews the adequacy of its recorded reserves by using a variety of generally accepted actuarial methods, including historical incurred and paid loss development methods. If actual loss activity differs substantially from expectations, an adjustment to recorded reserves may be warranted. As time passes, loss reserve estimates for a given year will rely more on actual loss activity and historical patterns than on initial assumptions based on pricing indications.

The actuarial methods described above are used to calculate a point estimate of loss and LAE reserves for each company within Sirius Group. These point estimates are then aggregated to produce an actuarial point estimate for the entire segment. Once a point estimate is established, Sirius Group’s actuaries estimate loss reserve ranges to measure the sensitivity of the actuarial assumptions used to set the point estimates. These ranges are calculated from historical variations in loss ratios, payment and reporting patterns by class and type of business.

Loss and Loss Adjustment Expense Reserve Summary

The following table summarizes the loss and LAE reserve activities of White Mountains’s insurance and reinsurance subsidiaries for the years ended December 31, 2014, 2013 and 2012:



	Year Ended December 31,
Millions	2014			2013			2012
Gross beginning balance	$	3,079.3		$	3,168.9		$	5,702.3
Less beginning reinsurance recoverable on unpaid losses	(428.1		)	(429.1		)	(2,507.3		)
Net loss and LAE reserves	2,651.2			2,739.8			3,195.0

Less: Beginning net loss and LAE reserves for AutoOne and the Runoff Transaction⁽¹⁾	—			—			(383.3		)

Loss and LAE reserves acquired⁽²⁾	45.4			37.7			17.0
Loss and LAE reserves consolidated — SSIE	13.6			—			—

Losses and LAE incurred relating to:
Current year losses	1,175.3			1,088.9			1,235.8
Prior year losses	(6.0		)	(48.4		)	(41.9		)
Total incurred losses and LAE	1,169.3			1,040.5			1,193.9

Accretion of fair value adjustment to net loss and LAE reserves	0.7			1.7			10.6
Foreign currency translation adjustment to net loss and LAE reserves	(36.0		)	.3			12.9

Loss and LAE paid relating to:
Current year losses	(345.3		)	(336.2		)	(404.7		)
Prior year losses	(823.0		)	(832.6		)	(901.6		)
Total loss and LAE payments	(1,168.3		)	(1,168.8		)	(1,306.3		)

Net ending balance	2,675.9			2,651.2			2,739.8
Plus ending reinsurance recoverable on unpaid losses	483.9			428.1			429.1
Gross ending balance	$	3,159.8		$	3,079.3		$	3,168.9


⁽¹⁾	Loss and LAE reserve balances from OneBeacon’s Runoff Business prior to December 31, 2012 were not classified as held for sale. Adjustment is to present loss and LAE reserve activities for continuing operations.


⁽²⁾	Loss and LAE reserves acquired in 2014 relate to Sirius Group’s purchase of Olympus Re and loss portfolio transfer from Transamerica. Loss and LAE reserves acquired in 2013 relate to WM Solutions’s purchases of Empire and Ashmere. Loss and LAE reserves acquired in 2012 relate to WM Solutions’s purchases of PICO, Citation, Woodridge and Oakwood.

Loss and LAE development —2014

During the year ended December 31, 2014, White Mountains experienced $6.0 million of net favorable loss reserve development, which consisted of $98.0 million of net favorable loss reserve development at Sirius Group, $89.8 million of net unfavorable loss reserve development at OneBeacon and $2.2 million of net unfavorable loss reserve development at SSIE.

Sirius Group’s net favorable loss reserve development primarily related to property ($54.0 million), aviation and space ($13.0 million), accident and health ($13.0 million) lines and casualty ($13.0 million). The casualty reduction is net of a $10.0 million increase in asbestos and environmental loss reserves. For the property loss estimates decrease, $24.0 million represented reduction of loss reserves previously held above the actuarial central estimate. This amount represented an IBNR provision established between 2010-2012 in response to the large catastrophe events, including the 2010 earthquake in Chile, the 2010/2011 earthquakes in New Zealand, the 2011 earthquake in Japan, and hurricane Sandy in 2012, and the inherent uncertainty associated with deriving initial loss estimates. When examined in 2014, the loss estimates for these events had stabilized and had proven to be redundant in aggregate; as a result, the additional amount above the actuarial central estimate was reversed.

OneBeacon 2014 Fourth Quarter Loss and LAE Reserve Increase

Through the first nine months of 2014, OneBeacon recorded $14.3 million of unfavorable loss and LAE reserve development, driven by greater-than-expected large losses in several underwriting units, primarily in the professional and management liability lines within Professional Insurance. This large loss activity, which occurred mostly during the second and third quarters of 2014, also impacted the current accident year loss and LAE estimates. Additionally, OneBeacon incurred higher-than-usual claim coverage determination costs, a component of LAE expenses, during the first nine months of 2014. Other underwriting units also reported increased claim activity, including the Entertainment, Government Risks, and Accident underwriting units.

Since the increased level of loss and LAE activity continued into the early part of the fourth quarter, the high level of activity in the second and third quarters no longer seemed to be isolated occurrences. As such, during the fourth quarter of 2014, OneBeacon enhanced its actuarial and claims review in several areas. OneBeacon isolated the recent large loss activity in each of its underwriting units and examined the emergence of large losses relative to the timing and amounts of expected large losses. OneBeacon also conducted additional analyses in the lawyers’ professional liability line within the Professional Insurance underwriting unit. These new analyses included a claim level review and the application of additional actuarial methods and loss development assumptions. The results of these analyses indicated that the assumed tail risk included in the loss development patterns used to record IBNR reserves for this line were insufficient and needed to be increased for remaining long-tail exposures. OneBeacon’s claims and actuarial staff also conducted an in-depth review of coverage determination, litigation and other claim-specific adjusting expenses as a result of an emerging trend of increased expenses in these areas over recent quarters, particularly coverage determination expenses. This review concluded that the ultimate costs of these loss adjustment expenses were larger than previously estimated, causing management to record an increase in estimated LAE expenses, primarily in Professional Insurance. Finally, OneBeacon also recorded unfavorable prior year development in other underwriting units, including Entertainment and Government Risks. The unfavorable loss development in Entertainment and Government Risks resulted from heavier than expected claim activity during the fourth quarter, predominantly in the general liability and commercial auto liability lines.

In order to fully reflect these recent trends, OneBeacon recorded a $109.2 million increase in loss and LAE reserves, which included a $75.5 million increase in prior accident year loss and LAE reserves and a $33.7 million increase in the current accident year loss and LAE reserves recorded at September 30, 2014. The components of the 2014 fourth quarter loss and LAE reserve increase and the net loss and LAE development for the full year are provided below:



Millions	2014 Fourth Quarter Reserve Increases								Full Year 2014
Underwriting Unit	Current Accident Year			Prior Accident Year			Total		Net Prior Year Development
Professional Insurance	$	22.9		$	46.4		$	69.3	$	59.1
Specialty Property	(1.1		)	5.7			4.6		1.1
Crop	3.8			—			3.8		—
Other	2.8			(.4		)	2.4		1.6
Specialty Products	28.4			51.7			80.1		61.8

Entertainment	1.5			11.6			13.1		13.5
Accident	—			3.5			3.5		6.0
Government Risks	1.2			7.1			8.3		8.5
Other	2.6			1.6			4.2		—
Specialty Industries	5.3			23.8			29.1		28.0

Total	$	33.7		$	75.5		$	109.2	$	89.8

As noted above, OneBeacon increased its provision for current accident year losses and LAE by $33.7 million in the fourth quarter of 2014. In making its loss and LAE reserve picks for the 2014 accident year, OneBeacon considered the results of the enhanced actuarial and claim review and the fact that reported large claims were approaching estimated ultimate held reserves for large losses sooner than originally expected. $3.8 million of the increase is related to higher-than-expected reports of crop losses that emerged in the fourth quarter. The remaining $29.9 million of the increase reflects an increase in management’s best estimate of current losses and LAE as of December 31, 2014 from those recorded in the first nine months of 2014. This increase primarily affected the Professional Insurance underwriting unit, which represented $22.9 million of the total provision.

Loss and LAE development —2013

During the year ended December 31, 2013, White Mountains experienced $48.4 million of net favorable loss reserve development, which related entirely to Sirius Group. Sirius Group’s net favorable loss reserve development included $23.9 million of favorable loss reserve development on prior years’ catastrophe losses. Other major reductions in loss reserve estimates recognized included property ($16.6 million), aviation/space ($10.1 million), and accident and health ($9.2 million) lines, partially offset by an $11.8 million increase in asbestos loss reserves.

During 2013, OneBeacon experienced no net loss and LAE reserve development on prior accident year reserves. OneBeacon experienced unfavorable development primarily related to property, general liability and accident and health lines, which was offset by favorable development in its other liability and ocean marine lines.

Loss and LAE development —2012

During the year ended December 31, 2012, White Mountains experienced $41.9 million of net favorable loss reserve development, which consisted of $7.4 million of net favorable loss reserve development at OneBeacon and $34.5 million of net favorable loss reserve development at Sirius Group.

During 2012, OneBeacon experienced $7.4 million of net favorable loss and LAE reserve development on prior accident year reserves. The favorable reserve development at OneBeacon was primarily from workers' compensation, multiple peril liability and general liability lines. This favorable development was offset somewhat by adverse development on excess property claims.

In 2012, Sirius Group had net favorable loss reserve development of $34.5 million. The major reductions in loss reserve estimates at Sirius Group were recognized in casualty runoff ($31.5 million), property ($28.4 million), marine/energy ($11.6 million), trade credit ($6.8 million) and aviation/space ($5.3 million) lines, partially offset by a $46.4 million increase in asbestos loss reserves and a $4.3 million increase in accident and health.

Fair value adjustment to loss and LAE reserves

In connection with purchase accounting for acquisitions, White Mountains is required to adjust loss and LAE reserves and the related reinsurance recoverables to fair value on their respective acquired balance sheets. The net reduction to loss and LAE reserves is being recognized through an income statement charge ratably with and over the period the claims are settled.

White Mountains recognized $0.7 million, $1.7 million and $10.6 million of such charges during 2014, 2013 and 2012. As of December 31, 2014, the pre-tax un-accreted adjustment was $4.0 million.

Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity

White Mountains’s reserves include provisions made for claims that assert damages from asbestos and environmental related exposures. Asbestos claims relate primarily to injuries asserted by those who came in contact with asbestos or products containing asbestos. Environmental claims relate primarily to pollution and related clean-up cost obligations, particularly as mandated by U.S. federal and state environmental protection agencies. In addition to the factors described above regarding the reserving process, White Mountains estimates its A&E reserves based upon, among other factors, facts surrounding reported cases and exposures to claims, such as policy limits and deductibles, current law, past and projected claim activity and past settlement values for similar claims, as well as analysis of industry studies and events, such as recent settlements and asbestos-related bankruptcies. The cost of administering A&E claims, which is an important factor in estimating loss reserves, tends to be higher than in the case of non-A&E claims due to the higher legal costs typically associated with A&E claims.

Substantially all of OneBeacon's reserves for unpaid loss and LAE for asbestos and environmental exposures were transferred to Armour at the closing of the Runoff Transaction (see Note 22). As of December 31, 2014, the remaining unpaid loss and LAE loss reserves for asbestos and environmental exposures related to continuing operations is less than $1.0 million on both a gross and net basis.

Sirius Group's A&E exposure is primarily from reinsurance contracts written between 1974 through 1985 by acquired companies, mainly MONY Reinsurance Company and Christiania General Insurance Company. The exposures are mostly higher layer excess of loss treaty and facultative coverages with relatively low limits exposed for each claim. In 2013 and 2012, Sirius Group increased its net A&E exposure through incoming runoff portfolios acquired by White Mountains Solutions. These acquisitions added $22.9 million in net asbestos reserves and $2.1 million in net environmental reserves in 2014, $13.0 million in net asbestos reserves and $1.0 million in net environmental reserves in 2013, and $11.0 million in net asbestos reserves and $0.7 million in net environmental reserves in 2012. The acquisition of companies having modest portfolios of A&E exposure has been typical of several prior White Mountains Solutions transactions and is likely to be an element of at least some future acquisitions. However, the acquisition of new A&E liabilities is undertaken only after careful due diligence and utilizing conservative reserving assumptions in relation to industry benchmarks. In the case of the portfolios acquired during 2013 and 2012, the exposures arise almost entirely from old assumed reinsurance contracts having small limits of liability.

Sirius Group recorded $8.0 million, $11.8 million and $46.4 million of asbestos-related incurred losses and LAE on its already existing asbestos reserves in 2014, 2013 and 2012. The 2013 incurred losses were primarily the result of management’s monitoring of a variety of metrics including actual paid and reported claims activity as compared to the most recent in-depth analysis performed in 2012, net paid and reported survival ratios, peer comparisons, and industry benchmarks. In 2012, the increase in net asbestos losses included $14.0 million in response to Sirius Group’s quarterly monitoring of newly reported claims and $33.0 million as a result of an in-depth analysis of all treaty and facultative contracts likely to have asbestos exposure which examined total expected asbestos losses and LAE from a variety of information sources, including previous asbestos studies, reported client data and external benchmarking scenarios.

Sirius Group recorded an increase of $1.6 million and $0.8 million of environmental losses in 2014 and 2013, and a decrease of $0.5 million of environmental losses in 2012 on its already existing reserves.

Sirius Group’s net reserves for A&E losses were $210.2 million and $193.9 million as of December 31, 2014 and 2013, respectively. Sirius Group’s A&E three-year net paid survival ratio was approximately 9.0 years and 8.0 years as of December 31, 2014 and 2013.

White Mountains’s reserves for A&E losses as of December 31, 2014 represent management’s best estimate of its ultimate liability based on information currently available. However, as case law expands, and medical and clean-up costs increase and industry settlement practices change, White Mountains may be subject to asbestos and environmental losses beyond currently estimated amounts. White Mountains cannot reasonably estimate at the present time loss reserve additions arising from any such future adverse developments and cannot be sure that allocated loss reserves, plus the remaining capacity under the NICO Cover and other reinsurance contracts, will be sufficient to cover additional liability arising from any such adverse developments.

Sirius Group



Net A&E Loss Reserve Activity	Year Ended December 31,
	2014						2013						2012
Millions	Gross			Net			Gross			Net			Gross			Net
Asbestos:
Beginning balance	$	207.4		$	178.7		$	208.2		$	174.2		$	185.1		$	146.2
Losses and LAE acquired	22.9			22.9			13.0			13.0			11.0			11.0
Incurred losses and LAE	7.4			8.0			12.1			11.8			46.8			46.4
Paid losses and LAE	(21.9		)	(16.8		)	(25.9		)	(20.3		)	(34.7		)	(29.4		)
Ending balance	215.8			192.8			207.4			178.7			208.2			174.2
Environmental:
Beginning balance	20.4			15.2			20.4			15.2			22.1			16.5
Losses and LAE acquired	2.1			2.1			1.0			1.0			0.7			0.7
Incurred losses and LAE	1.6			1.6			.8			.8			(0.1		)	(0.5		)
Paid losses and LAE	(1.4		)	(1.5		)	(1.8		)	(1.8		)	(2.3		)	(1.5		)
Ending balance	22.7			17.4			20.4			15.2			20.4			15.2
Total asbestos and environmental:
Beginning balance	227.8			193.9			228.6			189.4			207.2			162.7
Losses and LAE acquired	25.0			25.0			14.0			14.0			11.7			11.7
Incurred losses and LAE	9.0			9.6			12.9			12.6			46.7			45.9
Paid losses and LAE	(23.3		)	(18.3		)	(27.7		)	(22.1		)	(37.0		)	(30.9		)
Ending balance	$	238.5		$	210.2		$	227.8		$	193.9		$	228.6		$	189.4

Third Party Reinsurance

12 Months Ended

Dec. 31, 2014

Reinsurance Disclosures [Abstract]

Third-Party Reinsurance

In the normal course of business, White Mountains’s insurance and reinsurance subsidiaries seek to limit losses that may arise from catastrophes or other events by reinsuring with third-party reinsurers. White Mountains remains liable for risks reinsured in the event that the reinsurer does not honor its obligations under reinsurance contracts. The effects of reinsurance on White Mountains’s insurance and reinsurance subsidiaries’ written and earned premiums and on losses and LAE were as follows (see Note 10 for balances related to White Mountains financial guarantee business):



	Year ended December 31, 2014
Millions	OneBeacon			Sirius Group			HG/BAM ⁽¹⁾		Other ⁽²⁾			Total
Written premiums:
Direct	$	1,257.5		$	208.7		$	16.2	$	22.6		$	1,505.0
Assumed	65.9			927.9			—		—			993.8
Gross written premiums	1,323.4			1,136.6			16.2		22.6			2,498.8
Ceded	(106.5		)	(254.1		)	—		(16.7		)	(377.3		)
Net written premiums	$	1,216.9		$	882.5		$	16.2	$	5.9		$	2,121.5
Earned premiums:
Direct	$	1,209.1		$	200.2		$	1.8	$	22.6		$	1,433.7
Assumed	70.9			925.4			—		—			996.3
Gross earned premiums	1,280.0			1,125.6			1.8		22.6			2,430.0
Ceded	(102.9		)	(251.7		)	—		(16.5		)	(371.1		)
Net earned premiums	$	1,177.1		$	873.9		1.8		$	6.1		$	2,058.9
Losses and LAE:
Direct	$	830.7		$	117.8		$	—	$	24.1		$	972.6
Assumed	63.7			378.1			—		—			441.8
Gross losses and LAE	894.4			495.9			—		24.1			1,414.4
Ceded	(79.3		)	(150.6		)	—		(15.2		)	(245.1		)
Net losses and LAE	$	815.1		$	345.3		$	—	$	8.9		$	1,169.3

⁽¹⁾During 2014, BAM ceded $12.3 in written premiums ($1.4 in earned premiums) to HG Global, which have been eliminated within the HG/BAM segment.

⁽²⁾During 2014, SSIE ceded $16.0 in written premiums ($15.7 in earned premiums) to OneBeacon, which have been eliminated in consolidation.



	Year ended December 31, 2013
Millions	OneBeacon			Sirius Group			Total
Written premiums:
Direct	$	1,103.1		$	177.3		$	1,280.4
Assumed	59.8			943.1			1,002.9
Gross written premiums	1,162.9			1,120.4			2,283.3
Ceded	(74.3		)	(243.8		)	(318.1		)
Net written premiums	$	1,088.6		$	876.6		$	1,965.2
Earned premiums:
Direct	$	1,043.3		$	174.0		$	1,217.3
Assumed	148.5			938.6			1,087.1
Gross earned premiums	1,191.8			1,112.6			2,304.4
Ceded	(71.4		)	(246.2		)	(317.6		)
Net earned premiums	$	1,120.4		$	866.4		$	1,986.8
Losses and LAE:
Direct	$	584.9		$	98.1		$	683.0
Assumed	76.3			455.5			531.8
Gross losses and LAE	661.2			553.6			1,214.8
Ceded	(39.1		)	(135.2		)	(174.3		)
Net losses and LAE	$	622.1		$	418.4		$	1,040.5



	Year ended December 31, 2012
Millions	OneBeacon			Sirius Group			Total
Written premiums:
Direct	$	1,204.0		$	186.1		$	1,390.1
Assumed	55.2			992.7			1,047.9
Gross written premiums	1,259.2			1,178.8			2,438.0
Ceded	(80.0		)	(231.1		)	(311.1		)
Net written premiums	$	1,179.2		$	947.7		$	2,126.9
Earned premiums:
Direct	$	1,158.3		$	169.9		$	1,328.2
Assumed	52.8			988.3			1,041.1
Gross earned premiums	1,211.1			1,158.2			2,369.3
Ceded	(79.1		)	(226.6		)	(305.7		)
Net earned premiums	$	1,132.0		$	931.6		$	2,063.6
Losses and LAE:
Direct	$	687.5		$	96.9		$	784.4
Assumed	29.6			523.9			553.5
Gross losses and LAE	717.1			620.8			1,337.9
Ceded	(67.1		)	(76.9		)	(144.0		)
Net losses and LAE	$	650.0		$	543.9		$	1,193.9

OneBeacon

The timing and size of catastrophe losses are unpredictable and the level of losses experienced in any year could be material to OneBeacon’s operating results and financial condition. Examples of catastrophes include losses caused by earthquakes, wildfires, hurricanes and other types of storms and terrorist acts. The extent of losses caused by a catastrophic event is a function of severity and the amount and type of insured exposure in the affected area. In the normal course of business, OneBeacon's insurance subsidiaries seek to limit losses that may arise from catastrophes or other events through individual risk selection, imposing deductibles and limits, limiting its concentration of insurance in catastrophe-prone areas, such as coastal regions, and reinsuring with third-party reinsurers.

OneBeacon uses models (primarily AIR Worldwide (“AIR”) Touchstone version 2.0) to estimate potential losses from catastrophes. OneBeacon uses this model output in conjunction with other data to manage its exposure to catastrophe losses based on a probable maximum loss (“PML”) forecast to quantify its exposure to a 1-in-250-year catastrophe event.

OneBeacon purchases a general catastrophe reinsurance treaty with unaffiliated reinsurers to manage its exposure to large catastrophe losses. Effective May 1, 2014, OneBeacon renewed its property catastrophe reinsurance program through April 30, 2015. The program provides coverage for OneBeacon’s property business as well as certain acts of terrorism. Under the program, the first $20.0 million of losses resulting from any single catastrophe are retained and 100% of the next $110.0 million of losses resulting from the catastrophe are reinsured. The part of a catastrophe loss in excess of $130.0 million would be retained in full. In the event of a catastrophe, OneBeacon’s property catastrophe reinsurance program is reinstated for the remainder of the original contract term by paying a reinstatement premium that is based on the percentage of coverage reinstated and the original property catastrophe coverage premium.

OneBeacon's current third party reinsurance programs provide varying degrees of coverage for terrorism events. The Company's overall terrorism exposure is impacted by the Terrorism Risk Insurance Program (the “Terrorism Act”), which is a federal program administered by the Department of the Treasury that provides for a shared system of public and

private compensation for commercial property and casualty losses resulting from events that reach the threshold for losses

($100.0 million in 2015 and increasing $20.0 million in subsequent years until the threshold becomes $200.0 million in 2020). The Terrorism Act limits the industry's aggregate liability for losses from certified terrorist acts by requiring the federal government to share a set amount of losses (85% in 2015 and decreasing 1% in subsequent years until it reaches a floor of 80% in 2020) once a company meets a specific retention or deductible as determined by its prior year's direct written premiums. It also limits the aggregate liability to be paid by the government and industry without further action by Congress to $100.0 billion. In exchange for this “backstop,” primary insurers are required to make coverage available to commercial insureds for losses from acts of terrorism as specified in the Terrorism Act. The following types of coverage are excluded from the program: commercial automobile, burglary and theft, surety, farmowners multi-peril and all professional liability coverage except directors and officers coverage.

All losses that result from a nuclear, biological, chemical or radiological terrorist attack are excluded from the Company's current third party reinsurance program. OneBeacon's property catastrophe treaty also excludes acts of terrorism certified pursuant to the Terrorism Act and committed by an individual or individuals acting on behalf of any foreign person or foreign interest. OneBeacon's casualty clash treaty provides coverage for losses that result from certified and non-certified acts of terrorism, on an aggregated basis, subject to a maximum of one full treaty limit. OneBeacon's property per risk, casualty and workers compensation treaties each provide full coverage for certified acts of terrorism on behalf of a non-foreign person or interest, but are sublimited to one full treaty limit for certified acts of terrorism committed on behalf of any foreign person or foreign interest. OneBeacon's healthcare treaty is sublimited to one full treaty limit of coverage for all acts of terrorism.

OneBeacon estimates its individual retention level for commercial policies subject to the Terrorism Act to be approximately $120.0 million in 2015. The federal government will pay 85% of covered terrorism losses that exceed OneBeacon’s or the industry’s retention levels in 2015, up to a total of $100.0 billion. As indicated above, OneBeacon’s 15% copay will increase annually beginning in 2016 by 1% until it reaches a limit of 20% in 2020.

In addition to the corporate catastrophe reinsurance protection, OneBeacon also purchases dedicated reinsurance protection for certain lines of business. OneBeacon’s specialty property business purchases a dedicated property catastrophe program providing 100% coverage for $30.0 million of loss in excess of $10.0 million, which inures to the benefit of the property catastrophe reinsurance program described previously. This treaty limit cannot be reinstated.

OneBeacon also purchases property-per-risk reinsurance coverage to reduce large loss volatility. The property-per-risk reinsurance program reinsures 100% of losses in excess of $5.0 million, down from $10.0 million for 2013, up to $100.0 million. Individual risk facultative reinsurance is purchased above $100.0 million. The property-per-risk treaty provides one limit of reinsurance protection for losses in excess of $5.0 million up to $100.0 million on an individual risk basis for certified acts of terrorism committed on behalf of any foreign person or foreign interest. However, any nuclear events, or biological, chemical or radiological terrorist attacks are not covered.

OneBeacon also maintains a casualty reinsurance program that provides protection for individual policies involving general liability, automobile liability, professional liability or umbrella liability. OneBeacon's healthcare professional liability treaty covers losses in excess of $5.0 million up to $10.0 million with a 10% co-participation. All other casualty business is covered in a separate treaty covering losses in excess of $5.0 million up to $11.0 million with a 10.0% co-participation. Losses in excess of $10.0 million for business subject to the healthcare professional liability treaty up to $20.0 million, and losses in excess of $11.0 million for all other casualty business up to $21.0 million are 100% reinsured by a combined Second Casualty Excess of Loss treaty layer. OneBeacon also purchases a treaty to protect against large workers compensation losses that covers 100% of the loss in excess of $2.0 million up to $10.0 million per occurrence. Additionally, for casualty and/or workers compensation catastrophe losses, OneBeacon maintains a dedicated clash treaty, which provides coverage in the event that one loss event results in two or more claims, that covers losses up to $60.0 million in excess of a $10.0 million retention.

OneBeacon purchases a per-occurrence treaty for marine business, both inland and ocean, that protects against large occurrences, whether a single large claim or a catastrophe. The marine treaty attaches at $2.0 million per occurrence. The first layer of the marine treaty is $5.0 million in excess of $2.0 million, with annual aggregate deductibles of $1.5 million for individual ocean marine large claims, $1.5 million for individual inland marine large claims and $5.0 million for catastrophe losses. OneBeacon retains 60% of the loss from $2.0 million up to $7.0 million. Catastrophe coverage is provided up to $60.0 million. Retained catastrophe losses are subject to the corporate catastrophe treaty. Individual risk losses from inland marine exceeding $20.0 million are subject to the corporate property per risk treaty. Reinstatement premiums are paid in full or in part depending on the layer and the occurrence if the coverage is attached.

OneBeacon also purchases reinsurance for its surety underwriting operating segment. Effective October 1, 2014, this treaty covers 100% of losses in excess of $5.0 million up to $40.0 million per bond and up to $80.0 million in aggregate.

Additionally, effective January 1, 2014, OneBeacon placed an HMO/Provider Excess reinsurance agreement providing unlimited coverage excess of $5.0 million per member in two layers with no aggregate coverage maximum.

Effective January 1, 2014, OneBeacon entered into reinsurance treaties to provide coverage for the 2014 crop year. OneBeacon purchased an aggregate stop loss on its MPCI portfolio, providing 48.5% of coverage in excess of a 101.5% loss ratio on premiums covered by the contract and a separate aggregate stop loss providing 80% of coverage in excess of a 100% loss ratio on its crop-hail portfolio.

Effective June 1, 2014, OneBeacon also purchased reinsurance on its film completion bond business in excess of $2.0 million up to $30.0 million in three layers, with a facultative treaty layer providing coverage up to $50.0 million as needed.

As of December 31, 2014, OneBeacon had $12.2 million and $161.6 million of reinsurance recoverables on paid and unpaid losses. As reinsurance contracts do not relieve OneBeacon of its obligation to its policyholders, collectability of balances due from reinsurers is important to OneBeacon’s financial strength. OneBeacon is selective with its reinsurers, placing reinsurance with only those reinsurers having a strong financial condition. OneBeacon monitors the financial strength of its reinsurers on an ongoing basis. Uncollectible amounts historically have not been significant.

The following table summarizes Standard & Poor’s Financial Services LLC (“Standard & Poor’s”) ratings for OneBeacon’s reinsurers. The reinsurance balances associated with the Runoff Business are included in discontinued operations (see Note 22).



Standard & Poor’s Rating⁽¹⁾	Balance at December 31, 2014		% of Total
AA	$	53.8	31	%
A	93.2		54	%
BBB+, Not rated and other⁽²⁾	26.8		15	%
Total	$	173.8	100	%

⁽¹⁾Standard & Poor’s ratings as detailed above are: “AA” (Very strong), “A” (Strong) and “BBB+” (Adequate).

⁽²⁾ Includes $23.8 related to OBIC, an unrated entity sold to Armour as part of the Runoff Transaction.

Sirius Group

Sirius Group's reinsurance protection primarily consists of pro-rata and excess of loss protections to cover A&H, aviation, trade credit, and certain property exposures. Sirius Group's core proportional property reinsurance programs provide protection for parts of the non-proportional treaty accounts written in Europe, the Americas, Asia, the Middle East, and Australia. These reinsurance protections are designed to increase underwriting capacity where appropriate, and to reduce exposure both to large catastrophe losses and to a frequency of smaller loss events. At January 1, 2015, the protection provided by the proportional program for the United States has been enhanced with an additional quota share treaty covering non-proportional property catastrophe exposures, through which 20% of this business is ceded up to a per program limit of $15 million per cedant.

Sirius Group purchases excess of loss reinsurance protection for its facultative and direct property portfolios. The protection has been renewed at January 1, 2015 with the same structure as for 2014, with a $15.0 million in excess of a retention of $5.0 million for business written in Stockholm, Hamburg, London and Syndicate 1945. An additional $15.0 million of reinsurance protection in excess of the $20.0 million coverage is in place for the facultative and direct property portfolios written in Stockholm and Hamburg, as well as a further $2.5 million of second loss coverage in excess of a retention of $2.5 million. Sirius Group also has $5.0 million of protection in excess of a retention of $5.0 million for the London branch and Syndicate 1945 for facultative and direct U.S. catastrophe exposed business, which is in force through June 30, 2015.

Sirius Group has in place excess of loss retrocessional coverage for its non-U.S. and non-Japan earthquake-related exposures. This cover was renewed for one year at April 1, 2014, providing $40.0 million of reinsurance protection in excess of Sirius Group's retention of $35.0 million and a further $17.5 million of partially placed coverage in excess of $75.0 million.

In addition to the above, Sirius Group periodically purchases industry loss warranty (“ILW”) contracts to augment its overall retrocessional program. The following ILW contracts are currently in force:



Scope	Limit	Trigger	Expiration Date
European wind & flood	$5 million	$7.5 billion	March 31, 2015
European wind & flood	$5 million	$5 billion	March 31, 2015
European all natural perils	$15 million	$15 billion	December 31, 2015 (second event aggregate excess cover)
European wind & earthquake	$7.5 million	$5-$7.5 billion	March 31, 2016
United States all natural peril	$5 million	$20 billion	June 30, 2015
United States, European, Japan wind & earthquake	$30 million	$5-$10 billion	December 31, 2015 (multiple layer covers)

Sirius Group's aviation reinsurance program is intended to reduce exposure to a frequency of small losses, a single large loss or a combination of both. For the proportional and facultative aviation portfolios, reinsurance protection generally covers losses from events that cause a market loss in excess of $250.0 million up to a full policy limit of $2.0 billion. This program is in effect through November 2015. For the non-proportional aviation portfolio, reinsurance protection includes a 15% quota share treaty. In addition, the non-proportional portfolio is protected by ILWs with a limit of $29.5 million. The ILWs attach at industry loss levels between $350.0 million and $1.0 billion.

For the marine yacht portfolio written by the London branch and Syndicate 1945, reinsurance coverage is in place for $14.75 million in excess of a retention of $250,000. Also, an energy & marine excess of loss coverage for Syndicate 1945 is in place for $16.0 million in excess of retention of $1.5 million, protecting both risk and catastrophe losses. These programs are in effect through April 30, 2015.

For accident and health, Sirius Group has excess of loss protection for 2015 covering personal accident and life of €10.0 million ($12.0 million based on the December 31, 2014 EUR to USD exchange rate) of protection in excess of a €5.0 million ($6.0 million based on the December 31, 2014 EUR to USD exchange rate) retention for the Stockholm, Hamburg, Liege and Singapore branches. In addition, the Sirius America’s direct insurance portfolio includes quota share reinsurance of various percentages and a per claim high excess of loss cover, which has no limit for losses in excess of $1.0 million.

For 2014, Sirius Group ceded 20% and 50% of its trade credit and bond business, respectively, under a quota share retrocession, which supported growth in this line. The treaty was renewed for 2015 with a reduced cession of 10% for trade credit and 25% for the bond business.

For 2014, Sirius Group also ceded 30% of the direct contingency business written in the London branch and Syndicate 1945 on a proportional basis. The treaty was renewed at January 1, 2015. In addition, at January 1, 2015, a 20% variable quota share treaty cession was placed for risks exceeding $10.0 million.

Almost all of Sirius Group's excess of loss reinsurance protections, excluding ILWs which tend to cover only one loss event, include provisions that reinstate coverage at a cost of 100% or more of the original reinsurance premium.

As of December 31, 2014, Sirius Group had $11.4 million of reinsurance recoverables on paid losses and $322.2 million of reinsurance recoverables on unpaid losses that will become recoverable if claims are paid in accordance with current reserve estimates. Because retrocessional reinsurance contracts do not relieve Sirius Group of its obligation to its insureds, the collectability of balances due from Sirius Group's reinsurers is critical to its financial strength. Sirius Group monitors the financial strength and ratings of retrocessionaires on an ongoing basis.

The following table provides a listing of Sirius Group’s gross and net recoverable amounts by the reinsurer’s Standard & Poor’s rating and the percentage of total recoverables.



Rating⁽¹⁾	Gross		Collateral		Net		% of Net Total
AA	$	114.6	$	1.6	$	113.0	34	%
A	138.8		7.1		131.7		42	%
BBB+	8.9		—		8.9		3	%
BBB or lower	9.6		—		9.6		3	%
Not rated	61.7		21.5		40.2		18	%
Total	$	333.6	$	30.2	$	303.4	100	%

⁽¹⁾Standard & Poor’s ratings as detailed above are: “AAA” (Extremely strong), “AA” (Very strong), “A” (Strong), and “BBB+” and “BBB” (Adequate).

- Definition

The entire disclosure pertaining to the existence, magnitude and information about insurance that has been ceded to or assumed from another insurance company, including the methodologies and assumptions used in determining recorded amounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6816-158387

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 605
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27374-158547

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.6,13)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6811-158387

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 605
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 605
-Section 55
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=6588590&loc=d3e27795-158548

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 605
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=6588590&loc=d3e27703-158548

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6485557&loc=d3e21549-158491

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 6
-Article 7

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 13
-Article 7

+ Details

Investment Securities

12 Months Ended

Dec. 31, 2014

Investments, Debt and Equity Securities [Abstract]

Investment Securities

Net Investment Income

White Mountains’s net investment income is comprised primarily of interest income associated with White Mountains’s fixed maturity investments, dividend income from its equity investments and interest income from its short-term investments.

Pre-tax net investment income for 2014, 2013 and 2012 consisted of the following:



	Year Ended December 31,
Millions	2014			2013			2012
Investment income:
Fixed maturity investments	$	98.9		$	100.5		$	132.0
Short-term investments	1.5			3.4			3.1
Common equity securities	21.0			20.5			22.2
Convertible fixed maturity and preferred investments	2.5			2.9			6.0
Other long-term investments	1.9			3.0			3.1
Interest on funds held under reinsurance treaties	(.2		)	.3			.6
Total investment income	125.6			130.6			167.0
Third-party investment expenses	(20.6		)	(19.7		)	(13.4		)
Net investment income, pre-tax	$	105.0		$	110.9		$	153.6

Net Realized and Unrealized Investment Gains and Losses

Net realized and unrealized investment gains and losses consisted of the following:



	Year Ended December 31,
Millions	2014			2013			2012
Net realized investment gains, pre-tax	$	233.8		$	104.5		$	68.1
Net unrealized investment gains, pre-tax	50.1			57.2			50.1
Net realized and unrealized investment gains, pre-tax	283.9			161.7			118.2
Income tax expense attributable to net realized and unrealized investment gains	(69.7		)	(21.9		)	(26.8		)
Net realized and unrealized investment gains, after tax	$	214.2		$	139.8		$	91.4

Net realized investment gains (losses)

Net realized investment gains (losses) for 2014, 2013 and 2012 consisted of the following:



	Year ended December 31, 2014
Millions	Net realized gains (losses)			Net foreign exchange gains (losses)			Total changes in fair value reflected in earnings
Fixed maturity investments	$	23.9		$	21.0		$	44.9
Short-term investments	—			2.9			2.9
Common equity securities	150.9			.9			151.8
Convertible fixed maturity and preferred investments	5.9			—			5.9
Other long-term investments	27.7			.3			28.0
Forward contracts	.3			—			.3
Net realized investment gains (losses), pre-tax	208.7			25.1			233.8
Income taxes attributable to realized investment gains (losses)	(39.7		)	(8.0		)	(47.7		)
Net realized investment gains (losses), after-tax	$	169.0		$	17.1		$	186.1



	Year ended December 31, 2013
Millions	Net realized gains (losses)			Net foreign exchange gains (losses)			Total changes in fair value reflected in earnings
Fixed maturity investments	$	8.6		$	(15.0	)	$	(6.4	)
Short-term investments	.1			—			.1
Common equity securities	104.5			(3.7		)	100.8
Convertible fixed maturity and preferred investments	1.0			—			1.0
Other long-term investments	7.5			1.4			8.9
Forward contracts	.1			—			.1
Net realized investment gains (losses), pre-tax	121.8			(17.3		)	104.5
Income taxes attributable to realized investment gains (losses)	(30.0		)	5.5			(24.5		)
Net realized investment gains (losses), after-tax	$	91.8		$	(11.8	)	$	80.0



	Year ended December 31, 2012
Millions	Net realized gains (losses)			Net foreign exchange gains (losses)			Total changes in fair value reflected in earnings
Fixed maturity investments	$	82.5		$	(2.5	)	$	80.0
Short-term investments	—			(4.3		)	(4.3		)
Common equity securities	1.3			—			1.3
Convertible fixed maturity and preferred investments	(8.2		)	(1.8		)	(10.0		)
Other long-term investments	1.4			—			1.4
Forward contracts	(.3		)	—			(.3		)
Net realized investment gains (losses), pre-tax	76.7			(8.6		)	68.1
Income taxes attributable to realized investment gains (losses)	(23.8		)	2.2			(21.6		)
Net realized investment gains (losses), after-tax	$	52.9		$	(6.4	)	$	46.5

Net unrealized investment gains (losses)

The following table summarizes net unrealized investment gains (losses) and changes in the carrying value of investments measured at fair value:



	Year ended December 31, 2014
Millions	Net unrealized gains (losses)			Net foreign exchange gains (losses)			Total net unrealized gains (losses) reflected in earnings
Fixed maturity investments	$	30.9		$	111.7		$	142.6
Short-term investments	(.2		)	.1			(.1		)
Common equity securities	(83.0		)	(.1		)	(83.1		)
Convertible fixed maturity and preferred investments	(8.2		)	.4			(7.8		)
Other long-term investments	(5.7		)	4.2			(1.5		)
Net unrealized investment gains (losses), pre-tax	(66.2		)	116.3			50.1
Income taxes attributable to unrealized investment gains (losses)	6.0			(28.0		)	(22.0		)
Net unrealized investment gains (losses), after-tax	$	(60.2	)	$	88.3		$	28.1



	Year ended December 31, 2013
Millions	Net unrealized gains (losses)			Net foreign exchange gains (losses)			Total net unrealized gains (losses) reflected in earnings
Fixed maturity investments	$	(93.9	)	$	15.3		$	(78.6	)
Short-term investments	.1			—			.1
Common equity securities	119.2			(.4		)	118.8
Convertible fixed maturity and preferred investments	3.2			—			3.2
Other long-term investments	10.3			3.4			13.7
Net unrealized investment gains (losses), pre-tax	38.9			18.3			57.2
Income taxes attributable to unrealized investment gains (losses)	8.2			(5.6		)	2.6
Net unrealized investment gains (losses), after-tax	$	47.1		$	12.7		$	59.8



	Year ended December 31, 2012
Millions	Net unrealized gains (losses)			Net foreign exchange gains (losses)			Total net unrealized gains (losses) reflected in earnings
Fixed maturity investments	$	18.5		$	(45.9	)	$	(27.4	)
Short-term investments	—			.1			.1
Common equity securities	65.9			(.1		)	65.8
Convertible fixed maturity and preferred investments	1.1			—			1.1
Other long-term investments	13.2			(2.7		)	10.5
Net unrealized investment gains (losses), pre-tax	98.7			(48.6		)	50.1
Income taxes attributable to unrealized investment gains (losses)	(17.9		)	12.7			(5.2		)
Net unrealized investment gains (losses), after-tax	$	80.8		$	(35.9	)	$	44.9

White Mountains recognized gross realized investment gains of $270.0 million, $221.4 million and $162.2 million and gross realized investment losses of $36.2 million, $116.9 million and $94.1 million on sales of investment securities during 2014, 2013 and 2012.

The following table summarizes the amount of total gains (losses) included in earnings attributable to unrealized investment gains (losses) for Level 3 investments for the years ended December 31, 2014, 2013 and 2012.



	Year Ended December 31,
Millions	2014			2013			2012
Fixed maturity investments	$	1.2		$	(2.3	)	$	7.7
Common equity securities	5.9			.9			3.0
Convertible fixed maturity and preferred investments	.7			—			—
Other long-term investments	(4.1		)	11.2			7.0
Total net unrealized investment gains (losses), pre-tax - Level 3 investments	$	3.7		$	9.8		$	17.7

The components of White Mountains’s net realized and unrealized investment gains (losses), after-tax, as recorded on the statements of operations and comprehensive income were as follows:



	Year Ended December 31,
Millions	2014			2013			2012
Net change in pre-tax unrealized gains (losses) on investments in unconsolidated affiliates	$	81.2		$	(106.4	)	$	62.8
Income taxes	(5.9		)	8.3			(5.1		)
Net change in unrealized gains (losses) on investments in unconsolidated affiliates, after tax	75.3			(98.1		)	57.7
Net realized and unrealized foreign currency (losses) gains on investments through OCI	(274.3		)	11.3			95.5
Total investment (losses) gains through accumulated other comprehensive income	(199.0		)	(86.8		)	153.2
Net realized and unrealized investment gains, after-tax	214.2			139.8			91.4
Total investment gains recorded during the period, after-tax	$	15.2		$	53.0		$	244.6

Investment Holdings

The cost or amortized cost, gross unrealized investment gains and losses, net foreign currency gains and losses, and carrying values of White Mountains’s fixed maturity investments as of December 31, 2014 and 2013, were as follows:



	December 31, 2014
Millions	Cost or amortized cost		Gross unrealized gains		Gross unrealized losses			Net foreign currency gains (losses)			Carrying value
US Government and agency obligations	$	184.7	$	.1	$	(.3	)	$	3.6		$	188.1
Debt securities issued by corporations	2,221.3		45.2		(5.1		)	49.8			2,311.2
Municipal obligations	82.0		1.4		(.2		)	—			83.2
Mortgage-backed and asset-backed securities	1,811.1		7.6		(3.5		)	25.7			1,840.9
Foreign government, agency and provincial obligations	274.6		4.2		(1.0		)	(2.7		)	275.1
Preferred stocks	79.6		6.1		—			.1			85.8
Total fixed maturity investments	$	4,653.3	$	64.6	$	(10.1	)	$	76.5		$	4,784.3



	December 31, 2013
Millions	Cost or amortized cost		Gross unrealized gains		Gross unrealized losses			Net foreign currency losses			Carrying value
US Government and agency obligations	$	365.5	$	.5	$	(1.0	)	$	(2.5	)	$	362.5
Debt securities issued by corporations	2,330.7		44.0		(13.2		)	(14.3		)	2,347.2
Municipal obligations	18.3		—		(.4		)	—			17.9
Mortgage-backed and asset-backed securities	2,027.3		2.4		(9.9		)	(5.3		)	2,014.5
Foreign government, agency and provincial obligations	444.2		3.7		(3.2		)	(4.8		)	439.9
Preferred stocks	79.9		5.1		—			(.2		)	84.8
Total fixed maturity investments including assets held for sale	$	5,265.9	$	55.7	$	(27.7	)	$	(27.1	)	$	5,266.8
Fixed maturity investments reclassified to assets held for sale ⁽¹⁾											(236.3		)
Total fixed maturity investments											$	5,030.5


⁽¹⁾	Assets held for sale related to discontinued operations. See Note 22.

The weighted average duration of White Mountains’s fixed income portfolio as of December 31, 2014 was approximately 2.0 years, including short-term investments, and approximately 2.3 years excluding short-term investments.

The cost or amortized cost and carrying value of White Mountains’s fixed maturity and convertible fixed maturity investments as of December 31, 2014 is presented below by contractual maturity. Actual maturities could differ from contractual maturities because borrowers may have the right to call or prepay certain obligations with or without call or prepayment penalties.



	December 31, 2014
Millions	Cost or amortized cost		Carrying value
Due in one year or less	$	331.2	$	337.5
Due after one year through five years	1,968.3		2,032.3
Due after five years through ten years	434.4		453.9
Due after ten years	40.2		46.1
Mortgage-backed and asset-backed securities	1,811.1		1,840.9
Preferred stocks	79.6		85.8
Total	$	4,664.8	$	4,796.5

The cost or amortized cost, gross unrealized investment gains and losses, net foreign currency gains and losses, and carrying values of White Mountains’s common equity securities, convertible fixed maturity and preferred investments and other long-term investments as of December 31, 2014 and 2013 were as follows:



	December 31, 2014
Millions	Cost or amortized cost		Gross unrealized gains		Gross unrealized losses			Net foreign currency losses			Carrying value
Common equity securities	$	633.6	$	175.1	$	(5.2	)	$	(1.9	)	$	801.6
Convertible fixed maturity and preferred investments	$	19.1	$	.9	$	(.2	)	$	.7		$	20.5
Other long-term investments	$	344.5	$	73.0	$	(10.9	)	$	1.6		$	408.2



	December 31, 2013
Millions	Cost or amortized cost		Gross unrealized gains		Gross unrealized losses			Net foreign currency losses			Carrying value
Common equity securities	$	890.2	$	271.0	$	(3.6	)	$	(.8	)	$	1,156.8
Convertible fixed maturity and preferred investments	$	71.7	$	9.9	$	(.9	)	$	(.2	)	$	80.5
Other long-term investments	$	238.3	$	79.6	$	(26.6	)	$	(2.4	)	$	288.9

Proceeds from the sales and maturities of investments, excluding short-term investments, totaled $6,238.1 million, $4,924.8 million and $6,997.5 million for the years ended December 31, 2014, 2013 and 2012.

Investments Held on Deposit or as Collateral

As of December 31, 2014 and 2013, investments of $171.5 million and $170.4 million, respectively, were held in trusts required to be maintained in relation to various reinsurance agreements. White Mountains’s consolidated insurance and reinsurance operations are required to maintain deposits with certain insurance regulatory agencies in order to maintain their insurance licenses. The fair value of such deposits which are included within total investments totaled $130.3 million and $290.7 million as of December 31, 2014 and 2013.

As of December 31, 2014 and 2013, OneBeacon held unrestricted collateral from its customers, which is included in cash and invested assets, relating to its surety business of $81.0 million and $63.3 million. The obligation to return these funds is included in funds held under insurance and reinsurance contracts in the consolidated balance sheets.

As of December 31, 2014 and 2013, White Mountains held $9.5 million and $23.2 million of restricted collateral in the form of fixed maturities and $4.3 million and $2.0 million of restricted collateral in the form of short-term investments associated with variable annuity reinsurance and interest rate cap agreements. See Note 9.

Fair value measurements as of December 31, 2014

White Mountains used quoted market prices or other observable inputs to determine fair value for the 93% of its investment portfolio. Investments valued using Level 1 inputs include fixed maturity investments, primarily investments in U.S. Treasuries, common equities and short-term investments, which include U.S. Treasury Bills. Investments valued using Level 2 inputs consist of fixed maturity investments including corporate debt, state and other governmental debt, convertible fixed maturity securities and mortgage and asset-backed securities. Fair value estimates for investments that trade infrequently and have few or no observable market prices are classified as Level 3 measurements. Level 3 fair value estimates based upon unobservable inputs include White Mountains’s investments in hedge funds and private equity funds, as well as investments in certain debt securities where quoted market prices are unavailable. White Mountains uses brokers and outside pricing services to assist in determining fair values. For investments in active markets, White Mountains uses the quoted market prices provided by outside pricing services to determine fair value. The outside pricing services used by White Mountains have indicated that if no observable inputs are available for a security, they will not provide a price. In those circumstances, White Mountains estimates the fair value using industry standard pricing models and observable inputs such as benchmark interest rates, market comparables, broker quotes, issuer spreads, bids, offers, credit rating, prepayment speeds and other relevant inputs. White Mountains performs procedures to validate the market prices obtained from the outside pricing sources. Such procedures, which cover substantially all of its fixed maturity investments include, but are not limited to, evaluation of model pricing methodologies and review of the pricing services’ quality control processes and procedures on at least an annual basis, comparison of market prices to prices obtained from different independent pricing vendors on at least a semi-annual basis, monthly analytical reviews of certain prices, and review of assumptions utilized by the pricing service for selected measurements on an ad hoc basis throughout the year. White Mountains also performs back-testing of selected sales activity to determine whether there are any significant differences between the market price used to value the security prior to sale and the actual sale price on an ad-hoc basis throughout the year. Prices provided by the pricing services that vary by more than 5% and $1.0 million from the expected price based on these procedures are considered outliers. In circumstances where the results of White Mountains’s review process do not appear to support the market price provided by the pricing services, White Mountains challenges the price. If White Mountains cannot gain satisfactory evidence to support the challenged price, it relies upon its own pricing methodologies to estimate the fair value of the security in question. The fair values of such securities are considered to be Level 3 measurements.

White Mountains’s investments in debt securities are generally valued using matrix and other pricing models. Key inputs include benchmark yields, benchmark securities, reported trades, issuer spreads, bids, offers, credit ratings and prepayment speeds. Income on mortgage-backed and asset-backed securities is recognized using an effective yield based on anticipated prepayments and the estimated economic life of the securities. When actual prepayments differ significantly from anticipated prepayments, the estimated economic life is recalculated and the remaining unamortized premium or discount is amortized or accreted prospectively over the remaining economic life.

White Mountains employs a number of procedures to assess the reasonableness of the fair value measurements for its other long-term investments, including obtaining and reviewing the audited annual financial statements of each hedge fund and private equity fund and periodically discussing each fund’s pricing with the fund manager. However, since the fund managers do not provide sufficient information to evaluate the pricing inputs and methods for each underlying investment, the inputs are considered to be unobservable. Accordingly, the fair value of White Mountains’s investments in hedge funds and private equity funds has been classified as Level 3 measurements. The fair value of White Mountains’s investments in hedge funds and private equity funds has been determined using net asset value.

In addition to the investments described above, White Mountains has $38.0 million and $86.3 million of investment-related liabilities recorded at fair value and included in other liabilities as of December 31, 2014 and 2013. These liabilities relate to securities that have been sold short by limited partnerships in which White Mountains has investments and is required to consolidate under GAAP. All of the liabilities included have a Level 1 designation.

Fair Value Measurements by Level

The following tables summarize White Mountains’s fair value measurements for investments as of December 31, 2014 and 2013 by level. The fair value measurements for derivative assets associated with White Mountains’s variable annuity business are presented in Note 9.



	December 31, 2014
Millions	Fair value		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs
Fixed maturity investments:
U.S. Government and agency obligations	$	188.1	$	134.1	$	54.0	$	—
Debt securities issued by corporations:
Consumer	777.6		—		777.6		—
Financials	456.6		—		456.6		—
Industrial	285.0		—		285.0		—
Communications	237.5		—		237.5		—
Utilities	169.8		—		169.8		—
Energy	181.8		—		181.8		—
Basic Materials	108.6		—		103.0		5.6
Technology	87.9		—		87.9		—
Other	6.4		—		6.4		—
Total debt securities issued by corporations:	2,311.2		—		2,305.6		5.6

Mortgage-backed and asset-backed securities	1,840.9		—		1,840.9		—
Foreign government, agency and provincial obligations	275.1		21.3		253.8		—
Preferred stocks	85.8		—		14.7		71.1
Municipal obligations	83.2		—		83.2		—
Total fixed maturity investments	4,784.3		155.4		4,552.2		76.7

Short-term investments	871.7		868.8		2.9		—

Common equity securities:
Financials	233.9		193.7		—		40.2
Consumer	238.4		238.3		.1		—
Industrial	91.7		91.7		—		—
Energy	32.7		32.7		—		—
Technology	36.6		36.6		—		—
Communications	45.1		45.1		—		—
Basic materials	21.5		21.5		—		—
Utilities	9.5		9.4		.1		—
Other	92.2		18.9		73.3		—
Total common equity securities	801.6		687.9		73.5		40.2
Convertible fixed maturity and preferred investments	20.5		—		12.3		8.2
Other long-term investments ⁽¹⁾	385.0		—		—		385.0
Total investments ⁽¹⁾	$	6,863.1	$	1,712.1	$	4,640.9	$	510.1


⁽¹⁾	Excludes carrying value of $23.2 associated with other long-term investment limited partnerships accounted for using the equity method.



	December 31, 2013
Millions	Fair value		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs
Fixed maturity investments:
U.S. Government and agency obligations	$	362.5	$	295.8	$	66.7	$	—
Debt securities issued by corporations:
Consumer	754.4		—		754.4		—
Communications	265.0		—		265.0		—
Financials	434.4		—		434.4		—
Industrial	281.1		—		281.1		—
Basic Materials	149.1		—		149.1		—
Utilities	173.6		—		173.6		—
Energy	159.7		—		159.7		—
Technology	91.2		—		91.2		—
Other	38.7		—		38.7		—
Total debt securities issued by corporations:	2,347.2		—		2,347.2		—

Mortgage-backed and asset-backed securities	2,014.5		—		1,992.5		22.0
Foreign government, agency and provincial obligations	439.9		44.5		395.4		—
Preferred stocks	84.8		—		13.8		71.0
Municipal obligations	17.9		—		17.9		—
Total fixed maturity investments⁽¹⁾	5,266.8		340.3		4,833.5		93.0

Short-term investments	635.9		621.5		14.4		—

Common equity securities:
Financials	360.4		314.3		—		46.1
Consumer	308.2		308.2		—		—
Basic materials	53.4		53.4		—		—
Energy	78.6		78.6		—		—
Utilities	34.3		34.3		—		—
Technology	60.6		60.6		—		—
Industrial	105.4		105.4		—		—
Communications	57.1		57.1		—		—
Other	98.8		24.5		74.3		—
Total common equity securities	1,156.8		1,036.4		74.3		46.1
Convertible fixed maturity and preferred investments	80.5		—		74.4		6.1
Other long-term investments ⁽²⁾	262.4		—		—		262.4
Total investments	$	7,402.4	$	1,998.2	$	4,996.6	$	407.6


⁽¹⁾	Carrying value includes $236.3 that is classified as assets held for sale relating to discontinued operations.


⁽²⁾	Excludes carrying value of $26.6 associated with other long-term investment limited partnerships accounted for using the equity method and $(.1) related to foreign currency forward contracts.

Debt securities issued by corporations

The following table summarizes the ratings of the corporate debt securities held in White Mountains’s investment portfolio as of December 31, 2014 and 2013:



	Fair Value at
	December 31,
Millions	2014		2013
AAA	$	—	$	—
AA	236.9		228.8
A	957.8		1,039.5
BBB	1,105.9		1,075.5
BB	—		—
Other	10.6		3.4
Debt securities issued by corporations⁽¹⁾	$	2,311.2	$	2,347.2


⁽¹⁾	Credit ratings are assigned based on the following hierarchy: 1) Standard & Poor’s and 2) Moody’s.

Mortgage-backed, Asset-backed Securities

White Mountains purchases commercial and residential mortgage-backed securities with the goal of maximizing risk adjusted returns in the context of a diversified portfolio. White Mountains’s investments in hedge funds and private equity funds contain negligible amounts of sub-prime mortgage-backed securities as of December 31, 2014. White Mountains considers sub-prime mortgage-backed securities as those that have underlying loan pools that exhibit weak credit characteristics, or those that are issued from dedicated sub-prime shelves or dedicated second-lien shelf registrations (i.e., White Mountains considers investments backed primarily by second-liens to be sub-prime risks regardless of credit scores or other metrics).

White Mountains categorizes mortgage-backed securities as “non-prime” (also called “Alt A” or “A-”) if they are backed by collateral that has overall credit quality between prime and sub-prime based on White Mountains’s review of the characteristics of their underlying mortgage loan pools, such as credit scores and financial ratios. White Mountains’s non-agency residential mortgage-backed portfolio is generally moderate-term and structurally senior. White Mountains does not own any collateralized loan obligations. White Mountains does not own any collateralized debt obligations, with the exception of $45.1 million of non-agency residential mortgage resecuritization tranches, each a senior tranche in its own right and each collateralized by a single earlier vintage Super Senior or Senior non-agency residential mortgage backed security.



	December 31, 2014						December 31, 2013
Millions	Fair Value		Level 2		Level 3		Fair Value		Level 2		Level 3
Mortgage-backed securities:
Agency:
GNMA	$	411.2	$	411.2	$	—	$	512.3	$	512.3	$	—
FNMA	36.6		36.6		—		81.2		81.2		—
FHLMC	49.6		49.6		—		91.3		91.3		—
Total Agency⁽¹⁾	497.4		497.4		—		684.8		684.8		—
Non-agency:
Residential	131.2		131.2		—		125.7		125.7		—
Commercial	236.9		236.9		—		282.3		282.3		—
Total Non-agency	368.1		368.1		—		408.0		408.0		—

Total mortgage-backed securities	865.5		865.5		—		1,092.8		1,092.8		—
Asset-backed securities:
Credit card receivables	522.2		522.2		—		311.4		289.4		22.0
Vehicle receivables	289.4		289.4		—		365.0		365.0		—
Other	163.8		163.8		—		245.3		245.3		—
Total asset-backed securities	975.4		975.4		—		921.7		899.7		22.0
Total mortgage and asset-backed securities	$	1,840.9	$	1,840.9	$	—	$	2,014.5	$	1,992.5	$	22.0


⁽¹⁾	Represents publicly traded mortgage-backed securities which carry the full faith and credit guaranty of the U.S. government (i.e., GNMA) or are guaranteed by a government sponsored entity (i.e., FNMA, FHLMC).

Non-agency Mortgage-backed Securities

The security issuance years of White Mountains’s investments in non-agency RMBS and non-agency CMBS securities as of December 31, 2014 are as follows:



					Security Issuance Year
Millions	Fair Value		2004		2005		2006		2007		2008		2009		2010		2011		2012		2013		2014
Non-agency RMBS	$	131.2	$	14.2	$	14.7	$	9.9	$	—	$	16.5	$	—	$	14.7	$	21.4	$	—	$	29.7	$	10.1
Non-agency CMBS	236.9		—		—		8.5		—		—		—		11.7		—		20.7		79.9		116.1
Total	$	368.1	$	14.2	$	14.7	$	18.4	$	—	$	16.5	$	—	$	26.4	$	21.4	$	20.7	$	109.6	$	126.2

Non-agency Residential Mortgage-backed Securities

The classification of the underlying collateral quality and the tranche levels of White Mountains’s non-agency RMBS securities are as follows as of December 31, 2014:



Millions	Fair Value		Super Senior⁽¹⁾		Senior⁽²⁾		Subordinate⁽³⁾
Prime	$	119.4	$	71.6	$	47.8	$	—
Non-prime	9.3		—		9.3		—
Sub-prime	2.5		2.5		—		—
Total	$	131.2	$	74.1	$	57.1	$	—


⁽¹⁾	At issuance, Super Senior, or in the case of resecuritization, the underlying securities, were rated “AAA” by Standard & Poor’s, “Aaa” by Moody’s or “AAA” by Fitch Ratings (“Fitch”) and were senior to other “AAA” or “Aaa” bonds.


⁽²⁾	At issuance, Senior, or in the case of resecuritization, the underlying securities, were rated “AAA” by Standard & Poor’s, “Aaa” by Moody’s or “AAA” by Fitch and were senior to non-“AAA” or non-“Aaa” bonds.


⁽³⁾	At issuance, Subordinate were not rated “AAA” by Standard & Poor’s, “Aaa” by Moody’s or “AAA” by Fitch and were junior to “AAA” or “Aaa” bonds.

Non-agency Commercial Mortgage-backed Securities

White Mountains’s non-agency commercial mortgage-backed portfolio (“CMBS”) is generally short-term and structurally subordinate, with more than 25 points of subordination on average for both fixed rate CMBS and floating rate CMBS as of December 31, 2014. In general, subordination represents the percentage principal loss on the underlying collateral that would be absorbed by other securities lower in the capital structure before the more senior security incurs a loss. As of December 31, 2014, on average less than 1% of the underlying loans were reported as non-performing for all non-agency CMBS held by White Mountains.

The amount of fixed and floating rate securities and their tranche levels of White Mountains’s non-agency CMBS securities are as follows as of December 31, 2014:



Millions	Fair Value		Super Senior⁽¹⁾		Senior⁽²⁾		Subordinate⁽³⁾
Fixed rate CMBS	$	116.2	$	13.1	$	61.6	$	41.5
Floating rate CMBS	120.7		—		—		120.7
Total	$	236.9	$	13.1	$	61.6	$	162.2


⁽¹⁾	At issuance, Super Senior, or in the case of resecuritization, the underlying securities, were rated “AAA” by Standard & Poor’s, “Aaa” by Moody’s or “AAA” by Fitch and were senior to other “AAA” or “Aaa” bonds.


⁽²⁾	At issuance, Senior, or in the case of resecuritization, the underlying securities, were rated “AAA” by Standard & Poor’s, “Aaa” by Moody’s or “AAA” by Fitch and were senior to non-“AAA” or non-“Aaa” bonds.


⁽³⁾	At issuance, Subordinate were not rated “AAA” by Standard & Poor’s, “Aaa” by Moody’s or “AAA” by Fitch and were junior to “AAA” or “Aaa” bonds.

Other Long-term Investments

Other long-term investments consist of the following as of December 31, 2014 and 2013:



	Fair Value at
Millions	December 31, 2014		December 31, 2013
Hedge funds and private equity funds⁽¹⁾	$	242.9	$	239.0
Limited liability companies and private equity securities⁽¹⁾	69.7		20.3
OBIC Surplus Notes⁽¹⁾	65.1		—
Other⁽¹⁾	7.3		3.1
Forward contracts (see Note 9)	—		(.1		)
Total other-long term investments⁽²⁾	$	385.0	$	262.3

⁽¹⁾See Fair Value Measurements by Level table.

⁽²⁾Excludes carrying value of $23.2 and $26.6 associated with other long-term investment limited partnerships accounted for using the equity method.

Hedge Funds and Private Equity Funds

White Mountains holds investments in hedge funds and private equity funds, which are included in other long-term investments. The fair value of these investments has been estimated using the net asset value of the funds. As of December 31, 2014, White Mountains held investments in 12 hedge funds and 32 private equity funds. The largest investment in a single fund was $22.0 million as of December 31, 2014 and $18.3 million as of December 31, 2013. The following table summarizes investments in hedge funds and private equity interests by investment objective and sector as of December 31, 2014 and 2013:



	December 31, 2014				December 31, 2013
Millions	Fair Value		Unfunded Commitments		Fair Value		Unfunded Commitments
Hedge funds
Long/short equity	$	43.9	$	—	$	62.6	$	—
Long/short credit & distressed	21.4		—		22.8		—
Long/short equity REIT	20.3		—		18.3		—
Long/short equity activist	6.2		—		16.8		—
Long bank loan	.2		—		.2		—
Long diversified strategies	—		—		.1		—
Total hedge funds	92.0		—		120.8		—

Private equity funds
Energy infrastructure & services	59.6		11.0		45.9		13.1
Multi-sector	24.2		5.3		23.8		6.5
Manufacturing/Industrial	23.2		7.3		11.2		15.5
Private equity secondaries	8.5		3.1		9.5		3.1
Real estate	3.6		3.3		8.2		3.3
Aerospace/Defense/Government	20.7		5.1		5.8		19.2
Healthcare	6.1		2.8		5.6		2.8
International multi-sector, Europe	1.5		2.3		3.9		2.8
Insurance	2.1		41.2		2.3		41.3
Venture capital	1.4		.3		1.6		.3
Distressed residential real estate	—		—		.4		—
International multi-sector, Asia	—		—		—		2.7
Total private equity funds	150.9		81.7		118.2		110.6
Total hedge and private equity funds included in other long-term investments	$	242.9	$	81.7	$	239.0	$	110.6

In June 2014, White Mountains committed $21.0 million to fund a 50/50 joint venture with DavidShield Group(“DavidShield”) for the development, marketing and distribution of PassportCard travel insurance. The transaction is expected to close in the first quarter of 2015, subject to regulatory approvals.

Redemption of investments in certain hedge funds is subject to restrictions including lock-up periods where no redemptions or withdrawals are allowed, restrictions on redemption frequency and advance notice periods for redemptions. Amounts requested for redemptions remain subject to market fluctuations until the redemption effective date, which generally falls at the end of the defined redemption period. The following summarizes the December 31, 2014 fair value of hedge funds subject to restrictions on redemption frequency and advance notice period requirements for investments in active hedge funds:



	Notice Period
Millions Redemption frequency	30-59 days notice		60-89 days notice		90-119 days notice		120+ days notice		Total
Monthly	$	4.3	$	—	$	—	$	—	$	4.3
Quarterly	31.8		21.4		—		7.8		61
Semi-annual	—		22.1		—		—		22.1
Annual	—		—		4.4		.2		4.6
Total	$	36.1	$	43.5	$	4.4	$	8.0	$	92.0

Certain of the hedge fund and private equity fund investments in which White Mountains is invested are no longer active and are in the process of disposing of their underlying investments. Distributions from such funds are remitted to investors as the fund’s underlying investments are liquidated. As of December 31, 2014, distributions of $2.1 million were outstanding from these investments. The actual amount of the final distribution remittances remain subject to market fluctuations. The date at which such remittances will be received is not determinable as of December 31, 2014.

White Mountains has also submitted redemption requests for certain of its investments in active hedge funds. As of December 31, 2014, redemptions of $6.7 million are outstanding that would be subject to market fluctuations. The date at which such redemptions will be received is not determinable as of December 31, 2014. Redemptions are recorded as receivables when the investment is no longer subject to market fluctuations.

Investments in private equity funds are generally subject to a “lock-up” period during which investors may not request a redemption. Distributions prior to the expected termination date of the fund may be limited to dividends or proceeds arising from the liquidation of the fund’s underlying investments. In addition, certain private equity funds provide an option to extend the lock-up period at either the sole discretion of the fund manager or upon agreement between the fund and the investors.

As of December 31, 2014, investments in private equity funds were subject to lock-up periods as follows:



Millions	1-3 years		3 – 5 years		5 – 10 years		>10 years		Total
Private Equity Funds — expected lock-up period remaining	$	12.7	$	33.5	$	79.0	$	25.7	$	150.9

Rollforward of Fair Value Measurements by Level

White Mountains uses quoted market prices where available as the inputs to estimate fair value for its investments in active markets. Such measurements are considered to be either Level 1 or Level 2 measurements, depending on whether the quoted market price inputs are for identical securities (Level 1) or similar securities (Level 2). Level 3 measurements for fixed maturity investments, common equity securities, convertibles and other long-term investments as of December 31, 2014 and 2013 consist of securities for which the estimated fair value has not been determined based upon quoted market price inputs for identical or similar securities.

The following tables summarize the changes in White Mountains’s fair value measurements by level for the years ended December 31, 2014 and 2013:



							Level 3 Investments
Millions	Level 1 Investments			Level 2 Investments			Fixed maturity investments			Common equity securities			Convertible Fixed Maturity and Preferred Investments		Other long-term investments				Total
Balance at January 1, 2014	$	1,376.7		$	4,982.2		$	93.0		$	46.1		$	6.1	$	262.4		⁽¹⁾	$	6,766.5		^(1)(2)(3)
Total realized and unrealized gains	88.1			163.4			2.2			6.2			.6		26.0				286.5			⁽⁴⁾
Foreign currency losses in OCI	(24.8		)	(222.8		)	(1.0		)	—			—		(5.0		)		(253.6		)
Amortization/Accretion	(.6		)	(43.6		)	.1			—			—		—				(44.1		)
Purchases	1,599.2			3,772.4			71.7			5.0			1.5		152.3				5,602.1
Sales	(2,197.1		)	(4,122.6		)	—			(17.1		)	—		(50.7		)		(6,387.5		)
Net change in investments related to purchases and sales of consolidated affiliates	(2.7		)	24.2			—			—			—		—				21.5
Exchange	4.7			(13.0		)	8.3			—			—		—				—
Transfers in	—			97.8			—			—			—		—				97.8
Transfers out	(.2		)	—			(97.6		)	—			—		—				(97.8		)
Balance at December 31, 2014	$	843.3		$	4,638.0		$	76.7		$	40.2		$	8.2	$	385.0		⁽¹⁾	$	5,991.4		^(1)(2)(3)


⁽¹⁾	Excludes carrying value of $23.2 and $26.6 as of December 31, 2014 and January 1, 2014 associated with other long-term investments accounted for using the equity method.


⁽²⁾	Carrying value includes $236.3 as of January 1, 2014 that is classified as assets held for sale relating to discontinued operations.


⁽³⁾	Excludes carrying value of $871.7 and $635.9 as of December 31, 2014 and January 1, 2014 classified as short-term investments.


⁽⁴⁾	Excludes $4.3 of realized and unrealized losses associated with the Prospector Funds consolidation of investment-related liabilities and $2.8 of realized and unrealized gains associated with short-term investments.



							Level 3 Investments
Millions	Level 1 Investments			Level 2 Investments			Fixed maturity investments			Common equity securities			Convertible Fixed Maturity and Preferred Investments		Other long-term investments				Total
Balance at January 1, 2013	$	1,355.1		$	5,206.1		$	92.9		$	37.3		$	—	$	259.3		⁽¹⁾	$	6,950.7		^(1)(2)(3)
Total realized and unrealized gains (losses)	221.9			(56.9		)	(2.7		)	1.0			—		18.7				182.0
Foreign currency (losses) gains in OCI	(.3		)	12.5			.3			—			—		(0.9		)		11.6
Amortization/Accretion	(1.0		)	(51.2		)	—			—			—		—				(52.2		)
Purchases	862.1			3,689.6			37.9			8.8			—		37.1				4,635.5
Sales	(1,078.9		)	(3,842.8		)	(6.3		)	—			—		(51.8		)		(4,979.8		)
Net change in investments related to purchases and sales of consolidated affiliates	16.0			2.7			—			—			—		—				18.7
Transfers in	1.8			119.4			90.3			—			6.1		—				217.6
Transfers out	—			(97.2		)	(119.4		)	(1.0		)	—		—				(217.6		)
Balance at December 31, 2013	$	1,376.7		$	4,982.2		$	93.0		$	46.1		$	6.1	$	262.4		⁽¹⁾	$	6,766.5		^(1)(2)(3)


⁽¹⁾	Excludes carrying value of $26.6 and $35.0 as of December 31, 2013 and January 1, 2013 associated with other long-term investment limited partnerships accounted for using the equity method and $(.1) as of December 31, 2013 related to foreign currency forward contracts.


⁽²⁾	Carrying value includes $236.3 and $338.1 as of December 31, 2013 and January 1, 2013 that is classified as assets held for sale relating to AutoOne discontinued operations.


⁽³⁾	Excludes carrying value of $635.9 and $630.6 as of December 31, 2013 and January 1, 2013 classified as short-term investments.


⁽⁴⁾	Excludes $20.6 of realized and unrealized losses associated with the Prospector Funds consolidation of investment-related liabilities and $.2 of realized and unrealized gains associated with short-term investments.

Fair Value Measurements — transfers between levels

During 2014, six fixed maturity securities classified as Level 3 measurements in the prior period were recategorized as Level 2 measurements because quoted market prices for similar securities that were considered reliable and could be validated against an alternative source were available as of December 31, 2014. These measurements comprise “Transfers out” of Level 3 and “Transfers in” to Level 2 of $(97.6) million for the period ended December 31, 2014. During the third quarter of 2014, one convertible fixed maturity investment that was classified within level two was exchanged for common shares and a corporate debt security of the same entity. As of December 31, 2014, the common shares are classified within Level 1 since a quoted market price was available. As of December 31, 2014, the corporate debt security is classified within Level 3 since the fair value based upon observable market inputs has been adjusted to reflect a liquidity discount.

During 2013, three fixed maturity securities classified as Level 3 measurements in the prior period were recategorized as Level 2 measurements because quoted market prices for similar securities that were considered reliable and could be validated against an alternative source were available as of December 31, 2013. These measurements comprise “Transfers out” of Level 3 and “Transfers in” to Level 2 of $119.4 million for the period ended December 31, 2013. Included in these transfers is one asset-backed fixed maturity security classified within Level 2 as of June 30, 2013 that was recategorized to Level 3 as of September 30, 2013. The security represents “Transfers out” of Level 2 and “Transfer in” to Level 3 of $90.3 million as of September 30, 2013. As of September 30, 2013, the estimated fair value for this security determined using the industry standard pricing models was $1.3 million less than the estimated fair value based upon quoted prices provided by a third party pricing vendor. As of December 31, 2013, reliable quoted market prices provided by a third party pricing vendor were available for the security and the security was transferred back to Level 2.

Significant Unobservable Inputs

The following summarizes significant unobservable inputs used in estimating the fair value of investment securities classified within Level 3 other than hedge funds and private equities as December 31, 2014 and December 31, 2013. The fair value of investments in hedge funds and private equity funds, which are classified within Level 3, are estimated using the net asset value of the funds.

($ in Millions)

December 31, 2014

December 31, 2013

Description

Rating⁽²⁾

Valuation

Technique(s)

Fair
Value

Unobservable Input

Fair

Value

Unobservable Input

Preferred Stock⁽¹⁾

Discounted cash flow

$71.1

Discount yield

7.1%

$71.0

Discount yield

7.4%

Private equity security⁽¹⁾

Multiple of GAAP book value

$40.2

Book value multiple

1.10

$35.6

Book value multiple

1.00

Private equity security⁽¹⁾

Share price of recent transaction

$20.1

Share price

$1.06

$10.5

Share price

$1.10

Private equity security⁽¹⁾

Share price of recent transaction

$10.4

Share price

$290.96

N/A

Private equity security⁽¹⁾

Share price of recent transaction

$15.8

Share price

$0.13

N/A

Convertible preferred security⁽¹⁾

Share price of recent transaction

$4.5

Share price

$0.71

$3.0

Share price

$0.71

Convertible preferred security⁽¹⁾

Multiple of EBITDA

$3.8

EBITDA multiple

6.00

$3.1

EBITDA multiple

6.00

Debt security issued by corporation⁽¹⁾

Discounted cash flow

$5.6

Illiquidity discount⁽³⁾

10%

N/A

Asset-backed securities⁽¹⁾

AA+

Broker pricing

N/A

Broker quote

$22.0

Broker quote

Seller priority surplus note

Discounted cash flow

$44.0

Discount rate ⁽⁴⁾

9.3%

N/A

Timing of interest

payments⁽⁶⁾

5 years

N/A

Timing of interest

payments⁽⁶⁾

10 years

N/A

Pari passu surplus

note

Discounted cash flow

$21.1

Discount rate⁽⁵⁾

13.5%

N/A

Timing of interest

payments⁽⁶⁾

5 years

N/A

Timing of interest

payments⁽⁶⁾

10 years

N/A


⁽¹⁾	As of December 31, 2014 each asset type consists of one security.


⁽²⁾	Credit ratings are assigned based on the following hierarchy: 1) Standard & Poor’s and 2) Moody’s.


⁽³⁾	Judgmentally determined based on the Company’s limited trading ability of the issuer.

⁽⁴⁾

Stochastic modeling supporting the fair value estimation indicates that the average percentage of discounted payments missed on the seller priority note is roughly equivalent to that of a conventional debt security with a credit rating of ‘B’. The corresponding credit spread increased by an additional 250 bps to reflect both a liquidity discount for a private debt instrument and regulatory payment approval uncertainty, was added to the treasury rate to determine the discount rate for the seller priority note.

⁽⁵⁾

Stochastic modeling supporting the fair value estimation indicates that the average percentage of discounted payments missed on the pari passu note is roughly equivalent to that of a conventional debt security with a credit rating of ‘CCC’. The corresponding credit spread increased by an additional 250 bps to reflect both a liquidity discount for a private debt instrument and regulatory payment approval uncertainty, was added to the treasury rate to determine the discount rate for the seller priority note.


⁽⁶⁾	For estimated value purposes, the assumption has been made that interest payouts begin in year five and that principal repayments being on a graduated basis in year ten for the seller priority notes and year fifteen for the pari passu note.

- Definition

The entire disclosure for investments in certain debt and equity securities.

+ References + Details

Debt and Standby Letter of Credit Facilities

12 Months Ended

Dec. 31, 2014

Debt Disclosure [Abstract]

Debt and Standby Letter of Credit Facilities

White Mountains’s debt outstanding as of December 31, 2014 and 2013 consisted of the following:



	December 31,
Millions	2014			2013
OBH Senior Notes, at face value	$	275.0		$	275.0
Unamortized original issue discount	(.3		)	(.3		)
OBH Senior Notes, carrying value	274.7			274.7
SIG Senior Notes, at face value	400.0			400.0
Unamortized original issue discount	(.3		)	(.4		)
SIG Senior Notes, carrying value	399.7			399.6
WTM Bank Facility	—			—
Tranzact Bank Facility	68.7			—
Unamortized issuance cost	(1.3		)	—
Tranzact Bank Facility, carrying value	67.4			—
Other debt	4.8			2.1
Total debt	$	746.6		$	676.4

A schedule of contractual repayments of White Mountains’s debt as of December 31, 2014, follows:



Millions	December 31, 2014
Due in one year or less	$	6.0
Due in two to three years	424.6
Due in four to five years	42.9
Due after five years	275.0
Total	$	748.5

OBH Senior Notes

In November 2012, OneBeacon U.S. Holdings, Inc. (“OBH”), an intermediate holding company of OneBeacon, issued $275.0 million face value of senior unsecured notes (“OBH Senior Notes”) through a public offering, at an issue price of 99.9% and received $272.9 million of proceeds. The OBH Senior Notes bear an annual interest rate of 4.6% payable semi-annually in arrears on May 9 and November 9, until maturity on November 9, 2022, and are fully and unconditionally guaranteed as to the payment of principal and interest by OneBeacon Ltd. OBH incurred $2.8 million in expenses related to the issuance of the OBH Senior Notes (including $1.8 million in underwriting fees), which have been deferred and are being recognized as interest expense over the life of the OBH Senior Notes. Taking into effect the amortization of the original issue discount and all underwriting and issuance expenses, the OBH Senior Notes have an effective yield to maturity of approximately 4.7% per annum.

In December 2012, the proceeds from the OBH Senior Notes were utilized to repurchase the remaining $269.8 million of outstanding senior notes issued in 2003 by OBH with an annual interest rate of 5.875% for $275.9 million. The repurchase resulted in a $6.3 million loss, including transaction fees and the write-off of the remaining $0.2 million in unamortized deferred costs and original issue discount at the time of repurchase.

OBH recorded $13.0 million, $13.0 million and $16.9 million in interest expense on the OBH Senior Notes for the years ended December 31, 2014, 2013 and 2012.

SIG Senior Notes

In March 2007, Sirius International Group, Ltd. (“SIG”), an intermediate holding company of Sirius Group, issued $400.0 million face value of senior unsecured notes (“SIG Senior Notes”) at an issue price of 99.715% for net proceeds of $392.0 million after taking into effect both deferrable and non-deferrable issuance costs, including the interest rate lock agreement described below. The SIG Senior Notes were issued in an offering that was exempt from the registration requirements of the Securities Act of 1933. The SIG Senior Notes bear an annual interest rate of 6.375%, payable semi-annually in arrears on March 20 and September 20, until maturity in March 2017.

SIG incurred $3.6 million in expenses related to the issuance of the SIG Senior Notes (including $2.6 million in underwriting fees), which have been deferred and are being recognized into interest expense over the life of the SIG Senior Notes.

In anticipation of the issuance of the SIG Senior Notes, SIG entered into an interest rate lock agreement to hedge its interest rate exposure from the date of the agreement until the pricing of the SIG Senior Notes. The agreement was terminated on March 15, 2007 with a loss of $2.4 million, which was recorded in other comprehensive income. The loss is being reclassified from accumulated other comprehensive income over the life of the SIG Senior Notes using the interest method and is included in interest expense. As of December 31, 2014, the unamortized balance of the loss remaining in accumulated other comprehensive income was $1.0 million.

Taking into effect the amortization of the original issue discount and all underwriting and issuance expenses, including the interest rate lock agreement, the SIG Senior Notes yield an effective rate of approximately 6.5% per annum. White Mountains recorded $26.2 million of interest expense, inclusive of amortization of issuance costs and the interest rate lock agreement, on the SIG Senior Notes for each of the years ended December 31, 2014, 2013 and 2012.

WTM Bank Facility

On August 14, 2013, White Mountains entered into a revolving credit facility with a syndicate of lenders administered by Wells Fargo Bank, N.A. which has a total commitment of $425.0 million (the “WTM Bank Facility”) and has a maturity date of August 14, 2018 (the “WTM Bank Facility”). The WTM Bank Facility replaced White Mountains’s previous revolving credit facility administered by Bank of America, N.A. which had a total commitment of $375.0 million (the “Previous WTM Bank Facility”). During 2014, White Mountains borrowed and repaid a total of $65.0 million under the WTM Bank Facility at a blended interest rate of 3.65%. During 2013, White Mountains borrowed and repaid a total of $50.0 million under the WTM Bank Facility at a blended interest rate of 3.65%. As of December 31, 2014, the WTM Bank Facility was undrawn. White Mountains recorded $0.3 million of interest expense on the WTM Bank Facility for both the years ended December 31, 2014 and 2013.

During 2013, White Mountains also borrowed $150.0 million and repaid a total of $225.0 million under the Previous WTM Bank Facility at a blended interest rate of 2.83%. In December 2012, White Mountains borrowed $150.0 million under the Previous WTM Bank Facility at a blended interest rate of 3.53%. White Mountains repaid $75.0 million in December 2012 and the remaining balance in January 2013. White Mountains recorded $2.9 million and $1.7 million of interest expense on the Previous WTM Bank Facility for the years ended December 31, 2013 and 2012.

The WTM Bank Facility contains various affirmative, negative and financial covenants that White Mountains considers to be customary for such borrowings, including certain minimum net worth and maximum debt to capitalization standards. These covenants can restrict White Mountains in several ways, including its ability to incur additional indebtedness.

Tranzact Bank Facility

On October 10, 2014, Tranzact entered into a secured credit facility with a syndicate of lenders administered by The PrivateBank and Trust Company (the “Tranzact Bank Facility”). The term of the credit facility ends on October 10, 2019. The Tranzact Bank Facility consists of a $70.0 million term loan facility, which was fully drawn at closing and had an outstanding balance of $68.7 million as of December 31, 2014, and a revolving credit facility for an additional $4.5 million, which was undrawn as of December 31, 2014. The Tranzact Bank Facility is secured by intellectual property and the common stock of Tranzact and its subsidiaries. White Mountains recorded $0.7 million of interest expense on the Tranzact Bank Facility for the year ended December 31, 2014. The Tranzact Bank Facility carries a variable interest rate, at a margin over the U.S. dollar LIBOR rate. The margin over LIBOR may vary between 2.5% to 4.5%. At December 31, 2014 the variable interest rate on the debt was 4.15575%, including a margin over LIBOR of 2.5%. On October 10, 2014, Tranzact entered into an interest rate swap agreement to effectively fix the rate it pays on the $70.0 million term loan portion of the facility (see Note 9 for details).

The Tranzact Bank Facility contains various affirmative, negative and financial covenants which White Mountains considers to be customary for such borrowings, including a minimum fixed charge coverage ratio and a minimum leverage ratio. Failure to meet one or more of these covenants could result in an event of default, which ultimately could eliminate availability under these facilities and result in acceleration of principal repayment on any amounts outstanding.

Stand By Letter of Credit Facilities

On November 25, 2014, Sirius International entered into two stand by letter of credit facility agreements totaling $200.0 million to provide capital support for its Lloyds Syndicate 1945. One letter of credit is a $125.0 million facility from Nordea Bank Finland plc (the “Nordea facility”), $100.0 million of which is issued on an unsecured basis. The second letter of credit is a $75.0 million facility with Lloyds Bank plc (the “Lloyds Bank facility”), $25.0 million of which is issued on an unsecured basis. The Nordea facility and the Lloyds Bank facility are renewable annually.

The unsecured portions of the Nordea facility and the Lloyds Bank facility are subject to various affirmative, negative and financial covenants that White Mountains considers to be customary for such borrowings, including certain minimum net worth and maximum debt to capitalization standards.

Sirius International has other secured letter of credit and trust arrangements with various financial institutions to support its insurance operations.

Debt and Standby Letter of Credit Facility Covenants

As of December 31, 2014, White Mountains was in compliance with all of the covenants under the WTM Bank Facility, the OBH Senior Notes, the SIG Senior Notes, the Tranzact Bank Facility, the Nordea facility and the Lloyd’s Bank Facility.

Interest

Total interest expense incurred by White Mountains for its indebtedness was $41.9 million, $42.5 million and $44.8 million in 2014, 2013 and 2012. Total interest paid by White Mountains for its indebtedness was $42.0 million, $42.6 million, and $44.6 million in 2014, 2013 and 2012.

Goodwill and Other Intangible Assets

12 Months Ended

Dec. 31, 2014

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Other Intangible Assets

White Mountains has recognized goodwill and other identifiable intangible assets at the acquisition date fair values in connection with its purchases of subsidiaries. The following table shows the economic lives, acquisition date values, accumulated amortization and net carrying values for other intangible assets and goodwill, for each company acquired:



Millions	Weighted Average Economic life (in years)	December 31, 2014						December 31, 2013
		Acquisition date fair value		Accumulated amortization		Net carrying value		Acquisition date fair value		Accumulated amortization		Net carrying value
Tranzact:
Domain and trade names	6	$	25.6	$	.9	$	24.7	$	—	$	—	$	—
Customer relationships	10	107.5		2.1		105.4		—		—		—
Information technology	5	12.7		.5		12.2		—		—		—
Other	7	.5		—		.5		—		—		—
Subtotal		146.3		3.5		142.8		—		—		—

QuoteLab:
Customer relationships	4	6.5		1.2		5.3		—		—		—
Information technology	5	32.0		4.8		27.2		—		—		—
Subtotal		38.5		6.0		32.5		—		—		—

Wobi:
Trademark	8	2.1		.2		1.9		—		—		—
Information technology	3	.8		.2		.6		—		—		—
Subtotal		2.9		.4		2.5		—		—		—

Star & Shield:
Customer relationship	3	1.2		.4		.8		—		—		—

OneBeacon (EBI)	10	9.4		5.7		3.7		9.4		4.3		5.1

Sirius (WM Solutions) - Licenses	Indefinite	15.2		—		15.2		15.6		—		15.6

Total other intangible assets		213.5		16.0		197.5		25.0		4.3		20.7

Goodwill:
Tranzact	N/A	145.1		—		145.1		—		—		—
Quote Lab	N/A	18.3		—		18.3		—		—		—
Wobi	N/A	5.5		—		5.5		—		—		—
Total goodwill		168.9		—		168.9		—		—		—

Total goodwill and other intangible assets		$	382.4	$	16.0	$	366.4	$	25.0	$	4.3	$	20.7

The goodwill recognized for the above acquisitions is attributed to expected future cash flows. The acquisition date fair values of other intangible assets with finite lives are estimated using income approach techniques, which use future expected cash flows to develop a discounted present value amount.

The multiperiod-excess-earnings method estimates fair value using the present value of the incremental after-tax cash flows attributable solely to the intangible asset over its remaining life. This approach was used to estimate the fair value of intangible assets associated with trademarks, brand names, customer relationships and contracts and information technology.

The relief-from-royalty method was used to estimate fair value for intangible assets that relate to rights that could be obtained via a license from a third-party owner. Under this method, the fair value is estimated using the present value of license fees avoided by owning rather than leasing the asset. This technique was used to estimate the fair value of domain names.

The with-or-without method estimates the fair value of an intangible asset that provides an incremental benefit. Under this method, the fair value of the intangible asset is calculated by comparing the value of the entity with and without the intangible asset. This approach was used to estimate the fair value of favorable lease terms, which is included in other.

The following table shows the change in goodwill and other intangible assets:



	December 31,
Millions	2014					2013
	Goodwill		Other intangible assets			Goodwill		Other intangible assets
Beginning balance	$	—	$	20.7		$	—	$	16.9
Acquisitions of businesses	168.9		188.9			—		5.2
Dispositions of businesses	—		(.4		)	—		—
Amortization, including foreign currency translation	—		(11.7		)	—		(1.4		)
Ending balance	$	168.9	$	197.5		$	—	$	20.7

Amortization expense was $11.7 million, $1.4 million and $1.2 million for the years ended December 31, 2014, 2013 and 2012, respectively.

White Mountains expects to recognize amortization expense in each of the next five years as follows:



Millions	Amortization expense
2015	$	27.1
2016	27.0
2017	26.4
2018	24.6
2019	16.5
Total	$	121.6

- Definition

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References + Details

Income Taxes

12 Months Ended

Dec. 31, 2014

Income Tax Disclosure [Abstract]

Income Taxes

The Company and its Bermuda domiciled subsidiaries are not subject to Bermuda income tax under current Bermuda law. In the event there is a change in the current law such that taxes are imposed, the Company and its Bermuda domiciled subsidiaries would be exempt from such tax until March 31, 2035, pursuant to the Bermuda Exempted Undertakings Tax Protection Act of 1966. The Company has subsidiaries and branches that operate in various other jurisdictions around the world that are subject to tax in the jurisdictions in which they operate. The jurisdictions in which the Company’s subsidiaries and branches are subject to tax are Australia, Belgium, Canada, Denmark, Germany, Gibraltar, Israel, Luxembourg, Malaysia, the Netherlands, Peru, Singapore, Sweden, Switzerland, the United Kingdom and the United States.

The total income tax (expense) benefit for the years ended December 31, 2014, 2013 and 2012 consisted of the following:



	Year Ended December 31,
Millions	2014			2013			2012
Current tax (expense) benefit:
U.S. federal	$	(6.2	)	$	(19.0	)	$	8.2
State	(4.8		)	(1.4		)	(3.4		)
Non-U.S.	(45.0		)	(16.5		)	(5.9		)
Total current tax expense	(56.0		)	(36.9		)	(1.1		)
Deferred tax (expense) benefit:
U.S. federal	13.6			(24.4		)	(55.5		)
State	—			—			—
Non-U.S.	(10.9		)	(15.3		)	72.3
Total deferred tax benefit (expense)	2.7			(39.7		)	16.8
Total income tax (expense) benefit	$	(53.3	)	$	(76.6	)	$	15.7

Effective Rate Reconciliation

A reconciliation of taxes calculated using the 35% U.S. statutory rate (the tax rate at which the majority of White Mountains’s worldwide operations are taxed) to the income tax (expense) benefit on pre-tax income follows:



	Year Ended December 31,
Millions	2014			2013			2012
Tax (expense) benefit at the U.S. statutory rate	$	(105.6	)	$	(120.7	)	$	(92.0	)
Differences in taxes resulting from:
Non-U.S. earnings, net of foreign taxes	77.7			82.9			43.0
Change in valuation allowance	(18.1		)	(33.6		)	(14.1		)
Withholding tax	(5.6		)	(1.7		)	(2.9		)
Tax exempt interest and dividends	4.4			3.2			3.1
Tax reserve adjustments	(2.2		)	(10.2		)	(1.3		)
Purchase of subsidiaries	(.3		)	5.3			5.1
Tax rate change enacted in Sweden	—			—			65.4
Tax rate change enacted in Luxembourg	—			—			7.2
Other, net	(3.6		)	(1.8		)	2.2
Total income tax (expense) benefit on pre-tax income	$	(53.3	)	$	(76.6	)	$	15.7

In 2012, new tax legislation was enacted in Sweden, which was effective January 1, 2013, that reduces the corporate tax rate from 26.3% to 22.0%. This resulted in a reduction of $65.4 million in Sirius Group’s net deferred tax liabilities in Sweden.

The non-U.S. component of pre-tax income was $338.5 million, $294.3 million and $250.0 million for the years ended December 31, 2014, 2013 and 2012.

Tax Payments and Receipts

Net income tax payments to (receipts from) national governments (primarily the United States) totaled $9.4 million, $13.9 million, and $17.5 million for the years ended December 31, 2014, 2013 and 2012.

Deferred Tax Inventory

Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts for tax purposes.

An outline of the significant components of White Mountains’s deferred tax assets and liabilities follows:



	December 31,
Millions	2014			2013
Deferred income tax assets related to:
Non-U.S. net operating loss carryforwards	$	427.4		$	520.6
U.S. federal net operating and capital loss carryforwards	213.4			148.6
Loss reserve discount	79.3			74.9
Unearned premiums	46.0			38.9
Incentive compensation	42.0			53.9
Tax credit carryforwards	25.8			23.1
Runoff Transaction	12.6			24.2
Deferred compensation	8.9			10.3
Accrued interest	5.3			1.1
Fixed assets	3.6			4.9
Other items	8.4			6.9
Total gross deferred income tax assets	872.7			907.4
Less: valuation allowances	(274.6		)	(289.8		)
Total net deferred income tax assets	598.1			617.6
Deferred income tax liabilities related to:
Safety reserve	295.7			357.2
Net unrealized investment gains	45.3			44.6
Deferred acquisition costs	40.5			33.0
Investment basis difference	22.9			3.0
Members surplus contributions	10.3			5.4
Purchase accounting	7.0			7.2
Pension and benefit accruals	—			3.4
Other items	3.1			7.9
Total deferred income tax liabilities	424.8			461.7
Net deferred tax asset	$	173.3		$	155.9

White Mountains’s deferred tax assets are net of U.S. federal, state, and non-U.S. valuation allowances and, to the extent they relate to non-U.S. jurisdictions, they are shown at year-end exchange rates.

Of the $173.3 million net deferred tax asset as of December 31, 2014, $214.0 million relates to net deferred tax assets in U.S. subsidiaries, $240.5 million relates to net deferred tax assets in Luxembourg subsidiaries, $1.6 million relates to net deferred tax assets in United Kingdom subsidiaries and $282.8 million relates to net deferred tax liabilities in Sweden subsidiaries.

Valuation Allowance

White Mountains records a valuation allowance against deferred tax assets if it becomes more likely than not that all or a portion of a deferred tax asset will not be realized. Changes in valuation allowances from period to period are included in income tax expense in the period of change. In determining whether or not a valuation allowance, or change therein, is warranted, White Mountains considers factors such as prior earnings history, expected future earnings, carryback and carryforward periods and strategies that if executed would result in the realization of a deferred tax asset. It is possible that certain planning strategies or projected earnings in certain subsidiaries may not be feasible to utilize the entire deferred tax asset, which could result in material changes to White Mountains’s deferred tax assets and tax expense.

Of the $274.6 million valuation allowance as of December 31, 2014, $164.8 million relates to deferred tax assets on net operating losses and unrealized gains and losses in Luxembourg subsidiaries (discussed under “Net Operating Loss and Capital Loss Carryforwards”), $107.6 million relates to deferred tax assets on U.S. losses and other federal deferred tax benefits, $1.9 million relates to net operating losses in the Israel subsidiaries and $0.3 million relates to net operating losses in the Netherlands subsidiaries. Of the $289.8 million valuation allowance as of December 31, 2013, $195.8 million relates to deferred tax assets on net operating losses in Luxembourg subsidiaries (discussed under “Net Operating Loss and Capital Loss Carryforwards”), $93.7 million relates to deferred tax assets on U.S. losses and other federal deferred tax benefits; and $0.3 million relates to net operating losses in the Netherlands subsidiaries.

Luxembourg

During 2014 and 2013, White Mountains recorded a net tax expense of $1.2 million and $1.4 million which consisted of a tax benefit of $14.3 million and $16.7 million from the release of valuation allowances against deferred tax assets and a tax expense of $15.5 million and $18.1 million to establish valuation allowances against deferred tax assets related to additional net operating loss carryforwards at certain Luxembourg-domiciled subsidiaries.

During the fourth quarter of 2012, White Mountains recorded net tax benefits of $41.3 million from the net release of valuation allowances against deferred tax assets in Luxembourg-domiciled subsidiaries. These companies had built up substantial deferred tax assets due to net operating loss carryforwards. The loss carryforwards primarily relate to tax deductible write downs in 2007 and 2008 of investments in U.S. subsidiaries. There were partial valuation allowances on these deferred tax assets in periods prior to the fourth quarter of 2012 because the companies did not expect sufficient future taxable income to utilize them.

During the fourth quarter of 2012, Sirius Group undertook a series of reorganizations to optimize operational and capital efficiency. As part of the reorganizations, investments and outstanding internal debt instruments were contributed to Luxembourg-domiciled subsidiaries with net operating loss carryforwards. One of the companies, S.I. Holdings (Luxembourg) S.à r.l., (“SI Holdings”) (formerly OneBeacon Holdings (Luxembourg) S.à r.l.), was acquired from OneBeacon on January 24, 2012. As the plan for the Sirius Group to acquire SI Holdings and contribute the notes was in place on December 31, 2011, and this was a transaction between entities under common control, White Mountains accounted for the tax effects of the transaction as if it had occurred in 2011. An investment portfolio was contributed to SI Holdings in January 2013, pursuant to a plan in place on December 31, 2012, that will generate income utilizing the deferred tax asset over an extended period of time. The deferred tax assets for the remaining net operating loss carryforwards at the companies are offset by a valuation allowance as no additional taxable income is expected.

United States

During 2014 and 2013, White Mountains recorded tax expense of $7.2 million and $16.6 million to establish a valuation allowance against deferred tax assets of Guilford Holdings, Inc. and subsidiaries (“Guilford”), as White Mountains management does not anticipate sufficient taxable income to utilize the deferred tax assets. Guilford consists of service companies and certain other investments that are included in the Other Operations segment.

During the fourth quarter 2012, White Mountains recorded tax expense of $3.9 million to establish a valuation allowance against deferred tax assets related to foreign tax credit carryforwards at Sirius Re Holdings, Inc. and subsidiaries (“SRHI”) that expire in 2016 and 2017. At that time, SRHI was no longer expected to generate sufficient taxable income to utilize these credits before they expired. The majority of these credits of $3.8 million related to taxes paid by the Canadian branch of SRHI.

During 2014, SRHI amended Canadian tax returns for the years 2006 through 2012. This resulted in the Canadian taxes between 2006 and 2011 being reduced to zero with an increase in Canadian taxes for 2012. The majority of tax credits associated with the Canadian tax expire in 2022. SRHI projects there will be sufficient taxable income to utilize the foreign tax credits before they expire. As a result, the valuation allowance related to the $3.8 million was reversed. SRHI still has $0.1 million of a valuation allowance on foreign tax credits, which will expire in 2016 and 2017. SRHI has an additional $12.1 million of foreign tax credits that will expire between the years 2018 and 2024, which are expected to be fully utilized.

During 2014 and 2013, White Mountains recorded tax expense of $8.5 million and $21.3 million to establish valuation allowances against deferred tax assets of BAM, as it is uncertain if it will have sufficient taxable income to utilize its deferred tax assets. Also during 2014 and 2013, BAM has income in other comprehensive income that is available to offset its loss from continuing operations, as a result, BAM recorded a tax benefit of $4.9 million and $5.4 million, respectively, in continuing operations, with an offsetting tax expense in other comprehensive income. However, since BAM is a mutual insurance company that is owned by its members, its results do not affect White Mountains’s common shareholders’ equity, as they are attributable to non-controlling interests.

During 2014, Houston General Insurance Exchange (“Houston General Insurance”) recorded tax expense of $0.1 million, as it is uncertain if it will have sufficient taxable income to utilize its deferred tax assets. During 2013, Houston General Insurance recorded a tax benefit of $6.0 million to reduce a valuation allowance primarily due to the restructuring of a surplus note. Houston General Insurance is a reciprocal, which is included in the Company’s consolidated results as a variable interest entity. See Note 18.

During 2014, SSIE recorded tax expense of $3.2 million, as it is uncertain if it will have sufficient taxable income to utilize its deferred tax assets. SSIE is a reciprocal, which is included in the Company’s consolidated results as a variable interest entity. See Note 18.

Net Operating Loss and Capital Loss Carryforwards

Net operating loss and capital loss carryforwards as of December 31, 2014, the expiration dates and the deferred tax assets thereon are as follows:



	December 31, 2014
Millions	United States			Luxembourg			Sweden		Netherlands			UK		Israel			Total
2014	$	—		$	—		$	—	$	—		$	—	$	—		$	—
2015 - 2019	1.1			—			—		.5			—		—			1.6
2020 - 2024	9.6			—			—		.8			—		—			10.4
2025 - 2034	621.6			—			—		—			—		—			621.6
No expiration date	—			1,417.5			106.0		—			5.8		7.1			1,536.4
Total	$	632.3		$	1,417.5		$	106.0	$	1.3		$	5.8	$	7.1		$	2,170.0
Gross deferred tax asset	$	213.4		$	414.2		$	9.8	$	.3		$	1.2	$	1.9		$	640.8
Valuation allowance	(97.2		)	(166.1		)	—		(.3		)	—		(1.9		)	(265.5		)
Net deferred tax asset	$	116.2		$	248.1		$	9.8	$	—		$	1.2	$	—		$	375.3

White Mountains expects to utilize net operating loss carryforwards in Luxembourg of $983.4 million but does not expect to utilize the remainder as they belong to companies that are not expected to have sufficient income in the future. These losses primarily relate to tax deductible write-downs in 2007 and 2008 of investments in U.S. subsidiaries held by Luxembourg subsidiaries. Included in the U.S. net operating loss carryforwards are losses of $32.2 million subject to an annual limitation on utilization under Internal Revenue Code Section 382. These loss carryforwards will begin to expire in 2021. As of December 31, 2014, there are U.S. foreign tax credit carryforwards available of $12.7 million, which begin to expire in 2016. As of December 31, 2014, there are U.S. alternative minimum tax credit carryforwards of $2.0 million which do not expire. As of December 31, 2014, there are U.S. low income housing credit carryforwards of $11.1 million, which begin to expire in 2031.

Uncertain Tax Positions

Recognition of the benefit of a given tax position is based upon whether a company determines that it is more likely than not that a tax position will be sustained upon examination based upon the technical merits of the position. In evaluating the more-likely-than-not recognition threshold, White Mountains must presume that the tax position will be subject to examination by a taxing authority with full knowledge of all relevant information. If the recognition threshold is met, then the tax position is measured at the largest amount of benefit that is more than 50% likely of being realized upon ultimate settlement.

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows:



Millions	Permanent Differences⁽¹⁾			Temporary Differences⁽²⁾			Interest and Penalties⁽³⁾			Total
Balance at January 1, 2012	$	9.6		$	49.1		$	6.8		$	65.5
Changes in prior year tax positions	.5			—			1.4			1.9
Tax positions taken during the current year	—			(20.2		)	—			(20.2		)
Lapse in statute of limitations	—			—			—			—
Settlements with tax authorities	(.4		)	—			(.2		)	(.6		)
Balance at December 31, 2012	9.7			28.9			8.0			46.6
Changes in prior year tax positions	.6			(7.1		)	1.7			(4.8		)
Tax positions taken during the current year	7.9			.7			—			8.6
Settlements with tax authorities	—			—			(.4		)	(.4		)
Balance at December 31, 2013	18.2			22.5			9.3			50.0
Changes in prior year tax positions	(2.0		)	(.8		)	(2.0		)	(4.8		)
Tax positions taken during the current year	5.6			8.1			—			13.7
Lapse in statute of limitations	(.8		)	—			(.3		)	(1.1		)
Settlements with tax authorities	(.6		)	—			(.3		)	(.9		)
Balance at December 31, 2014	$	20.4		$	29.8		$	6.7		$	56.9


⁽¹⁾	Represents the amount of unrecognized tax benefits that, if recognized, would impact the effective tax rate.


⁽²⁾	Represents the amount of unrecognized tax benefits that, if recognized would create a temporary difference between the reported amount of an item in the Company’s Consolidated Balance Sheet and its tax basis.


⁽³⁾	Net of tax benefit.

If White Mountains determines in the future that its reserves for unrecognized tax benefits on permanent differences and interest and penalties are not needed, the reversal of $27.1 million of such reserves as of December 31, 2014 would be recorded as an income tax benefit and would impact the effective tax rate. If White Mountains determines in the future that its reserves for unrecognized tax benefits on temporary differences are not needed, the reversal of $29.8 million of such reserves as of December 31, 2014 would not impact the effective tax rate due to deferred tax accounting but would accelerate the payment of cash to the taxing authority. The vast majority of White Mountains’s reserves for unrecognized tax benefits on temporary differences relate to deductions for loss reserves where the timing of the deductions is uncertain.

White Mountains classifies all interest and penalties on unrecognized tax benefits as part of income tax expense. During the years ended December 31, 2014, 2013 and 2012, White Mountains recognized $(2.6) million, $1.3 million, $1.2 million in net interest (income) expense. The balance of accrued interest as of December 31, 2014 and 2013 is $6.7 million and $9.3 million, net of any tax benefit.

Tax Examinations

With few exceptions, White Mountains is no longer subject to U.S. federal, state or non-U.S. income tax examinations by tax authorities for years before 2005.

The IRS concluded an examination of income tax returns for 2005 and 2006 for certain U.S. subsidiaries of OneBeacon. On February 14, 2014, White Mountains received Form 870-AD (Offer to Waive Restrictions on Assessment and Collection Tax Deficiency and to Accept Over Assessment) from the IRS Appeals Office relating to the examination of tax years 2005 and 2006. All disputed items have now been agreed to and resolved with the Joint Committee. The total assessment, including interest, is $3.3 million. As the receipt of the Form 870-AD described above represents formal settlement, White Mountains recorded a tax benefit of approximately $5.0 million in the first quarter of 2014 relating to the settlement of the IRS examination for tax years 2005 and 2006.

On July 28, 2011, the IRS commenced an examination of the income tax returns 2007, 2008 and 2009 for certain U.S. subsidiaries of OneBeacon. On July 17, 2013, White Mountains received a revised Form 4549-A (Income Tax Discrepancy Adjustments) from the IRS relating to the examination of tax years 2007, 2008 and 2009. The estimated total assessment, including interest, utilization of alternative minimum and foreign tax credit carryovers and capital loss carrybacks, is $72.9 million. However, $60.2 million of the proposed adjustments relate to items for which the expense deduction has been disallowed in a year being examined, but ultimate deductibility is highly certain to occur in a later period. Because of the impact of deferred tax accounting, other than interest and penalties, the disallowance of the deduction in the exam period would not affect the effective tax rate but would accelerate the payment of cash to the taxing authority. White Mountains disagrees with the adjustments proposed by the IRS and is defending its position. Although the timing of the resolution of these issues is uncertain, it is reasonably possible that the resolution could occur within the next twelve months. An estimate of the range of potential outcomes cannot be made at this time. When ultimately settled, White Mountains does not expect the resolution of this examination to result in a material change to its financial position, results of operations and cash flows.

On September 2, 2013, the IRS commenced an examination of the income tax returns 2010, 2011 and 2012 for certain U.S. subsidiaries of OneBeacon. White Mountains does not expect the resolution of this examination to result in a material change to its financial position, results of operations and cash flows.

On December 18, 2014, the IRS commenced an examination of the 2012 income tax return for Guilford Holdings, Inc. and subsidiaries. White Mountains does not expect the resolution of this examination to result in a material change to its financial position, results of operations and cash flows.

Derivatives

12 Months Ended

Dec. 31, 2014

Derivative [Line Items]

Derivatives

Variable Annuity Reinsurance

Derivative [Line Items]

Derivatives

Variable Annuity Reinsurance

White Mountains has entered into agreements to reinsure death and living benefit guarantees associated with certain variable annuities in Japan. As of December 31, 2014, the total guarantee value was approximately ¥134.2 billion (approximately $1.1 billion at exchange rates on that date). The collective account values of the underlying variable annuities were approximately 113% of the guarantee value as of December 31, 2014.

The following table summarizes the pre-tax operating results of WM Life Re for the years ended December 31, 2014, 2013 and 2012:



	Year Ended December 31,
Millions	2014			2013			2012
Fees, included in other revenue	$	18.6		$	25.0		$	31.8
Change in fair value of variable annuity liability, included in other revenue	52.9			378.5			312.8
Change in fair value of derivatives, included in other revenue	(72.4		)	(402.0		)	(339.0		)
Foreign exchange, included in other revenue	(3.2		)	(14.5		)	(30.3		)
Other investment income and (losses) gains	(1.4		)	(7.1		)	2.5
Total revenues	(5.5		)	(20.1		)	(22.2		)
Change in fair value of variable annuity death benefit liabilities, included in general and administrative expenses	.6			10.2			14.2
Death benefit claims paid, included in general and administrative expenses	(.1		)	(1.9		)	(5.7		)
General and administrative expenses	(4.3		)	(4.9		)	(5.2		)
Pre-tax loss	$	(9.3	)	$	(16.7	)	$	(18.9	)

During 2013, the ratio of annuitants’ aggregate account values to the aggregate guarantee value provided by WM Life Re increased, and as a result, annuitants surrendered their policies at higher rates than WM Life Re observed in the past. In response to this trend, WM Life Re adjusted the projected surrender assumptions used in the valuation of its variable annuity reinsurance liability upward. In 2014, surrender rates continued to outpace assumptions and WM Life Re again adjusted the projected surrender assumptions. For the years ended December 31, 2014 and 2013, the change in the fair value of the variable annuity liability included $0.2 million of losses and $7.2 million of gains, respectively, associated with changes in projected surrender assumptions. There was no change in projected surrender assumptions in 2012.

All of White Mountains’s variable annuity reinsurance liabilities were classified as Level 3 measurements as of December 31, 2014.

The following summarizes realized and unrealized gains (losses) recognized in other revenues for the years ended December 31, 2014, 2013 and 2012 and the carrying values as of December 31, 2014 and 2013 by type of derivative instrument:



										Carrying Value
	Year Ended December 31,									December 31,
Millions	2014			2013			2012			2014			2013
Fixed income/interest rate	$	(33.7	)	$	(108.7	)	$	(149.5	)	$	(1.7	)	$	(9.7	)
Foreign exchange	(1.3		)	(96.7		)	(102.3		)	44.1			58.0
Equity	(37.4		)	(196.6		)	(87.2		)	14.0			20.9
Total	$	(72.4	)	$	(402.0	)	$	(339.0	)	$	56.4		$	69.2

The following table summarizes the changes in White Mountains’s variable annuity reinsurance liabilities and derivative instruments for the year ended December 31, 2014, 2013 and 2012:



	Variable Annuity (Liabilities)				Derivative Instruments
Millions	Level 3				Level 3⁽¹⁾⁽⁶⁾			Level 2⁽¹⁾⁽²⁾			Level 1⁽³⁾			Total⁽⁴⁾
Balance at January 1, 2014	$	(52.8	)		$	63.4		$	4.7		$	1.1		$	69.2
Purchases	—				—			—			—			—
Realized and unrealized gains (losses)	53.5			⁽⁵⁾	(38.6		)	(71.0		)	37.2			(72.4		)
Transfers in (out)	—				—			—			—			—
Sales/settlements	—				(5.9		)	100.1			(34.6		)	59.6
Balance at December 31, 2014	$	.7			$	18.9		$	33.8		$	3.7		$	56.4



	Variable Annuity (Liabilities)				Derivative Instruments
Millions	Level 3				Level 3⁽¹⁾⁽⁶⁾			Level 2⁽¹⁾⁽²⁾			Level 1⁽³⁾			Total⁽⁴⁾
Balance at January 1, 2013	$	(441.5	)		$	140.5		$	(20.5	)	$	(21.7	)	$	98.3
Purchases	—				59.4			—			—			59.4
Realized and unrealized gains (losses)	388.7			⁽⁵⁾	(136.5		)	(196.1		)	(69.4		)	(402.0		)
Transfers in (out)	—				—			—			—			—
Sales/settlements	—				—			221.3			92.2			313.5
Balance at December 31, 2013	$	(52.8	)		$	63.4		$	4.7		$	1.1		$	69.2



	Variable Annuity (Liabilities)				Derivative Instruments
Millions	Level 3				Level 3⁽¹⁾⁽⁶⁾			Level 2⁽¹⁾⁽²⁾			Level 1⁽³⁾			Total⁽⁴⁾
Balance at January 1, 2012	$	(768.5	)		$	247.1		$	39.2		$	4.1		$	290.4
Purchases	—				6.1			—			—			6.1
Realized and unrealized gains (losses)	327.0			⁽⁵⁾	(84.0		)	(186.9		)	(68.1		)	(339.0		)
Transfers in (out)	—				—			—			—			—
Sales/settlements	—				(28.7		)	127.2			42.3			140.8
Balance at December 31, 2012	$	(441.5	)		$	140.5		$	(20.5	)	$	(21.7	)	$	98.3


⁽¹⁾	Consists of over-the-counter instruments.


⁽²⁾	Consists of interest rate swaps, total return swaps, foreign currency forward contracts, and bond forwards. Fair value measurement based upon bid/ask pricing quotes for similar instruments that are actively traded, where available. Swaps for which an active market does not exist have been priced using observable inputs including the swap curve and the underlying bond index.


⁽³⁾	Consists of exchange traded equity index, foreign currency and interest rate futures. Fair value measurements based upon quoted prices for identical instruments that are actively traded.


⁽⁴⁾	In addition to derivative instruments, WM Life Re held cash, short-term and fixed maturity investments of $33.2, $81.3 and $393.6 as of December 31, 2014, 2013 and 2012 posted as collateral to its reinsurance counterparties.


⁽⁵⁾	Includes $0.6, $10.2, $14.2 for December 31, 2014, 2013 and 2012 related to the change in the fair value of variable annuity death benefit liabilities, which are included in general and administrative expenses.

⁽⁶⁾Consists of foreign currency options and equity options.

In addition, WM Life Re held cash and short-term investments posted as collateral to its variable annuity reinsurance and derivatives counterparties. The total collateral includes the following:



	December 31,
Millions	2014		2013
Cash	$	23.7	$	56.1
Short-term investments	—		2.0
Fixed maturity investments	9.5		23.2
Total	$	33.2	$	81.3

Collateral in the form of fixed maturity securities consists of Government of Japan Bonds, which are recorded at fair value. Collateral in the form of short-term investments consists of money-market instruments, carried at amortized cost, which approximates fair value.

All of White Mountains’s variable annuity reinsurance liabilities were classified as Level 3 measurements as of December 31, 2014 and 2013. The fair value of White Mountains’s variable annuity reinsurance liabilities are estimated using actuarial and capital market assumptions related to the projected discounted cash flows over the term of the reinsurance agreement. Assumptions regarding future policyholder behavior, including surrender and lapse rates, are generally unobservable inputs and significantly impact the fair value estimates. Market conditions including, but not limited to, changes in interest rates, equity indices, market volatility and foreign currency exchange rates as well as the variations in actuarial assumptions regarding policyholder behavior may result in significant fluctuations in the fair value estimates. Generally, the liabilities associated with these guarantees increase with declines in the equity markets, interest rates and currencies against the Japanese yen, as well as with increases in market volatilities. White Mountains uses derivative instruments, including put options, interest rate swaps, total return swaps on bond and equity indices and forwards and futures contracts on major equity indices, currency pairs and government bonds, to mitigate the risks associated with changes in the fair value of the reinsured variable annuity guarantees. The types of inputs used to estimate the fair value of these derivative instruments, with the exception of actuarial assumptions regarding policyholder behavior and risk margins, are generally the same as those used to estimate the fair value of variable annuity liabilities.

The following summarizes quantitative information about significant unobservable inputs associated with the fair value estimates for variable annuity reinsurance liabilities and derivative instruments that have been classified as Level 3 measurements:



($ in Millions)	December 31, 2014
Description	Fair Value		Valuation Technique(s)	Unobservable Input	Range				Weighted Average
Variable annuity benefit guarantee asset	$	.7	Discounted cash flows	Surrenders
				0-1 year	0.2	%	-	40.0%	40.0	%
				1-2 years	0.1	%	-	40.0%	32.1	%
				Mortality	0.0	%	-	5.9%	1.0	%
				Foreign exchange volatilities
				0-1 year	12.6	%	-	15.1%	13.3	%
				1-2 years	11.7	%	-	13.8%	12.6	%
				Index volatilities
				0-1 year	24.0	%	-	26.6%	25.6	%
				1-2 years	19.4	%	-	23.1%	21.8	%
Foreign Exchange Options	$	7.2	Counterparty valuations, adjusted for unwind quote discount	Adjustment to counterparty valuations	(0.5	)%	-	11.6%	3.6	%
Foreign Exchange Options			Counterparty valuations, adjusted for unwind quote discount	Adjustment to counterparty valuations
Equity Index Options	$	11.7	Counterparty valuations, adjusted for unwind quote discount	Adjustment to counterparty valuations	0.7	%	-	6.5%	2.0	%
Equity Index Options			Counterparty valuations, adjusted for unwind quote discount	Adjustment to counterparty valuations

WM Life Re enters into both over-the-counter (“OTC”) and exchange traded derivative instruments to economically hedge the liability from the variable annuity benefit guarantee. In the case of OTC derivatives, WM Life Re has exposure to credit risk for amounts that are uncollateralized by counterparties. WM Life Re’s internal risk management guidelines establish net counterparty exposure thresholds that take into account OTC counterparties’ credit ratings. The OTC derivative contracts are subject to restrictions on liquidation of the instruments and distribution of proceeds under collateral agreements.

In the case of exchange traded instruments, WM Life Re has exposure to credit risk for amounts uncollateralized by margin balances. WM Life Re has entered into master netting agreements with certain of its counterparties whereby the collateral provided (held) is calculated on a net basis. The following summarizes amounts offset under master netting agreements:



	December 31, 2014								December 31, 2013
Millions	Gross asset amounts before offsets⁽¹⁾		Gross liability amounts offset under master netting arrangements			Net amounts recognized in Other Assets			Gross asset amounts before offsets⁽¹⁾		Gross liability amounts offset under master netting arrangements			Net amounts recognized in Other Assets
Interest rate contracts
OTC	$	1.0	$	(5.4	)	$	(4.4	)	$	2.4	$	(11.7	)	$	(9.3	)
Exchange traded	2.8		(.1		)	2.7			1.0		(1.6		)	(.6		)
Foreign exchange contracts
OTC	45.5		—			45.5			67.8		(12.0		)	55.8
Exchange traded	—		(1.4		)	(1.4		)	2.3		—			2.3
Equity contracts
OTC	11.7		(.2		)	11.5			30.7		(9.2		)	21.5
Exchange traded	3.4		(.9		)	2.5			1.8		(2.3		)	(.5		)
Total⁽²⁾	$	64.4	$	(8.0	)	$	56.4		$	106.0	$	(36.8	)	$	69.2

⁽¹⁾Amount equal to fair value of instrument as recognized in other assets.

⁽²⁾ All derivative instruments held by WM Life Re are subject to master netting arrangements.

The following summarizes the value, collateral held or provided by WM Life Re and net exposure to credit losses on OTC and exchange traded derivative instruments by counterparty recorded within other assets:



	December 31, 2014
Millions	Net amount of assets reflected in Balance Sheet			Collateral provided to counterparty - Cash		Collateral provided to counter-party - Financial Instruments		Net amount of exposure after effect of collateral provided		Excess collateral provided to counter-party- Cash		Excess collateral provided - Financial Instruments		Counter-party collateral held by WM Life Re - Cash		Net amount of exposure to counter-party		Standard & Poor's Rating⁽¹⁾
JP Morgan	$	24.3		$	—	$	—	$	24.3	$	—	$	—	$	8.8	$	15.5	A	+
Bank of America	5.6			—		—		5.6		—		—		—		5.6		A
Nomura	(3.5		)	3.5		—		—		1.7		9.5		—		11.2		BBB	+
Citigroup - OTC	22.2			—		—		22.2		—		—		1.1		21.1		A
Citigroup - Exchange Traded	3.7			—		—		3.7		16.0		—		—		19.7		A
Royal Bank of Scotland	4.0			—		—		4.0		—		—		—		4.0		A	-
Barclays	.1			—		—		.1		—		—		—		.1		A
Total	$	56.4		$	3.5	$	—	$	59.9	$	17.7	$	9.5	$	9.9	$	77.2



	December 31, 2013
Millions	Net amount of assets reflected in Balance Sheet			Collateral provided to counterparty - Cash		Collateral provided to counter-party - Financial Instruments		Net amount of exposure after effect of collateral provided		Excess collateral provided to counter-party- Cash		Excess collateral provided - Financial Instruments		Counter-party collateral held by WM Life Re- Cash		Net amount of exposure to counter-party		Standard & Poor's Rating⁽¹⁾
JP Morgan	$	9.1		$	—	$	—	$	9.1	$	22.0	$	—	$	—	$	31.1	A	+
Bank of America	27.2			—		—		27.2		—		—		—		27.2		A
Nomura	(.4		)	—		.4		—		—		22.8		.8		22.0		BBB	+
Citigroup - OTC	19.4			—		—		19.4		2.3		—		—		21.7		A
Citigroup - Exchange Traded	1.2			—		—		1.2		19.8		—		—		21.0		A
Royal Bank of Scotland	11.3			—		—		11.3		—		—		—		11.3		A	-
Barclays	1.4			—		—		1.4		—		—		—		1.4		A
Total	$	69.2		$	—	$	.4	$	69.6	$	44.1	$	22.8	$	.8	$	135.7


⁽¹⁾	Standard & Poor’s ratings as detailed above are: “A+” (Strong, which is the fifth highest of twenty-one creditworthiness ratings),“A” (which is the sixth highest of twenty-one creditworthiness ratings), “A-” (which is the seventh highest of twenty-one creditworthiness ratings), and BBB+ (which is the eighth highest of twenty-one creditworthiness ratings).

Forward contracts

Derivative [Line Items]

Derivatives

Forward Contracts

Beginning in September 2012, White Mountains entered into foreign currency forward contracts at Sirius Group. White Mountains monitors its exposure to foreign currency and adjusts its forward positions within the risk guidelines and ranges established by senior management for each foreign currency, as necessary. While White Mountains actively manages its forward positions, mismatches between movements in foreign currency rates and its forward contracts may result in foreign currency positions being outside the pre-defined ranges and/or foreign currency losses. As of December 31, 2014, White Mountains held approximately $33.1 million (SEK 257.5 million) total gross notional value of foreign currency forward contracts.

All of White Mountains’s forward contracts are traded over-the-counter. The fair value of the contracts has been estimated using OTC quotes for similar instruments and accordingly, the measurements have been classified as Level 2 measurements as of December 31, 2014.

The net realized and unrealized derivative gains (losses) recognized in net realized and unrealized investment gains (losses) for the years ended December 31, 2014 and 2013 were 0.3 million and (0.1) million.

All of White Mountains’s forward contracts are subject to master netting agreements. The following summarizes amounts offset under master netting agreements. As of December 31, 2014, the gross liability amount offset under master netting arrangements and net amounts recognized in other investments approximately offset each other. As of December 31, 2013, the gross liability amount offset under master netting arrangements and the net amount recognized in other investments was $(0.1) million.

White Mountains does not hold or provide any collateral for the forward contracts. The following table summarizes the notional amounts and the uncollateralized balances associated with foreign currency forward contracts:



	December 31, 2014					December 31, 2013
Millions	Notional Amount		Carrying Value		Standard & Poor's Rating⁽¹⁾	Notional Amount		Carrying Value
Barclays Bank Plc	$	2.1	$	—	A	$	5.8	$	—
Deutsche Bank	—		—		A	7.7		—
Goldman Sachs	8.7		—		A	2.1		—
HSBC Bank Plc	11.2		—		AA-	3.3		(.1		)
JP Morgan	5.7		—		A+	1.3		—
Royal Bank of Canada	5.4		—		AA-	.2		—
Total	$	33.1	$	—		$	20.4	$	(.1	)


⁽¹⁾	Standard & Poor’s (“S&P”) ratings as detailed above are: “AA-” (Very Strong, which is the sixth highest of twenty-one creditworthiness ratings), “A+” (Strong, which is the seventh highest of twenty-one creditworthiness ratings) and “A” (Strong, which is the eighth highest of twenty-one creditworthiness ratings).

weather derivatives [Member]

Derivative [Line Items]

Derivatives

Weather Derivatives

For the year ended December 31, 2014 and 2013, Sirius Group recognized $0.2 million and $0.6 million of net gains on its weather and weather contingent derivatives portfolio. The fair values of the assumed contracts are subject to change in the near-term and reflect management’s best estimate based on various factors including, but not limited to, observed and forecasted weather conditions, changes in interest or foreign currency exchange rates and other market factors. Estimating the fair value of derivative instruments that do not have quoted market prices requires management’s judgment in determining amounts that could reasonably be expected to be received from or paid to a third party to settle the contracts. Such amounts could be materially different from the amounts that might be realized in an actual transaction to settle the contract with a third party. Because of the significance of the unobservable inputs used to estimate the fair value of Sirius Group’s weather risk contracts, the fair value measurements of the contracts are deemed to be Level 3 measurements in the fair value hierarchy.

Sirius Group | Interest Rate Cap

Derivative [Line Items]

Derivatives

Interest Rate Cap

In May 2007, SIG issued the SIG Preference Shares, with an initial fixed annual dividend rate of 7.506%. In June 2017, the fixed rate will move to a floating rate equal to the greater of (i) 7.506% or (ii) 3 month LIBOR plus 320 bps. In July 2013, SIG executed an interest rate cap for the period from June 2017 to June 2022 to protect against a significant increase in interest rates during that 5-year period (the “Interest Rate Cap”). The Interest Rate Cap economically fixes the annual dividend rate on the SIG Preference Shares from June 2017 to June 2022 at 8.30%. The cost of the Interest Rate Cap was an upfront premium of 395 bps of the $250.0 million notional value, or approximately $9.9 million for the full notional amount.

The Interest Rate Cap does not qualify for hedge accounting. It is recorded in other assets at fair value. Changes in fair value are recognized as unrealized gains or losses and are presented within other revenues. Collateral held is recorded within short-term investments with an equal amount recognized as a liability to return collateral. The fair value of the interest rate cap has been estimated using a single broker quote and accordingly, has been classified as a Level 3 measurement as of December 31, 2014.

The following table summarizes the change in the fair value of the Interest Rate Cap for the year ended December 31, 2014:



	December 31,
Millions	2014			2013
Beginning of period	$	11.1		$	—
Purchases	—			9.9
Net realized and unrealized gains	(7.0		)	1.2
Sales/settlements	—			—
End of period	$	4.1		$	11.1

White Mountains does not provide any collateral to the interest rate counterparties. Under the terms of the Interest Rate Cap, White Mountains holds collateral in respect of future amounts due. White Mountains’s liability to return that collateral is based on the amounts provided by the counterparties and investment earnings thereon. The following table summarizes the Interest Rate Cap collateral balances held by White Mountains and ratings by counterparty:



	December 31, 2014
Millions	Collateral Balances Held		Standard & Poor’s Rating⁽¹⁾
Barclays Bank Plc	$	3.0	A
Nordea Bank Finland Plc	1.3		AA-
Total	$	4.3


⁽¹⁾	Standard & Poor’s ratings as detailed above are: “A” (Strong, which is the sixth highest of twenty-one creditworthiness ratings) and “AA-” (Very Strong, which is the fourth highest of twenty-one creditworthiness ratings).

Tranzact [Member] | Interest Rate Swap [Member]

Derivative [Line Items]

Derivatives

Tranzact Interest Rate Swap

Tranzact has a $70.0 million term loan facility (see Note 7) that carries a variable rate equal to the U.S. dollar LIBOR rate, plus an applicable margin. At December 31, 2014 the variable interest rate on the term loan was 4.15575%, including a margin over LIBOR of 2.5%. Effective October 10, 2014, to effectively fix the rate it pays on this term loan, Tranzact entered into an interest rate swap agreement with a notional amount of $70.0 million at inception, which decreases over the term of the swap by amounts equivalent to scheduled principal repayments made on Tranzact’s term loan. As of December 31, 2014, the notional amount was $68.7 million, which was equal to the amount then outstanding under the $70.0 million term loan. Under the terms of the swap agreement, Tranzact pays a fixed rate of 1.34% and receives a variable rate, which is reset monthly, based on the then-current U.S. dollar LIBOR rate. The variable rate received by Tranzact under the swap agreement was 0.1518% at inception and 0.1558% at December 31, 2014.

The swap is measured at fair value with changes therein recognized within other revenues and is accounted for as a non-hedge derivative instrument. As of December 31, 2014, the estimated fair value of the swap was less than $0.1 million. There are no collateral arrangements associated with the swap.

- Definition

The entire disclosure for derivative instruments and hedging activities including, but not limited to, risk management strategies, non-hedging derivative instruments, assets, liabilities, revenue and expenses, and methodologies and assumptions used in determining the amounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 45
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-URI http://asc.fasb.org/extlink&oid=6441202&loc=d3e80720-113993

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624171-113959

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 815
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-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5579240-113959

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624177-113959

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5579245-113959

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624258-113959

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
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-URI http://asc.fasb.org/extlink&oid=7668309&loc=d3e80748-113994

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5708775-113959

Reference 13: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 815
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-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5708773-113959

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-URI http://asc.fasb.org/extlink&oid=7476318&loc=d3e41635-113959

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5618551-113959

Reference 16: http://www.xbrl.org/2003/role/presentationRef
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Reference 17: http://www.xbrl.org/2003/role/presentationRef
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Reference 19: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 20: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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+ Details

Municipal Bond Guarantee Insurance

12 Months Ended

Dec. 31, 2014

Insurance [Abstract]

Municipal Bond Guarantee Insurance

In 2012, HG Global was capitalized with $594.5 million from White Mountains and $14.5 million from non-controlling interests to fund BAM, a newly formed mutual municipal bond insurer. As of December 31, 2014, White Mountains owned 96.9% of HG Global’s preferred equity and 88.4% of its common equity. HG Global, together with its subsidiaries, provided the initial capitalization of BAM through the purchase of $503.0 million of BAM surplus notes. HG Global provides first loss reinsurance protection for policies underwritten by BAM of up to 15% of par outstanding on a per policy basis through HG Re, which had statutory capital of $449.1 million and $436.9 million as of December 31, 2014 and 2013. HG Re’s obligations to BAM are collateralized in trusts, and there is an aggregate loss limit that is equal to the total assets in the collateral trusts at any point in time. At December 31, 2014 and 2013, the collateral trusts held assets of $120.0 million and $105.4 million. As of December 31, 2014 and 2013, HG Global had pre-tax income of $18.3 million and $38.1 million, which included $15.7 million and $40.2 million of interest income on the BAM surplus notes. As of December 31, 2014 and 2013, BAM had a pre-tax loss of $40.5 million and $78.6 million that was recorded in net loss attributable to non-controlling interests, which included $15.7 million and $40.2 million of interest expense on the BAM surplus notes. As of December 31, 2014, HG Global has accrued $74.4 million of interest receivable on the BAM surplus notes.

The following table provides a schedule of BAM’s insured obligations:



	December 31, 2014		December 31, 2013
Contracts outstanding	1,750		701
Remaining weighted average contract period (in years)	12.8		13.8
Contractual debt service outstanding (in millions):
Principal	$	12,362.5	$	4,703.7
Interest	$	7,086.9	$	3,264.4
Gross unearned insurance premiums	$	27.6	$	13.2

Earnings Per Share

12 Months Ended

Dec. 31, 2014

Earnings Per Share [Abstract]

Earnings per share

Earnings Per Share

Basic earnings per share amounts are based on the weighted average number of common shares outstanding including unvested restricted shares that are considered participating securities. Diluted earnings per share amounts are based on the weighted average number of common shares including unvested restricted shares and the net effect of potentially dilutive common shares outstanding. The following table outlines the Company’s computation of earnings per share from continuing operations for the years ended December 31, 2014, 2013 and 2012 (see Note 22 for earnings per share amounts for discontinued operations):



	Year Ended December 31,
	2014			2013			2012
Basic and diluted earnings per share numerators (in millions):
Net income from continuing operations attributable to White Mountains’s common shareholders	$	316.1		$	317.3		$	322.4
Allocation of income for unvested restricted common shares⁽¹⁾	(4.1		)	(4.7		)	(4.3		)
Dividends declared on participating restricted common shares⁽¹⁾	(.1		)	(.1		)	(.1		)
Total allocation to restricted common shares	(4.2		)	(4.8		)	(4.4		)
Net income attributable to White Mountains’s common shareholders, net of restricted share amounts	$	311.9		$	312.5		$	318.0
Undistributed net earnings (in millions):
Net income attributable to White Mountains’s common shareholders, net of restricted common share amounts	$	311.9		$	312.5		$	318.0
Dividends declared net of restricted common share amounts⁽¹⁾	(6.1		)	(6.1		)	(6.5		)
Total undistributed net earnings, net of restricted common share amounts	$	305.8		$	306.4		$	311.5
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period	6,104.9			6,200.4			6,799.8
Average unvested restricted common shares⁽²⁾	(78.9		)	(91.4		)	(91.1		)
Basic earnings per share denominator	6,026.0			6,109.0			6,708.7
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period	6,104.9			6,200.4			6,799.8
Average unvested restricted common shares⁽²⁾	(78.9		)	(91.4		)	(91.1		)
Average outstanding dilutive options to acquire common shares⁽³⁾	—			—			—
Diluted earnings per share denominator	6,026.0			6,109.0			6,708.7
Basic earnings per share (in dollars):
Net income attributable to White Mountains’s common shareholders	$	51.77		$	51.15		$	47.41
Dividends declared and paid	(1.00		)	(1.00		)	(1.00		)
Undistributed earnings	$	50.77		$	50.15		$	46.41
Diluted earnings per share (in dollars)
Net income attributable to White Mountains’s common shareholders	$	51.77		$	51.15		$	47.41
Dividends declared and paid	(1.00		)	(1.00		)	(1.00		)
Undistributed earnings	$	50.77		$	50.15		$	46.41


⁽¹⁾	Restricted shares issued by White Mountains receive dividends, and therefore, are considered participating securities.


⁽²⁾	Restricted common shares outstanding vest either in equal annual installments or upon a stated date (see Note 13).


⁽³⁾	The diluted earnings per share denominator for the years ended December 31, 2014, 2013 and 2012 do not include the impact of 125,000 common shares issuable upon exercise of the non-qualified options outstanding as they are anti-dilutive to the calculation.

Retirement and Postretirement Plans

12 Months Ended

Dec. 31, 2014

Compensation and Retirement Disclosure [Abstract]

Retirement and Postretirement Plans

OneBeacon sponsors qualified and non-qualified, non-contributory, defined benefit pension plans covering substantially all employees who were employed as of December 31, 2001 and former employees who had met the eligibility requirements, as well as retirees. Current plans include the OneBeacon qualified pension plan (the “Qualified Plan”) and the OneBeacon non-qualified pension plan (the “Non-qualified Plan”) (collectively the “Plans”). The Plans were frozen and curtailed in 2002 and, as a result, the projected benefit obligation is equal to the accumulated benefit obligation.

The benefits for the Plans are based primarily on years of service and employees’ compensation through December 31, 2002. OneBeacon’s funding policy is consistent with the funding requirements of U.S. federal laws and regulations.

The following tables set forth the obligations and funded status, assumptions, plan assets and cash flows associated with the Plans as of December 31, 2014 and 2013:



	Pension Benefits December 31,
Millions	2014			2013
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$	102.9		$	119.5
Service cost	.6			.8
Interest cost	4.7			4.2
Special termination benefits expense	.3			.3
Assumption changes	17.5			(13.0		)
Actuarial loss (gain)	1.1			(.5		)
Benefits and expenses paid with plan assets	(5.2		)	(6.2		)
Benefits paid directly by OneBeacon	(2.2		)	(2.2		)
Projected benefit obligation at end of year	$	119.7		$	102.9
Change in plan assets:
Fair value of plan assets at beginning of year	$	142.8		$	124.7
Actual return on plan assets	8.4			24.3
Benefits and expenses paid	(5.2		)	(6.2		)
Fair value of plan assets at end of year	$	146.0		$	142.8
Funded status at end of year	$	26.3		$	39.9

The funded status of the consolidated pension plans as of December 31, 2014 was $26.3 million, which represents an over-funding of $53.4 million related to the Qualified Plan and an under-funding of $27.1 million related to the Non-qualified Plan. The Non-qualified Plan, which is unfunded, does not hold any assets. OneBeacon has set aside $18.2 million in an irrevocable rabbi trust for the benefit of Non-qualified Plan participants. Assets held in the rabbi trust are not reflected in the funded status of the consolidated pension plans as presented.

Amounts recognized in the financial statements as of December 31, 2014 and 2013 consist of:



	December 31,
Millions	2014			2013
Net assets of the Qualified Plan recorded in other assets	$	53.4		$	64.1
Net liabilities of the Non-qualified Plan recorded in other liabilities	(27.1		)	(24.2		)
Net amount accrued in the financial statements	$	26.3		$	39.9

Information for the Non-qualified Plan, which had accumulated benefit obligations in excess of plan assets, was as follows:



	December 31,
Millions	2014		2013
Projected benefit obligation	$	27.1	$	24.2
Accumulated benefit obligation	$	27.1	$	24.2
Fair value of plan assets	$	—	$	—

Information for the Qualified Plan, which had accumulated benefit obligations less than plan assets, was as follows:



	December 31,
Millions	2014		2013
Projected benefit obligation	$	92.6	$	78.7
Accumulated benefit obligation	$	92.6	$	78.7
Fair value of plan net assets	$	146.0	$	142.8

The amounts recognized in accumulated other comprehensive income (loss) on a pre-tax basis and before non-controlling interest for the years ended December 31, 2014 and 2013 were as follows:



	December 31,
Millions	2014			2013
Accumulated other comprehensive income (loss) beginning balance	$	10.5		$	(21.2	)
Increase (decrease) in accumulated other comprehensive income (loss):
Amortization of net actuarial losses recognized during the year	.3			.9
Net actuarial (losses) gains occurring during the year⁽¹⁾	(18.8		)	30.8
Accumulated other comprehensive (loss) income ending balance	$	(8.0	)	$	10.5


⁽¹⁾	Net actuarial gains (losses) resulted from investment returns and demographic experience different than assumed, as well as changes in assumptions in estimating the projected benefit obligation in the years ended December 31, 2014 and 2013.

During 2015, OneBeacon expects $1.2 million will be amortized from accumulated other comprehensive income (loss) into net periodic benefit cost. The components of net periodic benefit (income) cost for the years ended December 31, 2014, 2013 and 2012 were as follows:



	Year Ended December 31,
Millions	2014			2013			2012
Service cost	$	.6		$	.8		$	.7
Interest cost	4.7			4.2			4.7
Expected return on plan assets	(8.5		)	(7.1		)	(6.9		)
Amortization of unrecognized loss	.3			.9			.8
Net periodic pension income before settlements, curtailments and special termination benefits	(2.9		)	(1.2		)	(.7		)
Settlement loss	—			—			.6
Special termination benefits expense⁽¹⁾	.3			.3			.6
Total net periodic (income) benefit cost	$	(2.6	)	$	(.9	)	$	.5


⁽¹⁾	Special termination benefits represent additional payments made from the Qualified Plan to certain vested participants when their employment was terminated due to a reduction in force.

Assumptions

The weighted average discount rate assumptions used to determine benefit obligations was 3.91% and 4.66% as of December 31, 2014 and 2013. The weighted average assumptions used to determine net periodic benefit cost included a 4.66% discount rate and 6.00% expected long-term rate of return on plan assets for the year ended December 31, 2014. The weighted average assumptions used to determine net periodic benefit cost included a 3.64% discount rate and 5.75% expected long-term rate of return on plan assets for the year ended December 31, 2013.

OneBeacon’s discount rate assumptions used to account for the Plans reflect the rates at which the benefit obligations could be effectively settled. In addition to consideration of published yields for high quality long-term corporate bonds, U.S. Treasuries and insurance company annuity contract pricings, consideration was given to cash flow matching analyses.

OneBeacon performed an analysis of expected long-term rates of return based on the allocation of its Qualified Plan assets as of December 31, 2013 and 2012 to develop expected rates of return for 2014 and 2013 for each significant asset class or economic indicator. A range of returns was developed based both on forecasts and on broad market historical benchmarks for expected return, correlation, and volatility for each asset class.

Plan Assets

The majority of the Qualified Plans’ invested assets are managed by Prospector Partners, LLC (“Prospector”), a related party (see Note 20). The investment policy places an emphasis on preserving invested assets through a diversified portfolio of high-quality income producing investments and equity investments.

The investment management process integrates the risks and returns available in the investment markets with the risks and returns available to the Qualified Plan in establishing the proper allocation of invested assets. The asset classes may include fixed maturity, equity, convertible fixed maturity investments, and cash and short-term investments.

The factors examined in establishing the appropriate investment mix include the outlook for risk and return in the various investment markets and sectors and the long-term need for capital growth.

The Qualified Plan’s investments are stated at fair value. Many factors are considered in arriving at fair market value. In general, fixed maturity investments such as corporate bonds and government securities are valued based on yields currently available on comparable securities of issuers with similar credit ratings. Shares of common and preferred stock are valued at quoted market prices when available. Convertible fixed maturity investments are valued based on quoted market prices, analysis of listed markets and use of sensitivity analyses. Registered investment companies are valued at the net asset value as reported by the fund at year-end.

The fair value of the Qualified Plan’s assets and their related inputs as of December 31, 2014 and 2013 by asset category were as follows:



	December 31, 2014								December 31, 2013
Millions	Fair Value		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs		Fair Value		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs
Fixed maturity investments	$	24.2	$	—	$	24.2	$	—	$	—	$	—	$	—	$	—
Common equity securities	101.0		101.0		—		—		103.3		103.3		—		—
Convertible fixed maturity investments	12.8		—		12.8		—		29.9		—		29.9		—
Cash and short-term investments	5.2		4.8		.4		—		8.9		8.8		.1		—
Total	$	143.2	$	105.8	$	37.4	$	—	$	142.1	$	112.1	$	30.0	$	—

There were no transfers between Levels 1, 2 or 3 during the years ended December 31, 2014 and 2013.

The Qualified Plan’s asset allocations as of December 31, 2014 and 2013, by asset category were as follows:



	Plan Assets at December 31,
Asset Category	2014		2013
Fixed maturity investments	16.9	%	—	%
Common equity securities	70.6		72.7
Convertible fixed maturity investments	8.9		21.1
Cash and short-term investments	3.6		6.2
Total	100.0	%	100.0	%

As described above, the Qualified Plan’s investment securities are exposed to various risks such as interest rate, market, and credit risks. Market prices of common equity securities, in general, are subject to fluctuations which would cause the amount to be realized upon sale or exercise of the instruments to differ significantly from the current reported value. The fluctuations may result from perceived changes in the underlying economic characteristics of the investee, the relative price of alternative investments, general market conditions and supply and demand imbalances for a particular security. Increases and decreases in prevailing interest rates generally translate into decreases and increases in fair values of fixed maturity and convertible fixed maturity investments, respectively. Additionally, fair values of interest rate sensitive instruments may be affected by the creditworthiness of the issuer, prepayment options, relative values of alternative investments, the liquidity of the instrument and other general market conditions.

Cash Flows

OneBeacon does not expect to make a contribution to its Qualified Plan in 2015. OneBeacon anticipates contributing $2.2 million to the Non-qualified Plan in 2015, for which OneBeacon has assets held in a rabbi trust.

The following benefit payments, which reflect expected future service, as appropriate, are expected to be paid:



Millions	Expected Benefit Payments
2015	$	4.9
2016	5.3
2017	5.6
2018	5.9
2019	6.1
2020-2024	34.4

Other Benefit Plans

OneBeacon sponsors a defined contribution plan, the OneBeacon 401(k) Savings and Employee Stock Ownership Plan (“KSOP”), covering the majority of its employees. The contributory plan provides qualifying employees with matching contributions of 50% up to the first six percent of salary (subject to U.S. federal limits on allowable contributions in a given year). Total expense for matching contributions to the plan was $2.7 million, $2.3 million and $2.8 million in 2014, 2013 and 2012.

The employee stock ownership component of the KSOP provides all of its participants with an annual base contribution in common shares equal to 3% of their salary, up to the applicable Social Security wage base ($117,000 for 2014). Additionally, those participants not otherwise eligible to receive certain other OneBeacon benefits can earn a variable contribution of up to 6% of their salary, subject to the applicable IRS annual covered compensation limits ($260,000 for 2014) and contingent upon OneBeacon’s performance. White Mountains recorded $4.4 million, $6.3 million and $4.8 million in compensation expense to pay benefits and allocate common shares to participant’s accounts for the years ended 2014, 2013 and 2012.

OneBeacon had a post-employment benefit liability, which primarily relates to disability coverage for former employees, of $4.8 million and $5.8 million as of December 31, 2014 and 2013.

Sirius Group sponsors an employee savings plan (defined contribution plan) covering the majority of its U.S. employees. The contributory plan provides qualifying employees with matching contributions of 100% up to the first 2% and 50% of the next 4% of salary (subject to U.S. federal limits on allowable contributions in a given year). Total expense for matching contributions to the plan was $0.7 million, $0.6 million and $0.6 million in 2014, 2013 and 2012. Additionally, all participants in the plan can earn a variable contribution of up to 7% of their salary, subject to the applicable IRS annual covered compensation limits ($260,000 for 2014) and contingent upon Sirius Group’s performance. Total expense for variable contributions to the plan was $0.5 million, $0.7 million and $0.4 million in 2014, 2013 and 2012.

Sirius Group funds other governmental pension plans and other employee savings plans in various countries for its global employees. As of December 31, 2014 and 2013, the projected benefit obligation of Sirius Group’s other governmental pension plans was $14.1 million and $13.1 million, and the funded status was $(1.8) million and $(1.0) million. The expense for those plans totaled $10.3 million, $9.7 million and $7.5 million in 2014, 2013 and 2012.

Employee Share-Based Incentive Compensation Plans

12 Months Ended

Dec. 31, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Employee Share-Based Incentive Compensation Plans

White Mountains’s share-based incentive compensation plans are designed to incentivize key employees and service providers to maximize shareholder value over long periods of time. White Mountains believes that this is best pursued by utilizing a pay-for-performance program that closely aligns the financial interests of management with those of its shareholders. White Mountains accomplishes this by emphasizing highly variable long-term compensation that is contingent on performance over a number of years rather than entitlements. White Mountains expenses all its share-based compensation. As a result, White Mountains’s calculation of its owners’ returns includes the expense of all outstanding share-based compensation awards.

Incentive Compensation Plans

White Mountains’s Long-Term Incentive Plan (the “WTM Incentive Plan”) provides for grants of various types of share-based and non-share-based incentive awards to key employees and service providers of White Mountains. The WTM Incentive Plan was adopted by the Board, was approved by the Company’s sole shareholder in 1985 and was subsequently amended by its shareholders in 1995, 2001, 2003, 2005, 2010 and 2013. Share-based incentive awards that may be granted under the plan include performance shares, restricted shares, performance units, incentive stock options and non-qualified stock options (“Non-Qualified Options”). Performance shares are conditional grants of a specified maximum number of common shares or an equivalent amount of cash. Awards generally vest at the end of a three-year period, are subject to the attainment of pre-specified performance goals, and are valued based on the market value of common shares at the time awards are paid. Performance shares earned under the WTM Incentive Plan are typically paid in cash but may be paid in common shares or by deferral into certain non-qualified compensation plans of White Mountains. Compensation expense is recognized on a pro rata basis over the vesting period of the awards.

The OneBeacon Long-Term Incentive Plan (the “OneBeacon Incentive Plan”) provides for grants to key employees of OneBeacon various types of share-based incentive awards, including performance shares, restricted shares, restricted stock units and Non-Qualified Options.

The Sirius Group Performance Plan provides for granting phantom White Mountains performance shares (the “WTM Phantom Share Plan”) to certain key employees of Sirius Group. Beginning with the 2011-2013 performance cycle, employees of Sirius Group were granted performance shares from the WTM Incentive Plan. The performance goals for full payment of performance shares issued under these plans are identical to those of the WTM Incentive Plan. Performance shares earned under the WTM Phantom Share Plan are typically paid in cash but could be paid in common shares or by deferral into certain non-qualified compensation plans of White Mountains. Compensation expense is recognized on a pro rata basis over the vesting period of the awards.

White Mountains offers certain types of share-based compensation under qualified retirement plans. The defined contribution plans of OneBeacon and Sirius Group (the “401(k) Plans”) offer its U.S.-domiciled participants the ability to invest their balances in several different investment options, including the Company’s or OneBeacon’s common shares.

OneBeacon’s KSOP is an employer-funded benefit plan that provides all of its participants with an annual base contribution in common shares equal to 3% of their salary, up to the applicable Social Security wage base ($117,000 for 2014). Additionally, those participants not otherwise eligible to receive certain other OneBeacon benefits can earn a variable contribution of up to 6% of their salary, subject to the applicable IRS annual covered compensation limits ($260,000 for 2014) and contingent upon OneBeacon’s performance.

Performance Shares

Performance shares are designed to reward company-wide performance. The level of payout ranges from zero to two times the number of shares initially granted, depending on White Mountains’s financial performance. Performance shares become payable at the conclusion of a performance cycle (typically three years) if pre-defined financial targets are met.

The principal performance measure used for determining performance share payouts is after-tax growth in White Mountains’s intrinsic business value per share. The Compensation Committee historically has considered the growth in intrinsic business value per share to be based equally on the growth of economic value per share and growth in adjusted book value per share, both inclusive of dividends. Economic value is calculated by adjusting the GAAP book value per share for differences between the GAAP carrying values of certain assets and liabilities and White Mountains’s estimate of their underlying economic values (for example, the time value discount in loss reserves).

The following summarizes performance share activity for the years ended December 31, 2014, 2013 and 2012 for performance shares granted under the WTM Incentive Plan and the WTM Phantom Share Plan:



	Year Ended December 31,
	2014					2013					2012
Millions, except share amounts	Target Performance Shares Outstanding		Accrued Expense			Target Performance Shares Outstanding		Accrued Expense			Target Performance Shares Outstanding		Accrued Expense
Beginning of period	119,220		$	60.2		119,357		$	29.4		150,064		$	66.1
Shares paid or expired⁽¹⁾	(37,130	)	(26.7		)	(47,310	)	(11.0		)	(68,357	)	(58.3		)
New grants	45,660		—			47,170		—			38,432		—
Assumed forfeitures and cancellations⁽²⁾⁽³⁾	(4,201	)	(.7		)	3		(.6		)	(782	)	.6
Expense recognized	—		15.3			—		42.4			—		21.0
Ending December 31,	123,549		$	48.1		119,220		$	60.2		119,357		$	29.4

⁽¹⁾

WTM performance shares payments in 2014 for the 2011-2013 performance cycle ranged from 88% to 131.5% of target. WTM performance shares payments in 2013 for the 2010-2012 performance cycle ranged from 33% to 98% of target. WTM performance share payments in 2012 for the 2009-2011 performance cycle ranged from 147% to 155% of target. As of December 31, 2012, White Mountains paid $9.9 as a partial payment for the 2010-2012 performance cycle.


⁽²⁾	On November 19, 2014, the Compensation Committee canceled 3,040 WTM performance shares for the 2014-2016 performance cycle and issued the same number of WTM restricted shares.


⁽³⁾	Amounts include changes in assumed forfeitures, as required under GAAP.

For the 2011-2013 performance cycle, the Company issued common shares for 3,570 performance shares earned and all other performance shares earned were settled in cash. For the 2009-2011 performance cycle, the Company issued common shares for 9,577 performance shares earned and all other performance shares earned were settled in cash.

If the outstanding WTM performance shares had vested on December 31, 2014, the total additional compensation cost to be recognized would have been $16.9 million, based on accrual factors as of December 31, 2014 (common share price and payout assumptions).

Performance shares granted under the WTM Incentive Plan

The following table summarizes performance shares outstanding and accrued expense for performance shares awarded under the WTM Incentive Plan as of December 31, 2014 for each performance cycle:



Millions, except share amounts	Target WTM Performance Shares Outstanding		Accrued Expense
Performance cycle:
2014 – 2016	41,937		$	4.1
2013 – 2015	46,803		18.9
2012 – 2014	37,977		26.4
Sub-total	126,717		49.4
Assumed forfeitures	(3,168	)	(1.3		)
Total at December 31, 2014	123,549		$	48.1

The targeted performance goal for full payment of outstanding performance shares granted under the WTM Incentive Plan to non-investment personnel for the 2014-2016 performance cycles is an 9% growth in intrinsic business value per share. Growth of 3% or less would result in no payout and growth of 15% or more would result in a payout of 200%.

The targeted performance goal for full payment of outstanding performance shares granted under the WTM Incentive Plan to non-investment personnel for the 2013-2015 performance cycles is an 8% growth in intrinsic business value per share. Growth of 2% or less would result in no payout and growth of 14% or more would result in a payout of 200%.

The targeted performance goal for full payment of outstanding performance shares granted under the WTM Incentive Plan to non-investment personnel for the 2012-2014 performance cycles is a 8% growth in intrinsic business value per share. Growth of 2% or less would result in no payout and growth of 14% or more would result in a payout of 200%.

For investment personnel, the targeted performance goal for full payment of outstanding performance shares granted under the WTM Incentive Plan is based one-third on growth in intrinsic business value per share (as described above), one-third on achieving a total return on invested assets as measured against metrics based on U.S. Treasury Note returns and one-third on achieving a total return on invested assets as measured against metrics based on the Barclays U.S. Intermediate Aggregate Index returns.

For Prospector Partners, the targeted performance goal for full payment of outstanding performance shares granted under the WTM Incentive Plan is based equally on growth in intrinsic business value per share (as described above) and achieving a total return on invested assets as measured against metrics based on U.S. Treasury Note returns.

Restricted Shares

The following outlines the unrecognized compensation cost associated with the outstanding restricted share awards under the WTM Incentive Plan for the years ended December 31, 2014, 2013 and 2012:



	Year Ended December 31,
	2014					2013					2012
Millions, except share amounts	Restricted Shares		Unamortized Issue Date Fair Value			Restricted Shares		Unamortized Issue Date Fair Value			Restricted Shares		Unamortized Issue Date Fair Value
Non-vested,
Beginning of period	94,130		$	17.0		69,910		$	16.8		72,000		$	13.3
Issued ⁽¹⁾	23,440		13.1			25,720		14.4			32,160		15.7
Vested ⁽²⁾	(33,205	)	—			(1,500	)	—			(32,945	)	—
Forfeited	(1,051	)	(.5		)	—		—			(1,305	)	(.2		)
Expense recognized	—		(15.3		)	—		(14.2		)	—		(12.0		)
Non-vested at December 31,	83,314		$	14.3		94,130		$	17.0		69,910		$	16.8


⁽¹⁾	During 2012, the Compensation Committee accelerated the vesting date for an installment of 5,000 restricted shares from January 20, 2013 to December 31, 2012.


⁽²⁾	On November 19, 2014, the Compensation Committee canceled 3,040 WTM performance shares for the 2014-2016 performance cycle and issued the same number of WTM restricted shares.

During 2014, White Mountains issued 23,440 restricted shares that vest on January 1, 2017. During 2013, White Mountains issued 25,720 restricted shares that vest on January 1, 2016. During 2012, White Mountains issued 27,960 restricted shares that vest on January 1, 2015, 3,000 restricted shares that vest in two equal annual installments that began on February 22, 2014 and 1,200 restricted shares that vest on July 16, 2015. The unrecognized compensation cost as of December 31, 2014 is expected to be recognized ratably over the remaining vesting periods.

Stock Options

Non-Qualified Options

The Company’s Chairman and CEO holds 125,000 Non-Qualified Options, which are exercisable at $742 per common share and expire on January 20, 2017. The Non-Qualified Options have been fully amortized.

Share-Based Compensation Based on OneBeacon Ltd. Common Shares

OneBeacon Performance Shares

The following summarizes activity for the years ended December 31, 2014, 2013 and 2012 for OneBeacon performance shares granted under the OneBeacon Incentive Plan:



	Year Ended December 31,
	2014					2013					2012
Millions, except share amounts	Target Performance Shares Outstanding		Accrued Expense			Target Performance Shares Outstanding		Accrued Expense			Target Performance Shares Outstanding		Accrued Expense
Beginning of period	493,421		$	4.0		563,190		$	1.2		642,667		$	9.7
Payments and deferrals⁽¹⁾	(142,138	)	(1.0		)	(238,658	)	—			(258,901	)	(7.7		)
New awards	165,800		—			179,000		—			181,290		—
Forfeitures and cancellations⁽²⁾	387		—			(10,111	)	(.1		)	(1,866	)	—
Expense recognized	—		.4			—		2.9			—		(.8		)
End of period	517,470		$	3.4		493,421		$	4.0		563,190		$	1.2


⁽¹⁾	OneBeacon performance share payments in 2014 for the 2011-2013 performance cycle were at 37.1% of target. No payments were made in 2013 for the 2010-2012 OneBeacon performance cycle as the performance factor was zero. OneBeacon performance share payments in 2012 for the 2009-2011 performance cycle were at 138.6% of target.


⁽²⁾	Amounts include changes in assumed forfeitures, as required under GAAP.

The following summarizes OneBeacon performance shares outstanding awarded under the OneBeacon Incentive Plan as of December 31, 2014 for each performance cycle:



Millions, except share amounts	Target OneBeacon Performance Shares Outstanding		Accrued Expense
Performance cycle:
2014 – 2016	165,800		$	.5
2013 – 2015	179,000		1.4
2012 – 2014	181,290		1.5
Sub-total	526,090		3.4
Assumed forfeitures	(8,620	)	—
Total at December 31, 2014	517,470		$	3.4

If the outstanding OneBeacon performance shares had been vested on December 31, 2014, the total additional compensation cost to be recognized would have been $1.6 million, based on December 31, 2014 accrual factors (common share price and payout assumptions).

The targeted performance goal for full payment of the outstanding OneBeacon performance shares granted during 2014 is growth in book value per share of 14%. At a growth in book value per share of 7% or less, no performance shares would be earned and at a growth in book value per share of 21% or more, 200% of performance shares would be earned.

The targeted performance goal for full payment of the outstanding OneBeacon performance shares granted during 2013 is growth in book value per share of 13%. At a growth in book value per share of 6% or less, no performance shares would be earned and at a growth in book value per share of 20% or more, 200% of performance shares would be earned.

The targeted performance goal for full payment of the outstanding OneBeacon performance shares granted during 2012 is growth in book value per share of 10%. At a growth in book value per share of 3% or less, no performance shares would be earned and at a growth in book value per share of 17% or more, 200% of performance shares would be earned.

OneBeacon Restricted Shares

The following table summarizes the unrecognized compensation cost associated with the outstanding OneBeacon restricted stock awards for the years ended December 31, 2014, 2013 and 2012.



	Year Ended December 31,
	2014					2013					2012
Millions, except share amounts	Restricted Shares		Unamortized Issue Date Fair Value			Restricted Shares		Unamortized Issue Date Fair Value			Restricted Shares		Unamortized Issue Date Fair Value
Non-vested,
Beginning of period	915,000		$	6.5		927,000		$	9.6		630,000		$	7.7
Issued	—		—			—		—			300,000		4.5
Vested	(300,000	)	—			(9,000	)	—			(667	)	—
Forfeited	(2,500	)	—			(3,000	)	—			(2,333	)	—
Expense recognized	—		(3.0		)	—		(3.1		)	—		(2.6		)
End of period	612,500		$	3.5		915,000		$	6.5		927,000		$	9.6

On March 1, 2012, OneBeacon issued 300,000 restricted shares to key employees that vest in two equal installments on February 28, 2014 and 2015. On May 25, 2011, OneBeacon issued 630,000 restricted shares to its CEO that vest in four equal annual installments beginning on February 22, 2014, 2015, 2016 and 2017. Concurrently with the grant of the restricted shares, 35,000 OneBeacon performance shares issued to OneBeacon’s CEO for the 2011-2013 performance share cycle were forfeited and performance share awards to OneBeacon’s CEO for the subsequent 5 years have been or will also be reduced by 35,000 shares. The restricted shares contain dividend participation features, and therefore, are considered participating securities. The unrecognized compensation cost associated with outstanding restricted share awards as of December 31, 2014 is expected to be recognized ratably over the remaining vesting periods.

Share-based Compensation Under Qualified Retirement Plans

Contributions to the KSOP with respect to the years ended 2014, 2013 and 2012 were made with either the Company’s or OneBeacon Ltd.’s common shares, dependent on the employer. The variable contribution amounts for eligible participants of the KSOP constituted approximately 2%, 4% and 3% of salary for the years ended 2014, 2013 and 2012. White Mountains recorded $4.4 million, $6.3 million and $4.8 million in compensation expense to pay benefits and allocate common shares to participant’s accounts for the years ended 2014, 2013 and 2012. As of December 31, 2014 and 2013, the plans owned 3% or less of either of the Company’s or OneBeacon Ltd.’s total common shares outstanding. All White Mountains common shares held by the KSOP are considered outstanding for earnings (loss) per share computations.

Common Shareholders’ Equity and Non-controlling Interests

12 Months Ended

Dec. 31, 2014

Stockholders' Equity Note [Abstract]

Common Shareholder's Equity

Common Shareholders’ Equity and Non-controlling Interests

Common Shares Repurchased and Retired

During the past several years, White Mountains’s board of directors authorized the Company to repurchase its common shares, from time to time, subject to market conditions. Shares may be repurchased on the open market or through privately negotiated transactions. The repurchase authorizations do not have a stated expiration date. As of December 31, 2014, White Mountains may repurchase an additional 338,092 shares under these board authorizations. In addition, from time to time White Mountains has also repurchased its common shares through tender offers that were separately approved by its board of directors.

During 2014, the Company repurchased 217,879 common shares for $134.5 million at an average share price of $617, which were comprised of 207,404 common shares repurchased under the board authorization for $128.2 million at an average share price of $618 and 10,475 common shares repurchased pursuant to employee benefit plans. Shares repurchased pursuant to employee benefit plans do not fall under the board authorizations referred to above.

During 2013, the Company repurchased 141,535 common shares for $79.8 million at an average share price of $564, which were comprised of 140,000 common shares repurchased in a private transaction under the board authorization for $78.9 million at an average share price of $564 and 1,535 common shares repurchased pursuant to employee benefit plans.

During 2012, the Company repurchased 1,329,640 common shares for $669.1 million at an average share price of $503, which were comprised of (1) 502,801 common shares repurchased under the board authorization for $256.0 million at an average share price of $508; (2) 816,829 common shares repurchased through a fixed-price tender offer for $408.6 million at a share price of $500; and (3) 10,010 common shares repurchased pursuant to employee benefit plans.

Common Shares Issued

During 2014, the Company issued a total of 28,405 common shares, which consisted of 23,440 restricted shares issued to key management personnel, 3,570 shares issued in satisfaction of performance shares and 1,395 shares issued to directors of the Company. During 2013, the Company issued a total of 27,310 common shares, which consisted of 25,720 restricted shares issued to key management personnel and 1,590 shares issued to directors of the Company. During 2012, the Company issued a total of 44,054 common shares, which consisted of 32,160 restricted shares and 700 shares issued to key management personnel, 9,577 shares issued in satisfaction of performance shares and 1,617 shares issued to directors of the Company.

Dividends on Common Shares

For the years ended December 31, 2014, 2013 and 2012, the Company declared and paid cash dividends totaling $6.2 million, $6.2 million and $6.6 million (or $1.00 per common share).

Non-controlling Interests

Non-controlling interests consist of the ownership interests of non-controlling shareholders in consolidated entities and are presented separately on the balance sheet. The following table details the balance of non-controlling interests included in White Mountains’s total equity and the related percentage of each consolidated entity’s total equity owned by non-controlling shareholders as of December 31, 2014 and 2013:



	December 31, 2014					December 31, 2013
Millions	Non-controlling Percentage		Non-controlling Equity			Non-controlling Percentage		Non-controlling Equity
OneBeacon Ltd.	24.7	%	$	258.7		24.8	%	$	273.7
SIG Preference Shares	100.0		250.0			100.0		250.0

Other, excluding reciprocals
HG Global	3.1		17.9			2.7		16.6
QuoteLab	40.0		22.6			—		—
Tranzact	36.8		88.2			—		—
Wobi	36.7		5.4			—		—
Prospector Offshore Fund	23.4		31.1			28.3		32.1
Prospector Turtle Fund	—		—			31.1		14.1
Dewar	18.0		3.4			18.0		3.0
Total other, excluding reciprocals			168.6					65.8

Reciprocals
BAM	100.0		(121.9		)	100.0		(97.6		)
SSIE	100.0		(12.4		)	—		—
Total non-controlling interests			$	543.0				$	491.9

In 2012, HG Global was capitalized with $594.5 million from White Mountains and $14.5 million from certain management members of BAM, the latter of which is included in non-controlling interest. Upon closing, certain BAM management members also received additional common and preferred shares of HG Global that resulted in a $2.2 million allocation of the carrying value of White Mountains’s investment in HG Global to the non-controlling interest, which was recorded as an adjustment to paid-in surplus in White Mountains’s consolidated statement of changes in equity.

On May 24, 2007, SIG issued $250.0 million non-cumulative perpetual preference shares, with a $1,000 per share liquidation preference (the “SIG Preference Shares”), and received $245.7 million of proceeds, net of $4.3 million of issuance costs and commissions. These shares were issued in an offering that was exempt from the registration requirements of the Securities Act of 1933. Holders of the SIG Preference Shares receive dividends on a non-cumulative basis when and if declared by SIG. The holders of the SIG Preference Shares have the right to elect two directors to SIG’s board in the event of non-payment of dividends for six quarterly dividend periods. The right ceases upon the payment of dividends for four quarterly periods or the redemption of the SIG Preference Shares. In addition, SIG may not declare or pay dividends on its common shares (other than stock dividends and dividends paid for purposes of any employee benefit plans of SIG and its subsidiaries) unless it is current on its most recent dividend period. The dividend rate is fixed at an annual rate of 7.506% until June 30, 2017 and dividends are paid on a semi-annual basis. After June 30, 2017, the dividend rate will be paid at a floating annual rate, equal to the greater of (1) the 3 month LIBOR plus 320 bps or (2) 7.506% and dividends will be paid on a quarterly basis. The SIG Preference Shares are redeemable solely at the discretion of SIG on or after June 30, 2017 at their liquidation preference of $1,000 per share, plus any declared but unpaid dividends. In July 2013, SIG executed a 5-year forward LIBOR cap (the “Interest Rate Cap”) for the period from June 2017 to June 2022 to protect against a significant increase in interest rates during that 5-year period. The Interest Rate Cap fixes the annual dividend rate on the SIG Preference Shares from June 2017 to June 2022 at 8.30%. The Interest Rate Cap is recorded in other assets at fair value. Changes in fair value are recorded in other revenue.

Prior to June 30, 2017, SIG may elect to redeem the SIG Preference Shares at an amount equal to the greater of (1) the aggregate liquidation preference of the shares to be redeemed and (2) the sum of the present values of the aggregate liquidation preference of the shares to be redeemed and the remaining scheduled dividend payments on the shares to be redeemed (excluding June 30, 2017), discounted to the redemption date on a semi-annual basis at a rate equal to the rate on a comparable treasury issue plus 45 basis points. In the event of liquidation of SIG, the holders of the SIG Preference Shares would have preference over the common shareholders and would receive a distribution equal to the liquidation preference per share, subject to availability of funds. SIG Preference Shares and dividends thereon are included in non-controlling interest on the balance sheet and as non-controlling interest expense on the statement of income and comprehensive income.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(d),(e))
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Subparagraph (SX 210.3-04)
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
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Reference 10: http://www.xbrl.org/2003/role/presentationRef
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Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=6521494

Reference 12: http://www.xbrl.org/2003/role/presentationRef
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Reference 14: http://www.xbrl.org/2003/role/presentationRef
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Reference 15: http://www.xbrl.org/2003/role/presentationRef
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Reference 16: http://www.xbrl.org/2003/role/presentationRef
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Reference 17: http://www.xbrl.org/2003/role/presentationRef
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Reference 18: http://www.xbrl.org/2003/role/presentationRef
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Reference 19: http://www.xbrl.org/2003/role/presentationRef
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+ Details

Statutory Capital and Surplus	12 Months Ended
Statutory Capital and Surplus	Dec. 31, 2014
Insurance [Abstract]
Statutory Capital and Surplus	Statutory Capital and Surplus White Mountains’s insurance and reinsurance operations are subject to regulation and supervision in each of the jurisdictions where they are domiciled and licensed to conduct business. Generally, regulatory authorities have broad supervisory and administrative powers over such matters as licenses, standards of solvency, premium rates, policy forms, investments, security deposits, methods of accounting, form and content of financial statements, reserves for unpaid loss and LAE, reinsurance, minimum capital and surplus requirements, dividends and other distributions to shareholders, periodic examinations and annual and other report filings. In general, such regulation is for the protection of policyholders rather than shareholders. The NAIC uses risk-based capital (“RBC”) standards for U.S. property and casualty insurers as a means of monitoring certain aspects affecting the overall financial condition of insurance companies. As of December 31, 2014, White Mountains’s active U.S. insurance and reinsurance operating subsidiaries exceeded their respective RBC requirements. The Insurance Act 1978 of Bermuda and related regulations, as amended (“Insurance Act”), regulates the insurance business of Bermuda-domiciled insurers and reinsurers. Under the Insurance Act, insurers and reinsurers are required to maintain available statutory capital and surplus at a level equal to or in excess of its enhanced capital requirement which is established by reference to either a Bermuda Solvency Capital Requirement (“BSCR”) model or an approved internal capital model. Generally, the Bermuda Monetary Authority (“BMA”) has broad supervisory and administrative powers over such matters as licenses, standards of solvency, investments, methods of accounting, form and content of financial statements, minimum capital and surplus requirements, and annual and other report filings. OneBeacon: OneBeacon’s U.S. combined statutory surplus was $721.5 million and $866.2 million as of December 31, 2014 and 2013. OneBeacon’s combined U.S. statutory net (loss) income ended December 31, 2014, 2013 and 2012 was $(14.2) million, $100.1 million and $82.0 million. The minimum policyholders' surplus necessary to satisfy OneBeacon’s top tier regulated U.S. insurance operating subsidiary, Atlantic Specialty Insurance Company (“ASIC”), regulatory requirements was $136.0 million as of December 31, 2014, which equals the authorized control level of the NAIC risk-based capital of ASIC’s policyholders’ surplus. Split Rock’s statutory capital and surplus was $122.6 million and $96.4 million as of December 31, 2014 and 2013, which met Bermuda’s statutory capital and surplus requirements. Split Rock reported $46.2 million of statutory net income for the year ended December 31, 2014 and $38.7 million of statutory net loss for the year ended December 31, 2013. The principal differences between OneBeacon’s combined U.S. statutory amounts and Split Rock, and the amounts reported in accordance with GAAP include deferred acquisition costs, deferred taxes, and market value adjustments for debt securities. OneBeacon’s insurance subsidiaries' statutory policyholders’ surplus as of December 31, 2014 was in excess of the minimum requirements of relevant state and Bermuda insurance regulations. Sirius Group: In 2014, Sirius Group established Sirius Bermuda Insurance Ltd. (“Sirius Bermuda”) as a class 3A licensed Bermuda insurer, which is subject to the regulation and supervision of the BMA. Sirius Bermuda’s statutory capital and surplus was $2.4 billion as of December 31, 2014, which met Bermuda’s statutory capital and surplus requirements. The minimum regulatory capital held by Sirius Bermuda necessary to satisfy the requirements established by the BMA was $1.0 million as of December 31, 2014. Sirius International is subject to regulation and supervision in Sweden by the Financial Supervisory Authority (“FSA”). Sirius International’s total regulatory capital as of December 31, 2014 was $2.3 billion. In accordance with FSA regulations, Sirius International holds restricted equity of $1.4 billion as a component of Swedish regulatory capital. This restricted equity cannot be paid as dividends. The minimum regulatory capital held by Sirius International necessary to satisfy the requirements established by the FSA was $158.2 million as of December 31, 2014. Sirius America’s policyholders’ surplus, as reported to regulatory authorities as of December 31, 2014 and 2013, was $620.6 million and $548.4 million. Sirius America’s statutory net income for the years ended December 31, 2014, 2013 and 2012 was $56.1 million, $55.9 million and $26.2 million. The principal differences between Sirius America’s statutory amounts and the amounts reported in accordance with GAAP include deferred acquisition costs, deferred taxes, gains recognized under retroactive reinsurance contracts and market value adjustments for debt securities. The minimum policyholders’ surplus necessary to satisfy Sirius America’s regulatory requirements was $106.5 million as of December 31, 2014, which equals the authorized control level of the NAIC risk-based capital based on Sirius America’s policyholders’ surplus. Woodridge’s policyholders’ surplus, as reported to regulatory authorities as of December 31, 2014 and 2013, was $8.3 million and $8.4 million. Woodridge’s statutory net (loss) income for the years ended December 31, 2014, 2013 and 2012 was $(0.2) million, $(0.1) million, and $0.1 million. The minimum policyholders’ surplus necessary to satisfy Woodridge’s regulatory requirements was $2.0 million as of December 31, 2014, which equals the authorized control level of the NAIC risk-based capital based on Woodridge’s policyholders’ surplus. Oakwood’s policyholders’ surplus, as reported to regulatory authorities as of December 31, 2014 and 2013, was $29.4 million and $20.7 million. Oakwood’s statutory net (loss) income for the years ended December 31, 2014, 2013 and 2012 was $(0.8) million, $(0.9) million, and $3.9 million. The minimum policyholders’ surplus necessary to satisfy Oakwood’s regulatory requirements was $8.1 million as of December 31, 2014, which equals the authorized control level of the NAIC risk-based capital based on Oakwood’s policyholders’ surplus. Central National’s policyholders’ surplus, as reported to regulatory authorities as of December 31, 2013, was $9.3 million. The net assets of Central National were transferred to Oakwood and Central National was subsequently dissolved in 2014. Ashmere’s policyholders’ surplus, as reported to regulatory authorities as of December 31, 2014 and 2013, was $12.5 million and $12.7 million. Ashmere’s statutory net loss for the year ended December 31, 2014 and 2013 was $0.5 million and $0.4 million. The minimum policyholders’ surplus necessary to satisfy Ashmere’s regulatory requirements was $2.0 million as of December 31, 2014, and the NAIC risk-based capital authorized control level was $0.1 million. Empire’s policyholders’ surplus, as reported to regulatory authorities as of December 31, 2014 and 2013, was $10.5 million and $10.7 million. Empire’s statutory net loss for the year ended December 31, 2014 and 2013 was $0.6 million and 10.4 million. The minimum policyholders’ surplus necessary to satisfy Empire’s regulatory requirements was $3.4 million as of December 31, 2014, and the NAIC risk-based capital authorized control level was $1.2 million. White Shoals Re Ltd. (“White Shoals Re”) is also subject to regulation and supervision by the BMA. As of December 31, 2014 and 2013, White Shoals Re had statutory capital and surplus of $22.4 million and $14.6 million. The minimum regulatory capital held by White Shoals Re necessary to satisfy the requirements established by the BMA was $8.2 million and $6.2 million as of December 31, 2014 and 2013. Alstead Reinsurance Ltd. (“Alstead Re”) is also subject to regulation and supervision by the BMA. As of December 31, 2014, Alstead Re had statutory capital and surplus of $25.5 million. The minimum regulatory capital held by Alstead Re necessary to satisfy the requirements established by the BMA was $1.1 million as of December 31, 2014. Olympus Re is also subject to regulation and supervision by the BMA. As of December 31, 2014, Olympus Re had statutory capital and surplus of $12.3 million. The minimum regulatory capital held by Olympus Re necessary to satisfy the requirements established by the BMA was $2.6 million as of December 31, 2014. HG Global/BAM: HG Re is a Special Purpose Insurer under Bermuda insurance regulations and is subject to regulation and supervision by the BMA. As of December 31, 2014, HG Re had statutory capital of $444.5 million. As a Special Purpose Insurer, HG Re does not have minimum regulatory capital requirements. BAM is domiciled in New York and is subject to regulation by the New York State Department of Financial Services (“NYDFS”). New York financial guarantee insurance law establishes single risk and aggregate limits with respect to insured obligations insured by financial guarantee insurers. BAM’s members’ surplus, as reported to regulatory authorities as of December 31, 2014 was $448.7 million, which exceeds the minimum members’ surplus necessary for BAM to maintain its New York State financial guarantee insurance license of $66.0 million. Other Operations: WM Life Re is subject to regulation and supervision by the BMA. As of December 31, 2014 and 2013, WM Life Re had statutory capital and surplus of $76.0 million and $85.9 million. The minimum regulatory capital held by WM Life Re necessary to satisfy the requirements established by the BMA was $0.4 million as of December 31, 2014. SSIE’s policyholders’ surplus, as reported to regulatory authorities as of December 31, 2014, was $6.5 million. SSIE’s statutory net loss for the year ended December 31, 2014 was $9.5 million. The minimum policyholders’ surplus necessary to satisfy SSIE’s regulatory requirements was $2.8 million as of December 31, 2014, which equals the authorized control level of the NAIC risk-based capital based on SSIE’s policyholders’ surplus. Dividend Capacity There are no restrictions under Bermuda law or the law of any other jurisdiction on the payment of dividends from retained earnings by White Mountains. However, under the insurance laws of the states and jurisdictions under which White Mountains’s insurance and reinsurance operating subsidiaries are domiciled, an insurer is restricted with respect to the timing and the amount of dividends it may pay without prior approval by regulatory authorities. As of December 31, 2014, White Mountains’s top tier insurance and reinsurance subsidiaries have approximately $2.6 billion of GAAP shareholders’ equity (net of $199 million of non-controlling interest at OneBeacon), $0.5 billion of which can be distributed to White Mountains without prior regulatory approval. As a result, as of December 31, 2014, $2.1 billion of White Mountains’s GAAP shareholders’ equity held in its insurance and reinsurance subsidiaries was not available for the payment of dividends without prior regulatory approval, and approximately $958 million of White Mountains’s retained earnings is unrestricted with respect to the payment of dividends to White Mountains’s common shareholders. When determining whether to make distributions from its insurance and reinsurance operating subsidiaries, White Mountains also considers factors such as internal capital targets and rating agency capital requirements. Accordingly, there can be no assurance regarding the amount of such dividends that may be paid by such subsidiaries in the future. Following is a description of the dividend capacity of White Mountains’s insurance and reinsurance operating subsidiaries: OneBeacon: On December 23, 2014, OneBeacon Insurance Company (“OBIC”) distributed ASIC to its immediate parent at a value of $700.5 million as part of the Runoff Transaction. OBIC also distributed $151.2 million of cash and other securities to its immediate parent in accordance with the prescribed minimum capital to be included in the company at the time of its sale to Armour, as approved by the PID. ASIC has the ability to pay dividends to its immediate parent during any twelve-month period without the prior approval of regulatory authorities in an amount set by formula based on the lesser of net investment income, as defined by statute, or 10% of statutory surplus, in both cases as most recently reported to regulatory authorities, subject to the availability of earned surplus and subject to dividends paid in prior periods. Based upon the formula above, ASIC has the ability to pay $44.9 million of dividends during 2015 without prior approval of regulatory authorities. As of December 31, 2014, ASIC had $721.5 million of statutory surplus and $87.8 million of earned surplus. Also in 2014, OneBeacon contributed $67.0 million to ASIC. During 2013, ASIC paid a $190.0 million extraordinary return of capital to OBIC, which, in turn, distributed the $190.0 million to its immediate parent. During 2013, OneBeacon also contributed $35.0 million to OBIC. Split Rock has the ability to declare or pay dividends during any twelve-month period without the prior approval of Bermuda regulatory authorities on condition that any such declaration or payment of dividends does not cause a breach of any of its regulatory solvency and liquidity requirements. If Split Rock fails to meet its regulatory solvency or liquidity requirements on the last day of any financial year, it is prohibited from declaring or paying any dividends during the next financial year without the approval of the BMA. In addition, under the Companies Act 1981 of Bermuda (the “Companies Act”), Split Rock is prohibited from declaring or paying a dividend or making a distribution out of contributed surplus if there are reasonable grounds for believing that after such payment is made, Split Rock would be unable to pay its liabilities as they become due or the realizable value of its assets would be less than its liabilities. During 2015, Split Rock has the ability to make capital distributions without the prior approval of regulatory authorities, subject to meeting all appropriate liquidity and solvency requirements, of $18.8 million, which is equal to 15% of its December 31, 2014 statutory capital (excluding earned surplus). During 2014, Split Rock paid $10.0 million of dividends and $10.0 million of capital distributions to its immediate parent. During 2013, OneBeacon contributed $135.1 million to Split Rock. Split Rock did not pay any dividends in 2013. During 2014 and 2013, OneBeacon’s unregulated insurance operating subsidiaries paid $4.8 million and $17.3 million of dividends to their immediate parent. As of December 31, 2014, OneBeacon’s unregulated insurance operating subsidiaries had $78.1 million of net unrestricted cash, short-term investments and fixed maturity investments. As of December 31, 2014, OneBeacon’s unregulated insurance operating subsidiaries also held $101.0 million in par value of OBIC Surplus Notes, with a fair value of $65.1 million classified as other long-term investments. During 2014, OneBeacon Ltd. paid $80.0 million of regular quarterly dividends to its common shareholders. White Mountains received $60.3 million of these dividends. As of December 31, 2014, OneBeacon Ltd. and its intermediate holding companies held $107.0 million of net unrestricted cash, short-term investments and fixed maturity investments and $89.4 million of common equity securities, convertible fixed maturity and preferred investments and other long-term investments outside of its regulated and unregulated insurance operating subsidiaries. Sirius Group: Sirius Bermuda has the ability to declare or pay dividends or make capital distributions during any 12-month period without the prior approval of Bermuda regulatory authorities on the condition that any such declaration or payment of dividends or capital distributions does not cause a breach of any of its regulatory solvency and liquidity requirements. During 2015, Sirius Bermuda has the ability, subject to meeting all appropriate liquidity and solvency requirements, to make dividend or capital distributions without the prior approval of regulatory authorities, subject to meeting all appropriate liquidity and solvency requirements, of $350.0 million, which is equal to 15% of its December 31, 2014 statutory capital, excluding earned surplus. The amount of dividends available to be paid by Sirius Bermuda in any given year is also subject to cash flow and earnings generated by Sirius International’s business, as well as to dividends received from its subsidiaries, including Sirius International. Sirius International has the ability to pay dividends to Sirius Bermuda subject to the availability of unrestricted equity, calculated in accordance with the Swedish Act on Annual Accounts in Insurance Companies and the Swedish Supervisor Authorities (“Swedish FSA”). Unrestricted equity is calculated on a consolidated group account basis and on a parent account basis. Differences between the bases include but are not limited to accounting for goodwill, subsidiaries (with parent accounts stated at original foreign exchange rates), taxes and pensions. Sirius International’s ability to pay dividends is limited to the “lower of” unrestricted equity as calculated within the group and parent accounts. As of December 31, 2014, Sirius International had $467.0 million (based on the December 31, 2014 SEK to USD exchange rate) of unrestricted equity on a parent account basis (the lower of the two) available to pay dividends in 2015. The amount of dividends available to be paid by Sirius International in any given year is also subject to cash flow and earnings generated by Sirius International’s business, as well as to dividends received from its subsidiaries, including Sirius America. Earnings generated by Sirius International’s business that are allocated to the Safety Reserve are not available to pay dividends (see “Safety Reserve” on the next page). During 2014, Sirius International distributed $220.9 million of dividends to its immediate parent. Subject to certain limitations under Swedish law, Sirius International is permitted to transfer certain portions of its pre-tax income to its Swedish parent companies to minimize taxes (referred to as a group contribution). On January 1, 2013, new tax legislation became effective in Sweden that limits the deductibility of interest paid on certain intra-group debt instruments. Uncertainty exists with respect to the interpretation of the legislation on existing intra-group debt instruments within the Sirius Group structure. During 2014, Sirius International did not transfer any of its 2013 pre-tax income to its Swedish parent companies. Sirius America has the ability to pay dividends to Sirius International during any twelve-month period without the prior approval of regulatory authorities in an amount set by formula based on the lesser of net investment income, as defined by statute, or 10% of statutory surplus, in both cases as most recently reported to regulatory authorities, subject to the availability of earned surplus and subject to dividends paid in prior periods. Based upon the formula above, Sirius America does not have the ability to pay any dividends during 2015 without prior approval of regulatory authorities. As of December 31, 2014, Sirius America had $620.6 million of statutory surplus and $81.9 million of earned surplus. During 2014, Sirius America did not pay any dividends to its immediate parent. As of December 31, 2014, Sirius Group and its intermediate holding companies held $20.4 million of net unrestricted cash, short-term investments and fixed maturity investments outside of its regulated and unregulated insurance and reinsurance operating subsidiaries. During 2014, Sirius Group distributed $50.0 million to its immediate parent. Capital Maintenance There is a capital maintenance agreement between Sirius International and Sirius America which obligates Sirius International to make contributions to Sirius America’s surplus in order for Sirius America to maintain surplus equal to at least 125% of the company action level risk based capital as defined in the NAIC Property/Casualty Risk-Based Capital Report. The agreement provides for a maximum contribution to Sirius America of $200.0 million. Sirius International also provides Sirius America with accident year stop loss reinsurance, which protects Sirius America’s accident year loss and allocated loss adjustment expense ratio in excess of 70%, with a limit of $90.0 million. Safety Reserve Subject to certain limitations under Swedish law, Sirius International is permitted to transfer pre-tax amounts into an untaxed reserve referred to as a safety reserve. As of December 31, 2014, Sirius International’s safety reserve amounted to SEK 10.4 billion or $1.3 billion at the December 31, 2014 exchange rate of 7.77 USD to SEK. Under GAAP, an amount equal to the safety reserve, net of a related deferred tax liability established at the Swedish tax rate of 22.0%, is classified as shareholder’s equity. Generally, this deferred tax liability is only required to be paid by Sirius International if it fails to maintain prescribed levels of premium writings and loss reserves in future years. As a result of the indefinite deferral of these taxes, Swedish regulatory authorities apply no taxes to the safety reserve when calculating solvency capital under Swedish insurance regulations. Accordingly, under local statutory requirements, an amount equal to the deferred tax liability on Sirius International’s safety reserve ($295.7 million as of December 31, 2014) is included in solvency capital. Access to the safety reserve is restricted to coverage of insurance or reinsurance underwriting losses. Access for any other purpose requires the approval of Swedish regulatory authorities. Similar to the approach taken by Swedish regulatory authorities, most major rating agencies generally include the $1.3 billion balance of the safety reserve, without any provision for deferred taxes, in Sirius International’s regulatory capital when assessing Sirius International’s financial strength. HG Global/BAM: As of December 31, 2014, HG Global had $613.0 million face value of preferred shares outstanding, of which White Mountains owned 96.9%. Holders of the HG Global preferred shares receive cumulative dividends at a fixed annual rate of 6.0% on a quarterly basis, when and if declared by HG Global. HG Global did not declare or pay any preferred dividends in 2014. As of December 31, 2014, HG Global has accrued $96.2 million of dividends payable to holders of its preferred shares, $93.3 million of which is payable to White Mountains and eliminated in consolidation. HG Re is a Special Purpose Insurer subject to regulation and supervision by the BMA, but does not require regulatory approval to pay dividends. However, HG Re’s dividend capacity is limited by amounts held in the collateral trusts pursuant to the first loss reinsurance treaty (“FLRT”) with BAM. As of December 31, 2014, HG Re had statutory capital of $444.5 million, of which $402.6 million was held as collateral in the supplemental trust pursuant to the FLRT with BAM and $44.3 million relates to accrued interest on the BAM Surplus Notes held by HG Re. Effective January 1, 2014, HG Global and BAM agreed to change the interest rate on the BAM surplus notes for the five years ending December 31, 2018 from a fixed rate of 8.0% to a variable rate equal to the one-year U.S. treasury rate plus 300 basis points, set annually, which is 3.13% for 2014. Prior to the end of 2018, BAM has the option to extend the variable rate period for an additional three years. At the end of the variable rate period, the interest rate will be fixed at the higher of the then current variable rate or 8.0%. BAM is required to seek regulatory approval to pay interest and principal on its surplus notes only when adequate capital resources have accumulated beyond BAM’s initial capitalization and a level that continues to support its outstanding obligations, business plan and ratings. BAM did not pay any interest on the BAM Surplus Notes in 2013 or 2012. Other Operations: During 2014, White Mountains contributed $15.0 million to WM Advisors. During 2014, WM Advisors did not pay any dividends to its immediate parent. As of December 31, 2014, WM Advisors held $25.7 million of net unrestricted cash and short-term investments. As of December 31, 2014, the Company and its intermediate holding companies held $275.1 million of net unrestricted cash, short-term investments and fixed maturity investments, $172.7 million of common equity securities and and convertible fixed maturity investments and $106.4 million of other long-term investments included in its Other Operations segment. During 2014, White Mountains paid a $6.2 million common share dividend.

Segment Information

12 Months Ended

Dec. 31, 2014

Segment Reporting [Abstract]

Segment Information

White Mountains has determined that its reportable segments are OneBeacon, Sirius Group, HG Global/BAM and Other Operations.

White Mountains has made its segment determination based on consideration of the following criteria: (i) the nature of the business activities of each of the Company’s subsidiaries and affiliates; (ii) the manner in which the Company’s subsidiaries and affiliates are organized; (iii) the existence of primary managers responsible for specific subsidiaries and affiliates; and (iv) the organization of information provided to the chief operating decision makers and the Board of Directors.

OneBeacon is a specialty property and casualty insurance writer that offers a wide range of insurance products through independent agencies, regional and national brokers, wholesalers and managing general agencies.

Sirius Group provides insurance and reinsurance products for property, accident and health, aviation and space, trade credit, marine, agriculture and certain other exposures on a worldwide basis.

The HG Global/BAM segment consists of White Mountains’s investment in HG Global and the consolidated results of BAM. BAM is a municipal bond insurer domiciled in New York that was established to provide insurance on bonds issued to support essential U.S. public purposes such as schools, utilities, core governmental functions and existing transportation facilities. HG Global, together with its subsidiaries, provided the initial capitalization of BAM through the purchase of BAM Surplus Notes. HG Global also provides 15%-of-par, first loss reinsurance protection for policies underwritten by BAM. BAM's results are attributed to non-controlling interests.

Other Operations consists of the Company, the Company’s intermediate holding companies, WM Advisors, WM Life Re, Tranzact, Wobi, QuoteLab, Star & Shield and SSIE as well as and various other entities and investments. Significant intercompany transactions among White Mountains’s segments have been eliminated herein. SSIE’s results are attributed to non-controlling interests.

Financial information for White Mountains’s segments follows:



						HG Global/BAM
Millions	OneBeacon		Sirius Group			HG Global		BAM⁽¹⁾			Other Operations			Total
Year Ended December 31, 2014
Earned insurance and reinsurance premiums	$	1,177.1	$	873.9		$	1.4	$	.4		$	6.1		$	2,058.9
Net investment income	41.7		41.1			1.4		5.7			15.1			105.0
Net investment income (loss) - surplus note interest	—		—			15.7		(15.7		)	—			—
Net realized and unrealized investment gains	40.4		209.2			1.7		6.6			26.0			283.9
Other revenue (loss)	5.8		(62.4		)	—		.6			118.4			62.4
Total revenues	1,265.0		1,061.8			20.2		(2.4		)	165.6			2,510.2
Losses and LAE	815.1		345.3			—		—			8.9			1,169.3
Insurance and reinsurance acquisition expenses	203.3		193.6			.3		1.8			.8			399.8
Other underwriting expenses	179.2		129.7			—		.4			—			309.3
General and administrative expenses	13.8		30.5			1.6		35.9			206.4			288.2
Interest expense	13.0		26.3			—		—			2.6			41.9
Total expenses	1,224.4		725.4			1.9		38.1			218.7			2,208.5
Pre-tax income (loss)	$	40.6	$	336.4		$	18.3	$	(40.5	)	$	(53.1	)	$	301.7



					HG Global/BAM
Millions	OneBeacon		Sirius Group		HG Global			BAM⁽¹⁾			Other Operations		Total
Year Ended December 31, 2013
Earned insurance and reinsurance premiums	$	1,120.4	$	866.4	$	.4		$	.1		$	—	$	1,987.3
Net investment income	41.1		48.8		1.0			4.7			15.3		110.9
Net investment income (loss) - surplus note interest	—		—		40.2			(40.2		)	—		—
Net realized and unrealized investment gains (losses)	49.4		26.7		(2.0		)	(9.3		)	96.9		161.7
Other revenue	31.2		16.8		—			.4			9.1		57.5
Total revenues	1,242.1		958.7		39.6			(44.3		)	121.3		2,317.4
Losses and LAE	622.1		418.4		—			—			—		1,040.5
Insurance and reinsurance acquisition expenses	208.9		166.5		.1			1.4			—		376.9
Other underwriting expenses	204.8		126.1		—			.4			—		331.3
General and administrative expenses	12.0		32.2		1.4			32.5			103.2		181.3
Interest expense	13.0		26.3		—			—			3.2		42.5
Total expenses	1,060.8		769.5		1.5			34.3			106.4		1,972.5
Pre-tax income (loss)	$	181.3	$	189.2	$	38.1		$	(78.6	)	$	14.9	$	344.9



						HG Global/BAM
Millions	OneBeacon			Sirius Group		HG Global		BAM⁽¹⁾			Other Operations		Total
Year Ended December 31, 2012
Earned insurance and reinsurance premiums	$	1,132.0		$	931.6	$	—	$	—		$	—	$	2,063.6
Net investment income	53.6			65.0		.3		1.9			32.8		153.6
Net investment income (loss) - surplus note interest	—			—		18.4		(18.4		)	—		—
Net realized and unrealized investment gains	55.7			17.3		—		—			45.2		118.2
Other (loss) revenue	(.5		)	70.6		—		—			30.2		100.3
Total revenues	1,240.8			1,084.5		18.7		(16.5		)	108.2		2,435.7
Losses and LAE	650.0			543.9		—		—			—		1,193.9
Insurance and reinsurance acquisition expenses	249.4			180.8		—		—			—		430.2
Other underwriting expenses	205.2			116.4		—		.2			—		321.8
General and administrative expenses	13.4			45.9		4.5		19.6			98.8		182.2
Interest expense	16.9			26.2		—		—			1.7		44.8
Total expenses	1,134.9			913.2		4.5		19.8			100.5		2,172.9
Pre-tax income (loss)	$	105.9		$	171.3	$	14.2	$	(36.3	)	$	7.7	$	262.8



					HG Global/BAM
Selected Balance Sheet Data Millions	OneBeacon		Sirius Group		HG Global		BAM					Other Operations		Total
December 31, 2014:
Total investments	$	2,527.0	$	3,178.4	$	121.0	$	454.2				$	605.7	$	6,886.3
Reinsurance recoverable on paid and unpaid losses	173.8		333.6		—		—					.1		507.5
Assets held for sale	58.1		—		—		—					—		58.1
Total assets	3,561.0		5,034.7		704.4		(89.4		)	⁽²	⁾	1,246.2		10,456.9
Loss and LAE reserves	1,342.2		1,809.8		—		—					7.8		3,159.8
Total liabilities	2,510.5		3,180.6		120.9		32.5					72.8		5,917.3
Total White Mountains’s common shareholders’ equity	788.4		1,604.1		565.5		—					1,038.6		3,996.6
Non-controlling interest	262.1		250.0		17.9		(121.9		)			134.9		543.0
December 31, 2013:
Total investments	$	2,364.9	$	3,251.4	$	107.9	$	468.6				$	999.8	$	7,192.6
Reinsurance recoverable on paid and unpaid losses	89.9		363.6		—		—					—		453.5
Assets held for sale	1,880.1		—		—		—					—		1,880.1
Total assets	5,191.3		5,124.1		675.0		(77.9		)	⁽²	⁾	1,231.8		12,144.3
Loss and LAE reserves	1,054.3		2,025.0		—		—					—		3,079.3
Liabilities held for sale	1,880.1		—		—		—					—		1,880.1
Total liabilities	4,083.9		3,414.5		68.9		19.7					159.9		7,746.9
Total White Mountains’s common shareholders’ equity	830.6		1,459.6		589.5		—					1,025.8		3,905.5
Non-controlling interest	276.8		250.0		16.6		(97.6		)			46.1		491.9


⁽¹⁾	BAM manages its affairs on a statutory accounting basis. BAM’s statutory surplus includes surplus notes and is not reduced by accruals of interest expense on the surplus notes. BAM’s statutory surplus is reduced only after a payment of principal or interest has been approved by the New York Department of Financial Services.


⁽²⁾	BAM total assets reflect the elimination of $503.0 in surplus notes issued to HG Global and its subsidiaries, and $74.4 and $58.6 in accrued interest related to those surplus notes as of December 31, 2014 and 2013.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8981-108599

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8380-108599

Reference 6: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8933-108599

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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8844-108599

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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8984-108599

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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9031-108599

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-Name Accounting Standards Codification
-Topic 280
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9054-108599

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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8924-108599

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-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8906-108599

+ Details

Investments in Unconsolidated Affiliates

12 Months Ended

Dec. 31, 2014

Equity Method Investments and Joint Ventures [Abstract]

Investments in Unconsolidated Affiliates

White Mountains’s investments in unconsolidated affiliates represent investments in other companies in which White Mountains has a significant voting and economic interest but does not control the entity.



	December 31,
Millions	2014		2013
Symetra common shares	$	373.8	$	360.9
Unrealized gains (losses) from Symetra’s fixed maturity portfolio	37.6		(43.6		)
Carrying value of Symetra common shares	411.4		317.3

Hamer	3.0		4.1
Total investments in unconsolidated affiliates	$	414.4	$	321.4

Symetra

As of December 31, 2014 and 2013, White Mountains owned 20.05 million common shares of Symetra, a 17.31% and 17.03% common share ownership. White Mountains accounts for its investment in common shares of Symetra using the equity method. During 2014, White Mountains received cash dividends from Symetra of $34.1 million on its common share investment which is accounted for as a reduction of White Mountains’s investment in Symetra in accordance with equity accounting.

White Mountains previously owned warrants to acquire an additional 9.5 million common shares of Symetra at $11.49 per share. On June 20, 2013, White Mountains exercised these warrants in a cashless transaction and received 2.65 million common shares of Symetra in exchange for the warrants. Prior to their exercise, White Mountains accounted for its Symetra warrants as derivatives with changes in fair value recognized as a gain or loss recognized through other revenue in the income statement. White Mountains used a Black Scholes valuation model to determine the fair value of the Symetra warrants. During the six months ended June 30, 2013, White Mountains recognized a $10.8 million increase in the value of the warrants through other revenues based on the final Black Scholes valuation that was agreed upon between Symetra and White Mountains. During the six months ended June 30, 2013, White Mountains also received $1.5 million of dividends from Symetra on the warrants that were recorded in net investment income.

As of December 31, 2011, White Mountains concluded that its investment in Symetra common shares was other-than-temporarily impaired and wrote down the GAAP book value of the investment to its estimated fair value of $261.0 million or $15 per share. This impairment resulted in a basis difference between the GAAP carrying value of White Mountains’s investment in Symetra common shares and the amount derived by multiplying the percentage of White Mountains common share ownership by Symetra’s total GAAP equity. White Mountains recorded $45.9 million of after-tax equity in losses of unconsolidated affiliates and $136.6 million of after-tax equity in net unrealized losses of unconsolidated affiliates.

During 2013, Symetra repurchased 6.6 million of its common shares at an average price of $13.44. The net effect of Symetra’s share repurchases and the warrant exercises described above resulted in an additional basis difference between the GAAP carrying value of White Mountains’s investment in Symetra common shares and the amount derived by multiplying the percentage of White Mountains’s common share ownership by Symetra’s total GAAP equity. This basis difference totaled $19.3 million, of which $0.4 million was attributable to equity in earnings of unconsolidated affiliates and $18.9 million was attributable to equity in net unrealized gains of unconsolidated affiliates.

During 2014, further repurchases by Symetra of its common shares resulted in an additional basis difference between the GAAP carrying value of White Mountains’s investment in Symetra common shares and the amount derived by multiplying the percentage of White Mountains’s common share ownership by Symetra’s total GAAP equity. This basis difference totaled $2.4 million, of which $0.5 million was attributable to equity in earnings of unconsolidated affiliates and $1.9 million was attributable to equity in net unrealized gains of affiliates.

As a result of the various basis adjustments, White Mountains’s carrying value of its investment in Symetra differs from the carrying value by applying its ownership share against Symetra’s GAAP equity as normally done under the equity method. The pre-tax basis differences are being amortized over a 30-year period with a weighted average 28-years remaining. The amortization is based on estimated future cash flows associated with Symetra’s underlying assets and liabilities to which the basis differences have been attributed. White Mountains continues to record its equity in Symetra's earnings and net unrealized gains (losses). In addition, White Mountains recognizes the amortization of the basis differences through equity in earnings of unconsolidated affiliates and equity in net unrealized gains (losses) from investments in unconsolidated affiliates consistent with the original attribution of the basis differences between equity in earnings and equity in net unrealized gains (losses). For the year ended December 31, 2014, White Mountains recognized after-tax amortization of $2.8 million through equity in earnings of unconsolidated affiliates and $11.7 million through equity in net unrealized gains from investments in unconsolidated affiliates. As of December 31, 2014, the pre-tax unamortized basis difference was $170.4 million, of which $36.4 million is attributable to equity in earnings of unconsolidated affiliates and $134.0 million is attributable to equity in net unrealized gains of unconsolidated affiliates. Management does not believe that the investment in Symetra’s common shares is other-than-temporarily impaired as of December 31, 2014.

The following table summarizes amounts recorded by White Mountains relating to its investment in Symetra:



Millions	Common shares			Warrants			Total
Carrying value of investment in Symetra as of December 31, 2011⁽²⁾	$	261.0		$	12.6		$	273.6
Equity in earnings^(1)(3)(6)	32.3			—			32.3
Equity in net unrealized gains from Symetra’s fixed maturity portfolio⁽⁴⁾⁽⁵⁾	62.8			—			62.8
Dividends received	(4.9		)	—			(4.9		)
Increase in value of warrants	—			17.7			17.7
Carrying value of investment in Symetra as of December 31, 2012⁽²⁾	351.2			30.3			381.5
Equity in earnings^(1)(3)(6)	37.8			—			37.8
Equity in net unrealized losses from Symetra’s fixed maturity portfolio⁽⁴⁾⁽⁵⁾	(106.4		)	—			(106.4		)
Dividends received	(6.4		)	—			(6.4		)
Increase in value of warrants	—			10.8			10.8
Exercise of warrants	41.1			(41.1		)	—
Carrying value of investment in Symetra as of December 31, 2013⁽²⁾	317.3			—			317.3
Equity in earnings^(1)(3)(6)	47.0			—			47.0
Equity in net unrealized gains from Symetra’s fixed maturity portfolio⁽⁴⁾⁽⁵⁾	81.2			—			81.2
Dividends received	(34.1		)	—			(34.1		)
Carrying value of investment in Symetra as of December 31, 2014⁽²⁾⁽⁷⁾	$	411.4		$	—		$	411.4


⁽¹⁾	Equity in earnings for the years ended December 31, 2014, 2013 and 2012 excludes tax expense of $3.3, $2.8, and $2.6


⁽²⁾	Includes White Mountains’s equity in net unrealized gains (losses) from Symetra’s fixed maturity portfolio of $37.6, $(43.6), and $62.8 as of December 31, 2014, 2013 and 2012, which excludes tax (expense) benefit of $(2.7), $3.2 and $(5.1)


⁽³⁾	Equity in earnings for the years ended December 31, 2014, 2013 and 2012 includes $3.0, $3.0 and $3.5 increases relating to the pre-tax amortization of the Symetra common share basis difference.


⁽⁴⁾	Net unrealized gains for the years ended December 31, 2014, 2013 and 2012 includes $12.7, $11.8 and $13.1 increases relating to the pre-tax amortization of the Symetra common share basis difference.


⁽⁵⁾	Net unrealized gains (losses) from Symetra’s fixed maturity portfolio excludes tax (expense) benefit of $(5.9), $8.3 and $(5.1) for the years ended December 31, 2014, 2013 and 2012.


⁽⁶⁾	Equity in earnings for the years ended December 31, 2014, 2013 and 2012 includes $(0.1), $0.2, and $1.3 (gain) loss from the dilutive effect of Symetra’s yearly dividend and the issuance of restricted shares by Symetra


⁽⁷⁾	The aggregate value of White Mountains’s investment in common shares of Symetra was $462.1 based upon the quoted market price of $23.05 per share as of December 31, 2014.

The following table summarizes financial information for Symetra as of December 31, 2014 and 2013:



	December 31,
Millions	2014		2013
Symetra balance sheet data:
Total investments	$	30,634.3	$	27,901.1
Separate account assets	949.8		978.4
Total assets	32,994.2		30,129.5
Policyholder liabilities	27,276.0		25,328.8
Long-term debt	697.2		449.5
Separate account liabilities	949.8		978.4
Total liabilities	29,633.6		27,187.6
Common shareholders’ equity	3,360.6		2,941.9

The following table summarizes financial information for Symetra for the years ended December 31, 2014, 2013 and 2012:



	Years ended December 31,
Millions	2014		2013			2012
Symetra income statement data:
Net premiums earned	$	629.1	$	627.2		$	605.0
Net investment income	1,320.5		1,285.0			1,275.2
Total revenues	2,182.3		2,103.9			2,101.2
Policy benefits	1,399.6		1,394.9			1,371.8
Total expenses	1,882.4		1,865.3			1,831.1
Net income	254.4		220.7			205.4
Comprehensive net income (loss)	397.0		(777.6		)	549.3

Hamer and Bri-Mar

White Mountains received equity interests in Hamer and Bri-Mar, two small manufacturing companies distributed to White Mountains in connection with the dissolution of the Tuckerman Capital, LP fund (see Note 18). Effective October 1, 2012, these investments are accounted for under the equity method. For the years ended December 31, 2014, 2013 and 2012, White Mountains recorded equity in earnings of $1.9 million, $0.9 million and $0.4 million for Hamer. For December 31, 2014 and 2013, White Mountains also received $3.0 million and $0.8 million of cash dividends from Hamer. As of December 31, 2014, White Mountains’s investments in Hamer was $3.0 million.

On October 10, 2013, White Mountains sold its interest in Bri-Mar under an asset purchase agreement. For the year ended December 31, 2013, White Mountains recorded $1.1 million of cash proceeds from the sale and a $1.7 million loss on sale. Prior to the sale, White Mountains recorded equity in earnings of $0.9 million for Bri-Mar for the nine months ended September 30, 2013. White Mountains did not have any equity in earnings for Bri-Mar for the year ended December 31, 2012.

Pentelia

White Mountains obtained an equity interest of 33% in Pentelia Capital Management (“PCM”) for $1.6 million in April 2007. This investment is accounted for under the equity method. During the years ended December 31, 2013 and 2012, White Mountains recorded $0.1 million and $(1.3) million of equity in earnings in PCM. During the year ended December 31, 2013, White Mountains received $.4 million of cash dividends from PCM which liquidated White Mountains equity interest.

Variable Interest Entities	12 Months Ended
Variable Interest Entities	Dec. 31, 2014
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Variable Interest Entities	Variable Interest Entities BAM As a mutual insurance company, BAM is owned by its members and a portion of each member’s policy payments represents a contribution to member’s surplus. During 2012, White Mountains capitalized HG Global to fund BAM through the purchase of $503.0 million of BAM Surplus Notes. The equity at risk funded by BAM’s members is not sufficient to fund its operations without the additional subordinated financial support provided by the BAM Surplus Notes and accordingly, BAM is considered to be a VIE. BAM and HG Global, through its wholly-owned subsidiary, HG Re, entered into a first loss reinsurance treaty (“FLRT”), under which HG Re will provide first loss protection up to 15% of par outstanding on each bond insured by BAM in exchange for 60% of the premium, net of a ceding commission, charged by BAM. HG Re’s obligations under the FLRT are satisfied by the assets in two collateral trusts: a Regulation 114 Trust and a Supplemental Trust. Losses required to be reimbursed to BAM by HG Re are subject to an aggregate limit equal to the assets held in the collateral trusts at any point in time. In addition, HG Global has the right to designate two directors for election to BAM’s board of directors. White Mountains is required to consolidate the results of BAM. Since BAM is owned by its members, its equity and results of operations are included in non-controlling interests. Reciprocals Reciprocals are policyholder-owned insurance carriers organized as unincorporated associations. Each policyholder insured by the reciprocal shares risk with the other policyholders. Policyholders share profits and losses in the same proportion as the amount of insurance purchased but are not subject to assessment for net losses of the reciprocal. Houston General Insurance Exchange Houston General Management Company, a wholly-owned indirect subsidiary of OneBeacon provides management services for a fee to a reciprocal, Houston General Insurance Exchange (“HGIE”). As of December 31, 2014, OneBeacon holds a surplus note issued by HGIE, the remaining balance of which is $4.0 million as of December 31, 2014. The principal and interest on the surplus note is repayable to OneBeacon only with regulatory approval. The obligation to repay principal on the note is subordinated to all other liabilities including obligations to policyholders and claimants for benefits under insurance policies. OneBeacon has no ownership interest in the reciprocal. OneBeacon has determined that HGIE qualifies as a VIE. Furthermore, OneBeacon has determined that it is the primary beneficiary as a result of the management services provided to the reciprocal and the funds loaned to it. Accordingly, OneBeacon consolidates HGIE. As of December 31, 2014 and 2013, consolidated amounts related to HGIE included total assets of $2.4 million and $2.6 million and total liabilities of $4.0 million and $4.2 million. As of December 31, 2014, the net amount of capital at risk is equal to the surplus note of $4.0 million less the accumulated losses of $1.8 million which includes accrued interest on the surplus note of $0.2 million that eliminates in consolidation. Star & Shield Insurance Exchange Star & Shield Risk Management LLC, a wholly-owned indirect subsidiary of White Mountains provides management and other services for a fee to a reciprocal, Star & Shield Insurance Exchange (“SSIE”). As of December 31, 2014, White Mountains held $17.0 million of surplus notes issued by SSIE. The principal and interest on the surplus notes are repayable to White Mountains only with regulatory approval. The obligation to repay principal on the note is subordinated to all other liabilities including obligations to policyholders and claimants for benefits under insurance policies. Because SSIE is consolidated in White Mountains’s financial statements, the SSIE Surplus Notes and accrued interest are classified as intercompany notes, carried at face value and eliminated in consolidation. White Mountains has no ownership interest in SSIE. White Mountains has determined that SSIE qualifies as a VIE. Furthermore, White Mountains has determined that it is the primary beneficiary as a result of the management services provided to the reciprocal and the funds loaned to it. Accordingly, White Mountains consolidates SSIE. As of December 31, 2014, consolidated amounts related to SSIE included total assets of $13.5 million and total liabilities of $25.9 million. As of December 31, 2014, the net amount of capital at risk is equal to the surplus notes of $17.0 million less the accumulated losses of $12.4 million. Prospector Funds White Mountains determined that the Prospector Offshore Fund, Ltd. and Prospector Turtle Fund, Ltd. (collectively, the “Prospector Funds”) are VIEs for which White Mountains is the primary beneficiary and is required to consolidate. In 2014, White Mountains redeemed its interest in the Prospector Turtle Fund. As of December 31, 2014 and 2013, White Mountains consolidated total assets of $135.8 million and $249.2 million and total liabilities of $39.8 million and $90.6 million of the Prospector Funds. In addition, as of December 31, 2014 and 2013, White Mountains recorded non-controlling interest of $31.1 million and $46.2 million in the Prospector Funds. For the years ended December 31, 2014, 2013 and 2012, White Mountains recorded $5.6 million, $14.5 million, and $9.3 million of income and $1.9 million, $4.0 million and $2.7 million of non-controlling interest income related to the Prospector Funds. As of December 31, 2014, the net amount of capital at risk is equal to White Mountains’s investment in Prospector Offshore Fund of $64.9 million, which represents White Mountains’s ownership interest of 67.6% in the Prospector Offshore Fund. TaClaro In 2013, White Mountains invested $3.0 million in the convertible preferred shares of TaClaro Holdings B.V. (“TaClaro”), representing a 27% ownership interest on a fully converted basis. TaClaro owns TaCerto.com, a Brazilian online insurance broker. During 2014, White Mountains invested an additional $1.5 million in the convertible preferred shares, increasing the ownership percentage to 39% on a fully converted basis. Also, during 2014, in connection with a restructuring of TaClaro’s equity ownership, White Mountains invested an additional $2.0 million comprising of $1.7 million in loans and $0.3 million in common shares. As of December 31, 2014, White Mountains holds a 49% ownership share on a fully converted basis. The investments in TaClaro are included within other long term investments (see Note 5). White Mountains has determined that TaClaro is a VIE but White Mountains is not the primary beneficiary because it does not have the power to direct the activities of TaClaro that most significantly impact the entity’s economic performance. White Mountains’s exposure to loss is limited to the carrying value of its investments in TaClaro. Tranzutary White Mountains holds a 36.0% ownership interest in Tranzutary Holdings LLC (“Tranzutary”) through its investment in Tranzact Holdings. Tranzact Holdings has entered into a services agreement under which it manages the day-to-day operations of Tranzutary for a fee. White Mountains has determined that Tranzutary is a VIE. Further, White Mountains has determined that Tranzact Holdings is the primary beneficiary as a result of the services provided and Tranzact Holdings’s ownership interest in Tranzutary. As of December 31, 2014, consolidated amounts related to Tranzutary included total assets of $29.6 million, which includes other intangible assets of $28.9 million, and total liabilities of $4.1 million. Tuckerman Fund I, Hamer and Bri-Mar On December 31, 2011, the Tuckerman Capital, LP fund (“Tuckerman Fund I”) was dissolved and all of the net assets of the fund were distributed to the owners of the fund, of which White Mountains owned approximately 94%. In conjunction with the dissolution, White Mountains received a portion of the shares of Hamer and Bri-Mar, two small manufacturing companies that were owned by the Tuckerman Fund I. The consolidated results of Hamer and Bri-Mar are included in the Other Operations segment from January 1, 2012 through September 30, 2012, at which point the results of these companies were no longer consolidated by White Mountains. Prior to the dissolution, White Mountains had determined that Tuckerman Fund I was a VIE for which White Mountains was the primary beneficiary and was required to consolidate Tuckerman Fund I.

Fair Value of Financial Instruments

12 Months Ended

Dec. 31, 2014

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

White Mountains accounts for its financial instruments at fair value with the exception of the OBH Senior Notes and the SIG Senior Notes, which are recorded as debt liabilities at face value less unamortized original issue discount, and the SIG Preference Shares, which are recorded as non-controlling interest at face value.

The following table summarizes the fair value and book value of financial instruments as of December 31, 2014 and 2013:



	December 31, 2014				December 31, 2013
Millions	Fair Value		Carrying Value		Fair Value		Carrying Value
OBH Senior Notes	$	286.0	$	274.7	$	269.8	$	274.7
SIG Senior Notes	437.8		399.7		438.1		399.6
SIG Preference Shares	260.0		250.0		260.0		250.0

The fair value estimate for the OBH Senior Notes has been determined using quoted market prices. The OBH Senior Notes are considered a Level 2 measurement based upon the volume and frequency of observable transactions. The fair value estimates for the SIG Senior Notes and the SIG Preference Shares have been determined based on indicative broker quotes and are considered to be Level 3 measurements.

The Tranzact Bank Facility is a recently issued variable rate instrument. As a result it is considered a Level 2 measurement. As of December 31, 2014, the carrying value of the amount drawn on the Tranzact Debt Facility approximates fair value.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Transactions with Related Persons	12 Months Ended
Transactions with Related Persons	Dec. 31, 2014
Related Party Transactions [Abstract]
Transactions with Related Persons	Transactions with Related Persons Prospector Mr. John Gillespie, a director of White Mountains, is the founder and Managing Member of Prospector. Prospector serves as a discretionary adviser with respect to specified assets, primarily common equity securities and convertible fixed maturity investments, managed directly or through WM Advisors on behalf of White Mountains and other clients of WM Advisors. Pursuant to an investment management agreement with WM Advisors (the “WMA Agreement”), Prospector charges WM Advisors fees based on the following schedule: 100 basis points on the first $200.0 million of assets under management; 50 basis points on the next $200.0 million and 25 basis points on amounts over $400.0 million. As of December 31, 2014, Prospector managed a total of $195.7 million of assets for White Mountains (excluding OneBeacon and Symetra) under this arrangement. Prospector has a separate investment management agreement with Symetra that began on July 1, 2010. Until that date, Symetra was a party to the WMA Agreement and subject to the above fee schedule. Prospector has separate investment management agreements with OneBeacon (the “OneBeacon Agreements”) pursuant to which Prospector supervises and directs specified assets, primarily common equity securities and convertible fixed maturity investments, including assets in OneBeacon’s defined benefit and defined contribution plans (the “ERISA Assets”). All assets managed under the OneBeacon Agreements are subject to a single fee schedule that is substantially similar to the terms of the WMA Agreement fee schedule. As of December 31, 2014, Prospector managed $431.2 million of assets for OneBeacon under this arrangement, including $202.9 million of ERISA Assets. During 2014, 2013 and 2012, Prospector earned $6.5 million, $6.5 million, and $6.4 million in total fees pursuant to the WMA Agreement and the OneBeacon Agreements. Prospector also advises White Mountains on matters including capital management, asset allocation, private equity investments and mergers and acquisitions. Pursuant to a Consulting Agreement for those services, Prospector was granted 6,250 performance shares for the 2015-2017 cycle, 6,250 performance shares for the 2014-2016 cycle and 7,000 performance shares for the 2013-2015 cycle. In accordance with the terms of the WTM Incentive Plan, performance against target governing the performance shares will be confirmed by the Compensation Committee of the Board following the end of each performance cycle and the number of performance shares actually awarded at that time will range from 0% to 200% of the target number granted. Based on the Company’s performance, Prospector received 145.5% of the 7,750 performance shares granted for the 2012-2014 performance cycle for a total payout of $7.5 million. Unless and until the Consulting Agreement has been terminated, and subject to the approval of the Compensation Committee, at the beginning of each performance cycle Prospector is to be granted performance shares with a value of approximately $4.5 million. The Compensation Committee establishes the performance target for such performance shares. Pursuant to a revenue sharing agreement, Prospector has agreed to pay White Mountains 6% of the revenues in excess of $500,000 of certain of Prospector’s funds in return for White Mountains having made a founding investment in 1997. During 2014, 2013 and 2012, White Mountains earned $0.4 million, $0.9 million, and $0.5 million under this arrangement. As of December 31, 2014, White Mountains had $82.4 million invested in limited partnership investment interests managed by Prospector (the “Funds”). This total includes $15.8 million of OneBeacon assets. Under the limited partnership agreements, Prospector serves as general partner and general manager of the Funds and is paid management and incentive performance fees by White Mountains and OneBeacon. For the years ended December 31, 2014, 2013 and 2012, White Mountains and OneBeacon incurred $1.1 million, $1.3 million and $1.1 million in management fees and $0.7 million, $3.2 million and $1.3 million in incentive fees. Oakum Bay Capital Mr. Kernan Oberting, a Managing Director of White Mountains Capital and President of Sirius Capital Markets, founded Oakum Bay Capital (“OBC”). OBC serves as the general manager and owns general partnership interests in KVO Capital Partners (“KCP”) and the Trimarc Capital Fund (“TCF”) hedge funds. In connection with Mr. Oberting commencing employment with White Mountains Capital, on July 16, 2012, White Mountains purchased $2.0 million of preferred stock and received 7.5% of the common equity of OBC. After giving effect to the White Mountains’s investment, Mr. Oberting and his family beneficially owned 67.5% of the common equity of OBC. During 2013, Mr. Oberting and his family assigned all of their common equity interests to unaffiliated OBC management with effect from January 1, 2013. In September 2013, White Mountains exchanged its preferred stock and common equity interest in OBC for $500,000 in cash and a portion of OBC’s revenue for the next ten years. As of December 31, 2014, White Mountains investment in TCF was $7.8 million. Mr. Oberting is a limited partner in KCP and TCF. Mr. Barrette had a limited partnership investment in KCP that was redeemed in full in September 2012. For the year ended December 31, 2013, White Mountains paid investment management fees $0.1 million to OBC. Other Relationships and Transactions WM Advisors provides investment advisory and management services to Symetra. As of December 31, 2014 and 2013, WMA had $30.9 billion and $27.8 billion of assets under management from Symetra. During 2014, 2013 and 2012, WMA earned $18.4 million, $16.5 million and $15.9 million in fees from Symetra. On March 15, 2013, the Company repurchased 140,000 WTM common shares from the estate of John J. Byrne, a beneficial owner of the Company. The price per share was $563.57, the market price at the time the agreement was reached.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References + Details

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies White Mountains leases certain office space under non-cancellable operating leases that expire on various dates through 2021. Rental expense for all of White Mountains’s locations was $19.4 million, $20.2 million and $18.8 million for the years ended December 31, 2014, 2013 and 2012. White Mountains also has various other lease obligations that are immaterial in the aggregate. White Mountains’s future annual minimum rental payments required under non-cancellable leases, which are primarily for office space, are $16.5 million, $15.2 million, $13.6 million, and $54.7 million for 2015, 2016, 2017 and 2018 and thereafter, respectively. White Mountains also has future binding commitments to fund certain other-long term investments. These commitments, which total $81.7 million, do not have fixed funding dates. Capital Lease In December 2011, OneBeacon sold the majority of its fixed assets and capitalized software. OneBeacon entered into lease financing arrangements with US Bancorp and Fifth Third whereby OneBeacon sold furniture and equipment and capitalized software, respectively, at a cost equal to net book value. OneBeacon then leased the fixed assets back from US Bancorp for a lease term of five years and leased the capitalized software back from Fifth Third for a lease term of four years. OneBeacon received cash proceeds of $23.1 million as a result of entering into the sale-leaseback transactions. At the end of the lease terms, OneBeacon will have the obligation to purchase the leased assets for a nominal fee, after which all rights, title and interest would transfer back. In accordance with ASC 840, OBIC recorded the sale of the assets with no gain or loss recognized while OB Services has recorded a capital lease obligation and a capital lease asset. As of December 31, 2014 and 2013, OneBeacon had a capital lease obligation of $7.1 million and $12.5 million, respectively, included within other liabilities and a capital lease asset of $7.0 million and $10.9 million included within other assets. The underlying assets will continue to be depreciated over their respective useful lives. OneBeacon’s future annual minimum rental payments are $5.3 million for the year ended December 31, 2015 and $1.8 million for the year ended December 31, 2016. Assigned Risks As a condition of its license to do business in certain states, White Mountains’s insurance operations are required to participate in mandatory shared market mechanisms. Each state dictates the types of insurance and the level of coverage that must be provided. The total amount of business an insurer is required to accept is based on its market share of voluntary business in the state. In certain cases, White Mountains is obligated to write business from mandatory shared market mechanisms at some time in the future based on the market share of voluntary policies it is currently writing. Underwriting results related to assigned risk plans are typically adverse and are not subject to the predictability associated with White Mountains’s voluntarily written business. Under existing guaranty fund laws in all states, insurers licensed to do business in those states can be assessed for certain obligations of insolvent insurance companies to policyholders and claimants. White Mountains accrues any significant insolvencies when the loss is probable and the assessment amount can be reasonably estimated. The actual amount of such assessments will depend upon the final outcome of rehabilitation proceedings and will be paid over several years. As of December 31, 2014, the reserve for such assessments totaled $11.9 million. Legal Contingencies White Mountains, and the insurance and reinsurance industry in general, are routinely subject to claims related litigation and arbitration in the normal course of business, as well as litigation and arbitration that do not arise from, or are directly related to, claims activity. White Mountains’s estimates of the costs of settling matters routinely encountered in claims activity are reflected in the reserves for unpaid loss and LAE. See Note 3. White Mountains considers the requirements of ASC 450 when evaluating its exposure to non-claims related litigation and arbitration. ASC 450 requires that accruals be established for litigation and arbitration if it is probable that a loss has been incurred and it can be reasonably estimated. ASC 450 also requires that litigation and arbitration be disclosed if it is probable that a loss has been incurred or it there is a reasonable possibility that a loss may have been incurred. Although the ultimate outcome of claims and non-claims related litigation and arbitration, and the amount or range of potential loss at any particular time, is often inherently uncertain, management does not believe that the ultimate outcome of such claims and non-claims related litigation and arbitration will have a material adverse effect on White Mountains’s financial condition, results of operations or cash flows. The following summarizes significant legal contingencies, ongoing non-claims related litigation or arbitration as of December 31, 2014: Esurance On October 7, 2011, the Company completed the sale of its Esurance and Answer Financial subsidiaries (the “Transferred Subsidiaries”) to Allstate pursuant to a Stock Purchase Agreement dated as of May 17, 2011 (filed as an exhibit to the Company’s current report on Form 8-K on May 18, 2011, the “Agreement”). The Company has certain contingencies under the Agreement as follows: (i) subject to specified thresholds and limits, the Company generally indemnifies Allstate for breaches of its representations and warranties in the Agreement for a period of eighteen months (although longer for specified representations and warranties) from the closing, (ii) the Company indemnifies Allstate for breaches of certain covenants in the Agreement, including certain agreements by the Company not to solicit certain employees of the Transferred Subsidiaries for three years after the closing, and (iii) subject to specified thresholds and limits, the Company indemnifies Allstate for specified matters related to the pre-closing period, including (a) specified litigation matters, (b) losses of the Transferred Subsidiaries arising from extra-contractual claims and claims in excess of policy limits (“ECO/EPL losses”), (c) certain corporate reorganizations effected to remove entities from the Transferred Subsidiaries that were not being sold in the transaction, and (d) certain tax matters, including certain net operating losses being less than stated levels. In addition, the Company retains 90% of positive or negative development in the loss reserves of the Transferred Subsidiaries as of the closing date (net of ECO/EPL losses) through December 31, 2014. Runoff Transaction Subsequent to the closing of the Runoff Transaction, on January 22, 2015, three holders of insurance policies issued by the companies OneBeacon sold to Armour filed a Petition for Review with the Commonwealth Court of Pennsylvania (“Commonwealth Court”) requesting that the Commonwealth Court vacate the Pennsylvania Insurance Department’s (“PID”) orders approving the Runoff Transaction and denying their right to intervene in the PID’s regulatory review of the Runoff Transaction. White Mountains believes the claims made by the petitioners are without merit and intends to intervene in the proceedings before the Commonwealth Court to vigorously defend the propriety of the PID’s orders in their entirety. White Mountains believes that the possibility is remote that these proceedings could result in an adverse outcome or have a material financial impact on the Company’s results of operations or financial position in the future. Tribune Company In June 2011, Deutsche Bank Trust Company Americas, Law Debenture Company of New York and Wilmington Trust Company (collectively referred to as “Plaintiffs”), in their capacity as trustees for certain senior notes issued by the Tribune Company (“Tribune”), filed lawsuits in various jurisdictions (the “Noteholder Actions”) against numerous defendants including OneBeacon, OneBeacon-sponsored benefit plans and other affiliates of White Mountains in their capacity as former shareholders of Tribune seeking recovery of the proceeds from the sale of common stock of Tribune in connection with Tribune's leveraged buyout in 2007 (the “LBO”). Tribune filed for bankruptcy in 2008 in the Delaware bankruptcy court (the “Bankruptcy Court”). The Bankruptcy Court granted Plaintiffs permission to commence these LBO-related actions, and in 2011, the Judicial Panel on Multidistrict Litigation granted a motion to consolidate the actions for pretrial matters and transferred all such proceedings to the United States District Court for the Southern District of New York. Plaintiffs seek recovery of the proceeds received by the former Tribune shareholders on a theory of constructive fraudulent transfer asserting that Tribune purchased or repurchased its common shares without receiving fair consideration at a time when it was, or as a result of the purchases of shares, was rendered, insolvent. OneBeacon has entered into a joint defense agreement with other affiliates of White Mountains that are defendants in the action. Certain subsidiaries of White Mountains received approximately $39.0 million for Tribune common stock tendered in connection with the LBO. The Court granted an omnibus motion to dismiss the Noteholder Actions in September 2013 and Plaintiffs’ appeal is pending. In addition, OneBeacon, OneBeacon-sponsored benefit plans and other affiliates of White Mountains in their capacity as former shareholders of Tribune, along with thousands of former Tribune shareholders, have been named as defendants in an adversary proceeding brought by the Official Committee of Unsecured Creditors of the Tribune Company (the “Committee”), on behalf of the Tribune Company, which seeks to avoid the repurchase of shares by Tribune in the LBO on a theory of intentional fraudulent transfer (the “Committee Action”). Tribune emerged from bankruptcy in 2012, and a litigation trustee replaced the Committee as plaintiff in the Committee Action. This matter was consolidated for pretrial matters with the Noteholder Actions in the United States District Court for the Southern District of New York and was stayed pending the motion to dismiss in the Noteholder Action. An omnibus motion to dismiss the shareholder defendants in the Committee Action was filed in May 2014. No amount has been accrued in connection with this matter as of December 31, 2014, as the amount of loss, if any, cannot be reasonably estimated.

Discontinued Operations

12 Months Ended

Dec. 31, 2014

Discontinued Operations and Disposal Groups [Abstract]

Discontinued Operations

During 2014, White Mountains recorded a net loss on sale of discontinued operations of $1.6 million and a net loss from discontinued operations of $1.8 million. The net loss on sale of discontinued operations included a $18.8 million loss at OneBeacon on the Runoff Transaction, which included a $23.5 million after-tax loss from the change in the estimated value of the surplus notes issued with the Runoff Transaction, partially offset by a $4.8 million after-tax reduction in the loss on sale from the Runoff Transaction related to the change in the treatment of the $7.4 million pre-tax reserve charge recorded during the second quarter of 2013 (as described below). Previously, OneBeacon expected that the Runoff SPA would be amended to provide for the transfer of $7.4 million of additional assets to support the reserve charge. The Runoff SPA was instead revised to increase the cap on seller financing. The $18.8 million net loss on sale recorded in 2014 from the Runoff Transaction was partially offset by a $13.9 million gain from a payment received from Allianz, the purchaser of White Mountains’s former subsidiary Fireman’s Fund Insurance Company (“FFIC”), related to the utilization of alternative minimum tax credits associated with the tax loss on the sale of FFIC in 1991 and a $3.2 million gain from an interim payment from Allstate that primarily related to the favorable development on loss reserves transferred in the sale of Esurance and Answer Financial. The $1.8 million net loss from discontinued operations in 2014 related entirely to the Runoff Business.

During 2013, White Mountains recorded a net gain on sale of discontinued operations of $46.6 million and a net loss from discontinued operations of $42.1 million. During 2013, OneBeacon recorded a $78.9 million pre-tax loss and LAE provision for the Runoff Business. This reserve charge included a $7.4 million increase in loss and LAE reserves recorded in the second quarter of 2013, which partially offset $7.8 million of other revenue associated with a settlement award in the second quarter of 2013 in the Safeco v. American International Group, Inc. (“AIG”) class action related to AIG's alleged underreporting of workers' compensation premiums to the National Workers’ Compensation Reinsurance Pool. The net $71.5 million pre-tax ($46.5 million after-tax) of net losses from discontinued operations were fully offset by a $46.6 million after-tax reduction in the loss on sale of discontinued operations, as prescribed by the terms of the Runoff SPA, which stated that the buyer assumed the risk that loss and LAE reserves develop unfavorably from September 30, 2012 onward.

During 2012, White Mountains recorded a net loss from discontinued operations of $24.0 million and a net loss on sale of discontinued operations of $91.5 million, substantially all of which related to the Runoff Transaction and the results of the Runoff Business.

Runoff Transaction

As part of closing the Runoff Transaction on December 23, 2014, OneBeacon provided financing in the form of surplus notes with a par value of $101.0 million issued by OneBeacon Insurance Company (“OBIC”), one of the entities that were transferred from OneBeacon to Armour as part of the transaction (the “OBIC Surplus Notes”). At closing, the OBIC Surplus Notes had a fair value of $64.9 million, based on a discounted cash flow model, resulting in a total valuation adjustment of $36.1 million pre-tax ($23.5 million after-tax) included in loss from sale of discontinued operations. Subsequent to closing, the OBIC Surplus Notes are included in OneBeacon’s investment portfolio, categorized within other long-term investments, and subsequent changes in value thereon will be reflected in continuing operations. The fair value of the OBIC Surplus Notes did not materially change as of December 31, 2014.

AutoOne

On February 22, 2012, OneBeacon completed the sale of the AutoOne business to Interboro, which included the execution of a reinsurance agreement with certain subsidiaries of the Company pursuant to which OneBeacon cedes, on a 100% quota share basis, legacy AutoOne business not directly written by transferred entities.

During the year ended December 31, 2012, OneBeacon and Interboro reached conclusion on post-closing adjustments to the closing balance sheet resulting in OneBeacon recording a net gain of $0.5 million after tax, reflecting a true up of the estimated loss on sale of AutoOne.

Surplus Notes

In the fourth quarter of 2014, in conjunction with the Runoff Transaction, OneBeacon provided financing in the form of surplus notes with a par value of $101.0 million, which had a fair value of $64.9 million at the date of closing and as of December 31, 2014. The OBIC Surplus Notes, issued by one of the transferred entities, OBIC (“Issuer”), were in the form of both seller priority and pari passu notes.

Under the contractual terms of both the seller priority and pari passu notes, scheduled interest payments accrue at 6.0% until the scheduled maturity date of March 15, 2020 and at a floating interest rate thereafter, should any principal remain outstanding. All interest and principal due on the seller priority note must first be paid before any interest or principal can be paid on the pari passu note. As required by the PID, interest on the notes does not compound. The notes restrict the Issuer’s ability to make distributions to holders of its equity interest. All such distributions are prohibited while the seller priority note is outstanding, and while the pari passu note is outstanding, distributions are permitted only if the Issuer concurrently repays a pro rata amount of any outstanding principal on the pari passu note.

Pursuant to the notes, the Issuer shall seek to redeem the notes annually each March 15 at a requested redemption amount such that the Issuer’s total adjusted capital following the proposed redemption payment would equal 200% of the Issuer’s “authorized control level RBC”, as such term is defined by the insurance laws of the Commonwealth of Pennsylvania and as prescribed by the PID. All redemptions or repayments of principal and payments of interest on the notes are subject to approval by the PID.

Below is a table illustrating the valuation adjustments taken to arrive at the estimated fair value of the OBIC Surplus Notes as of December 31, 2014:



	Type of Surplus Note
Millions	Seller Priority			Pari Passu			Total
Par Value	$	57.9		$	43.1		$	101.0
Fair value adjustments to reflect:
Current market rates on public debt and contract-based repayments⁽¹⁾	1.6			(8.2		)	(6.6		)
Regulatory approval ⁽²⁾	(4.6		)	(8.0		)	(12.6		)
Liquidity adjustment ⁽³⁾	(11.0		)	(5.7		)	(16.7		)
Total adjustments	(14.0		)	(21.9		)	(35.9		)
Fair value	$	43.9		$	21.2		$	65.1


⁽¹⁾	Represents the value of the OBIC Surplus Notes, at current market yields on publicly traded debt, and assuming issuer is allowed to make principal and interest payments when its financial capacity is available, as measured by statutory capital in excess of a 250% RBC score.


⁽²⁾	Represents anticipated delay in securing regulatory approvals of interest and principal payments to reflect graduated changes in Issuer’s statutory surplus.


⁽³⁾	Represents impact of liquidity spread to account for OneBeacon’s sole ownership of the surplus notes, lack of a trading market and ongoing regulatory approval risk.

The internal valuation model used to estimate the fair value is based on discounted expected cash flows. The estimated fair value of the OBIC Surplus Notes is sensitive to changes in treasury rates and public debt credit spreads, as well as changes in estimates with respect to other variables including a discount to reflect the private nature of the notes (and the related lack of liquidity), the credit quality of the notes - based on the financial performance of the Issuer relative to expectations, and the timing, amount, and likelihood of interest and principal payments on the notes, which are subject to regulatory approval and therefore may vary from the contractual terms. OneBeacon has assumed for estimating the fair value that interest payouts begin in year five and principal repayments begin on a graduating basis in year ten. Although these variables involve considerable judgment, the Company does not currently expect any resulting changes in the estimated value of the surplus notes to be material to its financial position.

Summary of Reclassified Balances and Related Items

As of December 31, 2013, the Runoff Transaction met the criteria for held for sale accounting. As a result, the assets and liabilities associated with the Runoff Transaction are presented separately as single line items in the asset and liability sections of the December 31, 2013 consolidated balance sheet, the major categories of which are summarized below.

Net Assets Held for Sale

The following summarizes the assets and liabilities associated with the businesses classified as held for sale:



	December 31,
Millions	2013
Assets held for sale
Fixed maturity investments, at fair value	$	236.3
Reinsurance recoverable on unpaid losses	1,604.7
Reinsurance recoverable on paid losses	10.7
Insurance premiums receivable	9.1
Deferred tax asset	3.3
Other assets	16.0
Total assets held for sale	$	1,880.1
Liabilities held for sale
Loss and loss adjustment expense reserves	$	1,793.1
Unearned insurance premiums	.2
Ceded reinsurance payable	12.3
Other liabilities	74.5
Total liabilities held for sale	1,880.1
Net assets held for sale	$	—

Net Income (Loss) from Discontinued Operations

The following summarizes the results of operations, including related income taxes associated with the businesses classified as discontinued operations:



	Year Ended December 31,
Millions	2014			2013			2012
Revenues
Earned insurance premiums	$	.1		$	.8		$	10.6
Other revenue	—			10.8			—
Total revenues	.1			11.6			10.6
Expenses
Loss and loss adjustment expenses	(.7		)	78.9			48.4
Insurance and reinsurance acquisition expenses	.1			—			(2.1		)
Other underwriting expenses	3.5			(.2		)	1.7
Total expenses	2.9			78.7			48.0
Pre-tax loss	(2.8		)	(67.1		)	(37.4		)
Income tax benefit	1.0			25.0			13.4
Loss from discontinued operations	(1.8		)	(42.1		)	(24.0		)
Net (loss) gain from sales of discontinued operations	(1.6		)	46.6			(91.0		)
Net (loss) income from discontinued operations	$	(3.4	)	$	4.5		$	(115.0	)

The loss from sale of discontinued operations is subject to customary post-closing adjustments related to the true-up of the closing balance sheet.

Earnings (Loss) Per Share

Basic earnings (loss) per share amounts are based on the weighted average number of common shares outstanding including unvested restricted shares that are considered participating securities. Diluted earnings (loss) per share amounts are based on the weighted average number of common shares including unvested restricted shares and the net effect of potentially dilutive common shares outstanding. The following table outlines the computation of earnings (loss) per share for discontinued operations for the years ended December 31, 2014, 2013 and 2012:



	Year Ended December 31,
	2014			2013			2012
Basic and diluted earnings (loss) per share numerators (in millions):
Net (loss) income attributable to White Mountains’s common shareholders	$	(3.4	)	$	4.5		$	(115.0	)
Allocation of income for participating unvested restricted common shares ⁽¹⁾	—			—			1.5
Net (loss) income attributable to White Mountains’s common shareholders, net of restricted common share amounts ⁽²⁾	$	(3.4	)	$	4.5		$	(113.5	)
Basic earnings (loss) per share denominators (in thousands):
Total average common shares outstanding during the period	6,104.9			6,200.4			6,799.8
Average unvested restricted common shares ⁽³⁾	(78.9		)	(91.4		)	(91.1		)
Basic earnings (loss) per share denominator	6,026.0			6,109.0			6,708.7
Diluted earnings (loss) per share denominator (in thousands):
Total average common shares outstanding during the period	6,104.9			6,200.4			6,799.8
Average unvested restricted common shares⁽³⁾	(78.9		)	(91.4		)	(91.1		)
Average outstanding dilutive options to acquire common shares⁽⁴⁾	—			—			—
Diluted earnings (loss) per share denominator	6,026.0			6,109.0			6,708.7
Basic and diluted earnings (loss) per share (in dollars):	$	(.56	)	$	0.74		$	(16.91	)


⁽¹⁾	Restricted shares issued by White Mountains contain dividend participation features, and therefore, are considered participating securities.


⁽²⁾	Net income (loss) attributable to White Mountains’s common shareholders, net of restricted share amounts, is equal to undistributed earnings for the years ended December 31, 2014, 2013 and 2012.


⁽³⁾	Restricted common shares outstanding vest either in equal annual installments or upon a stated date (see Note 13).


⁽⁴⁾	The diluted earnings (loss) per share denominator for the years ended December 31, 2014, 2013 and 2012 does not include the impact of 125,000 common shares issuable upon exercise of the non-qualified options outstanding as they are anti-dilutive to the calculation.

- Definition

The entire disclosure for the facts and circumstances leading to the completed or expected disposal, manner and timing of disposal, the gain (loss) recognized in the income statement and the income statement caption that includes that gain (loss), amounts of revenues and pretax profit or loss reported in discontinued operations, the segment in which the disposal group was reported, and the classification (whether sold or classified as held for sale) and carrying value of the assets and liabilities comprising the disposal group. Includes all disposal groups, including those classified as components of the entity (discontinued operations).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1436-107760

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1474-107760

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1510-107760

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e957-107759

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e1020-107759

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e1012-107759

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=8077374&loc=d3e2443-110228

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6391110&loc=d3e2941-110230

+ Details

Selected Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2014

Quarterly Financial Information Disclosure [Abstract]

Selected Quartely Financial Data (Unaudited)

SELECTED QUARTERLY FINANCIAL DATA

(Unaudited)

Selected quarterly financial data for 2014 and 2013 is shown in the following table. The quarterly financial data includes, in the opinion of management, all recurring adjustments necessary for a fair presentation of the results of operations for the interim periods. As a result of the Esurance Sale, AutoOne Sale and the Runoff Business sale, the results of operations for Esurance, AutoOne and the Runoff Business have been classified as discontinued operations and are now presented, net of related income taxes, as such in the statement of comprehensive income. Prior year amounts have been reclassified to conform to the current period’s presentation (see Note 22).



	2014 Three Months Ended												2013 Three Months Ended
Millions, except per share amounts	Dec. 31			Sept. 30			June 30			Mar. 31			Dec. 31			Sept. 30			June 30		Mar. 31
Revenues	$	689.7		$	589.4		$	652.8		$	578.3		$	626.6		$	574.1		$	489.3	$	627.4
Expenses	643.5			555.0			543.8			466.2			492.4			518.8			485.7		475.6
Pre-tax income	46.2			34.4			109.0			112.1			134.2			55.3			3.6		151.8
Tax benefit (expense)	8.7			(7.8		)	(23.9		)	(30.3		)	(27.4		)	(8.2		)	.6		(41.6		)
Income from continuing operations	54.9			26.6			85.1			81.8			106.8			47.1			4.2		110.2
(Loss) income from discontinued operations, net of tax	(12.2		)	6.7			2.6			(.5		)	(.3		)	.4			3.9		.5
Non-controlling interest in consolidated subsidiaries	15.0			11.2			(4.6		)	.5			(.3		)	1.1			11.1		.5
Equity in earnings of unconsolidated affiliates	12.3			7.0			12.5			13.8			11.7			8.6			7.1		9.2
Income attributable to White Mountains’s common shareholders	$	70.0		$	51.5		$	95.6		$	95.6		$	117.9		$	57.2		$	26.3	$	120.4
Income (loss) attributable to White Mountains’s common shareholders per share:
Basic
Continuing operations	$	13.71		$	7.35		$	15.10		$	15.56		$	19.14		$	9.20		$	3.62	$	19.10
Discontinued operations	(2.03		)	1.10			.43			(.08		)	(.05		)	.06			.64		.07
Total consolidated operations	$	11.68		$	8.45		$	15.53		$	15.48		$	19.09		$	9.26		$	4.26	$	19.17
Diluted
Continuing operations	$	13.71		$	7.35		$	15.10		$	15.56		$	19.14		$	9.20		$	3.62	$	19.10
Discontinued operations	(2.03		)	1.10			.43			(.08		)	(.05		)	.06			.64		.07
Total consolidated operations	$	11.68		$	8.45		$	15.53		$	15.48		$	19.09		$	9.26		$	4.26	$	19.17

SCHEDULE I SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES

12 Months Ended

Dec. 31, 2014

Summary of Investments, Other than Investments in Related Parties [Abstract]

SCHEDULE I SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES

WHITE MOUNTAINS INSURANCE GROUP, LTD.

SUMMARY OF INVESTMENTS—OTHER THAN

INVESTMENTS IN RELATED PARTIES

At December 31, 2014



Millions	Cost		Carrying Value		Fair Value
Fixed maturity investments:
Bonds:
U.S. Government and government agencies and authorities	$	184.7	$	188.1	$	188.1
Debt securities issued by corporations	2,221.3		2,311.2		2,311.2
Mortgage-backed and asset-backed securities	1,811.1		1,840.9		1,840.9
States, municipalities and political subdivisions	82.0		83.2		83.2
Foreign governments	274.6		275.1		275.1
Redeemable preferred stocks	79.6		85.8		85.8
Total fixed maturity investments	4,653.3		4,784.3		4,784.3
Short-term investments	871.7		871.7		871.7
Common equity securities:
Banks, trust and insurance companies	167.0		233.9		233.9
Public utilities	7.9		9.5		9.5
Industrial, miscellaneous and other	458.7		558.2		558.2
Total common equity securities	633.6		801.6		801.6
Convertible fixed maturity and preferred investments	19.1		20.5		20.5
Other long-term investments⁽¹⁾	322.0		385.0		385.0
Total investments	$	6,499.7	$	6,863.1	$	6,863.1

⁽¹⁾ Excludes cost of $22.5 and carrying value of $23.2 associated with investments accounted for under the equity method.

Schedules of the Registrant should be read in conjunction with the Consolidated Financial Statements and Notes.

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT

12 Months Ended

Dec. 31, 2014

Condensed Financial Information of Parent Company Only Disclosure [Abstract]

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT

CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT

CONDENSED BALANCE SHEETS



	December 31,
Millions	2014			2013
Assets:
Cash	$	.2		$	.2
Fixed maturity investments, at fair value	—			31.8
Short-term investments, at amortized cost	31.0			1.4
Other assets	.2			.4
Investments in consolidated and unconsolidated affiliates	4,119.4			3,919.1
Total assets	$	4,150.8		$	3,952.9
Liabilities:
Revolving line of credit	$	—		$	—
Payable to subsidiary	161.6			47.0
Other liabilities	(7.4		)	.4
Total liabilities	154.2			47.4
White Mountains’s common shareholders’ equity	3,996.6			3,905.5
Total liabilities and equity	$	4,150.8		$	3,952.9

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS)



	Year Ended December 31,
Millions	2014			2013			2012
Revenues (including realized gains and losses)	$	.3		$	1.2		$	20.8
Expenses	32.3			39.0			32.4
Pre-tax loss	(32.0		)	(37.8		)	(11.6		)
Income tax benefit (expense)	.9			(.1		)	(.3		)
Net loss	(31.1		)	(37.9		)	(11.9		)
Net gain from discontinued operations, net of tax	13.9			—			—
Equity in earnings from consolidated and unconsolidated affiliates	329.9			359.7			219.3
Net income attributable to White Mountains’s common shareholders	312.7			321.8			207.4
Other comprehensive (loss) income items, after-tax	(101.6		)	(79.8		)	95.2
Comprehensive income attributable to White Mountains’s common shareholders	$	211.1		$	242.0		$	302.6
Computation of net income available to common shareholders:
Net income available to common shareholders	$	312.7		$	321.8		$	207.4

Schedules of the Registrant should be read in conjunction with the Consolidated Financial Statements and Notes.

SCHEDULE II

(continued)

CONDENSED STATEMENTS OF CASH FLOWS



	Year Ended December 31,
Millions	2014			2013			2012
Net income attributable to White Mountains’s common shareholders	$	312.7		$	321.8		$	207.4
Charges (credits) to reconcile net income to net cash from operations:
Net realized and unrealized gains on sales of investments	(.2		)	(.2		)	(11.0		)
Undistributed current earnings from subsidiaries	(329.9		)	(359.7		)	(219.3		)
Net gain on sale of other discontinued operations ⁽⁶⁾	(13.9		)	—			—
Other non-cash reconciling items including restricted share and option amortization	12.9			15.6			22.1
Net change in other assets and liabilities, net	(7.6		)	(2.9		)	(10.0		)
Net cash used for continuing operations	(26.0		)	(25.4		)	(10.8		)
Net cash provided from discontinued operations⁽⁶⁾	13.9			—			—
Net cash used for operations	(12.1		)	(25.4		)	(10.8		)
Cash flows from investing activities:
Net decrease in short-term investments	(29.6		)	7.5			63.3
Purchases of investment securities⁽²⁾	(7.6		)	(26.2		)	(706.2		)
Sales and maturities of investment securities⁽⁴⁾	39.4			61.1			2,009.7
Issuance of debt from (to) subsidiaries⁽³⁾	144.6			153.9			(121.0		)
Repayment of debt (to) from subsidiaries	(30.0		)	(10.3		)	28.5
Receipt of cash flows from discontinued operations⁽⁶⁾	13.9			—			—
Contributions to subsidiaries⁽⁴⁾	—			—			(663.0		)
Distributions from subsidiaries⁽¹⁾⁽²⁾	29.7			.1			—
Net cash provided from investing activities — continuing operations	160.4			186.1			611.3
Net cash used for investing activities — discontinued operations	(13.9		)	—			—
Net cash provided from investing activities	146.5			186.1			611.3
Cash flows from financing activities:
Draw down of revolving line of credit⁽⁵⁾	65.0			200.0			150.0
Repayment of revolving line of credit⁽³⁾⁽⁵⁾	(65.0		)	(275.0		)	(75.0		)
Proceeds from issuances of common shares	—			—			—
Repurchases and retirement of common shares⁽³⁾⁽⁴⁾	(128.2		)	(79.8		)	(669.1		)
Dividends paid on common shares	(6.2		)	(6.2		)	(6.6		)
Net cash used for financing activities — continuing operations	(134.4		)	(161.0		)	(600.7		)
Net cash (used for) provided from financing activities — discontinued operations	—			—			—
Net cash used for financing activities	(134.4		)	(161		)	(600.7		)
Net decrease in cash during the year	—			(.3		)	(.2		)
Cash balance at beginning of year	.2			.5			.7
Cash balance at end of year	$	.2		$	.2		$	.5
Supplemental cash flow information:
Interest paid	$	(.3	)	$	(2.0	)	$	(12.4	)


⁽¹⁾	During 2014, the Company received a distribution of $29.7 from Lone Tree Holdings, Ltd, a direct wholly-owned subsidiary.


⁽²⁾	During 2013, the Company received a distribution of $28.0 from Lone Tree Holdings, Ltd. The distribution included $27.9 of fixed maturities and $.1 of cash. Purchases of investment securities excludes the non-cash distribution of $27.9.


⁽³⁾	During 2013, the Company used cash proceeds received from the issuance of debt to repurchase $79.8 of its common shares and repay $75.0 of its revolving line of credit.


⁽⁴⁾	During 2012, the Company sold the majority of its fixed maturity investments and used the proceeds to (a) contribute $663.0 to its subsidiaries, the majority of which was used to fund HG Global and (b) repurchase 1,329,640 of its common shares for $669.1.


⁽⁵⁾	The WTM Bank Facility presented in Note 7 - “Debt” is a direct obligation of the Registrant.


⁽⁶⁾	During 2014, the Company received a payment from Allianz, the purchaser of White Mountains’s former subsidiary Fireman’s Fund Insurance Company (“FFIC”), related to the utilization of alternative minimum tax credits associated with the tax loss on the sale of FFIC in 1991. See Note 22 - “Discontinued Operations”.

Schedules of the Registrant should be read in conjunction with the Consolidated Financial Statements and Notes.

SCHEDULE III SUPPLEMENTARY INSURANCE INFORMATION

12 Months Ended

Dec. 31, 2014

Supplementary Insurance Information [Abstract]

SCHEDULE III SUPPLEMENTARY INSURANCE INFORMATION

WHITE MOUNTAINS INSURANCE GROUP, LTD.

SUPPLEMENTARY INSURANCE INFORMATION

(Millions)



Column A	Column B		Column C		Column D		Column E		Column F		Column G		Column H		Column I		Column J		Column K
Segment	Deferred acquisition costs		Future policy benefits, losses, claims and loss expenses		Unearned premiums		Other policy claims and benefits payable		Premiums earned		Net investment income⁽¹⁾		Benefits, claims, losses, and settlement expenses		Amortization of deferred policy acquisition costs		Other operating expenses		Premiums written
Years ended:
December 31, 2014
OneBeacon⁽²⁾	$	103.2	$	1,342.2	$	588.3	$	—	$	1,177.1	$	41.7	$	815.1	$	203.3	$	179.2	$	1,216.9
Sirius Group	69.9		1,809.8		338.6		—		873.9		41.1		345.3		193.6		129.7		882.5
HG Global/BAM	4.0		—		27.6		—		1.8		7.1		—		2.1		.4		16.2
Other operations⁽³⁾	—		7.8		.8		—		6.1		.2		8.9		.8		—		5.9
December 31, 2013
OneBeacon⁽²⁾	$	103.7	$	1,054.3	$	544.9	$	—	$	1,120.4	$	41.1	$	622.1	$	208.9	$	204.8	$	1,088.6
Sirius Group	69.3		2,025.0		343.3		—		866.4		30.3		418.4		166.5		126.1		876.6
HG Global/BAM	1.7		—		13.2		—		.5		5.7		—		1.5		.4		13.6
Other operations	—		—		—		—		—		.1		—		—		—		—
December 31, 2012
OneBeacon⁽²⁾	$	123.9	$	1,000.0	$	573.8	$	—	$	1,132.0	$	53.6	$	650.0	$	249.4	$	205.2	$	1,179.2
Sirius Group	71.4		2,168.9		350.2		—		931.6		65.0		543.9		180.8		116.4		947.7
Other operations	—		—		—		—		—		.5		—		—		—		—


⁽¹⁾	The amounts shown exclude net investment income relating to non-insurance operations of $14.9, $33.7 and $32.3 for the twelve months ended December 31, 2014, 2013 and 2012, respectively.


⁽²⁾	The amounts shown excludes balances reclassified to held for sale in the consolidated balance sheets related to the Runoff Transaction as of December 31, 2013 and 2012 and to AutoOne as of December 31, 2011. See Note 22 - “Discontinued Operations”.


⁽³⁾	The Other operations amounts shown relate to SSIE. SSIE’s results are attributed to non-controlling interests.

Schedules of the Registrant should be read in conjunction with the Consolidated Financial Statements and Notes.

SCHEDULE IV REINSURANCE

12 Months Ended

Dec. 31, 2014

Supplemental Schedule of Reinsurance Premiums for Insurance Companies [Abstract]

SCHEDULE IV REINSURANCE

WHITE MOUNTAINS INSURANCE GROUP, LTD.

REINSURANCE

(Millions)



Column A	Column B		Column C			Column D		Column E		Column F
Premiums earned	Gross amount		Ceded to other companies			Assumed from other companies		Net amount		Percentage of amount assumed to net
Years ended:
December 31, 2014
OneBeacon⁽¹⁾	$	1,209.1	$	(102.9	)	$	70.9	$	1,177.1	6.0	%
Sirius Group	200.2		(251.7		)	925.4		873.9		105.9	%
HG/BAM	1.8		—			—		1.8		—	%
Other operations⁽²⁾	22.6		(16.5		)	—		6.1		—
December 31, 2013
OneBeacon⁽¹⁾	$	1,043.3	$	(71.4	)	$	148.5	$	1,120.4	13.3	%
Sirius Group	174.0		(246.2		)	938.6		866.4		108.3	%
December 31, 2012
OneBeacon⁽¹⁾	$	1,158.3	$	(79.1	)	$	52.8	$	1,132.0	4.7	%
Sirius Group	169.9		(226.6		)	988.3		931.6		106.1	%


⁽¹⁾	The amounts shown excludes balances reclassified to discontinued operations in the consolidated income statement related to the Runoff Transaction as of December 31, 2014, 2013 and 2012. See Note 22 - “Discontinued Operations”.


⁽²⁾	The Other operations amounts shown relate to SSIE. SSIE’s results are attributed to non-controlling interests.

Schedules of the Registrant should be read in conjunction with the Consolidated Financial Statements and Notes.

SCHEDULE V VALUATION AND QUALIFYING ACCOUNTS

12 Months Ended

Dec. 31, 2014

Valuation and Qualifying Accounts [Abstract]

SCHEDULE V VALUATION AND QUALIFYING ACCOUNTS

WHITE MOUNTAINS INSURANCE GROUP, LTD.

VALUATION AND QUALIFYING ACCOUNTS



Column A	Column B		Column C						Column D			Column E
			Additions (subtractions)
Millions	Balance at beginning of period		Charged to costs and expenses			Charged to other accounts			Deductions described ⁽¹⁾			Balance at end of period
Years ended:

December 31, 2014
Reinsurance recoverable on paid losses:
Allowance for reinsurance balances	$	23.7	$	(1.1	)	$	—		$	(11.2	)	$	11.4
Property and casualty insurance and reinsurance premiums receivable:
Allowance for uncollectible accounts	4.0		(.2		)	(1.0		)	.1			2.9
Accounts receivable:
Allowance for uncollectible accounts	—		3.6			—			(.3		)	3.3

December 31, 2013
Reinsurance recoverable on paid losses:
Allowance for reinsurance balances	$	35.5	$	(.6	)	$	—		$	(11.2	)	$	23.7
Property and casualty insurance and reinsurance premiums receivable:
Allowance for uncollectible accounts	4.4		1.0			—			(1.4		)	4.0

December 31, 2012
Reinsurance recoverable on paid losses:
Allowance for reinsurance balances	$	34.4	$	(.6	)	$	—		$	1.7		$	35.5
Property and casualty insurance and reinsurance premiums receivable:
Allowance for uncollectible accounts	3.4		1.1			—			(0.1		)	4.4


⁽¹⁾	Represents net collections (charge-offs) of balances receivable and foreign currency translation.

Schedules of the Registrant should be read in conjunction with the Consolidated Financial Statements and Notes.

SCHEDULE VI SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS

12 Months Ended

Dec. 31, 2014

Supplemental Information for Property, Casualty Insurance Underwriters [Abstract]

SCHEDULE VI SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS

WHITE MOUNTAINS INSURANCE GROUP, LTD.

SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS

(Millions)



Column A	Column B		Column C		Column D			Column E		Column F		Column G		Column H					Column I		Column J		Column K
	Deferred acquisition costs⁽⁴⁾		Reserves for Unpaid Claims and Claims Adjustment Expenses		Discount, if any, deducted in Column C			Unearned Premiums		Earned Premiums		Net investment income		Claims and Claims Adjustment Expenses Incurred Related to					Amortization of deferred policy acquisition⁽⁴⁾ costs		Paid Claims and Claims Adjustment Expenses		Premiums written
Affiliation with registrant	Deferred acquisition costs⁽⁴⁾		Reserves for Unpaid Claims and Claims Adjustment Expenses		Discount, if any, deducted in Column C			Unearned Premiums		Earned Premiums		Net investment income		Current Year ⁽¹⁾		Prior Year ⁽²⁾			Amortization of deferred policy acquisition⁽⁴⁾ costs		Paid Claims and Claims Adjustment Expenses		Premiums written
OneBeacon⁽³⁾:
2014	$	103.2	$	1,342.2	$	1.0	⁽¹⁾	$	588.3	$	1,177.1	$	41.7	$	725.3	$	89.8		$	203.3	$	608.6	$	1,216.9
2013	103.7		1,054.3		3.0		⁽¹⁾	544.9		1,120.4		41.1		622.1		—			208.9		540.7		1,088.6
2012	123.9		1,000.0		4.6		⁽¹⁾	573.8		1,132.0		53.6		657.4		(7.4		)	249.4		565.1		1,179.2
Sirius Group:
2014	$	69.9	$	1,809.8	$	0.7	⁽²⁾	$	338.6	$	873.9	$	41.1	$	443.2	$	(98.0	)	$	193.6	$	544.9	$	882.5
2013	69.3		2,025.0		1.7		⁽²⁾	343.3		866.4		30.3		466.8		(48.4		)	166.5		628.1		876.6
2012	71.4		2,168.9		2.4		⁽²⁾	350.2		931.6		65.0		578.4		(34.5		)	180.8		741.2		947.7
Other operations⁽⁵⁾:
2014	$	—	$	7.8	$	—		$	—	$	0.8	$	0.2	$	6.7	$	2.2		$	—	$	14.8	$	5.9
2013	—		—		—			—		—		—		—		—			—		—		—
2012	—		—		—			—		—		—		—		—			—		—		—

⁽¹⁾

The amounts shown represent OneBeacon’s discount on its long-term workers compensation loss and LAE reserves, as such liabilities constitute unpaid but settled claims under which the payment pattern and ultimate costs are fixed and determinable on an individual basis. OneBeacon discounts these reserves using a discount rate which is determined based on the facts and circumstances applicable at the time the claims are settled (2.5%, 3.5% and 3.5% as of December 31, 2014, 2013 and 2012).


⁽²⁾	The amount shown represents unamortized fair value adjustments to reserves for unpaid claims and claims adjustment expenses made in purchase accounting as a result of White Mountains’s purchase of Sirius International during 2004.


⁽³⁾	The amounts shown excludes balances reclassified to held for sale in the consolidated balance sheets related to the Runoff Transaction as of December 31, 2013 and 2012. See Note 22 - “Discontinued Operations”.


⁽⁴⁾	In 2012, the Company adopted ASU 2010-26, Accounting for Costs Associated with Acquiring or Renewing Insurance Contracts (ASC 944). See Note 1 - “Summary of Significant Accounting Policies”.


⁽⁵⁾	The Other operations amounts shown relate to SSIE. SSIE’s results are attributed to non-controlling interests.

Schedules of the Registrant should be read in conjunction with the Consolidated Financial Statements and Notes.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2014

Accounting Policies [Abstract]

Investment securities

Investment Securities

Other long-term investments

Other Long-term Investments

Derivative financial instruments

Derivative Financial Instruments

Warrants

Derivatives - Variable annuity reinsurance

Derivatives—Variable Annuity Reinsurance

WM Life Re includes the effect of counterparty credit risk when determining the fair value of its derivative contracts and its GMAB and GMDB liabilities.

Cash

Insurance and reinsurance operations

Insurance and Reinsurance Operations

Municipal Bond Insurance

Funds Held Under Reinsurance Contracts Policy [Policy Text Block]

Funds Held

Mandatory Shared Market Mechanisms

Insurance-Related Assessments

Insurance-related Assessments

Deferred Software Costs

Federal and foreign income taxes

Federal and Foreign Income Taxes

Foreign currency exchange

Foreign Currency Exchange

The following rates of exchange for the U.S. dollar have been used for the most significant operations:



Currency	Opening Rate 2014	Closing Rate 2014	Opening Rate 2013	Closing Rate 2013
Swedish kronor	6.4339	7.7737	6.4973	6.4339
British pound	0.6044	0.6426	0.6154	0.6044
Euro	0.7259	0.8245	0.7564	0.7259

Goodwill and Other Intangible Assets

Noncontrolling Interest

Non-controlling Interest

Variable Interest Entities

Recent Accounting Pronouncements

Recently Adopted Changes in Accounting Principles

Unrecognized Tax Benefits

Recent Accounting Pronouncements

Pushdown Accounting

Share-Based Compensation Awards

Revenue Recognition

Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity

Qualified Affordable Housing Projects

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2014

Accounting Policies [Abstract]

Schedule of rates of exchange for the U.S. dollar that have been used for the most significant operations

The following rates of exchange for the U.S. dollar have been used for the most significant operations:



Currency	Opening Rate 2014	Closing Rate 2014	Opening Rate 2013	Closing Rate 2013
Swedish kronor	6.4339	7.7737	6.4973	6.4339
British pound	0.6044	0.6426	0.6154	0.6044
Euro	0.7259	0.8245	0.7564	0.7259

Reserves for Unpaid Losses and Loss Adjustment Expenses (Tables)

12 Months Ended

Dec. 31, 2014

Insurance Loss Reserves [Abstract]

Loss and LAE reserve activities

The following table summarizes the loss and LAE reserve activities of White Mountains’s insurance and reinsurance subsidiaries for the years ended December 31, 2014, 2013 and 2012:



	Year Ended December 31,
Millions	2014			2013			2012
Gross beginning balance	$	3,079.3		$	3,168.9		$	5,702.3
Less beginning reinsurance recoverable on unpaid losses	(428.1		)	(429.1		)	(2,507.3		)
Net loss and LAE reserves	2,651.2			2,739.8			3,195.0

Less: Beginning net loss and LAE reserves for AutoOne and the Runoff Transaction⁽¹⁾	—			—			(383.3		)

Loss and LAE reserves acquired⁽²⁾	45.4			37.7			17.0
Loss and LAE reserves consolidated — SSIE	13.6			—			—

Losses and LAE incurred relating to:
Current year losses	1,175.3			1,088.9			1,235.8
Prior year losses	(6.0		)	(48.4		)	(41.9		)
Total incurred losses and LAE	1,169.3			1,040.5			1,193.9

Accretion of fair value adjustment to net loss and LAE reserves	0.7			1.7			10.6
Foreign currency translation adjustment to net loss and LAE reserves	(36.0		)	.3			12.9

Loss and LAE paid relating to:
Current year losses	(345.3		)	(336.2		)	(404.7		)
Prior year losses	(823.0		)	(832.6		)	(901.6		)
Total loss and LAE payments	(1,168.3		)	(1,168.8		)	(1,306.3		)

Net ending balance	2,675.9			2,651.2			2,739.8
Plus ending reinsurance recoverable on unpaid losses	483.9			428.1			429.1
Gross ending balance	$	3,159.8		$	3,079.3		$	3,168.9


⁽¹⁾	Loss and LAE reserve balances from OneBeacon’s Runoff Business prior to December 31, 2012 were not classified as held for sale. Adjustment is to present loss and LAE reserve activities for continuing operations.


⁽²⁾	Loss and LAE reserves acquired in 2014 relate to Sirius Group’s purchase of Olympus Re and loss portfolio transfer from Transamerica. Loss and LAE reserves acquired in 2013 relate to WM Solutions’s purchases of Empire and Ashmere. Loss and LAE reserves acquired in 2012 relate to WM Solutions’s purchases of PICO, Citation, Woodridge and Oakwood.

Schedule of asbestos and environmental loss and LAE reserve activities

Sirius Group



Net A&E Loss Reserve Activity	Year Ended December 31,
	2014						2013						2012
Millions	Gross			Net			Gross			Net			Gross			Net
Asbestos:
Beginning balance	$	207.4		$	178.7		$	208.2		$	174.2		$	185.1		$	146.2
Losses and LAE acquired	22.9			22.9			13.0			13.0			11.0			11.0
Incurred losses and LAE	7.4			8.0			12.1			11.8			46.8			46.4
Paid losses and LAE	(21.9		)	(16.8		)	(25.9		)	(20.3		)	(34.7		)	(29.4		)
Ending balance	215.8			192.8			207.4			178.7			208.2			174.2
Environmental:
Beginning balance	20.4			15.2			20.4			15.2			22.1			16.5
Losses and LAE acquired	2.1			2.1			1.0			1.0			0.7			0.7
Incurred losses and LAE	1.6			1.6			.8			.8			(0.1		)	(0.5		)
Paid losses and LAE	(1.4		)	(1.5		)	(1.8		)	(1.8		)	(2.3		)	(1.5		)
Ending balance	22.7			17.4			20.4			15.2			20.4			15.2
Total asbestos and environmental:
Beginning balance	227.8			193.9			228.6			189.4			207.2			162.7
Losses and LAE acquired	25.0			25.0			14.0			14.0			11.7			11.7
Incurred losses and LAE	9.0			9.6			12.9			12.6			46.7			45.9
Paid losses and LAE	(23.3		)	(18.3		)	(27.7		)	(22.1		)	(37.0		)	(30.9		)
Ending balance	$	238.5		$	210.2		$	227.8		$	193.9		$	228.6		$	189.4

Loss and LAE Reserve and Net Loss and LAE Development [Table Text Block]

The components of the 2014 fourth quarter loss and LAE reserve increase and the net loss and LAE development for the full year are provided below:



Millions	2014 Fourth Quarter Reserve Increases								Full Year 2014
Underwriting Unit	Current Accident Year			Prior Accident Year			Total		Net Prior Year Development
Professional Insurance	$	22.9		$	46.4		$	69.3	$	59.1
Specialty Property	(1.1		)	5.7			4.6		1.1
Crop	3.8			—			3.8		—
Other	2.8			(.4		)	2.4		1.6
Specialty Products	28.4			51.7			80.1		61.8

Entertainment	1.5			11.6			13.1		13.5
Accident	—			3.5			3.5		6.0
Government Risks	1.2			7.1			8.3		8.5
Other	2.6			1.6			4.2		—
Specialty Industries	5.3			23.8			29.1		28.0

Total	$	33.7		$	75.5		$	109.2	$	89.8

Third Party Reinsurance (Tables)

12 Months Ended

Dec. 31, 2014

Ceded Credit Risk [Line Items]

Schedule of direct assumed and ceded amounts

The effects of reinsurance on White Mountains’s insurance and reinsurance subsidiaries’ written and earned premiums and on losses and LAE were as follows (see Note 10 for balances related to White Mountains financial guarantee business):



	Year ended December 31, 2014
Millions	OneBeacon			Sirius Group			HG/BAM ⁽¹⁾		Other ⁽²⁾			Total
Written premiums:
Direct	$	1,257.5		$	208.7		$	16.2	$	22.6		$	1,505.0
Assumed	65.9			927.9			—		—			993.8
Gross written premiums	1,323.4			1,136.6			16.2		22.6			2,498.8
Ceded	(106.5		)	(254.1		)	—		(16.7		)	(377.3		)
Net written premiums	$	1,216.9		$	882.5		$	16.2	$	5.9		$	2,121.5
Earned premiums:
Direct	$	1,209.1		$	200.2		$	1.8	$	22.6		$	1,433.7
Assumed	70.9			925.4			—		—			996.3
Gross earned premiums	1,280.0			1,125.6			1.8		22.6			2,430.0
Ceded	(102.9		)	(251.7		)	—		(16.5		)	(371.1		)
Net earned premiums	$	1,177.1		$	873.9		1.8		$	6.1		$	2,058.9
Losses and LAE:
Direct	$	830.7		$	117.8		$	—	$	24.1		$	972.6
Assumed	63.7			378.1			—		—			441.8
Gross losses and LAE	894.4			495.9			—		24.1			1,414.4
Ceded	(79.3		)	(150.6		)	—		(15.2		)	(245.1		)
Net losses and LAE	$	815.1		$	345.3		$	—	$	8.9		$	1,169.3

⁽¹⁾During 2014, BAM ceded $12.3 in written premiums ($1.4 in earned premiums) to HG Global, which have been eliminated within the HG/BAM segment.

⁽²⁾During 2014, SSIE ceded $16.0 in written premiums ($15.7 in earned premiums) to OneBeacon, which have been eliminated in consolidation.



	Year ended December 31, 2013
Millions	OneBeacon			Sirius Group			Total
Written premiums:
Direct	$	1,103.1		$	177.3		$	1,280.4
Assumed	59.8			943.1			1,002.9
Gross written premiums	1,162.9			1,120.4			2,283.3
Ceded	(74.3		)	(243.8		)	(318.1		)
Net written premiums	$	1,088.6		$	876.6		$	1,965.2
Earned premiums:
Direct	$	1,043.3		$	174.0		$	1,217.3
Assumed	148.5			938.6			1,087.1
Gross earned premiums	1,191.8			1,112.6			2,304.4
Ceded	(71.4		)	(246.2		)	(317.6		)
Net earned premiums	$	1,120.4		$	866.4		$	1,986.8
Losses and LAE:
Direct	$	584.9		$	98.1		$	683.0
Assumed	76.3			455.5			531.8
Gross losses and LAE	661.2			553.6			1,214.8
Ceded	(39.1		)	(135.2		)	(174.3		)
Net losses and LAE	$	622.1		$	418.4		$	1,040.5



	Year ended December 31, 2012
Millions	OneBeacon			Sirius Group			Total
Written premiums:
Direct	$	1,204.0		$	186.1		$	1,390.1
Assumed	55.2			992.7			1,047.9
Gross written premiums	1,259.2			1,178.8			2,438.0
Ceded	(80.0		)	(231.1		)	(311.1		)
Net written premiums	$	1,179.2		$	947.7		$	2,126.9
Earned premiums:
Direct	$	1,158.3		$	169.9		$	1,328.2
Assumed	52.8			988.3			1,041.1
Gross earned premiums	1,211.1			1,158.2			2,369.3
Ceded	(79.1		)	(226.6		)	(305.7		)
Net earned premiums	$	1,132.0		$	931.6		$	2,063.6
Losses and LAE:
Direct	$	687.5		$	96.9		$	784.4
Assumed	29.6			523.9			553.5
Gross losses and LAE	717.1			620.8			1,337.9
Ceded	(67.1		)	(76.9		)	(144.0		)
Net losses and LAE	$	650.0		$	543.9		$	1,193.9

Industry Loss Warranty



Scope	Limit in millions	Trigger in billions		Expiration Date
European wind & flood	5.0	7.5		March 31, 2015
European wind & flood	5.0	5.0		March 31, 2015
European all natural perils	15.0	15.0		December 31, 2015 (second event aggregate excess cover)
European wind & earthquake	7.5	5.0	7.5	March 31, 2016
United States all natural peril	5.0	20.0		June 30, 2015
United States, European, Japan wind & earthquake	30.0	5.0	10.0	December 31, 2015 (multiple layer covers)

OneBeacon

Ceded Credit Risk [Line Items]

Ceded Credit Risk

The reinsurance balances associated with the Runoff Business are included in discontinued operations (see Note 22).



Standard & Poor’s Rating⁽¹⁾	Balance at December 31, 2014		% of Total
AA	$	53.8	31	%
A	93.2		54	%
BBB+, Not rated and other⁽²⁾	26.8		15	%
Total	$	173.8	100	%

⁽¹⁾Standard & Poor’s ratings as detailed above are: “AA” (Very strong), “A” (Strong) and “BBB+” (Adequate).

Sirius Group

Ceded Credit Risk [Line Items]

Ceded Credit Risk

The following table provides a listing of Sirius Group’s gross and net recoverable amounts by the reinsurer’s Standard & Poor’s rating and the percentage of total recoverables.



Rating⁽¹⁾	Gross		Collateral		Net		% of Net Total
AA	$	114.6	$	1.6	$	113.0	34	%
A	138.8		7.1		131.7		42	%
BBB+	8.9		—		8.9		3	%
BBB or lower	9.6		—		9.6		3	%
Not rated	61.7		21.5		40.2		18	%
Total	$	333.6	$	30.2	$	303.4	100	%

⁽¹⁾Standard & Poor’s ratings as detailed above are: “AAA” (Extremely strong), “AA” (Very strong), “A” (Strong), and “BBB+” and “BBB” (Adequate).

Investment Securities (Tables)

12 Months Ended

Dec. 31, 2014

Investments, Debt and Equity Securities [Abstract]

Pre-tax net investment income

Pre-tax net investment income for 2014, 2013 and 2012 consisted of the following:



	Year Ended December 31,
Millions	2014			2013			2012
Investment income:
Fixed maturity investments	$	98.9		$	100.5		$	132.0
Short-term investments	1.5			3.4			3.1
Common equity securities	21.0			20.5			22.2
Convertible fixed maturity and preferred investments	2.5			2.9			6.0
Other long-term investments	1.9			3.0			3.1
Interest on funds held under reinsurance treaties	(.2		)	.3			.6
Total investment income	125.6			130.6			167.0
Third-party investment expenses	(20.6		)	(19.7		)	(13.4		)
Net investment income, pre-tax	$	105.0		$	110.9		$	153.6

Net Realized and Unrealized Investment Gains and Losses

Net realized and unrealized investment gains and losses consisted of the following:



	Year Ended December 31,
Millions	2014			2013			2012
Net realized investment gains, pre-tax	$	233.8		$	104.5		$	68.1
Net unrealized investment gains, pre-tax	50.1			57.2			50.1
Net realized and unrealized investment gains, pre-tax	283.9			161.7			118.2
Income tax expense attributable to net realized and unrealized investment gains	(69.7		)	(21.9		)	(26.8		)
Net realized and unrealized investment gains, after tax	$	214.2		$	139.8		$	91.4

Net unrealized investment gains (losses) for Level 3 investments



	Year Ended December 31,
Millions	2014			2013			2012
Fixed maturity investments	$	1.2		$	(2.3	)	$	7.7
Common equity securities	5.9			.9			3.0
Convertible fixed maturity and preferred investments	.7			—			—
Other long-term investments	(4.1		)	11.2			7.0
Total net unrealized investment gains (losses), pre-tax - Level 3 investments	$	3.7		$	9.8		$	17.7

Net realized and unrealized investment gains, after-tax, as recorded on the statements of operations and comprehensive income (losses)

The components of White Mountains’s net realized and unrealized investment gains (losses), after-tax, as recorded on the statements of operations and comprehensive income were as follows:



	Year Ended December 31,
Millions	2014			2013			2012
Net change in pre-tax unrealized gains (losses) on investments in unconsolidated affiliates	$	81.2		$	(106.4	)	$	62.8
Income taxes	(5.9		)	8.3			(5.1		)
Net change in unrealized gains (losses) on investments in unconsolidated affiliates, after tax	75.3			(98.1		)	57.7
Net realized and unrealized foreign currency (losses) gains on investments through OCI	(274.3		)	11.3			95.5
Total investment (losses) gains through accumulated other comprehensive income	(199.0		)	(86.8		)	153.2
Net realized and unrealized investment gains, after-tax	214.2			139.8			91.4
Total investment gains recorded during the period, after-tax	$	15.2		$	53.0		$	244.6

Realized Gain (Loss) on Investments

Net realized investment gains (losses)

Net realized investment gains (losses) for 2014, 2013 and 2012 consisted of the following:



	Year ended December 31, 2014
Millions	Net realized gains (losses)			Net foreign exchange gains (losses)			Total changes in fair value reflected in earnings
Fixed maturity investments	$	23.9		$	21.0		$	44.9
Short-term investments	—			2.9			2.9
Common equity securities	150.9			.9			151.8
Convertible fixed maturity and preferred investments	5.9			—			5.9
Other long-term investments	27.7			.3			28.0
Forward contracts	.3			—			.3
Net realized investment gains (losses), pre-tax	208.7			25.1			233.8
Income taxes attributable to realized investment gains (losses)	(39.7		)	(8.0		)	(47.7		)
Net realized investment gains (losses), after-tax	$	169.0		$	17.1		$	186.1



	Year ended December 31, 2013
Millions	Net realized gains (losses)			Net foreign exchange gains (losses)			Total changes in fair value reflected in earnings
Fixed maturity investments	$	8.6		$	(15.0	)	$	(6.4	)
Short-term investments	.1			—			.1
Common equity securities	104.5			(3.7		)	100.8
Convertible fixed maturity and preferred investments	1.0			—			1.0
Other long-term investments	7.5			1.4			8.9
Forward contracts	.1			—			.1
Net realized investment gains (losses), pre-tax	121.8			(17.3		)	104.5
Income taxes attributable to realized investment gains (losses)	(30.0		)	5.5			(24.5		)
Net realized investment gains (losses), after-tax	$	91.8		$	(11.8	)	$	80.0



	Year ended December 31, 2012
Millions	Net realized gains (losses)			Net foreign exchange gains (losses)			Total changes in fair value reflected in earnings
Fixed maturity investments	$	82.5		$	(2.5	)	$	80.0
Short-term investments	—			(4.3		)	(4.3		)
Common equity securities	1.3			—			1.3
Convertible fixed maturity and preferred investments	(8.2		)	(1.8		)	(10.0		)
Other long-term investments	1.4			—			1.4
Forward contracts	(.3		)	—			(.3		)
Net realized investment gains (losses), pre-tax	76.7			(8.6		)	68.1
Income taxes attributable to realized investment gains (losses)	(23.8		)	2.2			(21.6		)
Net realized investment gains (losses), after-tax	$	52.9		$	(6.4	)	$	46.5

Unrealized Gain (Loss) on Investments

Net unrealized investment gains (losses)

The following table summarizes net unrealized investment gains (losses) and changes in the carrying value of investments measured at fair value:



	Year ended December 31, 2014
Millions	Net unrealized gains (losses)			Net foreign exchange gains (losses)			Total net unrealized gains (losses) reflected in earnings
Fixed maturity investments	$	30.9		$	111.7		$	142.6
Short-term investments	(.2		)	.1			(.1		)
Common equity securities	(83.0		)	(.1		)	(83.1		)
Convertible fixed maturity and preferred investments	(8.2		)	.4			(7.8		)
Other long-term investments	(5.7		)	4.2			(1.5		)
Net unrealized investment gains (losses), pre-tax	(66.2		)	116.3			50.1
Income taxes attributable to unrealized investment gains (losses)	6.0			(28.0		)	(22.0		)
Net unrealized investment gains (losses), after-tax	$	(60.2	)	$	88.3		$	28.1



	Year ended December 31, 2013
Millions	Net unrealized gains (losses)			Net foreign exchange gains (losses)			Total net unrealized gains (losses) reflected in earnings
Fixed maturity investments	$	(93.9	)	$	15.3		$	(78.6	)
Short-term investments	.1			—			.1
Common equity securities	119.2			(.4		)	118.8
Convertible fixed maturity and preferred investments	3.2			—			3.2
Other long-term investments	10.3			3.4			13.7
Net unrealized investment gains (losses), pre-tax	38.9			18.3			57.2
Income taxes attributable to unrealized investment gains (losses)	8.2			(5.6		)	2.6
Net unrealized investment gains (losses), after-tax	$	47.1		$	12.7		$	59.8



	Year ended December 31, 2012
Millions	Net unrealized gains (losses)			Net foreign exchange gains (losses)			Total net unrealized gains (losses) reflected in earnings
Fixed maturity investments	$	18.5		$	(45.9	)	$	(27.4	)
Short-term investments	—			.1			.1
Common equity securities	65.9			(.1		)	65.8
Convertible fixed maturity and preferred investments	1.1			—			1.1
Other long-term investments	13.2			(2.7		)	10.5
Net unrealized investment gains (losses), pre-tax	98.7			(48.6		)	50.1
Income taxes attributable to unrealized investment gains (losses)	(17.9		)	12.7			(5.2		)
Net unrealized investment gains (losses), after-tax	$	80.8		$	(35.9	)	$	44.9

Investment holdings, fixed maturity investments



	December 31, 2014
Millions	Cost or amortized cost		Gross unrealized gains		Gross unrealized losses			Net foreign currency gains (losses)			Carrying value
US Government and agency obligations	$	184.7	$	.1	$	(.3	)	$	3.6		$	188.1
Debt securities issued by corporations	2,221.3		45.2		(5.1		)	49.8			2,311.2
Municipal obligations	82.0		1.4		(.2		)	—			83.2
Mortgage-backed and asset-backed securities	1,811.1		7.6		(3.5		)	25.7			1,840.9
Foreign government, agency and provincial obligations	274.6		4.2		(1.0		)	(2.7		)	275.1
Preferred stocks	79.6		6.1		—			.1			85.8
Total fixed maturity investments	$	4,653.3	$	64.6	$	(10.1	)	$	76.5		$	4,784.3



	December 31, 2013
Millions	Cost or amortized cost		Gross unrealized gains		Gross unrealized losses			Net foreign currency losses			Carrying value
US Government and agency obligations	$	365.5	$	.5	$	(1.0	)	$	(2.5	)	$	362.5
Debt securities issued by corporations	2,330.7		44.0		(13.2		)	(14.3		)	2,347.2
Municipal obligations	18.3		—		(.4		)	—			17.9
Mortgage-backed and asset-backed securities	2,027.3		2.4		(9.9		)	(5.3		)	2,014.5
Foreign government, agency and provincial obligations	444.2		3.7		(3.2		)	(4.8		)	439.9
Preferred stocks	79.9		5.1		—			(.2		)	84.8
Total fixed maturity investments including assets held for sale	$	5,265.9	$	55.7	$	(27.7	)	$	(27.1	)	$	5,266.8
Fixed maturity investments reclassified to assets held for sale ⁽¹⁾											(236.3		)
Total fixed maturity investments											$	5,030.5


⁽¹⁾	Assets held for sale related to discontinued operations. See Note 22.

Schedule of contractual maturities of fixed maturities



	December 31, 2014
Millions	Cost or amortized cost		Carrying value
Due in one year or less	$	331.2	$	337.5
Due after one year through five years	1,968.3		2,032.3
Due after five years through ten years	434.4		453.9
Due after ten years	40.2		46.1
Mortgage-backed and asset-backed securities	1,811.1		1,840.9
Preferred stocks	79.6		85.8
Total	$	4,664.8	$	4,796.5

Investment holdings, equity securities, convertible fixed maturities and other long-term investments



	December 31, 2014
Millions	Cost or amortized cost		Gross unrealized gains		Gross unrealized losses			Net foreign currency losses			Carrying value
Common equity securities	$	633.6	$	175.1	$	(5.2	)	$	(1.9	)	$	801.6
Convertible fixed maturity and preferred investments	$	19.1	$	.9	$	(.2	)	$	.7		$	20.5
Other long-term investments	$	344.5	$	73.0	$	(10.9	)	$	1.6		$	408.2



	December 31, 2013
Millions	Cost or amortized cost		Gross unrealized gains		Gross unrealized losses			Net foreign currency losses			Carrying value
Common equity securities	$	890.2	$	271.0	$	(3.6	)	$	(.8	)	$	1,156.8
Convertible fixed maturity and preferred investments	$	71.7	$	9.9	$	(.9	)	$	(.2	)	$	80.5
Other long-term investments	$	238.3	$	79.6	$	(26.6	)	$	(2.4	)	$	288.9

Fair value measurements by level, investment securities



	December 31, 2014
Millions	Fair value		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs
Fixed maturity investments:
U.S. Government and agency obligations	$	188.1	$	134.1	$	54.0	$	—
Debt securities issued by corporations:
Consumer	777.6		—		777.6		—
Financials	456.6		—		456.6		—
Industrial	285.0		—		285.0		—
Communications	237.5		—		237.5		—
Utilities	169.8		—		169.8		—
Energy	181.8		—		181.8		—
Basic Materials	108.6		—		103.0		5.6
Technology	87.9		—		87.9		—
Other	6.4		—		6.4		—
Total debt securities issued by corporations:	2,311.2		—		2,305.6		5.6

Mortgage-backed and asset-backed securities	1,840.9		—		1,840.9		—
Foreign government, agency and provincial obligations	275.1		21.3		253.8		—
Preferred stocks	85.8		—		14.7		71.1
Municipal obligations	83.2		—		83.2		—
Total fixed maturity investments	4,784.3		155.4		4,552.2		76.7

Short-term investments	871.7		868.8		2.9		—

Common equity securities:
Financials	233.9		193.7		—		40.2
Consumer	238.4		238.3		.1		—
Industrial	91.7		91.7		—		—
Energy	32.7		32.7		—		—
Technology	36.6		36.6		—		—
Communications	45.1		45.1		—		—
Basic materials	21.5		21.5		—		—
Utilities	9.5		9.4		.1		—
Other	92.2		18.9		73.3		—
Total common equity securities	801.6		687.9		73.5		40.2
Convertible fixed maturity and preferred investments	20.5		—		12.3		8.2
Other long-term investments ⁽¹⁾	385.0		—		—		385.0
Total investments ⁽¹⁾	$	6,863.1	$	1,712.1	$	4,640.9	$	510.1


⁽¹⁾	Excludes carrying value of $23.2 associated with other long-term investment limited partnerships accounted for using the equity method.



	December 31, 2013
Millions	Fair value		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs
Fixed maturity investments:
U.S. Government and agency obligations	$	362.5	$	295.8	$	66.7	$	—
Debt securities issued by corporations:
Consumer	754.4		—		754.4		—
Communications	265.0		—		265.0		—
Financials	434.4		—		434.4		—
Industrial	281.1		—		281.1		—
Basic Materials	149.1		—		149.1		—
Utilities	173.6		—		173.6		—
Energy	159.7		—		159.7		—
Technology	91.2		—		91.2		—
Other	38.7		—		38.7		—
Total debt securities issued by corporations:	2,347.2		—		2,347.2		—

Mortgage-backed and asset-backed securities	2,014.5		—		1,992.5		22.0
Foreign government, agency and provincial obligations	439.9		44.5		395.4		—
Preferred stocks	84.8		—		13.8		71.0
Municipal obligations	17.9		—		17.9		—
Total fixed maturity investments⁽¹⁾	5,266.8		340.3		4,833.5		93.0

Short-term investments	635.9		621.5		14.4		—

Common equity securities:
Financials	360.4		314.3		—		46.1
Consumer	308.2		308.2		—		—
Basic materials	53.4		53.4		—		—
Energy	78.6		78.6		—		—
Utilities	34.3		34.3		—		—
Technology	60.6		60.6		—		—
Industrial	105.4		105.4		—		—
Communications	57.1		57.1		—		—
Other	98.8		24.5		74.3		—
Total common equity securities	1,156.8		1,036.4		74.3		46.1
Convertible fixed maturity and preferred investments	80.5		—		74.4		6.1
Other long-term investments ⁽²⁾	262.4		—		—		262.4
Total investments	$	7,402.4	$	1,998.2	$	4,996.6	$	407.6


⁽¹⁾	Carrying value includes $236.3 that is classified as assets held for sale relating to discontinued operations.


⁽²⁾	Excludes carrying value of $26.6 associated with other long-term investment limited partnerships accounted for using the equity method and $(.1) related to foreign currency forward contracts.

Debt securities issued by corporations, credit ratings

The following table summarizes the ratings of the corporate debt securities held in White Mountains’s investment portfolio as of December 31, 2014 and 2013:



	Fair Value at
	December 31,
Millions	2014		2013
AAA	$	—	$	—
AA	236.9		228.8
A	957.8		1,039.5
BBB	1,105.9		1,075.5
BB	—		—
Other	10.6		3.4
Debt securities issued by corporations⁽¹⁾	$	2,311.2	$	2,347.2


⁽¹⁾	Credit ratings are assigned based on the following hierarchy: 1) Standard & Poor’s and 2) Moody’s.

Mortgage-backed, asset-backed securities



	December 31, 2014						December 31, 2013
Millions	Fair Value		Level 2		Level 3		Fair Value		Level 2		Level 3
Mortgage-backed securities:
Agency:
GNMA	$	411.2	$	411.2	$	—	$	512.3	$	512.3	$	—
FNMA	36.6		36.6		—		81.2		81.2		—
FHLMC	49.6		49.6		—		91.3		91.3		—
Total Agency⁽¹⁾	497.4		497.4		—		684.8		684.8		—
Non-agency:
Residential	131.2		131.2		—		125.7		125.7		—
Commercial	236.9		236.9		—		282.3		282.3		—
Total Non-agency	368.1		368.1		—		408.0		408.0		—

Total mortgage-backed securities	865.5		865.5		—		1,092.8		1,092.8		—
Asset-backed securities:
Credit card receivables	522.2		522.2		—		311.4		289.4		22.0
Vehicle receivables	289.4		289.4		—		365.0		365.0		—
Other	163.8		163.8		—		245.3		245.3		—
Total asset-backed securities	975.4		975.4		—		921.7		899.7		22.0
Total mortgage and asset-backed securities	$	1,840.9	$	1,840.9	$	—	$	2,014.5	$	1,992.5	$	22.0


⁽¹⁾	Represents publicly traded mortgage-backed securities which carry the full faith and credit guaranty of the U.S. government (i.e., GNMA) or are guaranteed by a government sponsored entity (i.e., FNMA, FHLMC).

Schedule of security issuance years of investments in non-agency RMBS and non-agency CMBS securities

The security issuance years of White Mountains’s investments in non-agency RMBS and non-agency CMBS securities as of December 31, 2014 are as follows:



					Security Issuance Year
Millions	Fair Value		2004		2005		2006		2007		2008		2009		2010		2011		2012		2013		2014
Non-agency RMBS	$	131.2	$	14.2	$	14.7	$	9.9	$	—	$	16.5	$	—	$	14.7	$	21.4	$	—	$	29.7	$	10.1
Non-agency CMBS	236.9		—		—		8.5		—		—		—		11.7		—		20.7		79.9		116.1
Total	$	368.1	$	14.2	$	14.7	$	18.4	$	—	$	16.5	$	—	$	26.4	$	21.4	$	20.7	$	109.6	$	126.2

Non-agency residential mortgage securities, collateral quality and tranche levels

The classification of the underlying collateral quality and the tranche levels of White Mountains’s non-agency RMBS securities are as follows as of December 31, 2014:



Millions	Fair Value		Super Senior⁽¹⁾		Senior⁽²⁾		Subordinate⁽³⁾
Prime	$	119.4	$	71.6	$	47.8	$	—
Non-prime	9.3		—		9.3		—
Sub-prime	2.5		2.5		—		—
Total	$	131.2	$	74.1	$	57.1	$	—


⁽¹⁾	At issuance, Super Senior, or in the case of resecuritization, the underlying securities, were rated “AAA” by Standard & Poor’s, “Aaa” by Moody’s or “AAA” by Fitch Ratings (“Fitch”) and were senior to other “AAA” or “Aaa” bonds.


⁽²⁾	At issuance, Senior, or in the case of resecuritization, the underlying securities, were rated “AAA” by Standard & Poor’s, “Aaa” by Moody’s or “AAA” by Fitch and were senior to non-“AAA” or non-“Aaa” bonds.


⁽³⁾	At issuance, Subordinate were not rated “AAA” by Standard & Poor’s, “Aaa” by Moody’s or “AAA” by Fitch and were junior to “AAA” or “Aaa” bonds.

Non-agency commercial mortgage securities, type of interest rate and tranche levels

The amount of fixed and floating rate securities and their tranche levels of White Mountains’s non-agency CMBS securities are as follows as of December 31, 2014:



Millions	Fair Value		Super Senior⁽¹⁾		Senior⁽²⁾		Subordinate⁽³⁾
Fixed rate CMBS	$	116.2	$	13.1	$	61.6	$	41.5
Floating rate CMBS	120.7		—		—		120.7
Total	$	236.9	$	13.1	$	61.6	$	162.2

Other long-term investments

Other long-term investments consist of the following as of December 31, 2014 and 2013:



	Fair Value at
Millions	December 31, 2014		December 31, 2013
Hedge funds and private equity funds⁽¹⁾	$	242.9	$	239.0
Limited liability companies and private equity securities⁽¹⁾	69.7		20.3
OBIC Surplus Notes⁽¹⁾	65.1		—
Other⁽¹⁾	7.3		3.1
Forward contracts (see Note 9)	—		(.1		)
Total other-long term investments⁽²⁾	$	385.0	$	262.3

⁽¹⁾See Fair Value Measurements by Level table.

⁽²⁾Excludes carrying value of $23.2 and $26.6 associated with other long-term investment limited partnerships accounted for using the equity method.

The following table summarizes investments in hedge funds and private equity interests by investment objective and sector as of December 31, 2014 and 2013:



	December 31, 2014				December 31, 2013
Millions	Fair Value		Unfunded Commitments		Fair Value		Unfunded Commitments
Hedge funds
Long/short equity	$	43.9	$	—	$	62.6	$	—
Long/short credit & distressed	21.4		—		22.8		—
Long/short equity REIT	20.3		—		18.3		—
Long/short equity activist	6.2		—		16.8		—
Long bank loan	.2		—		.2		—
Long diversified strategies	—		—		.1		—
Total hedge funds	92.0		—		120.8		—

Private equity funds
Energy infrastructure & services	59.6		11.0		45.9		13.1
Multi-sector	24.2		5.3		23.8		6.5
Manufacturing/Industrial	23.2		7.3		11.2		15.5
Private equity secondaries	8.5		3.1		9.5		3.1
Real estate	3.6		3.3		8.2		3.3
Aerospace/Defense/Government	20.7		5.1		5.8		19.2
Healthcare	6.1		2.8		5.6		2.8
International multi-sector, Europe	1.5		2.3		3.9		2.8
Insurance	2.1		41.2		2.3		41.3
Venture capital	1.4		.3		1.6		.3
Distressed residential real estate	—		—		.4		—
International multi-sector, Asia	—		—		—		2.7
Total private equity funds	150.9		81.7		118.2		110.6
Total hedge and private equity funds included in other long-term investments	$	242.9	$	81.7	$	239.0	$	110.6

Fair value of hedge funds subject to restrictions on redemption frequency and advance notice period requirements for investments in active hedge funds

The following summarizes the December 31, 2014 fair value of hedge funds subject to restrictions on redemption frequency and advance notice period requirements for investments in active hedge funds:



	Notice Period
Millions Redemption frequency	30-59 days notice		60-89 days notice		90-119 days notice		120+ days notice		Total
Monthly	$	4.3	$	—	$	—	$	—	$	4.3
Quarterly	31.8		21.4		—		7.8		61
Semi-annual	—		22.1		—		—		22.1
Annual	—		—		4.4		.2		4.6
Total	$	36.1	$	43.5	$	4.4	$	8.0	$	92.0

Fair Value of private equity funds subject to lock-up periods

As of December 31, 2014, investments in private equity funds were subject to lock-up periods as follows:



Millions	1-3 years		3 – 5 years		5 – 10 years		>10 years		Total
Private Equity Funds — expected lock-up period remaining	$	12.7	$	33.5	$	79.0	$	25.7	$	150.9

Rollforward of fair value investments by level

The following tables summarize the changes in White Mountains’s fair value measurements by level for the years ended December 31, 2014 and 2013:



							Level 3 Investments
Millions	Level 1 Investments			Level 2 Investments			Fixed maturity investments			Common equity securities			Convertible Fixed Maturity and Preferred Investments		Other long-term investments				Total
Balance at January 1, 2014	$	1,376.7		$	4,982.2		$	93.0		$	46.1		$	6.1	$	262.4		⁽¹⁾	$	6,766.5		^(1)(2)(3)
Total realized and unrealized gains	88.1			163.4			2.2			6.2			.6		26.0				286.5			⁽⁴⁾
Foreign currency losses in OCI	(24.8		)	(222.8		)	(1.0		)	—			—		(5.0		)		(253.6		)
Amortization/Accretion	(.6		)	(43.6		)	.1			—			—		—				(44.1		)
Purchases	1,599.2			3,772.4			71.7			5.0			1.5		152.3				5,602.1
Sales	(2,197.1		)	(4,122.6		)	—			(17.1		)	—		(50.7		)		(6,387.5		)
Net change in investments related to purchases and sales of consolidated affiliates	(2.7		)	24.2			—			—			—		—				21.5
Exchange	4.7			(13.0		)	8.3			—			—		—				—
Transfers in	—			97.8			—			—			—		—				97.8
Transfers out	(.2		)	—			(97.6		)	—			—		—				(97.8		)
Balance at December 31, 2014	$	843.3		$	4,638.0		$	76.7		$	40.2		$	8.2	$	385.0		⁽¹⁾	$	5,991.4		^(1)(2)(3)


⁽¹⁾	Excludes carrying value of $23.2 and $26.6 as of December 31, 2014 and January 1, 2014 associated with other long-term investments accounted for using the equity method.


⁽²⁾	Carrying value includes $236.3 as of January 1, 2014 that is classified as assets held for sale relating to discontinued operations.


⁽³⁾	Excludes carrying value of $871.7 and $635.9 as of December 31, 2014 and January 1, 2014 classified as short-term investments.


⁽⁴⁾	Excludes $4.3 of realized and unrealized losses associated with the Prospector Funds consolidation of investment-related liabilities and $2.8 of realized and unrealized gains associated with short-term investments.



							Level 3 Investments
Millions	Level 1 Investments			Level 2 Investments			Fixed maturity investments			Common equity securities			Convertible Fixed Maturity and Preferred Investments		Other long-term investments				Total
Balance at January 1, 2013	$	1,355.1		$	5,206.1		$	92.9		$	37.3		$	—	$	259.3		⁽¹⁾	$	6,950.7		^(1)(2)(3)
Total realized and unrealized gains (losses)	221.9			(56.9		)	(2.7		)	1.0			—		18.7				182.0
Foreign currency (losses) gains in OCI	(.3		)	12.5			.3			—			—		(0.9		)		11.6
Amortization/Accretion	(1.0		)	(51.2		)	—			—			—		—				(52.2		)
Purchases	862.1			3,689.6			37.9			8.8			—		37.1				4,635.5
Sales	(1,078.9		)	(3,842.8		)	(6.3		)	—			—		(51.8		)		(4,979.8		)
Net change in investments related to purchases and sales of consolidated affiliates	16.0			2.7			—			—			—		—				18.7
Transfers in	1.8			119.4			90.3			—			6.1		—				217.6
Transfers out	—			(97.2		)	(119.4		)	(1.0		)	—		—				(217.6		)
Balance at December 31, 2013	$	1,376.7		$	4,982.2		$	93.0		$	46.1		$	6.1	$	262.4		⁽¹⁾	$	6,766.5		^(1)(2)(3)


⁽¹⁾	Excludes carrying value of $26.6 and $35.0 as of December 31, 2013 and January 1, 2013 associated with other long-term investment limited partnerships accounted for using the equity method and $(.1) as of December 31, 2013 related to foreign currency forward contracts.


⁽²⁾	Carrying value includes $236.3 and $338.1 as of December 31, 2013 and January 1, 2013 that is classified as assets held for sale relating to AutoOne discontinued operations.


⁽³⁾	Excludes carrying value of $635.9 and $630.6 as of December 31, 2013 and January 1, 2013 classified as short-term investments.


⁽⁴⁾	Excludes $20.6 of realized and unrealized losses associated with the Prospector Funds consolidation of investment-related liabilities and $.2 of realized and unrealized gains associated with short-term investments.

Schedule of significant unobservable inputs used in estimating the fair value of investment securities

he fair value of investments in hedge funds and private equity funds, which are classified within Level 3, are estimated using the net asset value of the funds.

($ in Millions)

December 31, 2014

December 31, 2013

Description

Rating⁽²⁾

Valuation

Technique(s)

Fair
Value

Unobservable Input

Fair

Value

Unobservable Input

Preferred Stock⁽¹⁾

Discounted cash flow

$71.1

Discount yield

7.1%

$71.0

Discount yield

7.4%

Private equity security⁽¹⁾

Multiple of GAAP book value

$40.2

Book value multiple

1.10

$35.6

Book value multiple

1.00

Private equity security⁽¹⁾

Share price of recent transaction

$20.1

Share price

$1.06

$10.5

Share price

$1.10

Private equity security⁽¹⁾

Share price of recent transaction

$10.4

Share price

$290.96

N/A

Private equity security⁽¹⁾

Share price of recent transaction

$15.8

Share price

$0.13

N/A

Convertible preferred security⁽¹⁾

Share price of recent transaction

$4.5

Share price

$0.71

$3.0

Share price

$0.71

Convertible preferred security⁽¹⁾

Multiple of EBITDA

$3.8

EBITDA multiple

6.00

$3.1

EBITDA multiple

6.00

Debt security issued by corporation⁽¹⁾

Discounted cash flow

$5.6

Illiquidity discount⁽³⁾

10%

N/A

Asset-backed securities⁽¹⁾

AA+

Broker pricing

N/A

Broker quote

$22.0

Broker quote

Seller priority surplus note

Discounted cash flow

$44.0

Discount rate ⁽⁴⁾

9.3%

N/A

Timing of interest

payments⁽⁶⁾

5 years

N/A

Timing of interest

payments⁽⁶⁾

10 years

N/A

Pari passu surplus

note

Discounted cash flow

$21.1

Discount rate⁽⁵⁾

13.5%

N/A

Timing of interest

payments⁽⁶⁾

5 years

N/A

Timing of interest

payments⁽⁶⁾

10 years

N/A


⁽¹⁾	As of December 31, 2014 each asset type consists of one security.


⁽²⁾	Credit ratings are assigned based on the following hierarchy: 1) Standard & Poor’s and 2) Moody’s.


⁽³⁾	Judgmentally determined based on the Company’s limited trading ability of the issuer.

⁽⁴⁾

⁽⁵⁾


⁽⁶⁾	For estimated value purposes, the assumption has been made that interest payouts begin in year five and that principal repayments being on a graduated basis in year ten for the seller priority notes and year fifteen for the pari passu note.

Debt and Standby Letter of Credit Facilities (Tables)

12 Months Ended

Dec. 31, 2014

Debt Disclosure [Abstract]

Schedule of debt outstanding

White Mountains’s debt outstanding as of December 31, 2014 and 2013 consisted of the following:



	December 31,
Millions	2014			2013
OBH Senior Notes, at face value	$	275.0		$	275.0
Unamortized original issue discount	(.3		)	(.3		)
OBH Senior Notes, carrying value	274.7			274.7
SIG Senior Notes, at face value	400.0			400.0
Unamortized original issue discount	(.3		)	(.4		)
SIG Senior Notes, carrying value	399.7			399.6
WTM Bank Facility	—			—
Tranzact Bank Facility	68.7			—
Unamortized issuance cost	(1.3		)	—
Tranzact Bank Facility, carrying value	67.4			—
Other debt	4.8			2.1
Total debt	$	746.6		$	676.4

Schedule of contractual repayments of debt

A schedule of contractual repayments of White Mountains’s debt as of December 31, 2014, follows:



Millions	December 31, 2014
Due in one year or less	$	6.0
Due in two to three years	424.6
Due in four to five years	42.9
Due after five years	275.0
Total	$	748.5

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21538-112644

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21521-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 22
-Article 5

+ Details

Goodwill and Other Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2014

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Intangible Assets and Goodwill [Table Text Block]

The following table shows the economic lives, acquisition date values, accumulated amortization and net carrying values for other intangible assets and goodwill, for each company acquired:



Millions	Weighted Average Economic life (in years)	December 31, 2014						December 31, 2013
		Acquisition date fair value		Accumulated amortization		Net carrying value		Acquisition date fair value		Accumulated amortization		Net carrying value
Tranzact:
Domain and trade names	6	$	25.6	$	.9	$	24.7	$	—	$	—	$	—
Customer relationships	10	107.5		2.1		105.4		—		—		—
Information technology	5	12.7		.5		12.2		—		—		—
Other	7	.5		—		.5		—		—		—
Subtotal		146.3		3.5		142.8		—		—		—

QuoteLab:
Customer relationships	4	6.5		1.2		5.3		—		—		—
Information technology	5	32.0		4.8		27.2		—		—		—
Subtotal		38.5		6.0		32.5		—		—		—

Wobi:
Trademark	8	2.1		.2		1.9		—		—		—
Information technology	3	.8		.2		.6		—		—		—
Subtotal		2.9		.4		2.5		—		—		—

Star & Shield:
Customer relationship	3	1.2		.4		.8		—		—		—

OneBeacon (EBI)	10	9.4		5.7		3.7		9.4		4.3		5.1

Sirius (WM Solutions) - Licenses	Indefinite	15.2		—		15.2		15.6		—		15.6

Total other intangible assets		213.5		16.0		197.5		25.0		4.3		20.7

Goodwill:
Tranzact	N/A	145.1		—		145.1		—		—		—
Quote Lab	N/A	18.3		—		18.3		—		—		—
Wobi	N/A	5.5		—		5.5		—		—		—
Total goodwill		168.9		—		168.9		—		—		—

Total goodwill and other intangible assets		$	382.4	$	16.0	$	366.4	$	25.0	$	4.3	$	20.7

Schedule of Goodwill and Intangible Assets Rollforward

The following table shows the change in goodwill and other intangible assets:



	December 31,
Millions	2014					2013
	Goodwill		Other intangible assets			Goodwill		Other intangible assets
Beginning balance	$	—	$	20.7		$	—	$	16.9
Acquisitions of businesses	168.9		188.9			—		5.2
Dispositions of businesses	—		(.4		)	—		—
Amortization, including foreign currency translation	—		(11.7		)	—		(1.4		)
Ending balance	$	168.9	$	197.5		$	—	$	20.7

Schedule of Finite-Lived Intangible Assets, Future Amortization Expense

White Mountains expects to recognize amortization expense in each of the next five years as follows:



Millions	Amortization expense
2015	$	27.1
2016	27.0
2017	26.4
2018	24.6
2019	16.5
Total	$	121.6

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2014

Income Tax Disclosure [Abstract]

Schedule of total income tax benefit (expense)

The total income tax (expense) benefit for the years ended December 31, 2014, 2013 and 2012 consisted of the following:



	Year Ended December 31,
Millions	2014			2013			2012
Current tax (expense) benefit:
U.S. federal	$	(6.2	)	$	(19.0	)	$	8.2
State	(4.8		)	(1.4		)	(3.4		)
Non-U.S.	(45.0		)	(16.5		)	(5.9		)
Total current tax expense	(56.0		)	(36.9		)	(1.1		)
Deferred tax (expense) benefit:
U.S. federal	13.6			(24.4		)	(55.5		)
State	—			—			—
Non-U.S.	(10.9		)	(15.3		)	72.3
Total deferred tax benefit (expense)	2.7			(39.7		)	16.8
Total income tax (expense) benefit	$	(53.3	)	$	(76.6	)	$	15.7

Reconciliation of the U.S. federal statutory income tax rate and actual effective tax rate on pre-tax income



	Year Ended December 31,
Millions	2014			2013			2012
Tax (expense) benefit at the U.S. statutory rate	$	(105.6	)	$	(120.7	)	$	(92.0	)
Differences in taxes resulting from:
Non-U.S. earnings, net of foreign taxes	77.7			82.9			43.0
Change in valuation allowance	(18.1		)	(33.6		)	(14.1		)
Withholding tax	(5.6		)	(1.7		)	(2.9		)
Tax exempt interest and dividends	4.4			3.2			3.1
Tax reserve adjustments	(2.2		)	(10.2		)	(1.3		)
Purchase of subsidiaries	(.3		)	5.3			5.1
Tax rate change enacted in Sweden	—			—			65.4
Tax rate change enacted in Luxembourg	—			—			7.2
Other, net	(3.6		)	(1.8		)	2.2
Total income tax (expense) benefit on pre-tax income	$	(53.3	)	$	(76.6	)	$	15.7

Schedule of components of deferred income tax assets and liabilities

An outline of the significant components of White Mountains’s deferred tax assets and liabilities follows:



	December 31,
Millions	2014			2013
Deferred income tax assets related to:
Non-U.S. net operating loss carryforwards	$	427.4		$	520.6
U.S. federal net operating and capital loss carryforwards	213.4			148.6
Loss reserve discount	79.3			74.9
Unearned premiums	46.0			38.9
Incentive compensation	42.0			53.9
Tax credit carryforwards	25.8			23.1
Runoff Transaction	12.6			24.2
Deferred compensation	8.9			10.3
Accrued interest	5.3			1.1
Fixed assets	3.6			4.9
Other items	8.4			6.9
Total gross deferred income tax assets	872.7			907.4
Less: valuation allowances	(274.6		)	(289.8		)
Total net deferred income tax assets	598.1			617.6
Deferred income tax liabilities related to:
Safety reserve	295.7			357.2
Net unrealized investment gains	45.3			44.6
Deferred acquisition costs	40.5			33.0
Investment basis difference	22.9			3.0
Members surplus contributions	10.3			5.4
Purchase accounting	7.0			7.2
Pension and benefit accruals	—			3.4
Other items	3.1			7.9
Total deferred income tax liabilities	424.8			461.7
Net deferred tax asset	$	173.3		$	155.9

Schedule of net operating and capital loss carryforwards by expiration dates and the deferred tax assets thereon

Net operating loss and capital loss carryforwards as of December 31, 2014, the expiration dates and the deferred tax assets thereon are as follows:



	December 31, 2014
Millions	United States			Luxembourg			Sweden		Netherlands			UK		Israel			Total
2014	$	—		$	—		$	—	$	—		$	—	$	—		$	—
2015 - 2019	1.1			—			—		.5			—		—			1.6
2020 - 2024	9.6			—			—		.8			—		—			10.4
2025 - 2034	621.6			—			—		—			—		—			621.6
No expiration date	—			1,417.5			106.0		—			5.8		7.1			1,536.4
Total	$	632.3		$	1,417.5		$	106.0	$	1.3		$	5.8	$	7.1		$	2,170.0
Gross deferred tax asset	$	213.4		$	414.2		$	9.8	$	.3		$	1.2	$	1.9		$	640.8
Valuation allowance	(97.2		)	(166.1		)	—		(.3		)	—		(1.9		)	(265.5		)
Net deferred tax asset	$	116.2		$	248.1		$	9.8	$	—		$	1.2	$	—		$	375.3

Reconciliation of changes in the amount of unrecognized tax benefits

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows:



Millions	Permanent Differences⁽¹⁾			Temporary Differences⁽²⁾			Interest and Penalties⁽³⁾			Total
Balance at January 1, 2012	$	9.6		$	49.1		$	6.8		$	65.5
Changes in prior year tax positions	.5			—			1.4			1.9
Tax positions taken during the current year	—			(20.2		)	—			(20.2		)
Lapse in statute of limitations	—			—			—			—
Settlements with tax authorities	(.4		)	—			(.2		)	(.6		)
Balance at December 31, 2012	9.7			28.9			8.0			46.6
Changes in prior year tax positions	.6			(7.1		)	1.7			(4.8		)
Tax positions taken during the current year	7.9			.7			—			8.6
Settlements with tax authorities	—			—			(.4		)	(.4		)
Balance at December 31, 2013	18.2			22.5			9.3			50.0
Changes in prior year tax positions	(2.0		)	(.8		)	(2.0		)	(4.8		)
Tax positions taken during the current year	5.6			8.1			—			13.7
Lapse in statute of limitations	(.8		)	—			(.3		)	(1.1		)
Settlements with tax authorities	(.6		)	—			(.3		)	(.9		)
Balance at December 31, 2014	$	20.4		$	29.8		$	6.7		$	56.9


⁽¹⁾	Represents the amount of unrecognized tax benefits that, if recognized, would impact the effective tax rate.


⁽²⁾	Represents the amount of unrecognized tax benefits that, if recognized would create a temporary difference between the reported amount of an item in the Company’s Consolidated Balance Sheet and its tax basis.


⁽³⁾	Net of tax benefit.

Derivatives (Tables)

12 Months Ended

Dec. 31, 2014

Forward contracts

Derivative [Line Items]

Schedule of Derivative Instruments

The following table summarizes the notional amounts and the uncollateralized balances associated with foreign currency forward contracts:



	December 31, 2014					December 31, 2013
Millions	Notional Amount		Carrying Value		Standard & Poor's Rating⁽¹⁾	Notional Amount		Carrying Value
Barclays Bank Plc	$	2.1	$	—	A	$	5.8	$	—
Deutsche Bank	—		—		A	7.7		—
Goldman Sachs	8.7		—		A	2.1		—
HSBC Bank Plc	11.2		—		AA-	3.3		(.1		)
JP Morgan	5.7		—		A+	1.3		—
Royal Bank of Canada	5.4		—		AA-	.2		—
Total	$	33.1	$	—		$	20.4	$	(.1	)


⁽¹⁾	Standard & Poor’s (“S&P”) ratings as detailed above are: “AA-” (Very Strong, which is the sixth highest of twenty-one creditworthiness ratings), “A+” (Strong, which is the seventh highest of twenty-one creditworthiness ratings) and “A” (Strong, which is the eighth highest of twenty-one creditworthiness ratings).

Variable Annuity Reinsurance

Derivative [Line Items]

Pre-tax operating results

The following table summarizes the pre-tax operating results of WM Life Re for the years ended December 31, 2014, 2013 and 2012:



	Year Ended December 31,
Millions	2014			2013			2012
Fees, included in other revenue	$	18.6		$	25.0		$	31.8
Change in fair value of variable annuity liability, included in other revenue	52.9			378.5			312.8
Change in fair value of derivatives, included in other revenue	(72.4		)	(402.0		)	(339.0		)
Foreign exchange, included in other revenue	(3.2		)	(14.5		)	(30.3		)
Other investment income and (losses) gains	(1.4		)	(7.1		)	2.5
Total revenues	(5.5		)	(20.1		)	(22.2		)
Change in fair value of variable annuity death benefit liabilities, included in general and administrative expenses	.6			10.2			14.2
Death benefit claims paid, included in general and administrative expenses	(.1		)	(1.9		)	(5.7		)
General and administrative expenses	(4.3		)	(4.9		)	(5.2		)
Pre-tax loss	$	(9.3	)	$	(16.7	)	$	(18.9	)

Fair Value of Assets and Liabilities Measured on Recurring and Non-recurring Basis Table

The following table summarizes the changes in White Mountains’s variable annuity reinsurance liabilities and derivative instruments for the year ended December 31, 2014, 2013 and 2012:



	Variable Annuity (Liabilities)				Derivative Instruments
Millions	Level 3				Level 3⁽¹⁾⁽⁶⁾			Level 2⁽¹⁾⁽²⁾			Level 1⁽³⁾			Total⁽⁴⁾
Balance at January 1, 2014	$	(52.8	)		$	63.4		$	4.7		$	1.1		$	69.2
Purchases	—				—			—			—			—
Realized and unrealized gains (losses)	53.5			⁽⁵⁾	(38.6		)	(71.0		)	37.2			(72.4		)
Transfers in (out)	—				—			—			—			—
Sales/settlements	—				(5.9		)	100.1			(34.6		)	59.6
Balance at December 31, 2014	$	.7			$	18.9		$	33.8		$	3.7		$	56.4



	Variable Annuity (Liabilities)				Derivative Instruments
Millions	Level 3				Level 3⁽¹⁾⁽⁶⁾			Level 2⁽¹⁾⁽²⁾			Level 1⁽³⁾			Total⁽⁴⁾
Balance at January 1, 2013	$	(441.5	)		$	140.5		$	(20.5	)	$	(21.7	)	$	98.3
Purchases	—				59.4			—			—			59.4
Realized and unrealized gains (losses)	388.7			⁽⁵⁾	(136.5		)	(196.1		)	(69.4		)	(402.0		)
Transfers in (out)	—				—			—			—			—
Sales/settlements	—				—			221.3			92.2			313.5
Balance at December 31, 2013	$	(52.8	)		$	63.4		$	4.7		$	1.1		$	69.2



	Variable Annuity (Liabilities)				Derivative Instruments
Millions	Level 3				Level 3⁽¹⁾⁽⁶⁾			Level 2⁽¹⁾⁽²⁾			Level 1⁽³⁾			Total⁽⁴⁾
Balance at January 1, 2012	$	(768.5	)		$	247.1		$	39.2		$	4.1		$	290.4
Purchases	—				6.1			—			—			6.1
Realized and unrealized gains (losses)	327.0			⁽⁵⁾	(84.0		)	(186.9		)	(68.1		)	(339.0		)
Transfers in (out)	—				—			—			—			—
Sales/settlements	—				(28.7		)	127.2			42.3			140.8
Balance at December 31, 2012	$	(441.5	)		$	140.5		$	(20.5	)	$	(21.7	)	$	98.3


⁽¹⁾	Consists of over-the-counter instruments.


⁽²⁾	Consists of interest rate swaps, total return swaps, foreign currency forward contracts, and bond forwards. Fair value measurement based upon bid/ask pricing quotes for similar instruments that are actively traded, where available. Swaps for which an active market does not exist have been priced using observable inputs including the swap curve and the underlying bond index.


⁽³⁾	Consists of exchange traded equity index, foreign currency and interest rate futures. Fair value measurements based upon quoted prices for identical instruments that are actively traded.


⁽⁴⁾	In addition to derivative instruments, WM Life Re held cash, short-term and fixed maturity investments of $33.2, $81.3 and $393.6 as of December 31, 2014, 2013 and 2012 posted as collateral to its reinsurance counterparties.


⁽⁵⁾	Includes $0.6, $10.2, $14.2 for December 31, 2014, 2013 and 2012 related to the change in the fair value of variable annuity death benefit liabilities, which are included in general and administrative expenses.

⁽⁶⁾Consists of foreign currency options and equity options.

Schedule of collateral

In addition, WM Life Re held cash and short-term investments posted as collateral to its variable annuity reinsurance and derivatives counterparties. The total collateral includes the following:



	December 31,
Millions	2014		2013
Cash	$	23.7	$	56.1
Short-term investments	—		2.0
Fixed maturity investments	9.5		23.2
Total	$	33.2	$	81.3

Schedule of significant unobservable inputs associated with the fair value estimates for variable annuity reinsurance liabilities and derivative instruments



($ in Millions)	December 31, 2014
Description	Fair Value		Valuation Technique(s)	Unobservable Input	Range				Weighted Average
Variable annuity benefit guarantee asset	$	.7	Discounted cash flows	Surrenders
				0-1 year	0.2	%	-	40.0%	40.0	%
				1-2 years	0.1	%	-	40.0%	32.1	%
				Mortality	0.0	%	-	5.9%	1.0	%
				Foreign exchange volatilities
				0-1 year	12.6	%	-	15.1%	13.3	%
				1-2 years	11.7	%	-	13.8%	12.6	%
				Index volatilities
				0-1 year	24.0	%	-	26.6%	25.6	%
				1-2 years	19.4	%	-	23.1%	21.8	%
Foreign Exchange Options	$	7.2	Counterparty valuations, adjusted for unwind quote discount	Adjustment to counterparty valuations	(0.5	)%	-	11.6%	3.6	%
Foreign Exchange Options			Counterparty valuations, adjusted for unwind quote discount	Adjustment to counterparty valuations
Equity Index Options	$	11.7	Counterparty valuations, adjusted for unwind quote discount	Adjustment to counterparty valuations	0.7	%	-	6.5%	2.0	%
Equity Index Options			Counterparty valuations, adjusted for unwind quote discount	Adjustment to counterparty valuations

Offestting Assets and Liabilities

The following summarizes amounts offset under master netting agreements:



	December 31, 2014								December 31, 2013
Millions	Gross asset amounts before offsets⁽¹⁾		Gross liability amounts offset under master netting arrangements			Net amounts recognized in Other Assets			Gross asset amounts before offsets⁽¹⁾		Gross liability amounts offset under master netting arrangements			Net amounts recognized in Other Assets
Interest rate contracts
OTC	$	1.0	$	(5.4	)	$	(4.4	)	$	2.4	$	(11.7	)	$	(9.3	)
Exchange traded	2.8		(.1		)	2.7			1.0		(1.6		)	(.6		)
Foreign exchange contracts
OTC	45.5		—			45.5			67.8		(12.0		)	55.8
Exchange traded	—		(1.4		)	(1.4		)	2.3		—			2.3
Equity contracts
OTC	11.7		(.2		)	11.5			30.7		(9.2		)	21.5
Exchange traded	3.4		(.9		)	2.5			1.8		(2.3		)	(.5		)
Total⁽²⁾	$	64.4	$	(8.0	)	$	56.4		$	106.0	$	(36.8	)	$	69.2

⁽¹⁾Amount equal to fair value of instrument as recognized in other assets.

⁽²⁾ All derivative instruments held by WM Life Re are subject to master netting arrangements.

Offsetting Assets



	December 31, 2014
Millions	Net amount of assets reflected in Balance Sheet			Collateral provided to counterparty - Cash		Collateral provided to counter-party - Financial Instruments		Net amount of exposure after effect of collateral provided		Excess collateral provided to counter-party- Cash		Excess collateral provided - Financial Instruments		Counter-party collateral held by WM Life Re - Cash		Net amount of exposure to counter-party		Standard & Poor's Rating⁽¹⁾
JP Morgan	$	24.3		$	—	$	—	$	24.3	$	—	$	—	$	8.8	$	15.5	A	+
Bank of America	5.6			—		—		5.6		—		—		—		5.6		A
Nomura	(3.5		)	3.5		—		—		1.7		9.5		—		11.2		BBB	+
Citigroup - OTC	22.2			—		—		22.2		—		—		1.1		21.1		A
Citigroup - Exchange Traded	3.7			—		—		3.7		16.0		—		—		19.7		A
Royal Bank of Scotland	4.0			—		—		4.0		—		—		—		4.0		A	-
Barclays	.1			—		—		.1		—		—		—		.1		A
Total	$	56.4		$	3.5	$	—	$	59.9	$	17.7	$	9.5	$	9.9	$	77.2



	December 31, 2013
Millions	Net amount of assets reflected in Balance Sheet			Collateral provided to counterparty - Cash		Collateral provided to counter-party - Financial Instruments		Net amount of exposure after effect of collateral provided		Excess collateral provided to counter-party- Cash		Excess collateral provided - Financial Instruments		Counter-party collateral held by WM Life Re- Cash		Net amount of exposure to counter-party		Standard & Poor's Rating⁽¹⁾
JP Morgan	$	9.1		$	—	$	—	$	9.1	$	22.0	$	—	$	—	$	31.1	A	+
Bank of America	27.2			—		—		27.2		—		—		—		27.2		A
Nomura	(.4		)	—		.4		—		—		22.8		.8		22.0		BBB	+
Citigroup - OTC	19.4			—		—		19.4		2.3		—		—		21.7		A
Citigroup - Exchange Traded	1.2			—		—		1.2		19.8		—		—		21.0		A
Royal Bank of Scotland	11.3			—		—		11.3		—		—		—		11.3		A	-
Barclays	1.4			—		—		1.4		—		—		—		1.4		A
Total	$	69.2		$	—	$	.4	$	69.6	$	44.1	$	22.8	$	.8	$	135.7


⁽¹⁾	Standard & Poor’s ratings as detailed above are: “A+” (Strong, which is the fifth highest of twenty-one creditworthiness ratings),“A” (which is the sixth highest of twenty-one creditworthiness ratings), “A-” (which is the seventh highest of twenty-one creditworthiness ratings), and BBB+ (which is the eighth highest of twenty-one creditworthiness ratings).

Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values, by the type of instrument



										Carrying Value
	Year Ended December 31,									December 31,
Millions	2014			2013			2012			2014			2013
Fixed income/interest rate	$	(33.7	)	$	(108.7	)	$	(149.5	)	$	(1.7	)	$	(9.7	)
Foreign exchange	(1.3		)	(96.7		)	(102.3		)	44.1			58.0
Equity	(37.4		)	(196.6		)	(87.2		)	14.0			20.9
Total	$	(72.4	)	$	(402.0	)	$	(339.0	)	$	56.4		$	69.2

Interest Rate Cap

Derivative [Line Items]

Schedule of collateral

The following table summarizes the Interest Rate Cap collateral balances held by White Mountains and ratings by counterparty:



	December 31, 2014
Millions	Collateral Balances Held		Standard & Poor’s Rating⁽¹⁾
Barclays Bank Plc	$	3.0	A
Nordea Bank Finland Plc	1.3		AA-
Total	$	4.3


⁽¹⁾	Standard & Poor’s ratings as detailed above are: “A” (Strong, which is the sixth highest of twenty-one creditworthiness ratings) and “AA-” (Very Strong, which is the fourth highest of twenty-one creditworthiness ratings).

Fair Value of Assets and Liabilities Measured on Recurring and Non-recurring Basis Table

The following table summarizes the change in the fair value of the Interest Rate Cap for the year ended December 31, 2014:



	December 31,
Millions	2014			2013
Beginning of period	$	11.1		$	—
Purchases	—			9.9
Net realized and unrealized gains	(7.0		)	1.2
Sales/settlements	—			—
End of period	$	4.1		$	11.1

Municipal Bond Guarantee Insurance (Tables)

12 Months Ended

Dec. 31, 2014

Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]

Schedule of Municipal Guarantee Insured Obligations [Table Text Block]

The following table provides a schedule of BAM’s insured obligations:



	December 31, 2014		December 31, 2013
Contracts outstanding	1,750		701
Remaining weighted average contract period (in years)	12.8		13.8
Contractual debt service outstanding (in millions):
Principal	$	12,362.5	$	4,703.7
Interest	$	7,086.9	$	3,264.4
Gross unearned insurance premiums	$	27.6	$	13.2

Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2014

Earnings Per Share [Abstract]

Computation of earnings per share

The following table outlines the Company’s computation of earnings per share from continuing operations for the years ended December 31, 2014, 2013 and 2012 (see Note 22 for earnings per share amounts for discontinued operations):



	Year Ended December 31,
	2014			2013			2012
Basic and diluted earnings per share numerators (in millions):
Net income from continuing operations attributable to White Mountains’s common shareholders	$	316.1		$	317.3		$	322.4
Allocation of income for unvested restricted common shares⁽¹⁾	(4.1		)	(4.7		)	(4.3		)
Dividends declared on participating restricted common shares⁽¹⁾	(.1		)	(.1		)	(.1		)
Total allocation to restricted common shares	(4.2		)	(4.8		)	(4.4		)
Net income attributable to White Mountains’s common shareholders, net of restricted share amounts	$	311.9		$	312.5		$	318.0
Undistributed net earnings (in millions):
Net income attributable to White Mountains’s common shareholders, net of restricted common share amounts	$	311.9		$	312.5		$	318.0
Dividends declared net of restricted common share amounts⁽¹⁾	(6.1		)	(6.1		)	(6.5		)
Total undistributed net earnings, net of restricted common share amounts	$	305.8		$	306.4		$	311.5
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period	6,104.9			6,200.4			6,799.8
Average unvested restricted common shares⁽²⁾	(78.9		)	(91.4		)	(91.1		)
Basic earnings per share denominator	6,026.0			6,109.0			6,708.7
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period	6,104.9			6,200.4			6,799.8
Average unvested restricted common shares⁽²⁾	(78.9		)	(91.4		)	(91.1		)
Average outstanding dilutive options to acquire common shares⁽³⁾	—			—			—
Diluted earnings per share denominator	6,026.0			6,109.0			6,708.7
Basic earnings per share (in dollars):
Net income attributable to White Mountains’s common shareholders	$	51.77		$	51.15		$	47.41
Dividends declared and paid	(1.00		)	(1.00		)	(1.00		)
Undistributed earnings	$	50.77		$	50.15		$	46.41
Diluted earnings per share (in dollars)
Net income attributable to White Mountains’s common shareholders	$	51.77		$	51.15		$	47.41
Dividends declared and paid	(1.00		)	(1.00		)	(1.00		)
Undistributed earnings	$	50.77		$	50.15		$	46.41


⁽¹⁾	Restricted shares issued by White Mountains receive dividends, and therefore, are considered participating securities.


⁽²⁾	Restricted common shares outstanding vest either in equal annual installments or upon a stated date (see Note 13).


⁽³⁾	The diluted earnings per share denominator for the years ended December 31, 2014, 2013 and 2012 do not include the impact of 125,000 common shares issuable upon exercise of the non-qualified options outstanding as they are anti-dilutive to the calculation.

Retirement and Postretirement Plans (Tables)

12 Months Ended

Dec. 31, 2014

Compensation and Retirement Disclosure [Abstract]

Schedule of changes in projected benefit obligations and fair value of plan assets and funded status of plan assets

The following tables set forth the obligations and funded status, assumptions, plan assets and cash flows associated with the Plans as of December 31, 2014 and 2013:



	Pension Benefits December 31,
Millions	2014			2013
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$	102.9		$	119.5
Service cost	.6			.8
Interest cost	4.7			4.2
Special termination benefits expense	.3			.3
Assumption changes	17.5			(13.0		)
Actuarial loss (gain)	1.1			(.5		)
Benefits and expenses paid with plan assets	(5.2		)	(6.2		)
Benefits paid directly by OneBeacon	(2.2		)	(2.2		)
Projected benefit obligation at end of year	$	119.7		$	102.9
Change in plan assets:
Fair value of plan assets at beginning of year	$	142.8		$	124.7
Actual return on plan assets	8.4			24.3
Benefits and expenses paid	(5.2		)	(6.2		)
Fair value of plan assets at end of year	$	146.0		$	142.8
Funded status at end of year	$	26.3		$	39.9

Schedule of amounts recorded in financial statements

Amounts recognized in the financial statements as of December 31, 2014 and 2013 consist of:



	December 31,
Millions	2014			2013
Net assets of the Qualified Plan recorded in other assets	$	53.4		$	64.1
Net liabilities of the Non-qualified Plan recorded in other liabilities	(27.1		)	(24.2		)
Net amount accrued in the financial statements	$	26.3		$	39.9

Information for the Non-qualified Plan, which has accumulated benefit obligations in excess of plan assets

Information for the Non-qualified Plan, which had accumulated benefit obligations in excess of plan assets, was as follows:



	December 31,
Millions	2014		2013
Projected benefit obligation	$	27.1	$	24.2
Accumulated benefit obligation	$	27.1	$	24.2
Fair value of plan assets	$	—	$	—

Information for the Qualified Plan, which had accumulated benefit obligations less than plan assets

Information for the Qualified Plan, which had accumulated benefit obligations less than plan assets, was as follows:



	December 31,
Millions	2014		2013
Projected benefit obligation	$	92.6	$	78.7
Accumulated benefit obligation	$	92.6	$	78.7
Fair value of plan net assets	$	146.0	$	142.8

Schedule of amounts recognized in accumulated other comprehensive income (loss) on a pre-tax basis and before noncontrolling interest

The amounts recognized in accumulated other comprehensive income (loss) on a pre-tax basis and before non-controlling interest for the years ended December 31, 2014 and 2013 were as follows:



	December 31,
Millions	2014			2013
Accumulated other comprehensive income (loss) beginning balance	$	10.5		$	(21.2	)
Increase (decrease) in accumulated other comprehensive income (loss):
Amortization of net actuarial losses recognized during the year	.3			.9
Net actuarial (losses) gains occurring during the year⁽¹⁾	(18.8		)	30.8
Accumulated other comprehensive (loss) income ending balance	$	(8.0	)	$	10.5


⁽¹⁾	Net actuarial gains (losses) resulted from investment returns and demographic experience different than assumed, as well as changes in assumptions in estimating the projected benefit obligation in the years ended December 31, 2014 and 2013.

Schedule of components of net periodic benefit cost (income)

The components of net periodic benefit (income) cost for the years ended December 31, 2014, 2013 and 2012 were as follows:



	Year Ended December 31,
Millions	2014			2013			2012
Service cost	$	.6		$	.8		$	.7
Interest cost	4.7			4.2			4.7
Expected return on plan assets	(8.5		)	(7.1		)	(6.9		)
Amortization of unrecognized loss	.3			.9			.8
Net periodic pension income before settlements, curtailments and special termination benefits	(2.9		)	(1.2		)	(.7		)
Settlement loss	—			—			.6
Special termination benefits expense⁽¹⁾	.3			.3			.6
Total net periodic (income) benefit cost	$	(2.6	)	$	(.9	)	$	.5


⁽¹⁾	Special termination benefits represent additional payments made from the Qualified Plan to certain vested participants when their employment was terminated due to a reduction in force.

Schedule of fair value of the Plan assets and their related inputs

The fair value of the Qualified Plan’s assets and their related inputs as of December 31, 2014 and 2013 by asset category were as follows:



	December 31, 2014								December 31, 2013
Millions	Fair Value		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs		Fair Value		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs
Fixed maturity investments	$	24.2	$	—	$	24.2	$	—	$	—	$	—	$	—	$	—
Common equity securities	101.0		101.0		—		—		103.3		103.3		—		—
Convertible fixed maturity investments	12.8		—		12.8		—		29.9		—		29.9		—
Cash and short-term investments	5.2		4.8		.4		—		8.9		8.8		.1		—
Total	$	143.2	$	105.8	$	37.4	$	—	$	142.1	$	112.1	$	30.0	$	—

There were no transfers between Levels 1, 2 or 3 during the years ended December 31, 2014 and 2013.

The Qualified Plan’s asset allocations as of December 31, 2014 and 2013, by asset category were as follows:



	Plan Assets at December 31,
Asset Category	2014		2013
Fixed maturity investments	16.9	%	—	%
Common equity securities	70.6		72.7
Convertible fixed maturity investments	8.9		21.1
Cash and short-term investments	3.6		6.2
Total	100.0	%	100.0	%

Schedule of expected future benefit payments

The following benefit payments, which reflect expected future service, as appropriate, are expected to be paid:



Millions	Expected Benefit Payments
2015	$	4.9
2016	5.3
2017	5.6
2018	5.9
2019	6.1
2020-2024	34.4

Employee Share-Based Incentive Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2014

White Mountains

Share-based compensation arrangement by share-based payment award

Summary of performance share activity

The following summarizes performance share activity for the years ended December 31, 2014, 2013 and 2012 for performance shares granted under the WTM Incentive Plan and the WTM Phantom Share Plan:



	Year Ended December 31,
	2014					2013					2012
Millions, except share amounts	Target Performance Shares Outstanding		Accrued Expense			Target Performance Shares Outstanding		Accrued Expense			Target Performance Shares Outstanding		Accrued Expense
Beginning of period	119,220		$	60.2		119,357		$	29.4		150,064		$	66.1
Shares paid or expired⁽¹⁾	(37,130	)	(26.7		)	(47,310	)	(11.0		)	(68,357	)	(58.3		)
New grants	45,660		—			47,170		—			38,432		—
Assumed forfeitures and cancellations⁽²⁾⁽³⁾	(4,201	)	(.7		)	3		(.6		)	(782	)	.6
Expense recognized	—		15.3			—		42.4			—		21.0
Ending December 31,	123,549		$	48.1		119,220		$	60.2		119,357		$	29.4

⁽¹⁾


⁽²⁾	On November 19, 2014, the Compensation Committee canceled 3,040 WTM performance shares for the 2014-2016 performance cycle and issued the same number of WTM restricted shares.


⁽³⁾	Amounts include changes in assumed forfeitures, as required under GAAP.

Summary of performance shares outstanding and accrued expense for performance shares awarded under an Incentive Plan

The following table summarizes performance shares outstanding and accrued expense for performance shares awarded under the WTM Incentive Plan as of December 31, 2014 for each performance cycle:



Millions, except share amounts	Target WTM Performance Shares Outstanding		Accrued Expense
Performance cycle:
2014 – 2016	41,937		$	4.1
2013 – 2015	46,803		18.9
2012 – 2014	37,977		26.4
Sub-total	126,717		49.4
Assumed forfeitures	(3,168	)	(1.3		)
Total at December 31, 2014	123,549		$	48.1

Schedule of Nonvested Restricted Stock Activity [Table Text Block]

The following outlines the unrecognized compensation cost associated with the outstanding restricted share awards under the WTM Incentive Plan for the years ended December 31, 2014, 2013 and 2012:



	Year Ended December 31,
	2014					2013					2012
Millions, except share amounts	Restricted Shares		Unamortized Issue Date Fair Value			Restricted Shares		Unamortized Issue Date Fair Value			Restricted Shares		Unamortized Issue Date Fair Value
Non-vested,
Beginning of period	94,130		$	17.0		69,910		$	16.8		72,000		$	13.3
Issued ⁽¹⁾	23,440		13.1			25,720		14.4			32,160		15.7
Vested ⁽²⁾	(33,205	)	—			(1,500	)	—			(32,945	)	—
Forfeited	(1,051	)	(.5		)	—		—			(1,305	)	(.2		)
Expense recognized	—		(15.3		)	—		(14.2		)	—		(12.0		)
Non-vested at December 31,	83,314		$	14.3		94,130		$	17.0		69,910		$	16.8


⁽¹⁾	During 2012, the Compensation Committee accelerated the vesting date for an installment of 5,000 restricted shares from January 20, 2013 to December 31, 2012.


⁽²⁾	On November 19, 2014, the Compensation Committee canceled 3,040 WTM performance shares for the 2014-2016 performance cycle and issued the same number of WTM restricted shares.

OneBeacon

Share-based compensation arrangement by share-based payment award

Summary of performance share activity

The following summarizes activity for the years ended December 31, 2014, 2013 and 2012 for OneBeacon performance shares granted under the OneBeacon Incentive Plan:



	Year Ended December 31,
	2014					2013					2012
Millions, except share amounts	Target Performance Shares Outstanding		Accrued Expense			Target Performance Shares Outstanding		Accrued Expense			Target Performance Shares Outstanding		Accrued Expense
Beginning of period	493,421		$	4.0		563,190		$	1.2		642,667		$	9.7
Payments and deferrals⁽¹⁾	(142,138	)	(1.0		)	(238,658	)	—			(258,901	)	(7.7		)
New awards	165,800		—			179,000		—			181,290		—
Forfeitures and cancellations⁽²⁾	387		—			(10,111	)	(.1		)	(1,866	)	—
Expense recognized	—		.4			—		2.9			—		(.8		)
End of period	517,470		$	3.4		493,421		$	4.0		563,190		$	1.2


⁽¹⁾	OneBeacon performance share payments in 2014 for the 2011-2013 performance cycle were at 37.1% of target. No payments were made in 2013 for the 2010-2012 OneBeacon performance cycle as the performance factor was zero. OneBeacon performance share payments in 2012 for the 2009-2011 performance cycle were at 138.6% of target.


⁽²⁾	Amounts include changes in assumed forfeitures, as required under GAAP.

Summary of performance shares outstanding and accrued expense for performance shares awarded under an Incentive Plan

The following summarizes OneBeacon performance shares outstanding awarded under the OneBeacon Incentive Plan as of December 31, 2014 for each performance cycle:



Millions, except share amounts	Target OneBeacon Performance Shares Outstanding		Accrued Expense
Performance cycle:
2014 – 2016	165,800		$	.5
2013 – 2015	179,000		1.4
2012 – 2014	181,290		1.5
Sub-total	526,090		3.4
Assumed forfeitures	(8,620	)	—
Total at December 31, 2014	517,470		$	3.4

Schedule of Nonvested Restricted Stock Activity [Table Text Block]

The following table summarizes the unrecognized compensation cost associated with the outstanding OneBeacon restricted stock awards for the years ended December 31, 2014, 2013 and 2012.



	Year Ended December 31,
	2014					2013					2012
Millions, except share amounts	Restricted Shares		Unamortized Issue Date Fair Value			Restricted Shares		Unamortized Issue Date Fair Value			Restricted Shares		Unamortized Issue Date Fair Value
Non-vested,
Beginning of period	915,000		$	6.5		927,000		$	9.6		630,000		$	7.7
Issued	—		—			—		—			300,000		4.5
Vested	(300,000	)	—			(9,000	)	—			(667	)	—
Forfeited	(2,500	)	—			(3,000	)	—			(2,333	)	—
Expense recognized	—		(3.0		)	—		(3.1		)	—		(2.6		)
End of period	612,500		$	3.5		915,000		$	6.5		927,000		$	9.6

Common Shareholders’ Equity and Non-controlling Interests Common Shareholders’ Equity and Non-controlling Interests (Tables)

12 Months Ended

Dec. 31, 2014

Noncontrolling Interest [Line Items]

Noncontrolling Interest Disclosure [Text Block]

Non-controlling Interests



	December 31, 2014					December 31, 2013
Millions	Non-controlling Percentage		Non-controlling Equity			Non-controlling Percentage		Non-controlling Equity
OneBeacon Ltd.	24.7	%	$	258.7		24.8	%	$	273.7
SIG Preference Shares	100.0		250.0			100.0		250.0

Other, excluding reciprocals
HG Global	3.1		17.9			2.7		16.6
QuoteLab	40.0		22.6			—		—
Tranzact	36.8		88.2			—		—
Wobi	36.7		5.4			—		—
Prospector Offshore Fund	23.4		31.1			28.3		32.1
Prospector Turtle Fund	—		—			31.1		14.1
Dewar	18.0		3.4			18.0		3.0
Total other, excluding reciprocals			168.6					65.8

Reciprocals
BAM	100.0		(121.9		)	100.0		(97.6		)
SSIE	100.0		(12.4		)	—		—
Total non-controlling interests			$	543.0				$	491.9

Segment Information (Tables)

12 Months Ended

Dec. 31, 2014

Segment Reporting [Abstract]

Financial information for White Mountains' segments

Financial information for White Mountains’s segments follows:



						HG Global/BAM
Millions	OneBeacon		Sirius Group			HG Global		BAM⁽¹⁾			Other Operations			Total
Year Ended December 31, 2014
Earned insurance and reinsurance premiums	$	1,177.1	$	873.9		$	1.4	$	.4		$	6.1		$	2,058.9
Net investment income	41.7		41.1			1.4		5.7			15.1			105.0
Net investment income (loss) - surplus note interest	—		—			15.7		(15.7		)	—			—
Net realized and unrealized investment gains	40.4		209.2			1.7		6.6			26.0			283.9
Other revenue (loss)	5.8		(62.4		)	—		.6			118.4			62.4
Total revenues	1,265.0		1,061.8			20.2		(2.4		)	165.6			2,510.2
Losses and LAE	815.1		345.3			—		—			8.9			1,169.3
Insurance and reinsurance acquisition expenses	203.3		193.6			.3		1.8			.8			399.8
Other underwriting expenses	179.2		129.7			—		.4			—			309.3
General and administrative expenses	13.8		30.5			1.6		35.9			206.4			288.2
Interest expense	13.0		26.3			—		—			2.6			41.9
Total expenses	1,224.4		725.4			1.9		38.1			218.7			2,208.5
Pre-tax income (loss)	$	40.6	$	336.4		$	18.3	$	(40.5	)	$	(53.1	)	$	301.7



					HG Global/BAM
Millions	OneBeacon		Sirius Group		HG Global			BAM⁽¹⁾			Other Operations		Total
Year Ended December 31, 2013
Earned insurance and reinsurance premiums	$	1,120.4	$	866.4	$	.4		$	.1		$	—	$	1,987.3
Net investment income	41.1		48.8		1.0			4.7			15.3		110.9
Net investment income (loss) - surplus note interest	—		—		40.2			(40.2		)	—		—
Net realized and unrealized investment gains (losses)	49.4		26.7		(2.0		)	(9.3		)	96.9		161.7
Other revenue	31.2		16.8		—			.4			9.1		57.5
Total revenues	1,242.1		958.7		39.6			(44.3		)	121.3		2,317.4
Losses and LAE	622.1		418.4		—			—			—		1,040.5
Insurance and reinsurance acquisition expenses	208.9		166.5		.1			1.4			—		376.9
Other underwriting expenses	204.8		126.1		—			.4			—		331.3
General and administrative expenses	12.0		32.2		1.4			32.5			103.2		181.3
Interest expense	13.0		26.3		—			—			3.2		42.5
Total expenses	1,060.8		769.5		1.5			34.3			106.4		1,972.5
Pre-tax income (loss)	$	181.3	$	189.2	$	38.1		$	(78.6	)	$	14.9	$	344.9



						HG Global/BAM
Millions	OneBeacon			Sirius Group		HG Global		BAM⁽¹⁾			Other Operations		Total
Year Ended December 31, 2012
Earned insurance and reinsurance premiums	$	1,132.0		$	931.6	$	—	$	—		$	—	$	2,063.6
Net investment income	53.6			65.0		.3		1.9			32.8		153.6
Net investment income (loss) - surplus note interest	—			—		18.4		(18.4		)	—		—
Net realized and unrealized investment gains	55.7			17.3		—		—			45.2		118.2
Other (loss) revenue	(.5		)	70.6		—		—			30.2		100.3
Total revenues	1,240.8			1,084.5		18.7		(16.5		)	108.2		2,435.7
Losses and LAE	650.0			543.9		—		—			—		1,193.9
Insurance and reinsurance acquisition expenses	249.4			180.8		—		—			—		430.2
Other underwriting expenses	205.2			116.4		—		.2			—		321.8
General and administrative expenses	13.4			45.9		4.5		19.6			98.8		182.2
Interest expense	16.9			26.2		—		—			1.7		44.8
Total expenses	1,134.9			913.2		4.5		19.8			100.5		2,172.9
Pre-tax income (loss)	$	105.9		$	171.3	$	14.2	$	(36.3	)	$	7.7	$	262.8



					HG Global/BAM
Selected Balance Sheet Data Millions	OneBeacon		Sirius Group		HG Global		BAM					Other Operations		Total
December 31, 2014:
Total investments	$	2,527.0	$	3,178.4	$	121.0	$	454.2				$	605.7	$	6,886.3
Reinsurance recoverable on paid and unpaid losses	173.8		333.6		—		—					.1		507.5
Assets held for sale	58.1		—		—		—					—		58.1
Total assets	3,561.0		5,034.7		704.4		(89.4		)	⁽²	⁾	1,246.2		10,456.9
Loss and LAE reserves	1,342.2		1,809.8		—		—					7.8		3,159.8
Total liabilities	2,510.5		3,180.6		120.9		32.5					72.8		5,917.3
Total White Mountains’s common shareholders’ equity	788.4		1,604.1		565.5		—					1,038.6		3,996.6
Non-controlling interest	262.1		250.0		17.9		(121.9		)			134.9		543.0
December 31, 2013:
Total investments	$	2,364.9	$	3,251.4	$	107.9	$	468.6				$	999.8	$	7,192.6
Reinsurance recoverable on paid and unpaid losses	89.9		363.6		—		—					—		453.5
Assets held for sale	1,880.1		—		—		—					—		1,880.1
Total assets	5,191.3		5,124.1		675.0		(77.9		)	⁽²	⁾	1,231.8		12,144.3
Loss and LAE reserves	1,054.3		2,025.0		—		—					—		3,079.3
Liabilities held for sale	1,880.1		—		—		—					—		1,880.1
Total liabilities	4,083.9		3,414.5		68.9		19.7					159.9		7,746.9
Total White Mountains’s common shareholders’ equity	830.6		1,459.6		589.5		—					1,025.8		3,905.5
Non-controlling interest	276.8		250.0		16.6		(97.6		)			46.1		491.9

Schedule of selected balance sheet data by segment



					HG Global/BAM
Selected Balance Sheet Data Millions	OneBeacon		Sirius Group		HG Global		BAM					Other Operations		Total
December 31, 2014:
Total investments	$	2,527.0	$	3,178.4	$	121.0	$	454.2				$	605.7	$	6,886.3
Reinsurance recoverable on paid and unpaid losses	173.8		333.6		—		—					.1		507.5
Assets held for sale	58.1		—		—		—					—		58.1
Total assets	3,561.0		5,034.7		704.4		(89.4		)	⁽²	⁾	1,246.2		10,456.9
Loss and LAE reserves	1,342.2		1,809.8		—		—					7.8		3,159.8
Total liabilities	2,510.5		3,180.6		120.9		32.5					72.8		5,917.3
Total White Mountains’s common shareholders’ equity	788.4		1,604.1		565.5		—					1,038.6		3,996.6
Non-controlling interest	262.1		250.0		17.9		(121.9		)			134.9		543.0
December 31, 2013:
Total investments	$	2,364.9	$	3,251.4	$	107.9	$	468.6				$	999.8	$	7,192.6
Reinsurance recoverable on paid and unpaid losses	89.9		363.6		—		—					—		453.5
Assets held for sale	1,880.1		—		—		—					—		1,880.1
Total assets	5,191.3		5,124.1		675.0		(77.9		)	⁽²	⁾	1,231.8		12,144.3
Loss and LAE reserves	1,054.3		2,025.0		—		—					—		3,079.3
Liabilities held for sale	1,880.1		—		—		—					—		1,880.1
Total liabilities	4,083.9		3,414.5		68.9		19.7					159.9		7,746.9
Total White Mountains’s common shareholders’ equity	830.6		1,459.6		589.5		—					1,025.8		3,905.5
Non-controlling interest	276.8		250.0		16.6		(97.6		)			46.1		491.9


⁽¹⁾	BAM manages its affairs on a statutory accounting basis. BAM’s statutory surplus includes surplus notes and is not reduced by accruals of interest expense on the surplus notes. BAM’s statutory surplus is reduced only after a payment of principal or interest has been approved by the New York Department of Financial Services.


⁽²⁾	BAM total assets reflect the elimination of $503.0 in surplus notes issued to HG Global and its subsidiaries, and $74.4 and $58.6 in accrued interest related to those surplus notes as of December 31, 2014 and 2013.

Investments in Unconsolidated Affiliates (Tables)

12 Months Ended

Dec. 31, 2014

Investments in unconsolidated affiliates

Schedule of investments in unconsolidated affiliates



	December 31,
Millions	2014		2013
Symetra common shares	$	373.8	$	360.9
Unrealized gains (losses) from Symetra’s fixed maturity portfolio	37.6		(43.6		)
Carrying value of Symetra common shares	411.4		317.3

Hamer	3.0		4.1
Total investments in unconsolidated affiliates	$	414.4	$	321.4

Schedule of changes in unconsolidated affiliates

The following table summarizes amounts recorded by White Mountains relating to its investment in Symetra:



Millions	Common shares			Warrants			Total
Carrying value of investment in Symetra as of December 31, 2011⁽²⁾	$	261.0		$	12.6		$	273.6
Equity in earnings^(1)(3)(6)	32.3			—			32.3
Equity in net unrealized gains from Symetra’s fixed maturity portfolio⁽⁴⁾⁽⁵⁾	62.8			—			62.8
Dividends received	(4.9		)	—			(4.9		)
Increase in value of warrants	—			17.7			17.7
Carrying value of investment in Symetra as of December 31, 2012⁽²⁾	351.2			30.3			381.5
Equity in earnings^(1)(3)(6)	37.8			—			37.8
Equity in net unrealized losses from Symetra’s fixed maturity portfolio⁽⁴⁾⁽⁵⁾	(106.4		)	—			(106.4		)
Dividends received	(6.4		)	—			(6.4		)
Increase in value of warrants	—			10.8			10.8
Exercise of warrants	41.1			(41.1		)	—
Carrying value of investment in Symetra as of December 31, 2013⁽²⁾	317.3			—			317.3
Equity in earnings^(1)(3)(6)	47.0			—			47.0
Equity in net unrealized gains from Symetra’s fixed maturity portfolio⁽⁴⁾⁽⁵⁾	81.2			—			81.2
Dividends received	(34.1		)	—			(34.1		)
Carrying value of investment in Symetra as of December 31, 2014⁽²⁾⁽⁷⁾	$	411.4		$	—		$	411.4


⁽¹⁾	Equity in earnings for the years ended December 31, 2014, 2013 and 2012 excludes tax expense of $3.3, $2.8, and $2.6


⁽²⁾	Includes White Mountains’s equity in net unrealized gains (losses) from Symetra’s fixed maturity portfolio of $37.6, $(43.6), and $62.8 as of December 31, 2014, 2013 and 2012, which excludes tax (expense) benefit of $(2.7), $3.2 and $(5.1)


⁽³⁾	Equity in earnings for the years ended December 31, 2014, 2013 and 2012 includes $3.0, $3.0 and $3.5 increases relating to the pre-tax amortization of the Symetra common share basis difference.


⁽⁴⁾	Net unrealized gains for the years ended December 31, 2014, 2013 and 2012 includes $12.7, $11.8 and $13.1 increases relating to the pre-tax amortization of the Symetra common share basis difference.


⁽⁵⁾	Net unrealized gains (losses) from Symetra’s fixed maturity portfolio excludes tax (expense) benefit of $(5.9), $8.3 and $(5.1) for the years ended December 31, 2014, 2013 and 2012.


⁽⁶⁾	Equity in earnings for the years ended December 31, 2014, 2013 and 2012 includes $(0.1), $0.2, and $1.3 (gain) loss from the dilutive effect of Symetra’s yearly dividend and the issuance of restricted shares by Symetra


⁽⁷⁾	The aggregate value of White Mountains’s investment in common shares of Symetra was $462.1 based upon the quoted market price of $23.05 per share as of December 31, 2014.

Symetra

Investments in unconsolidated affiliates

Summarized statement of financial position of Symetra

The following table summarizes financial information for Symetra as of December 31, 2014 and 2013:



	December 31,
Millions	2014		2013
Symetra balance sheet data:
Total investments	$	30,634.3	$	27,901.1
Separate account assets	949.8		978.4
Total assets	32,994.2		30,129.5
Policyholder liabilities	27,276.0		25,328.8
Long-term debt	697.2		449.5
Separate account liabilities	949.8		978.4
Total liabilities	29,633.6		27,187.6
Common shareholders’ equity	3,360.6		2,941.9

The following table summarizes financial information for Symetra for the years ended December 31, 2014, 2013 and 2012:



	Years ended December 31,
Millions	2014		2013			2012
Symetra income statement data:
Net premiums earned	$	629.1	$	627.2		$	605.0
Net investment income	1,320.5		1,285.0			1,275.2
Total revenues	2,182.3		2,103.9			2,101.2
Policy benefits	1,399.6		1,394.9			1,371.8
Total expenses	1,882.4		1,865.3			1,831.1
Net income	254.4		220.7			205.4
Comprehensive net income (loss)	397.0		(777.6		)	549.3

Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2014

Fair Value Disclosures [Abstract]

Summary of the fair value and carrying value of financial instruments

The following table summarizes the fair value and book value of financial instruments as of December 31, 2014 and 2013:



	December 31, 2014				December 31, 2013
Millions	Fair Value		Carrying Value		Fair Value		Carrying Value
OBH Senior Notes	$	286.0	$	274.7	$	269.8	$	274.7
SIG Senior Notes	437.8		399.7		438.1		399.6
SIG Preference Shares	260.0		250.0		260.0		250.0

Discontinued Operations (Tables)

12 Months Ended

Dec. 31, 2014

Discontinued Operations and Disposal Groups [Abstract]

Schedule illustrating the valuation adjustments between par and fair value [Table Text Block]

Below is a table illustrating the valuation adjustments taken to arrive at the estimated fair value of the OBIC Surplus Notes as of December 31, 2014:



	Type of Surplus Note
Millions	Seller Priority			Pari Passu			Total
Par Value	$	57.9		$	43.1		$	101.0
Fair value adjustments to reflect:
Current market rates on public debt and contract-based repayments⁽¹⁾	1.6			(8.2		)	(6.6		)
Regulatory approval ⁽²⁾	(4.6		)	(8.0		)	(12.6		)
Liquidity adjustment ⁽³⁾	(11.0		)	(5.7		)	(16.7		)
Total adjustments	(14.0		)	(21.9		)	(35.9		)
Fair value	$	43.9		$	21.2		$	65.1


⁽¹⁾	Represents the value of the OBIC Surplus Notes, at current market yields on publicly traded debt, and assuming issuer is allowed to make principal and interest payments when its financial capacity is available, as measured by statutory capital in excess of a 250% RBC score.


⁽²⁾	Represents anticipated delay in securing regulatory approvals of interest and principal payments to reflect graduated changes in Issuer’s statutory surplus.


⁽³⁾	Represents impact of liquidity spread to account for OneBeacon’s sole ownership of the surplus notes, lack of a trading market and ongoing regulatory approval risk.

Schedule of discontinued operations balance sheet and income statement

The following summarizes the assets and liabilities associated with the businesses classified as held for sale:



	December 31,
Millions	2013
Assets held for sale
Fixed maturity investments, at fair value	$	236.3
Reinsurance recoverable on unpaid losses	1,604.7
Reinsurance recoverable on paid losses	10.7
Insurance premiums receivable	9.1
Deferred tax asset	3.3
Other assets	16.0
Total assets held for sale	$	1,880.1
Liabilities held for sale
Loss and loss adjustment expense reserves	$	1,793.1
Unearned insurance premiums	.2
Ceded reinsurance payable	12.3
Other liabilities	74.5
Total liabilities held for sale	1,880.1
Net assets held for sale	$	—

Net Income (Loss) from Discontinued Operations

The following summarizes the results of operations, including related income taxes associated with the businesses classified as discontinued operations:



	Year Ended December 31,
Millions	2014			2013			2012
Revenues
Earned insurance premiums	$	.1		$	.8		$	10.6
Other revenue	—			10.8			—
Total revenues	.1			11.6			10.6
Expenses
Loss and loss adjustment expenses	(.7		)	78.9			48.4
Insurance and reinsurance acquisition expenses	.1			—			(2.1		)
Other underwriting expenses	3.5			(.2		)	1.7
Total expenses	2.9			78.7			48.0
Pre-tax loss	(2.8		)	(67.1		)	(37.4		)
Income tax benefit	1.0			25.0			13.4
Loss from discontinued operations	(1.8		)	(42.1		)	(24.0		)
Net (loss) gain from sales of discontinued operations	(1.6		)	46.6			(91.0		)
Net (loss) income from discontinued operations	$	(3.4	)	$	4.5		$	(115.0	)

Discontinued operations, computation of earnings per share

The following table outlines the computation of earnings (loss) per share for discontinued operations for the years ended December 31, 2014, 2013 and 2012:



	Year Ended December 31,
	2014			2013			2012
Basic and diluted earnings (loss) per share numerators (in millions):
Net (loss) income attributable to White Mountains’s common shareholders	$	(3.4	)	$	4.5		$	(115.0	)
Allocation of income for participating unvested restricted common shares ⁽¹⁾	—			—			1.5
Net (loss) income attributable to White Mountains’s common shareholders, net of restricted common share amounts ⁽²⁾	$	(3.4	)	$	4.5		$	(113.5	)
Basic earnings (loss) per share denominators (in thousands):
Total average common shares outstanding during the period	6,104.9			6,200.4			6,799.8
Average unvested restricted common shares ⁽³⁾	(78.9		)	(91.4		)	(91.1		)
Basic earnings (loss) per share denominator	6,026.0			6,109.0			6,708.7
Diluted earnings (loss) per share denominator (in thousands):
Total average common shares outstanding during the period	6,104.9			6,200.4			6,799.8
Average unvested restricted common shares⁽³⁾	(78.9		)	(91.4		)	(91.1		)
Average outstanding dilutive options to acquire common shares⁽⁴⁾	—			—			—
Diluted earnings (loss) per share denominator	6,026.0			6,109.0			6,708.7
Basic and diluted earnings (loss) per share (in dollars):	$	(.56	)	$	0.74		$	(16.91	)


⁽¹⁾	Restricted shares issued by White Mountains contain dividend participation features, and therefore, are considered participating securities.


⁽²⁾	Net income (loss) attributable to White Mountains’s common shareholders, net of restricted share amounts, is equal to undistributed earnings for the years ended December 31, 2014, 2013 and 2012.


⁽³⁾	Restricted common shares outstanding vest either in equal annual installments or upon a stated date (see Note 13).


⁽⁴⁾	The diluted earnings (loss) per share denominator for the years ended December 31, 2014, 2013 and 2012 does not include the impact of 125,000 common shares issuable upon exercise of the non-qualified options outstanding as they are anti-dilutive to the calculation.

- Definition

Tabular disclosure of disposal groups, which may include the gain (loss) recognized in the income statement and the income statement caption that includes that gain (loss), amounts of revenues and pretax profit or loss reported in discontinued operations, the classification and carrying value of the assets and liabilities comprising the disposal group, and the segment in which the disposal group was reported. Also may include the amount of adjustments to amounts previously reported in discontinued operations such as resolution of contingencies arising from the disposal transaction or the operations of the component prior to disposal.

+ References + Details

Selected Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2014

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information



	2014 Three Months Ended												2013 Three Months Ended
Millions, except per share amounts	Dec. 31			Sept. 30			June 30			Mar. 31			Dec. 31			Sept. 30			June 30		Mar. 31
Revenues	$	689.7		$	589.4		$	652.8		$	578.3		$	626.6		$	574.1		$	489.3	$	627.4
Expenses	643.5			555.0			543.8			466.2			492.4			518.8			485.7		475.6
Pre-tax income	46.2			34.4			109.0			112.1			134.2			55.3			3.6		151.8
Tax benefit (expense)	8.7			(7.8		)	(23.9		)	(30.3		)	(27.4		)	(8.2		)	.6		(41.6		)
Income from continuing operations	54.9			26.6			85.1			81.8			106.8			47.1			4.2		110.2
(Loss) income from discontinued operations, net of tax	(12.2		)	6.7			2.6			(.5		)	(.3		)	.4			3.9		.5
Non-controlling interest in consolidated subsidiaries	15.0			11.2			(4.6		)	.5			(.3		)	1.1			11.1		.5
Equity in earnings of unconsolidated affiliates	12.3			7.0			12.5			13.8			11.7			8.6			7.1		9.2
Income attributable to White Mountains’s common shareholders	$	70.0		$	51.5		$	95.6		$	95.6		$	117.9		$	57.2		$	26.3	$	120.4
Income (loss) attributable to White Mountains’s common shareholders per share:
Basic
Continuing operations	$	13.71		$	7.35		$	15.10		$	15.56		$	19.14		$	9.20		$	3.62	$	19.10
Discontinued operations	(2.03		)	1.10			.43			(.08		)	(.05		)	.06			.64		.07
Total consolidated operations	$	11.68		$	8.45		$	15.53		$	15.48		$	19.09		$	9.26		$	4.26	$	19.17
Diluted
Continuing operations	$	13.71		$	7.35		$	15.10		$	15.56		$	19.14		$	9.20		$	3.62	$	19.10
Discontinued operations	(2.03		)	1.10			.43			(.08		)	(.05		)	.06			.64		.07
Total consolidated operations	$	11.68		$	8.45		$	15.53		$	15.48		$	19.09		$	9.26		$	4.26	$	19.17

Summary of Significant Accounting Policies (Basis of Presentation) (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013
Basis of Presentation
Assets held for sale	$ 58.1	$ 1,880.1
Percentage of par value of policy reinsured	15.00%
OneBeacon Ltd.
Basis of Presentation
Ownership interest (as a percent)	75.30%	75.20%
HG Global
Basis of Presentation
Surplus notes	$ 503.0	$ 503.0
Percentage of par value of policy reinsured	15.00%
Star & Shield Insurance Exchange [Member]
Basis of Presentation
Surplus notes	$ 17.0
Redeemable preferred stocks \| HG Global
Basis of Presentation
Ownership interest (as a percent)	96.90%	97.30%
Common Stock \| HG Global
Basis of Presentation
Ownership interest (as a percent)	88.40%	88.70%
Wholly Owned Properties [Member] \| OneBeacon Ltd.
Basis of Presentation
Assets held for sale	$ 58.1

Summary of Significant Accounting Policies (Investment Securities) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2014 USD ($) security	Dec. 31, 2013
Accounting Policies [Abstract]
Percentage of investments recorded at fair value	93.00%	95.00%
Minimum percentage of variation expected	5.00%
Minimum variation expected \| $	$ 1.0
Securities outside variance threshold \| security	21

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Warrants) (Details) - shares shares in Thousands	Jun. 20, 2013	Dec. 31, 2012
Symetra
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Investments in unconsolidated affiliates on conversion of warrants	2,650	9,490

Summary of Significant Accounting Policies (Insurance and Reinsurance Operations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Workers compensation discount percent	2.50%	3.50%
Workers compensation discount amount	$ 1.0	$ 3.0
OneBeacon Runoff
Workers compensation discount amount		$ 61.7

Summary of Significant Accounting Policies (Deferred Softward Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Deferred software costs	$ 26.0	$ 23.8
Minimum \| Software and Software Development Costs
Useful lives	3 years
Maximum \| Software and Software Development Costs
Useful lives	5 years

Summary of Significant Accounting Policies (Foreign Currency Exchange) (Details) $ in Millions	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012
Significant Transactions
Net unrealized foreign currency translation (losses) gains	$ (79.8)	$ 88.4
SEK
Significant Transactions
Foreign currency exchange rate	7.7737	6.4339	6.4973
GBP
Significant Transactions
Foreign currency exchange rate	0.6426	0.6044	0.6154
Canada, Dollars
Significant Transactions
Foreign currency exchange rate	0.8245	0.7259	0.7564

Summary of Significant Accounting Policies Revenue recognition (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
White Mountains Advisors LLC
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Investment Advisory, Management and Administrative Fees	$ 18.4	$ 16.6	$ 15.9

Significant Transactions Significant Transactions (Acquisitions) (Details) ₪ in Millions, $ in Millions			1 Months Ended	2 Months Ended		3 Months Ended								12 Months Ended
	Oct. 10, 2014 USD ($)	Dec. 03, 2012 USD ($)	Jan. 31, 2014 USD ($)	Feb. 19, 2014 ILS (₪) business	Feb. 19, 2014 USD ($) business	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Sep. 30, 2013 USD ($)	Jun. 30, 2013 USD ($)	Mar. 31, 2013 USD ($)	Dec. 31, 2015	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Mar. 14, 2014 USD ($)
Unusual or Infrequent Item [Line Items]
Assets						$ 10,456.9				$ 12,144.3					$ 10,456.9	$ 12,144.3
Liabilities						5,917.3				7,746.9					5,917.3	7,746.9
White Mountains’s common shareholders’ equity, including portion attributable to NCI						4,539.6				4,397.4					4,539.6	4,397.4
Other assets						356.1				437.4					356.1	437.4
Goodwill						168.9				0.0					168.9	0.0	$ 0.0
Intangible Assets, Net (Excluding Goodwill)						197.5				20.7					197.5	20.7	16.9
Payments to Acquire Businesses and Interest in Affiliates															199.2	(15.9)	41.3
Non-controlling interest in consolidated subsidiaries						(15.0)	$ (11.2)	$ 4.6	$ (0.5)	0.3	$ (1.1)	$ (11.1)	$ (0.5)		(22.1)	(12.4)	$ (14.0)
Olympus [Member]
Unusual or Infrequent Item [Line Items]
Payments to Acquire Interest in Subsidiaries and Affiliates						11.5
Assets						24.6									24.6
Liabilities						13.1									13.1
Tranzact [Member]
Unusual or Infrequent Item [Line Items]
Payments to Acquire Interest in Subsidiaries and Affiliates	$ 177.7
Assets	332.8
Liabilities	$ 108.7
Ownership interest (as a percent)	63.20%
Distributed Earnings	$ 44.2
White Mountains’s common shareholders’ equity, including portion attributable to NCI	281.2
Goodwill	145.1					145.1				0.0					145.1	0.0
Intangible Assets, Net (Excluding Goodwill)	146.3					142.8				0.0					142.8	0.0
Business Combination, Contingent Consideration, Liability	7.4
QuoteLab [Member]
Unusual or Infrequent Item [Line Items]
Payments to Acquire Interest in Subsidiaries and Affiliates									28.1
Assets																		$ 70.1
Liabilities																		$ 10.0
Ownership interest (as a percent)																		60.00%
Goodwill						18.3				0.0					18.3	0.0		$ 18.3
Intangible Assets, Net (Excluding Goodwill)						$ 32.5				0.0					$ 32.5	0.0		38.5
Business Combination, Contingent Consideration, Liability																		$ 7.9
WOBI [Member]
Unusual or Infrequent Item [Line Items]
Liabilities					$ 0.7
Ownership interest (as a percent)						63.30%									63.30%
Premiums Written, Percentage of Total				85.00%	85.00%
Goodwill					$ 5.5	$ 5.5				0.0					$ 5.5	0.0
Intangible Assets, Net (Excluding Goodwill)						2.5				0.0					2.5	0.0
Number of lines of business \| business				4	4
Star & Shield LLC [Member]
Unusual or Infrequent Item [Line Items]
Payments to Acquire Businesses and Interest in Affiliates			$ 1.8
Star & Shield Insurance Exchange [Member]
Unusual or Infrequent Item [Line Items]
Assets						13.5									13.5
Liabilities						25.9									25.9
Purchase of Surplus Notes						17.0									17.0
Surplus notes						17.0									17.0
HG Global-BAM
Unusual or Infrequent Item [Line Items]
Capital contributions																594.5
HG Global
Unusual or Infrequent Item [Line Items]
Surplus notes						$ 503.0				$ 503.0					503.0	$ 503.0
Total \| WOBI [Member]
Unusual or Infrequent Item [Line Items]
Ownership interest (as a percent)					54.00%
Israel, New Shekels \| Preferred stocks \| WOBI [Member]
Unusual or Infrequent Item [Line Items]
Payments to Acquire Businesses and Interest in Affiliates \| ₪				₪ 31.5
Israel, New Shekels \| Total \| WOBI [Member]
Unusual or Infrequent Item [Line Items]
Payments to Acquire Businesses and Interest in Affiliates \| ₪				₪ 14.4
United States of America, Dollars \| Preferred stocks \| WOBI [Member]
Unusual or Infrequent Item [Line Items]
Payments to Acquire Businesses and Interest in Affiliates					$ 9.0
United States of America, Dollars \| Total \| WOBI [Member]
Unusual or Infrequent Item [Line Items]
Payments to Acquire Businesses and Interest in Affiliates					4.1
American Fuji [Member] \| WM Solutions
Unusual or Infrequent Item [Line Items]
Business Combination, Bargain Purchase, Gain Recognized, Amount													$ 6.9
Empire [Member] \| WM Solutions
Unusual or Infrequent Item [Line Items]
Business Combination, Bargain Purchase, Gain Recognized, Amount									$ 7.3
WOBI [Member]
Unusual or Infrequent Item [Line Items]
Assets					13.4
Intangible Assets, Net (Excluding Goodwill)					$ 2.9
Runoff Entities [Member] \| WM Solutions
Unusual or Infrequent Item [Line Items]
Business Combination, Bargain Purchase, Gain Recognized, Amount		$ 14.5
Non-controlling Interests \| Star & Shield Insurance Exchange [Member]
Unusual or Infrequent Item [Line Items]
Non-controlling interest in consolidated subsidiaries															$ (12.4)
Scenario, Forecast [Member] \| QuoteLab [Member]
Unusual or Infrequent Item [Line Items]
Percent of gross profit														62.50%
Tangible Assets [Member] \| Tranzact [Member]
Unusual or Infrequent Item [Line Items]
Other assets	$ 41.4

Significant Transactions (Dispositions) (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
	Dec. 23, 2014	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 31, 2014
Significant Transactions
(Loss) gain on sale of discontinued operations, net of tax			$ (1.6)	$ 46.6	$ (91.0)
Gain (Loss) on Disposition of Stock in Subsidiary			0.7	21.3	0.0
Premiums Written, Net			2,121.5
OneBeacon Runoff
Significant Transactions
Surplus notes	$ 101.0
Ashmere [Member] \| WM Solutions
Significant Transactions
Excess amount over statutory surplus						$ 6.0
Gain (Loss) on Disposition of Stock in Subsidiary			1.0
Citation [Member] \| WM Solutions
Significant Transactions
Gain (Loss) on Disposition of Stock in Subsidiary		$ 0.7
Essentia \| OneBeacon
Significant Transactions
Gain (Loss) on Disposition of Stock in Subsidiary				23.0
Gain (Loss) on Disposition of Stock in Subsidiary, After Tax				15.0
Underwriting Agreement [Member] \| Essentia \| OneBeacon
Significant Transactions
Premiums Written, Net					$ 179.7
Premiums Written, Percentage of Total					8.00%
Fair Value [Member] \| Other long-term investments \| OneBeacon Runoff
Significant Transactions
Surplus notes	64.9
Discontinued Operations
Significant Transactions
(Loss) gain on sale of discontinued operations, net of tax			(1.6)	$ 46.6	$ (91.0)
Discontinued Operations \| OneBeacon Runoff
Significant Transactions
Surplus notes			101.0
(Loss) gain on sale of discontinued operations, net of tax			(35.9)		$ 91.5
Discontinued Operations \| Surplus Note \| OneBeacon Runoff
Significant Transactions
(Loss) gain on sale of discontinued operations, net of tax			(23.5)
Discontinued Operations \| Fair Value [Member] \| OneBeacon Runoff
Significant Transactions
Surplus notes			65.1
Surplus Note \| Discontinued Operations \| OneBeacon Runoff
Significant Transactions
(Loss) gain on sale of discontinued operations, net of tax	$ 36.1		$ 36.1

Reserves for Unpaid Losses and Loss Adjustment Expenses (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year		$ (6.0)	$ (48.4)	$ (41.9)
Increase (decrease) in reserves		1,169.3	1,040.5	1,193.9
Current Accident Year		1,175.3	1,088.9	1,235.8
Accretion of fair value adjustment to net loss and LAE reserves		0.7	1.7	10.6
Un-accreted fair value, adjustment to loss and loss adjustment expense reserves, before tax		4.0
Sirius Group
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year		(98.0)	(23.9)	(34.5)
Liability for asbestos and environmental claims, gross		238.5	227.8	228.6	$ 207.2
Liability for asbestos claims, net, period increase (decrease)		8.0	11.8	33.0	46.4
Liability for asbestos and environmental claims		210.2	193.9	189.4	162.7
Liability for Asbestos Claims, Net, Period Increase (Decrease) Based on Quarterly Reporting				14.0
Liabilty for environmental claims, net, period increase (decrease)		$ 1.6	$ 0.8	0.5
Asbestos and Environmental Loss Three Year Survival Ratio Period		9 years	8 years
OneBeacon
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year	$ 14.3	$ 75.5		(7.4)
Increase (decrease) in reserves		109.2	$ 89.8
Current Accident Year	$ 33.7	33.7
Liability for asbestos and environmental claims, gross		1.0
Star & Shield Insurance Exchange [Member]
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year		2.2
Asbestos \| Sirius Group
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Liability for asbestos and environmental claims, gross		215.8	207.4	208.2	185.1
Liability for asbestos and environmental claims		192.8	178.7	174.2	146.2
Environmental \| Sirius Group
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Liability for asbestos and environmental claims, gross		22.7	20.4	20.4	22.1
Liability for asbestos and environmental claims		17.4	15.2	15.2	$ 16.5
WM Solutions \| Sirius Group
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Liability for asbestos claims, net, period increase (decrease)		22.9	13.0	11.0
Liabilty for environmental claims, net, period increase (decrease)		2.1	1.0	0.7
Property [Member] \| Sirius Group
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year		(54.0)	(16.6)	(28.4)
Professional Insurance \| OneBeacon
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year		46.4
Increase (decrease) in reserves		69.3	59.1
Current Accident Year		22.9
Property, Liability and Casualty Insurance Product Line \| Sirius Group
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year		(13.0)
asbestos and environmental [Member] \| Sirius Group
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year		10.0
Property Loss Held Above Actuarial Central Estimate [Member] \| Sirius Group
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year		(24.0)
Aviation Space [Member] \| Sirius Group
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year		13.0	(10.1)	(5.3)
Accident and Health Insurance Product Line [Member] \| Sirius Group
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year		(13.0)	(9.2)
Crop \| OneBeacon
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year		0.0
Increase (decrease) in reserves		3.8	0.0
Current Accident Year		3.8
Specialty Products \| OneBeacon
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year		51.7
Increase (decrease) in reserves		80.1	61.8
Current Accident Year		28.4
Asbestos [Member] \| Sirius Group
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year			$ 11.8	46.4
Casualty Runoff [Member] \| Sirius Group
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year				(31.5)
Marine Energy [Member] \| Sirius Group
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year				(11.6)
Trade Credit [Member] \| Sirius Group
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year				(6.8)
Accident and Health \| Sirius Group
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Prior Accident Year				$ 4.3
Management's estimate [Member] \| Specialty Products \| OneBeacon
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Current Accident Year		$ 29.9

Reserves for Unpaid Losses and Loss Adjustment Expenses (Reserve Summary) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross beginning balance	$ 3,079.3	$ 3,168.9	$ 5,702.3
Less beginning reinsurance recoverable on unpaid losses	(428.1)	(429.1)	(2,507.3)
Net loss and LAE reserves	2,651.2	2,739.8	3,195.0
Current Accident Year	1,175.3	1,088.9	1,235.8
Prior Accident Year	(6.0)	(48.4)	(41.9)
Total incurred losses and LAE	1,169.3	1,040.5	1,193.9
Accretion of fair value adjustment to net loss and LAE reserves	0.7	1.7	10.6
Foreign currency translation adjustment to net loss and LAE reserves	(36.0)	0.3	12.9
Loss and LAE paid relating to current year losses	(345.3)	(336.2)	(404.7)
Loss and LAE paid relating to prior year losses	(823.0)	(832.6)	(901.6)
Total loss and LAE payments	(1,168.3)	(1,168.8)	(1,306.3)
Net loss and LAE reserves	2,675.9	2,651.2	2,739.8
Plus ending reinsurance recoverable on unpaid losses	483.9	428.1	429.1
Gross ending balance	3,159.8	3,079.3	3,168.9
AutoOne
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Net loss and LAE reserves	0.0		0.0
Net loss and LAE reserves		0.0
Sirius Group
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Loss and LAE reserves acquired	45.4	37.7	17.0
Star & Shield Insurance Exchange [Member]
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Loss and LAE reserves consolidated — SSIE	$ 13.6	$ 0.0	$ 0.0

Reserves for Unpaid Losses and Loss Adjustment Expenses Reserves for Unpaid Losses and Loss Adjustment Expenses (Reserve Development) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Premiums earned
Current Accident Year		$ 1,175.3	$ 1,088.9	$ 1,235.8
Prior Accident Year		(6.0)	(48.4)	(41.9)
Total incurred losses and LAE		1,169.3	1,040.5	1,193.9
OneBeacon
Premiums earned
Current Accident Year	$ 33.7	33.7
Prior Accident Year	$ 14.3	75.5		$ (7.4)
Total incurred losses and LAE		109.2	89.8
Professional Insurance \| OneBeacon
Premiums earned
Current Accident Year		22.9
Prior Accident Year		46.4
Total incurred losses and LAE		69.3	59.1
Specialty Property \| OneBeacon
Premiums earned
Current Accident Year		(1.1)
Prior Accident Year		5.7
Total incurred losses and LAE		4.6	1.1
Crop \| OneBeacon
Premiums earned
Current Accident Year		3.8
Prior Accident Year		0.0
Total incurred losses and LAE		3.8	0.0
Other \| OneBeacon
Premiums earned
Current Accident Year		2.8
Prior Accident Year		(0.4)
Total incurred losses and LAE		2.4	1.6
Specialty Products \| OneBeacon
Premiums earned
Current Accident Year		28.4
Prior Accident Year		51.7
Total incurred losses and LAE		80.1	61.8
Entertainment \| OneBeacon
Premiums earned
Current Accident Year		1.5
Prior Accident Year		11.6
Total incurred losses and LAE		13.1	13.5
Accident \| OneBeacon
Premiums earned
Current Accident Year		0.0
Prior Accident Year		3.5
Total incurred losses and LAE		3.5	6.0
Government Risks \| OneBeacon
Premiums earned
Current Accident Year		1.2
Prior Accident Year		7.1
Total incurred losses and LAE		8.3	8.5
Other \| OneBeacon
Premiums earned
Current Accident Year		2.6
Prior Accident Year		1.6
Total incurred losses and LAE		4.2	0.0
Specialty Industries \| OneBeacon
Premiums earned
Current Accident Year		5.3
Prior Accident Year		23.8
Total incurred losses and LAE		$ 29.1	$ 28.0

Reserves for Unpaid Losses and Loss Adjustment Expenses (LAE Reserve Activity) (Details) - Sirius Group - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Loss and Loss Adjustment, Expense Reserves [Line Items]
Liability for asbestos claims, net, period increase (decrease)	$ 8.0	$ 11.8	$ 33.0	$ 46.4
Liabilty for environmental claims, net, period increase (decrease)	1.6	0.8	0.5
Gross
Beginning balance	227.8	228.6	207.2
Losses and LAE acquired	25.0	14.0	11.7
Incurred losses and LAE	9.0	12.9	46.7
Paid losses and LAE	(23.3)	(27.7)	(37.0)
Ending balance	238.5	227.8	228.6	207.2
Net
Beginning balance	193.9	189.4	162.7
Losses and LAE acquired Central National	25.0	14.0	11.7
Incurred losses and LAE	9.6	12.6	45.9
Liability for unpaid claims and claims adjustment expense	(18.3)	(22.1)	(30.9)
Ending balance	210.2	193.9	189.4	162.7
Asbestos
Gross
Beginning balance	207.4	208.2	185.1
Losses and LAE acquired	22.9	13.0	11.0
Incurred losses and LAE	7.4	12.1	46.8
Paid losses and LAE	(21.9)	(25.9)	(34.7)
Ending balance	215.8	207.4	208.2	185.1
Net
Beginning balance	178.7	174.2	146.2
Losses and LAE acquired Central National	22.9	13.0	11.0
Incurred losses and LAE	8.0	11.8	46.4
Liability for unpaid claims and claims adjustment expense	(16.8)	(20.3)	(29.4)
Ending balance	192.8	178.7	174.2	146.2
Environmental
Gross
Beginning balance	20.4	20.4	22.1
Losses and LAE acquired	2.1	1.0	0.7
Incurred losses and LAE	1.6	0.8	(0.1)
Paid losses and LAE	(1.4)	(1.8)	(2.3)
Ending balance	22.7	20.4	20.4	22.1
Net
Beginning balance	15.2	15.2	16.5
Losses and LAE acquired Central National	2.1	1.0	0.7
Incurred losses and LAE	1.6	0.8	(0.5)
Liability for unpaid claims and claims adjustment expense	(1.5)	(1.8)	(1.5)
Ending balance	17.4	15.2	15.2	$ 16.5
WM Solutions
Loss and Loss Adjustment, Expense Reserves [Line Items]
Liability for asbestos claims, net, period increase (decrease)	22.9	13.0	11.0
Liabilty for environmental claims, net, period increase (decrease)	$ 2.1	$ 1.0	$ 0.7

Third Party Reinsurance (Written and Earned Premiums) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Written premiums:
Direct	$ 1,505.0
Assumed	993.8
Gross written premiums	2,498.8
Ceded	377.3
Net written premiums	2,121.5
Earned premiums:
Gross amount	1,433.7
Assumed from other companies	996.3
Gross earned premiums	2,430.0
Ceded	371.1
Net earned premiums	2,058.9	$ 1,987.3	$ 2,063.6
Losses and LAE:
Direct	972.6
Policyholder Benefits and Claims Incurred, Assumed	441.8
Gross losses and LAE	1,414.4
Ceded	(245.1)
Total incurred losses and LAE	1,169.3	1,040.5	1,193.9
OneBeacon
Written premiums:
Direct	1,257.5	1,103.1	1,204.0
Assumed	65.9	59.8	55.2
Gross written premiums	1,323.4	1,162.9	1,259.2
Ceded	106.5	74.3	80.0
Net written premiums	1,216.9	1,088.6	1,179.2
Earned premiums:
Gross amount	1,209.1	1,043.3	1,158.3
Assumed from other companies	70.9	148.5	52.8
Gross earned premiums	1,280.0	1,191.8	1,211.1
Ceded	102.9	71.4	79.1
Net earned premiums	1,177.1	1,120.4	1,132.0
Losses and LAE:
Direct	830.7	584.9	687.5
Policyholder Benefits and Claims Incurred, Assumed	63.7	76.3	29.6
Gross losses and LAE	894.4	661.2	717.1
Ceded	(79.3)	(39.1)	(67.1)
Total incurred losses and LAE	815.1	622.1	650.0
Sirius Group
Written premiums:
Direct	208.7	177.3	186.1
Assumed	927.9	943.1	992.7
Gross written premiums	1,136.6	1,120.4	1,178.8
Ceded	254.1	243.8	231.1
Net written premiums	882.5	876.6	947.7
Earned premiums:
Gross amount	200.2	174.0	169.9
Assumed from other companies	925.4	938.6	988.3
Gross earned premiums	1,125.6	1,112.6	1,158.2
Ceded	251.7	246.2	226.6
Net earned premiums	873.9	866.4	931.6
Losses and LAE:
Direct	117.8	98.1	96.9
Policyholder Benefits and Claims Incurred, Assumed	378.1	455.5	523.9
Gross losses and LAE	495.9	553.6	620.8
Ceded	(150.6)	(135.2)	(76.9)
Total incurred losses and LAE	345.3	418.4	543.9
HG/BAM
Written premiums:
Direct	16.2
Assumed	0.0
Gross written premiums	16.2
Ceded	0.0
Net written premiums	16.2
Earned premiums:
Gross amount	1.8
Assumed from other companies	0.0
Gross earned premiums	1.8
Ceded	0.0
Net earned premiums	1.8
Losses and LAE:
Direct	0.0
Policyholder Benefits and Claims Incurred, Assumed	0.0
Gross losses and LAE	0.0
Ceded	0.0
Total incurred losses and LAE	0.0
HG/BAM [Member]
Written premiums:
Ceded	12.3
Earned premiums:
Ceded	1.4
Star & Shield Insurance Exchange [Member]
Written premiums:
Ceded	16.0
Earned premiums:
Ceded	15.7
Other Segments
Written premiums:
Direct	22.6
Assumed	0.0
Gross written premiums	22.6
Ceded	16.7
Net written premiums	5.9
Earned premiums:
Gross amount	22.6
Assumed from other companies	0.0
Gross earned premiums	22.6
Ceded	16.5
Net earned premiums	6.1	0.0	0.0
Losses and LAE:
Direct	24.1
Policyholder Benefits and Claims Incurred, Assumed	0.0
Gross losses and LAE	24.1
Ceded	(15.2)
Total incurred losses and LAE	$ 8.9	0.0	0.0
OneBeacon and Sirius Group
Written premiums:
Direct		1,280.4	1,390.1
Assumed		1,002.9	1,047.9
Gross written premiums		2,283.3	2,438.0
Ceded		318.1	311.1
Net written premiums		1,965.2	2,126.9
Earned premiums:
Gross amount		1,217.3	1,328.2
Assumed from other companies		1,087.1	1,041.1
Gross earned premiums		2,304.4	2,369.3
Ceded		317.6	305.7
Net earned premiums		1,986.8	2,063.6
Losses and LAE:
Direct		683.0	784.4
Policyholder Benefits and Claims Incurred, Assumed		531.8	553.5
Gross losses and LAE		1,214.8	1,337.9
Ceded		(174.3)	(144.0)
Total incurred losses and LAE		$ 1,040.5	$ 1,193.9

Third-Party Reinsurance (OneBeacon) (Details) - USD ($) $ in Millions	3 Months Ended		7 Months Ended	12 Months Ended					60 Months Ended
	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2020	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2020	Dec. 31, 2012	Dec. 31, 2011
Effects of Reinsurance [Line Items]
Reinsurance recoverable on unpaid losses	$ 483.9		$ 483.9				$ 483.9	$ 428.1		$ 429.1	$ 2,507.3
OneBeacon
Effects of Reinsurance [Line Items]
Catastrophe Event Ratio							0.40%
Reinsurance Recoverables	$ 173.8		$ 173.8				$ 173.8
Reinsurance recoverables, percentage of total	100.00%		100.00%				100.00%
OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance recoverable on paid losses	$ 12.2		$ 12.2				$ 12.2
Reinsurance recoverable on unpaid losses	161.6		161.6				161.6
Property Catastrophe Program [Member] \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage		100.00%
Reinsurance Retention Policy Excess Retention Amount Reinsured Net Of Participation							110.0
Property Catastrophe Program [Member] \| Maximum \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							130.0
Property Catastrophe Program [Member] \| Minimum \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance retention policy, amount retained							20.0
Property Catastrophe Reinsurance [Member] \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							$ 30.0
Reinsurance Retention Policy, Reinsured Risk, Percentage							100.00%
Property Catastrophe Reinsurance [Member] \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance retention policy, amount retained							$ 10.0
Casualty Reinsurance Program \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance retention policy, amount retained							10.0
Reinsurance retention policy, excess retention, amount reinsured							$ 60.0
Property Per-Risk, Acts of Terrorism \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage							100.00%
Property Per-Risk, Acts of Terrorism \| Maximum \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							$ 100,000.0
Property Per-Risk, Acts of Terrorism \| OneBeacon \| Maximum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							100.0
Property Per-Risk, Acts of Terrorism \| OneBeacon \| Minimum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							5.0
Property Per Risk Reinsurance Program \| OneBeacon \| Maximum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							100.0
Property Per Risk Reinsurance Program \| OneBeacon \| Minimum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							5.0	$ 10.0
Individual Risk Facultative [Member] \| OneBeacon \| Maximum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							100.0
Inland and Ocean Marine \| Marine Treaty Per Occurrence \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance retention policy, amount retained							2.0
Inland and Ocean Marine \| Marine Treaty \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							$ 60.0
Inland and Ocean Marine \| Layer One \| Marine Treaty \| OneBeacon
Effects of Reinsurance [Line Items]
Property Catastrophe Reinsurance Treaty First Layer Co-Partipation Percentage							60.00%
Inland and Ocean Marine \| Layer One \| Marine Treaty \| OneBeacon \| Maximum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							$ 7.0
Inland and Ocean Marine \| Layer One \| Marine Treaty \| OneBeacon \| Minimum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							2.0
Inland and Ocean Marine \| Layer One \| Property Per Risk Treaty \| OneBeacon \| Maximum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, amount retained							20.0
Inland and Ocean Marine \| Layer One \| Catastrophic Losses [Member] \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance retention policy, amount retained							2.0
Annual Aggregate Deductible to Reinsurance Retention Policy							1.5
Reinsurance retention policy, excess retention, amount reinsured							5.0
Catastrophic Losses [Member] \| Layer One \| Catastrophic Losses [Member] \| OneBeacon
Effects of Reinsurance [Line Items]
Annual Aggregate Deductible to Reinsurance Retention Policy							5.0
Health Insurance Product Line \| Casualty Reinsurance Program \| OneBeacon \| Maximum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							10.0
Health Insurance Product Line \| Casualty Reinsurance Program \| OneBeacon \| Minimum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							5.0
Health Insurance Product Line \| HMO Provider Excess Reinsurance [Member] \| OneBeacon \| Minimum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							$ 5.0
Health Insurance Product Line \| Layer One \| Casualty Reinsurance Program \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage							10.00%
Property, Liability and Casualty Insurance Product Line \| Casualty Reinsurance Program \| OneBeacon \| Maximum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							$ 11.0
Property, Liability and Casualty Insurance Product Line \| Casualty Reinsurance Program \| OneBeacon \| Minimum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							$ 5.0
Property, Liability and Casualty Insurance Product Line \| Layer One \| Casualty Reinsurance Program \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage							10.00%
Workers compensation \| Casualty Reinsurance Program \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage							100.00%
Workers compensation \| Casualty Reinsurance Program \| OneBeacon \| Maximum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							$ 10.0
Workers compensation \| Casualty Reinsurance Program \| OneBeacon \| Minimum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							2.0
Healthcare Professional Liability [Member] \| Second Casualty Excess of Loss [Member] \| OneBeacon \| Maximum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							20.0
Healthcare Professional Liability [Member] \| Second Casualty Excess of Loss [Member] \| OneBeacon \| Minimum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							10.0
Other Casualty Business [Member] \| Second Casualty Excess of Loss [Member] \| OneBeacon \| Maximum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							$ 21.0
Reinsurance Retention Policy, Reinsured Risk, Percentage							100.00%
Other Casualty Business [Member] \| Second Casualty Excess of Loss [Member] \| OneBeacon \| Minimum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured							$ 11.0
Surety Product Line [Member] \| Surety Reinsurance Program [Member] \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured	$ 40.0
Reinsurance Retention Policy, Reinsured Risk, Percentage	100.00%
Surety Product Line [Member] \| Surety Reinsurance Program [Member] \| OneBeacon \| Maximum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured	$ 80.0
Surety Product Line [Member] \| Surety Reinsurance Program [Member] \| OneBeacon \| Minimum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured	5.0
Crop \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage							48.50%
Reinsurance Retention Policy, Loss Ratio Reinsured risk, Percentage							101.50%
Crop-hail insurance [Member] \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance Retention Policy, Reinsured Risk, Percentage							80.00%
Reinsurance Retention Policy, Loss Ratio Reinsured risk, Percentage							100.00%
Film Completion Bond Business [Member] \| OneBeacon \| Maximum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured			30.0
Film Completion Bond Business [Member] \| OneBeacon \| Minimum
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured			2.0
Film Completion Bond Business [Member] \| Facultative Treaty Layer [Member] \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured			50.0
AA \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance Recoverables	$ 53.8		$ 53.8				$ 53.8
Reinsurance recoverables, percentage of total	31.00%		31.00%				31.00%
A \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance Recoverables	$ 93.2		$ 93.2				$ 93.2
Reinsurance recoverables, percentage of total	54.00%		54.00%				54.00%
BBB plus \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance Recoverables	$ 26.8		$ 26.8				$ 26.8
Reinsurance recoverables, percentage of total	15.00%		15.00%				15.00%
OneBeacon Runoff \| BBB plus \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance Recoverables	$ 23.8		$ 23.8				$ 23.8
Scenario, Forecast [Member] \| OneBeacon
Effects of Reinsurance [Line Items]
Percentage of certified losses required to be shared by federal government subject to terrorism risk insurance act				80.00%		85.00%
Decreasing Annual Percentage of Certified Losses Required to be Shared by Federal Government Subject to Terrorism Risk Insurance Act									1.00%
Retained Percentage Relating To Certified Losses Required to be Shared by Federal Government Subject to Terrorism Risk Insurance Act				20.00%		15.00%
Increased Annual Retained Percentage Relating to Certified Losses Required to be Shared by Federal Government Subject to Terrorism Risk Insurance Act					1.00%
Scenario, Forecast [Member] \| Property Per-Risk, Acts of Terrorism \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance retention policy, amount retained						$ 120.0
Reinsurance Retention Policy, Reinsured Risk, Percentage						85.00%
Scenario, Forecast [Member] \| Property Per-Risk, Acts of Terrorism \| Maximum \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance retention policy, amount retained						$ 100,000.0
Department of Treasury [Member] \| Scenario, Forecast [Member] \| Property and Casualty, Commercial Insurance Product Line [Member] \| OneBeacon
Effects of Reinsurance [Line Items]
Reinsurance retention policy, excess retention, amount reinsured				$ 200.0		$ 100.0			$ 20.0

Third Party Reinsurance (Sirius Group) (Details) € in Millions		2 Months Ended	12 Months Ended
	Jan. 01, 2015 USD ($)	Feb. 28, 2014 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2014 EUR (€)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)
Reinsurance Retention Policy [Line Items]
Reinsurance recoverable on unpaid losses			$ 483,900,000		$ 428,100,000	$ 429,100,000	$ 2,507,300,000
Sirius Group
Reinsurance Retention Policy [Line Items]
Percentage of Business Ceded			20.00%	20.00%
Reinsurance Program Limit Per Cedant			$ 15,000,000
Percentage of trade credit business ceded under quota share retrocession			20.00%	20.00%
Percentage of bond business ceded under renewed quota share retrocession			50.00%	50.00%
Direct contingency business ceded			30.00%	30.00%
Percentage of property catastrophe reinsurance treaty reinstatement premiums			100.00%	100.00%
Reinsurance recoverable on paid losses			$ 11,400,000
Reinsurance recoverable on unpaid losses			322,200,000
OneBeacon
Reinsurance Retention Policy [Line Items]
Reinsurance recoverable on paid losses			12,200,000
Reinsurance recoverable on unpaid losses			161,600,000
Faculative and Direct Property Portfolios \| Sirius Group
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained			5,000,000
Reinsurance retention policy, excess retention, amount reinsured			15,000,000
Faculative and Direct Property Portfolios \| Lloyds Syndicate 1945 [Member]
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained		$ 2,500,000
Reinsurance retention policy, excess retention, amount reinsured		$ 2,500,000
Faculative and Direct U.S. Catastophe Exposed Business \| Lloyds Syndicate 1945 [Member]
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained			5,000,000
Reinsurance retention policy, excess retention, amount reinsured			5,000,000
Non U.S and Non Japan Earthquake Related Exposure \| Sirius Group
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained			35,000,000
Reinsurance retention policy, excess retention, amount reinsured			40,000,000
Non U.S and Non Japan Earth Quake Related Exposure Partial Coverage \| Sirius Group
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained			75,000,000
Reinsurance retention policy, excess retention, amount reinsured			17,500,000
Aviation Reinsurance \| Sirius Group
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, excess retention, amount reinsured			$ 29,500,000
Percentage of quota share reinsurance agreement			15.00%	15.00%
Aviation Reinsurance \| Minimum \| Sirius Group
Reinsurance Retention Policy [Line Items]
Insurance Market Loss			$ 250,000,000
Aviation reinsurance program cover in first event industry loss warranties			350,000,000
Aviation Reinsurance \| Maximum \| Sirius Group
Reinsurance Retention Policy [Line Items]
Insurance Market Loss			2,000,000,000
Aviation reinsurance program cover in first event industry loss warranties			1,000,000,000
Marine Yacht Portfolio, London Branch and Syndicate 1945 \| Sirius Group
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained			250,000
Reinsurance retention policy, excess retention, amount reinsured			14,750,000
Energy & Marine [Member] \| Sirius Group
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained			1,500,000
Reinsurance retention policy, excess retention, amount reinsured			16,000,000
Quota Share Reinsurance [Member] \| Sirius Group
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, excess retention, amount reinsured \| €				€ 1.0
Subsequent Event \| Sirius Group
Reinsurance Retention Policy [Line Items]
Percentage of trade credit business ceded under quota share retrocession	10.00%
Percentage of bond business ceded under renewed quota share retrocession	25.00%
Subsequent Event \| Direct Contingency [Member] \| Sirius Group
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained	$ 10,000,000
Percentage of quota share reinsurance agreement	20.00%
Hamburg and Stockholm [Member] \| Faculative and Direct Property Portfolios \| Lloyds Syndicate 1945 [Member]
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained			20,000,000
Reinsurance retention policy, excess retention, amount reinsured			15,000,000
Euro Member Countries, Euro \| Accident and Health \| Sirius Group
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained \| €				5.0
Reinsurance retention policy, excess retention, amount reinsured \| €				€ 10.0
United States of America, Dollars \| Accident and Health \| Sirius Group
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained			6,000,000
Reinsurance retention policy, excess retention, amount reinsured			12,000,000
Expiration March 2015 [Member] \| Wind and flood [Member] \| Industry Loss Warranty [Member] \| Minimum
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained			5,000,000,000
Reinsurance retention policy, excess retention, amount reinsured			5,000,000
Expiration March 2015 [Member] \| Wind and flood [Member] \| Industry Loss Warranty [Member] \| Maximum
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained			7,500,000,000
Reinsurance retention policy, excess retention, amount reinsured			5,000,000
Expiration December 2015 [Member] \| All Natural Perils [Member] \| Industry Loss Warranty [Member]
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained			15,000,000,000
Reinsurance retention policy, excess retention, amount reinsured			15,000,000
Expiration December 2015 [Member] \| Wind and earthquake [Member] \| Industry Loss Warranty [Member]
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, excess retention, amount reinsured			30,000,000
Expiration December 2015 [Member] \| Wind and earthquake [Member] \| Industry Loss Warranty [Member] \| Minimum
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained			5,000,000,000
Expiration December 2015 [Member] \| Wind and earthquake [Member] \| Industry Loss Warranty [Member] \| Maximum
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained			10,000,000,000
Expiration March 2016 [Member] \| Wind and earthquake [Member] \| Industry Loss Warranty [Member]
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, excess retention, amount reinsured			7,500,000
Expiration March 2016 [Member] \| Wind and earthquake [Member] \| Industry Loss Warranty [Member] \| Minimum
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained			5,000,000,000
Expiration March 2016 [Member] \| Wind and earthquake [Member] \| Industry Loss Warranty [Member] \| Maximum
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained			7,500,000,000
Expiration June 2015 [Member] \| Wind and flood [Member] \| Industry Loss Warranty [Member]
Reinsurance Retention Policy [Line Items]
Reinsurance retention policy, amount retained			20,000,000,000
Reinsurance retention policy, excess retention, amount reinsured			$ 5,000,000

Third Party Reinsurance (Recoverable Amounts by Reinsurer) (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013
Reinsurance Retention Policy [Line Items]
Reinsurance recoverable on paid and unpaid losses	$ 507.5	$ 453.5
Sirius Group
Reinsurance Retention Policy [Line Items]
Reinsurance recoverable on paid and unpaid losses	333.6	$ 363.6
Reinsurance Recoverables Allowance	30.2
Reinsurance Recoverables	$ 303.4
Reinsurance recoverables, percentage of total	100.00%
AA \| Sirius Group
Reinsurance Retention Policy [Line Items]
Reinsurance recoverable on paid and unpaid losses	$ 114.6
Reinsurance Recoverables Allowance	1.6
Reinsurance Recoverables	$ 113.0
Reinsurance recoverables, percentage of total	34.00%
A \| Sirius Group
Reinsurance Retention Policy [Line Items]
Reinsurance recoverable on paid and unpaid losses	$ 138.8
Reinsurance Recoverables Allowance	7.1
Reinsurance Recoverables	$ 131.7
Reinsurance recoverables, percentage of total	42.00%
BBB plus \| Sirius Group
Reinsurance Retention Policy [Line Items]
Reinsurance recoverable on paid and unpaid losses	$ 8.9
Reinsurance Recoverables Allowance	0.0
Reinsurance Recoverables	$ 8.9
Reinsurance recoverables, percentage of total	3.00%
BBB \| Sirius Group
Reinsurance Retention Policy [Line Items]
Reinsurance recoverable on paid and unpaid losses	$ 9.6
Reinsurance Recoverables Allowance	0.0
Reinsurance Recoverables	$ 9.6
Reinsurance recoverables, percentage of total	3.00%
Not rated \| Sirius Group
Reinsurance Retention Policy [Line Items]
Reinsurance recoverable on paid and unpaid losses	$ 61.7
Reinsurance Recoverables Allowance	21.5
Reinsurance Recoverables	$ 40.2
Reinsurance recoverables, percentage of total	18.00%

Investment Securities (Net Investment Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investment income:
Total investment income	$ 125.6	$ 130.6	$ 167.0
Third-party investment expenses	(20.6)	(19.7)	(13.4)
Net investment income, pre-tax	105.0	110.9	153.6
Fixed maturity investments
Investment income:
Total investment income	98.9	100.5	132.0
Short-term investments
Investment income:
Total investment income	1.5	3.4	3.1
Common Stock
Investment income:
Total investment income	21.0	20.5	22.2
Convertible fixed maturity and preferred investments
Investment income:
Total investment income	2.5	2.9	6.0
Other long-term investments
Investment income:
Total investment income	1.9	3.0	3.1
Interest on funds held under reinsurance treaties
Investment income:
Total investment income	$ (0.2)	$ 0.3	$ 0.6

Investment Securities (Net Realized and Unrealized Investement Gains and Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investments, Debt and Equity Securities [Abstract]
Net realized investment gains, pre-tax	$ 233.8	$ 104.5	$ 68.1
Net unrealized investment gains, pre-tax	50.1	57.2	50.1
Net realized and unrealized investment gains, pre-tax	283.9	161.7	118.2
Income tax expense attributable to net realized and unrealized investment gains	(69.7)	(21.9)	(26.8)
Net realized and unrealized investment gains, after tax	$ 214.2	$ 139.8	$ 91.4

Investment Securities Investment Securities (Net Realized Investment Gain (losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investment securities
Trading Securities, Realized Gain (Loss)	$ 208.7	$ 121.8	$ 76.7
Foreign Currency Transaction Gain (Loss), Realized	25.1	(17.3)	(8.6)
Net realized investment gains, pre-tax	233.8	104.5	68.1
Trading securities, Tax on Realized Holding Gain (Loss) on Investments	(39.7)	(30.0)	(23.8)
Trading Securities, Tax on Realized Foreign Currency Transaction Gain (Loss) Tax	(8.0)	5.5	2.2
Tax on Net Realized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities	(47.7)	(24.5)	(21.6)
Trading Securities Realized Holding Gain (Loss) on Investments after Tax	169.0	91.8	52.9
Trading Securities, Realized Foreign Currency Gain (Loss) Net of Tax	17.1	(11.8)	(6.4)
Net Realized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities Net of Tax	186.1	80.0	46.5
Fixed maturity investments
Investment securities
Trading Securities, Realized Gain (Loss)	23.9	8.6	82.5
Foreign Currency Transaction Gain (Loss), Realized	21.0	(15.0)	(2.5)
Net realized investment gains, pre-tax	44.9	(6.4)	80.0
Short-term investments
Investment securities
Trading Securities, Realized Gain (Loss)	0.0	0.1	0.0
Foreign Currency Transaction Gain (Loss), Realized	2.9	0.0	(4.3)
Net realized investment gains, pre-tax	2.9	0.1	(4.3)
Common equity securities
Investment securities
Trading Securities, Realized Gain (Loss)	150.9	104.5	1.3
Foreign Currency Transaction Gain (Loss), Realized	0.9	(3.7)	0.0
Net realized investment gains, pre-tax	151.8	100.8	1.3
Convertible fixed maturity and preferred investments
Investment securities
Trading Securities, Realized Gain (Loss)	5.9	1.0	(8.2)
Foreign Currency Transaction Gain (Loss), Realized	0.0	0.0	(1.8)
Net realized investment gains, pre-tax	5.9	1.0	(10.0)
Other long-term investments
Investment securities
Trading Securities, Realized Gain (Loss)	27.7	7.5	1.4
Foreign Currency Transaction Gain (Loss), Realized	0.3	1.4	0.0
Net realized investment gains, pre-tax	28.0	8.9	1.4
Forward contracts
Investment securities
Trading Securities, Realized Gain (Loss)	0.3	0.1	(0.3)
Foreign Currency Transaction Gain (Loss), Realized	0.0	0.0	0.0
Net realized investment gains, pre-tax	$ 0.3	$ 0.1	$ (0.3)

Investment Securities Investment Securities (Net Unrealized Investment Gains (Losses)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investment securities
Trading Securities, Change in Unrealized Holding Gain (Loss)	$ (66.2)	$ 38.9	$ 98.7
Foreign Currency Transaction Gain (Loss), Unrealized	116.3	18.3	(48.6)
Net unrealized investment gains, pre-tax	50.1	57.2	50.1
Trading Securities, Tax on Unrealized Holding Gain (Loss) on Investments	6.0	8.2	(17.9)
Trading Securities, Unrealized Foreign Currency Transaction Gain (Loss) Tax	(28.0)	(5.6)	12.7
Net Unrealized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities Tax	(22.0)	2.6	(5.2)
Trading Securities Unrealized Holding Gain (Loss) on Investments after Tax	(60.2)	47.1	80.8
Trading Securities, Unrealized Foreign Currency Gain (Loss) Net of Tax	88.3	12.7	(35.9)
Net Unrealized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities Net of Tax	28.1	59.8	44.9
Fixed maturity investments
Investment securities
Trading Securities, Change in Unrealized Holding Gain (Loss)	30.9	(93.9)	18.5
Foreign Currency Transaction Gain (Loss), Unrealized	111.7	15.3	(45.9)
Net unrealized investment gains, pre-tax	142.6	(78.6)	(27.4)
Short-term investments
Investment securities
Trading Securities, Change in Unrealized Holding Gain (Loss)	(0.2)	0.1	0.0
Foreign Currency Transaction Gain (Loss), Unrealized	0.1	0.0	0.1
Net unrealized investment gains, pre-tax	(0.1)	0.1	0.1
Common equity securities
Investment securities
Trading Securities, Change in Unrealized Holding Gain (Loss)	(83.0)	119.2	65.9
Foreign Currency Transaction Gain (Loss), Unrealized	(0.1)	(0.4)	(0.1)
Net unrealized investment gains, pre-tax	(83.1)	118.8	65.8
Convertible fixed maturity and preferred investments
Investment securities
Trading Securities, Change in Unrealized Holding Gain (Loss)	(8.2)	3.2	1.1
Foreign Currency Transaction Gain (Loss), Unrealized	0.4	0.0	0.0
Net unrealized investment gains, pre-tax	(7.8)	3.2	1.1
Other long-term investments
Investment securities
Trading Securities, Change in Unrealized Holding Gain (Loss)	(5.7)	10.3	13.2
Foreign Currency Transaction Gain (Loss), Unrealized	4.2	3.4	(2.7)
Net unrealized investment gains, pre-tax	$ (1.5)	$ 13.7	$ 10.5

Investment Securities (Investment Gains (Losses) For Level 3) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investment securities
Realized gains	$ 270.0	$ 221.4		$ 162.2
Realized losses	36.2	116.9		$ 94.1
Level 3 Inputs
Investment securities
Total pre-tax gains (losses) included in earnings attributable to unrealized investment gains (losses) for Level 3 investments	3.7	9.8	$ 17.7
Fixed maturity investments \| Level 3 Inputs
Investment securities
Total pre-tax gains (losses) included in earnings attributable to unrealized investment gains (losses) for Level 3 investments	1.2	(2.3)	7.7
Common equity securities \| Level 3 Inputs
Investment securities
Total pre-tax gains (losses) included in earnings attributable to unrealized investment gains (losses) for Level 3 investments	5.9	0.9	3.0
Convertible fixed maturity and preferred investments \| Level 3 Inputs
Investment securities
Total pre-tax gains (losses) included in earnings attributable to unrealized investment gains (losses) for Level 3 investments	0.7	0.0	0.0
Other long-term investments \| Level 3 Inputs
Investment securities
Total pre-tax gains (losses) included in earnings attributable to unrealized investment gains (losses) for Level 3 investments	$ (4.1)	$ 11.2	$ 7.0

Investment Securities (Net Realized and Unrealized Gains (Losses) After Tax) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investments, Debt and Equity Securities [Abstract]
Net change in pre-tax unrealized gains (losses) on investments in unconsolidated affiliates	$ 81.2	$ (106.4)	$ 62.8
Income taxes	(5.9)	8.3	(5.1)
Net change in unrealized gains (losses) on investments in unconsolidated affiliates, after tax	75.3	(98.1)	57.7
Net realized and unrealized foreign currency (losses) gains on investments through OCI	(274.3)	11.3	95.5
Total investment (losses) gains through accumulated other comprehensive income	(199.0)	(86.8)	153.2
Net Realized and Unrealized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities Net of Tax	214.2	139.8	91.4
Total investment gains recorded during the period, after-tax	$ 15.2	$ 53.0	$ 244.6

Investment Securities (Investment Holdings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Investment securities
Fixed maturity investments, at fair value	$ 4,784.3	$ 5,030.5
Including Short Term Fixed
Investment securities
Duration of Fixed Maturities	2 years
US Government and agency obligations
Investment securities
Trading Securities, Cost	$ 184.7	365.5
Net foreign currency gains (losses)	3.6	(2.5)
Fixed maturity investments, at fair value	188.1	362.5
Trading Securities, Unrealized Holding Gain	0.1	0.5
Trading Securities, Unrealized Holding Loss	(0.3)	(1.0)
Debt securities issued by corporations
Investment securities
Trading Securities, Cost	2,221.3	2,330.7
Net foreign currency gains (losses)	49.8	(14.3)
Fixed maturity investments, at fair value	2,311.2	2,347.2
Trading Securities, Unrealized Holding Gain	45.2	44.0
Trading Securities, Unrealized Holding Loss	(5.1)	(13.2)
Municipal obligations
Investment securities
Trading Securities, Cost	82.0	18.3
Net foreign currency gains (losses)	0.0	0.0
Fixed maturity investments, at fair value	83.2	17.9
Trading Securities, Unrealized Holding Gain	1.4	0.0
Trading Securities, Unrealized Holding Loss	(0.2)	(0.4)
Mortgage-backed and asset-backed securities
Investment securities
Trading Securities, Cost	1,811.1	2,027.3
Net foreign currency gains (losses)	25.7	(5.3)
Fixed maturity investments, at fair value	1,840.9	2,014.5
Trading Securities, Unrealized Holding Gain	7.6	2.4
Trading Securities, Unrealized Holding Loss	(3.5)	(9.9)
Foreign government, agency and provincial obligations
Investment securities
Trading Securities, Cost	274.6	444.2
Net foreign currency gains (losses)	(2.7)	(4.8)
Fixed maturity investments, at fair value	275.1	439.9
Trading Securities, Unrealized Holding Gain	4.2	3.7
Trading Securities, Unrealized Holding Loss	(1.0)	(3.2)
Preferred stocks
Investment securities
Trading Securities, Cost	79.6	79.9
Net foreign currency gains (losses)	0.1	(0.2)
Fixed maturity investments, at fair value	85.8	84.8
Trading Securities, Unrealized Holding Gain	6.1	5.1
Trading Securities, Unrealized Holding Loss	0.0	0.0
Fixed Income Investments [Member]
Investment securities
Trading Securities, Cost	4,653.3	5,265.9
Net foreign currency gains (losses)	76.5	(27.1)
Total fixed maturity investments	4,784.3	5,266.8
Trading Securities, Unrealized Holding Gain	64.6	55.7
Trading Securities, Unrealized Holding Loss	$ (10.1)	(27.7)
Excluding Short Term Investments
Investment securities
Duration of Fixed Maturities	2 years 3 months 18 days
OneBeacon Runoff
Investment securities
Fixed maturity investments reclassified to assets held for sale (1)		$ (236.3)

Investment Securities (Cost and Amortized Cost Maturity Schedule) (Details) $ in Millions	Dec. 31, 2014 USD ($)
Trading Securities by Maturity Cost or Amortized Cost
Cost or amortized cost	$ 4,664.8
Trading Securities by Maturity, Fair Value
Trading Securities	4,796.5
Fixed Maturities and Convertible Fixed Maturities Excluding A B S M B S and Preferred Stock
Trading Securities by Maturity Cost or Amortized Cost
Due in one year or less	331.2
Due after one year through five years	1,968.3
Due after five years through ten years	434.4
Due after ten years	40.2
Trading Securities by Maturity, Fair Value
Due in one year or less	337.5
Due after one year through five years	2,032.3
Due after five years through ten years	453.9
Due after ten years	46.1
Mortgage-backed and asset-backed securities
Trading Securities by Maturity Cost or Amortized Cost
Trading Securities, Maturities without Single Maturity Date, Amortized Cost	1,811.1
Trading Securities by Maturity, Fair Value
Trading Securities, Maturities without Single Maturity Date, Carrying Value	1,840.9
Preferred stocks
Trading Securities by Maturity Cost or Amortized Cost
Trading Securities, Maturities without Single Maturity Date, Amortized Cost	79.6
Trading Securities by Maturity, Fair Value
Trading Securities, Maturities without Single Maturity Date, Carrying Value	$ 85.8

Investment Securities (Cost or Amortized Cost, Gross Unrealized Investment Gains and Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investment securities
Fixed maturity investments, at fair value	$ 4,784.3	$ 5,030.5
Sales and maturities of investment securities	6,238.1	4,924.8	$ 6,997.5
Common Stock
Investment securities
Trading Securities, Cost	633.6	890.2
Net foreign currency gains (losses)	(1.9)	(0.8)
Fixed maturity investments, at fair value	801.6	1,156.8
Trading Securities, Unrealized Holding Gain	175.1	271.0
Trading Securities, Unrealized Holding Loss	(5.2)	(3.6)
Convertible fixed maturity investments
Investment securities
Trading Securities, Cost	19.1	71.7
Net foreign currency gains (losses)	0.7	(0.2)
Fixed maturity investments, at fair value	20.5	80.5
Trading Securities, Unrealized Holding Gain	0.9	9.9
Trading Securities, Unrealized Holding Loss	(0.2)	(0.9)
Other long-term investments
Investment securities
Trading Securities, Cost	344.5	238.3
Net foreign currency gains (losses)	1.6	(2.4)
Fixed maturity investments, at fair value	408.2	288.9
Trading Securities, Unrealized Holding Gain	73.0	79.6
Trading Securities, Unrealized Holding Loss	$ (10.9)	$ (26.6)

Investment Securities (Investments Held on Deposit or as Collateral) (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013
Investment securities
Investments held in trusts	$ 171.5	$ 170.4
Assets held by insurance regulators	130.3	290.7
Surety Product Line [Member] \| OneBeacon
Investment securities
Assets Held in Collateral	81.0	63.3
Fixed maturity investments \| White Mountains Life Re
Investment securities
Derivative Collateral Right to Reclaim	9.5	23.2
Short-term investments \| White Mountains Life Re
Investment securities
Derivative Collateral Right to Reclaim	0.0	$ 2.0
Interest Rate Cap
Investment securities
Derivative Collateral Right to Reclaim	$ 4.3

Investment Securities (Debt Securities Issued By Corporation) (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investment securities
Fair value investments	$ 5,991.4	$ 6,766.5	$ 6,950.7
Debt securities issued by corporations
Investment securities
Fair value investments	2,311.2	2,347.2
Other Standard Poors Rating [Member] \| Debt securities issued by corporations
Investment securities
Fair value investments	10.6	3.4
Standard & Poor's, BB Rating [Member] \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
BBB \| Debt securities issued by corporations
Investment securities
Fair value investments	1,105.9	1,075.5
A \| Debt securities issued by corporations
Investment securities
Fair value investments	957.8	1,039.5
AA \| Debt securities issued by corporations
Investment securities
Fair value investments	236.9	228.8
AAA \| Debt securities issued by corporations
Investment securities
Fair value investments	$ 0.0	$ 0.0

Investment Securities (Mortgage-backed Asset Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investment securities
Fair value investments	$ 5,991.4	$ 6,766.5	$ 6,950.7
GNMA
Investment securities
Fair value investments	411.2	512.3
FNMA
Investment securities
Fair value investments	36.6	81.2
FHLMC
Investment securities
Fair value investments	49.6	91.3
Total Agency
Investment securities
Fair value investments	497.4	684.8
Residential
Investment securities
Fair value investments	131.2	125.7
Commercial
Investment securities
Fair value investments	236.9	282.3
Total Non-agency
Investment securities
Fair value investments	368.1	408.0
Total mortgage-backed securities
Investment securities
Fair value investments	865.5	1,092.8
Credit card receivables
Investment securities
Fair value investments	522.2	311.4
Vehicle receivables
Investment securities
Fair value investments	289.4	365.0
Other
Investment securities
Fair value investments	163.8	245.3
Total asset-backed securities
Investment securities
Fair value investments	975.4	921.7
Total mortgage and asset- backed securities
Investment securities
Fair value investments	1,840.9	2,014.5
Non-Agency Residential Mortgage
Investment securities
Fair value investments	45.1
Level 2 Inputs
Investment securities
Fair value investments	4,638.0	4,982.2	$ 5,206.1
Level 2 Inputs \| GNMA
Investment securities
Fair value investments	411.2	512.3
Level 2 Inputs \| FNMA
Investment securities
Fair value investments	36.6	81.2
Level 2 Inputs \| FHLMC
Investment securities
Fair value investments	49.6	91.3
Level 2 Inputs \| Total Agency
Investment securities
Fair value investments	497.4	684.8
Level 2 Inputs \| Residential
Investment securities
Fair value investments	131.2	125.7
Level 2 Inputs \| Commercial
Investment securities
Fair value investments	236.9	282.3
Level 2 Inputs \| Total Non-agency
Investment securities
Fair value investments	368.1	408.0
Level 2 Inputs \| Total mortgage-backed securities
Investment securities
Fair value investments	865.5	1,092.8
Level 2 Inputs \| Credit card receivables
Investment securities
Fair value investments	522.2	289.4
Level 2 Inputs \| Vehicle receivables
Investment securities
Fair value investments	289.4	365.0
Level 2 Inputs \| Other
Investment securities
Fair value investments	163.8	245.3
Level 2 Inputs \| Total asset-backed securities
Investment securities
Fair value investments	975.4	899.7
Level 2 Inputs \| Total mortgage and asset- backed securities
Investment securities
Fair value investments	1,840.9	1,992.5
Level 3 Inputs \| GNMA
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| FNMA
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| FHLMC
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| Total Agency
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| Residential
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| Commercial
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| Total Non-agency
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| Total mortgage-backed securities
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| Credit card receivables
Investment securities
Fair value investments	0.0	22.0
Level 3 Inputs \| Vehicle receivables
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| Other
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| Total asset-backed securities
Investment securities
Fair value investments	0.0	22.0
Level 3 Inputs \| Total mortgage and asset- backed securities
Investment securities
Fair value investments	$ 0.0	$ 22.0

Investment Securities (Non-agency Mortgage-backed Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investment securities
Fair value investments	$ 5,991.4	$ 6,766.5	$ 6,950.7
Residential
Investment securities
Fair value investments	131.2	125.7
Commercial
Investment securities
Fair value investments	236.9	282.3
Total Non-agency
Investment securities
Fair value investments	368.1	$ 408.0
Securities Issued in 2004 [Member] \| Residential
Investment securities
Fair value investments	14.2
Securities Issued in 2004 [Member] \| Commercial
Investment securities
Fair value investments	0.0
Securities Issued in 2004 [Member] \| Total Non-agency
Investment securities
Fair value investments	14.2
2005 \| Residential
Investment securities
Fair value investments	14.7
2005 \| Commercial
Investment securities
Fair value investments	0.0
2005 \| Total Non-agency
Investment securities
Fair value investments	14.7
2006 \| Residential
Investment securities
Fair value investments	9.9
2006 \| Commercial
Investment securities
Fair value investments	8.5
2006 \| Total Non-agency
Investment securities
Fair value investments	18.4
2007 \| Residential
Investment securities
Fair value investments	0.0
2007 \| Commercial
Investment securities
Fair value investments	0.0
2007 \| Total Non-agency
Investment securities
Fair value investments	0.0
2008 \| Residential
Investment securities
Fair value investments	16.5
2008 \| Commercial
Investment securities
Fair value investments	0.0
2008 \| Total Non-agency
Investment securities
Fair value investments	16.5
2009 \| Residential
Investment securities
Fair value investments	0.0
2009 \| Commercial
Investment securities
Fair value investments	0.0
2009 \| Total Non-agency
Investment securities
Fair value investments	0.0
2010 \| Residential
Investment securities
Fair value investments	14.7
2010 \| Commercial
Investment securities
Fair value investments	11.7
2010 \| Total Non-agency
Investment securities
Fair value investments	26.4
2011 \| Residential
Investment securities
Fair value investments	21.4
2011 \| Commercial
Investment securities
Fair value investments	0.0
2011 \| Total Non-agency
Investment securities
Fair value investments	21.4
2012 \| Residential
Investment securities
Fair value investments	0.0
2012 \| Commercial
Investment securities
Fair value investments	20.7
2012 \| Total Non-agency
Investment securities
Fair value investments	20.7
2013 \| Residential
Investment securities
Fair value investments	29.7
2013 \| Commercial
Investment securities
Fair value investments	79.9
2013 \| Total Non-agency
Investment securities
Fair value investments	109.6
2014 \| Residential
Investment securities
Fair value investments	10.1
2014 \| Commercial
Investment securities
Fair value investments	116.1
2014 \| Total Non-agency
Investment securities
Fair value investments	$ 126.2

Investment Securities (Non-agency Residential Mortgage-backed Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investment securities
Fair value investments	$ 5,991.4	$ 6,766.5	$ 6,950.7
Residential
Investment securities
Fair value investments	131.2	$ 125.7
Residential \| Prime
Investment securities
Fair value investments	119.4
Residential \| Non-prime
Investment securities
Fair value investments	9.3
Residential \| Sub-prime
Investment securities
Fair value investments	2.5
Residential \| Super Senior
Investment securities
Fair value investments	74.1
Residential \| Super Senior \| Prime
Investment securities
Fair value investments	71.6
Residential \| Super Senior \| Non-prime
Investment securities
Fair value investments	0.0
Residential \| Super Senior \| Sub-prime
Investment securities
Fair value investments	2.5
Residential \| Senior
Investment securities
Fair value investments	57.1
Residential \| Senior \| Prime
Investment securities
Fair value investments	47.8
Residential \| Senior \| Non-prime
Investment securities
Fair value investments	9.3
Residential \| Senior \| Sub-prime
Investment securities
Fair value investments	0.0
Residential \| Subordinate
Investment securities
Fair value investments	0.0
Residential \| Subordinate \| Prime
Investment securities
Fair value investments	0.0
Residential \| Subordinate \| Non-prime
Investment securities
Fair value investments	0.0
Residential \| Subordinate \| Sub-prime
Investment securities
Fair value investments	$ 0.0

Investment Securities (Other Long-Term Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investment securities
Other Investments	$ 385.0	$ 262.3
Other long-term investments
Investment securities
Carrying value of investment accounted for using the equity method	23.2
Limited Liability Company and Private Equity Securities
Investment securities
Other Investments	69.7	20.3
Surplus Note
Investment securities
Other Investments	65.1	0.0
Total hedge and private equity funds included in other long-term investments
Investment securities
Other Investments	242.9	239.0
Other Debt Obligations [Member]
Investment securities
Other Investments	7.3	3.1
Forward contracts
Investment securities
Other Investments	0.0	(0.1)
Fair value measured on a recurring basis \| Level 3 Inputs \| Other long-term investments
Investment securities
Carrying value of investment accounted for using the equity method	$ 23.2	$ 26.6	$ 35.0

Investment Securities (Non-agency Commercial Mortgage-backed Securities) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Investment securities
Fair value investments	$ 5,991.4	$ 6,766.5	$ 6,950.7
Fixed rate CMBS
Investment securities
Average Basis Points of Subordination	0.25
Fair value investments	$ 116.2
Fixed rate CMBS \| Super Senior
Investment securities
Fair value investments	13.1
Fixed rate CMBS \| Senior
Investment securities
Fair value investments	61.6
Fixed rate CMBS \| Subordinate
Investment securities
Fair value investments	41.5
Floating rate CMBS
Investment securities
Fair value investments	120.7
Floating rate CMBS \| Super Senior
Investment securities
Fair value investments	0.0
Floating rate CMBS \| Senior
Investment securities
Fair value investments	0.0
Floating rate CMBS \| Subordinate
Investment securities
Fair value investments	120.7
Commercial
Investment securities
Fair value investments	236.9	$ 282.3
Commercial \| Super Senior
Investment securities
Fair value investments	13.1
Commercial \| Senior
Investment securities
Fair value investments	61.6
Commercial \| Subordinate
Investment securities
Fair value investments	$ 162.2
Maximum \| Commercial
Investment securities
Loans and Leases Receivable, Ratio of Nonperforming Loans to All Loans	1.00%

Investment Securities (Fair Value of Hedge Funds Subject to Restrictions on Redemption Frequency) (Details) $ in Millions	Dec. 31, 2014 USD ($) fund	Dec. 31, 2013 USD ($)
Private equity funds
Investment securities
Number of Investments Held \| fund	32
Trading Securities, Other	$ 150.9
Hedge funds
Investment securities
Number of Investments Held \| fund	12
Trading Securities, Other	$ 92.0
Total hedge and private equity funds included in other long-term investments
Investment securities
Trading Securities, Other	242.9	$ 239.0
Fair value unfunded commitments	81.7	110.6
Other Long-term Investments Largest Single Investment	22.0	18.3
Private equity funds \| Private equity funds
Investment securities
Trading Securities, Other	150.9	118.2
Fair value unfunded commitments	81.7	110.6
Private equity funds \| Multi-sector
Investment securities
Trading Securities, Other	24.2	23.8
Fair value unfunded commitments	5.3	6.5
Private equity funds \| Energy infrastructure & services
Investment securities
Trading Securities, Other	59.6	45.9
Fair value unfunded commitments	11.0	13.1
Private equity funds \| Distressed residential real estate
Investment securities
Trading Securities, Other	0.0	0.4
Fair value unfunded commitments	0.0	0.0
Private equity funds \| Real estate
Investment securities
Trading Securities, Other	3.6	8.2
Fair value unfunded commitments	3.3	3.3
Private equity funds \| Private equity secondaries
Investment securities
Trading Securities, Other	8.5	9.5
Fair value unfunded commitments	3.1	3.1
Private equity funds \| International multi-sector, Europe
Investment securities
Trading Securities, Other	1.5	3.9
Fair value unfunded commitments	2.3	2.8
Private equity funds \| Manufacturing/Industrial
Investment securities
Trading Securities, Other	23.2	11.2
Fair value unfunded commitments	7.3	15.5
Private equity funds \| Healthcare
Investment securities
Trading Securities, Other	6.1	5.6
Fair value unfunded commitments	2.8	2.8
Private equity funds \| International multi-sector, Asia
Investment securities
Trading Securities, Other	0.0	0.0
Fair value unfunded commitments	0.0	2.7
Private equity funds \| Insurance
Investment securities
Trading Securities, Other	2.1	2.3
Fair value unfunded commitments	41.2	41.3
Private equity funds \| Aerospace/Defense/Government
Investment securities
Trading Securities, Other	20.7	5.8
Fair value unfunded commitments	5.1	19.2
Private equity funds \| Venture capital
Investment securities
Trading Securities, Other	1.4	1.6
Fair value unfunded commitments	0.3	0.3
Hedge funds \| Hedge funds
Investment securities
Trading Securities, Other	92.0	120.8
Fair value unfunded commitments	0.0	0.0
Hedge funds \| Long/short equity
Investment securities
Trading Securities, Other	43.9	62.6
Fair value unfunded commitments	0.0	0.0
Hedge funds \| Long/short credit & distressed
Investment securities
Trading Securities, Other	21.4	22.8
Fair value unfunded commitments	0.0	0.0
Hedge funds \| Long diversified strategies
Investment securities
Trading Securities, Other	0.0	0.1
Fair value unfunded commitments	0.0	0.0
Hedge funds \| Long/short equity REIT
Investment securities
Trading Securities, Other	20.3	18.3
Fair value unfunded commitments	0.0	0.0
Hedge funds \| Long/short equity activist
Investment securities
Trading Securities, Other	6.2	16.8
Fair value unfunded commitments	0.0	0.0
Hedge funds \| Long bank loan
Investment securities
Trading Securities, Other	0.2	0.2
Fair value unfunded commitments	0.0	$ 0.0
DavidShield [Member]
Investment securities
Fair value unfunded commitments	$ 21.0

Investment Securities (Restrictions on Redemption Frequency and Advance Notice Requirements) (Details) - Hedge funds $ in Millions	Dec. 31, 2014 USD ($)
Investment securities
Trading Securities, Other	$ 92.0
Distributions from inactive hedge funds	2.1
Outstanding redemptions	6.7
30-59 days notice
Investment securities
Trading Securities, Other	36.1
60-89 days notice
Investment securities
Trading Securities, Other	43.5
90-119 days notice
Investment securities
Trading Securities, Other	4.4
120 days notice
Investment securities
Trading Securities, Other	8.0
Monthly
Investment securities
Trading Securities, Other	4.3
Monthly \| 30-59 days notice
Investment securities
Trading Securities, Other	4.3
Monthly \| 60-89 days notice
Investment securities
Trading Securities, Other	0.0
Monthly \| 90-119 days notice
Investment securities
Trading Securities, Other	0.0
Monthly \| 120 days notice
Investment securities
Trading Securities, Other	0.0
Quarterly
Investment securities
Trading Securities, Other	61.0
Quarterly \| 30-59 days notice
Investment securities
Trading Securities, Other	31.8
Quarterly \| 60-89 days notice
Investment securities
Trading Securities, Other	21.4
Quarterly \| 90-119 days notice
Investment securities
Trading Securities, Other	0.0
Quarterly \| 120 days notice
Investment securities
Trading Securities, Other	7.8
Semi-annual
Investment securities
Trading Securities, Other	22.1
Semi-annual \| 30-59 days notice
Investment securities
Trading Securities, Other	0.0
Semi-annual \| 60-89 days notice
Investment securities
Trading Securities, Other	22.1
Semi-annual \| 90-119 days notice
Investment securities
Trading Securities, Other	0.0
Semi-annual \| 120 days notice
Investment securities
Trading Securities, Other	0.0
Annual
Investment securities
Trading Securities, Other	4.6
Annual \| 30-59 days notice
Investment securities
Trading Securities, Other	0.0
Annual \| 60-89 days notice
Investment securities
Trading Securities, Other	0.0
Annual \| 90-119 days notice
Investment securities
Trading Securities, Other	4.4
Annual \| 120 days notice
Investment securities
Trading Securities, Other	$ 0.2

Investment Securities (Investments In Private Equity Funds Subject to Lock-Up Periods) (Details) - Private equity funds $ in Millions	Dec. 31, 2014 USD ($)
Investment securities
Trading Securities, Other	$ 150.9
1-3 years
Investment securities
Trading Securities, Other	12.7
3 – 5 years
Investment securities
Trading Securities, Other	33.5
5 – 10 years
Investment securities
Trading Securities, Other	79.0
10 years
Investment securities
Trading Securities, Other	$ 25.7

Investment Securities (Rollforward of Fair Value Measurements by Level) (Details) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2013 USD ($)	Dec. 31, 2014 USD ($) Investment	Dec. 31, 2013 USD ($) Investment	Dec. 31, 2012 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	$ 6,950.7	$ 6,766.5	$ 6,950.7
Total realized and unrealized gains (losses)		286.5	182.0
Foreign currency gains (losses) through OCI		(253.6)	11.6
Amortization/Accretion		(44.1)	52.2
Purchases		5,602.1	4,635.5
Sales		(6,387.5)	(4,979.8)
Net change in investments related to purchases and sales of consolidated/unconsolidated affiliates		21.5
Fair Value, Assets Measured on Recurring Basis, Exchange		0.0
Transfers in		97.8	217.6
Transfers out		(97.8)	(217.6)
Fair value investments		5,991.4	6,766.5	$ 6,950.7
Maximum price difference provided by pricing services	1.3	1.0
Net realized and unrealized investment gains		283.9	161.7	118.2
Discontinued Operations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fixed maturity investments reclassified to assets held for sale (1)			(236.3)	(338.1)
Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		7,402.4
Fair value investments		6,863.1	7,402.4
Fixed maturity investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		5,266.8
Fair value investments		4,784.3	5,266.8
Convertible fixed maturity investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		80.5
Fair value investments		20.5	80.5
Other long-term investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Carrying value of investment accounted for using the equity method		23.2
Other long-term investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		262.4
Fair value investments		385.0	262.4
Short-term investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		635.9		630.6
Fair value investments		871.7	635.9
Level 1 Inputs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	1,355.1	1,376.7	1,355.1
Total realized and unrealized gains (losses)		88.1	221.9
Foreign currency gains (losses) through OCI		(24.8)	(0.3)
Amortization/Accretion		(0.6)	(1.0)
Purchases		1,599.2	862.1
Sales		(2,197.1)	(1,078.9)
Net change in investments related to purchases and sales of consolidated/unconsolidated affiliates		(2.7)
Fair Value, Assets Measured on Recurring Basis, Exchange		4.7
Transfers in		0.0	1.8
Transfers out		(0.2)	0.0
Fair value investments		843.3	1,376.7	1,355.1
Level 1 Inputs \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		1,998.2
Fair value investments		1,712.1	1,998.2
Level 1 Inputs \| Fixed maturity investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		340.3
Fair value investments		155.4	340.3
Level 1 Inputs \| Convertible fixed maturity investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		0.0
Fair value investments		0.0	0.0
Level 1 Inputs \| Other long-term investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		0.0
Fair value investments		0.0	0.0
Level 1 Inputs \| Short-term investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		621.5
Fair value investments		868.8	621.5
Level 2 Inputs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	5,206.1	4,982.2	5,206.1
Total realized and unrealized gains (losses)		163.4	(56.9)
Foreign currency gains (losses) through OCI		(222.8)	12.5
Amortization/Accretion		(43.6)	(51.2)
Purchases		3,772.4	3,689.6
Sales		(4,122.6)	(3,842.8)
Net change in investments related to purchases and sales of consolidated/unconsolidated affiliates		24.2
Fair Value, Assets Measured on Recurring Basis, Exchange		(13.0)
Transfers in		97.8	119.4
Transfers out		0.0	(97.2)
Fair value investments		4,638.0	4,982.2	5,206.1
Level 2 Inputs \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		4,996.6
Fair value investments		4,640.9	4,996.6
Level 2 Inputs \| Fixed maturity investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		4,833.5
Fair value investments		4,552.2	4,833.5
Level 2 Inputs \| Convertible fixed maturity investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		74.4
Fair value investments		12.3	74.4
Level 2 Inputs \| Other long-term investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		0.0
Fair value investments		0.0	0.0
Level 2 Inputs \| Forward contracts \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Change in fair value of derivatives, included in other revenue			(0.1)
Level 2 Inputs \| Short-term investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		14.4
Fair value investments		2.9	14.4
Level 3 Inputs \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		407.6
Fair value investments		510.1	407.6
Level 3 Inputs \| Fixed maturity investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	92.9	93.0	92.9
Total realized and unrealized gains (losses)		2.2	(2.7)
Foreign currency gains (losses) through OCI		(1.0)	0.3
Amortization/Accretion		0.1	0.0
Purchases		71.7	37.9
Sales		0.0	(6.3)
Net change in investments related to purchases and sales of consolidated/unconsolidated affiliates		0.0
Fair Value, Assets Measured on Recurring Basis, Exchange		8.3
Transfers in	90.3	0.0	90.3
Transfers out		(97.6)	(119.4)
Fair value investments		$ 76.7	$ 93.0	92.9
Number of investments \| Investment		6	3
Level 3 Inputs \| Fixed maturity investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		$ 93.0
Fair value investments		76.7	$ 93.0
Level 3 Inputs \| Common equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	37.3	46.1	37.3
Total realized and unrealized gains (losses)		6.2	1.0
Foreign currency gains (losses) through OCI		0.0	0.0
Amortization/Accretion		0.0	0.0
Purchases		5.0	8.8
Sales		(17.1)	0.0
Net change in investments related to purchases and sales of consolidated/unconsolidated affiliates		0.0
Fair Value, Assets Measured on Recurring Basis, Exchange		0.0
Transfers in		0.0	0.0
Transfers out		0.0	(1.0)
Fair value investments		40.2	46.1	37.3
Level 3 Inputs \| Convertible fixed maturity investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	0.0	6.1	0.0
Total realized and unrealized gains (losses)		0.6	0.0
Foreign currency gains (losses) through OCI		0.0	0.0
Amortization/Accretion		0.0	0.0
Purchases		1.5	0.0
Sales		0.0	0.0
Net change in investments related to purchases and sales of consolidated/unconsolidated affiliates		0.0
Fair Value, Assets Measured on Recurring Basis, Exchange		0.0
Transfers in		0.0	6.1
Transfers out		0.0	0.0
Fair value investments		8.2	6.1	0.0
Level 3 Inputs \| Convertible fixed maturity investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		6.1
Fair value investments		8.2	6.1
Level 3 Inputs \| Other long-term investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	$ 259.3	262.4	259.3
Total realized and unrealized gains (losses)		26.0	18.7
Foreign currency gains (losses) through OCI		(5.0)	(0.9)
Amortization/Accretion		0.0	0.0
Purchases		152.3	37.1
Sales		(50.7)	(51.8)
Net change in investments related to purchases and sales of consolidated/unconsolidated affiliates		0.0
Fair Value, Assets Measured on Recurring Basis, Exchange		0.0
Transfers in		0.0	0.0
Transfers out		0.0	0.0
Fair value investments		385.0	262.4	259.3
Level 3 Inputs \| Other long-term investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		262.4
Fair value investments		385.0	262.4
Carrying value of investment accounted for using the equity method		23.2	26.6	$ 35.0
Level 3 Inputs \| Short-term investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		0.0
Fair value investments		0.0	0.0
Prospector
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized and unrealized investment gains		4.3	20.6
Short-term investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Net realized and unrealized investment gains		$ 2.8	$ 0.2

Investment Securities (Significant Unobservable Inputs) (Details)	12 Months Ended
	Dec. 31, 2014 USD ($) input Investment	Dec. 31, 2013 USD ($)
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Assets Measured on Recurring Basis, Transfers out	$ 97,800,000	$ 217,600,000
Number of Investments with Significant Unobseravble Inputs \| Investment	1
Standard Poors NR Rating [Member] \| Redeemable preferred stocks \| Discounted cash flows
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, Fair Value Disclosure	$ 71,100,000	$ 71,000,000
Standard Poors NR Rating [Member] \| Redeemable preferred stocks \| Discount Yield
Quantitative information for Level 3 Fair Value Measurements Assets
Discount Yield (as a percent)	7.10%	7.40%
Standard Poors NR Rating [Member] \| Private equity funds \| Multiple of GAAP book value
Quantitative information for Level 3 Fair Value Measurements Assets
Book Value Multiple to Calculate Fair Value	110.00%	100.00%
Assets, Fair Value Disclosure	$ 40,200,000	$ 35,600,000
Standard Poors NR Rating [Member] \| Private equity funds \| Recent transaction [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, Fair Value Disclosure	20,100,000	10,500,000
Standard Poors NR Rating [Member] \| Private equity funds \| Average Share Price [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Average Share Price Used As Unobservable Input	1.06	1.10
Standard Poors NR Rating [Member] \| Private equity securities \| Recent transaction [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Average Share Price Used As Unobservable Input		0.71
Assets, Fair Value Disclosure	$ 4,500,000	3,000,000
Standard Poors NR Rating [Member] \| Private equity securities \| Multiple of EBITDA [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Unobservable Inputs \| input	6.00
Assets, Fair Value Disclosure	$ 3,800,000
Standard Poors NR Rating [Member] \| Mortgage-backed and asset-backed securities \| Broker Pricing
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, Fair Value Disclosure		22,000,000
Standard Poors NR Rating [Member] \| Seller Priority Surplus Note [Member] \| Discounted cash flows
Quantitative information for Level 3 Fair Value Measurements Assets
Timing of Interest Payments	5 years
Discount Yield (as a percent)	9.30%
Assets, Fair Value Disclosure	$ 44,000,000
Timing of principal payments	10 years
Standard Poors NR Rating [Member] \| Pari Passu Surplus Note [Member] \| Discounted cash flows
Quantitative information for Level 3 Fair Value Measurements Assets
Timing of Interest Payments	5 years
Discount Yield (as a percent)	13.50%
Assets, Fair Value Disclosure	$ 21,100,000
Timing of principal payments	10 years
Level 2
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Assets Measured on Recurring Basis, Transfers out	$ 0	97,200,000
Level 3 Inputs \| Fixed maturity investments
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Assets Measured on Recurring Basis, Transfers out	97,600,000	$ 119,400,000
durchblicker.at [Member] \| Standard Poors NR Rating [Member] \| Private equity funds \| Recent Transaction Two [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Average Share Price Used As Unobservable Input	290.96
Assets, Fair Value Disclosure	10,400,000
BE Reinsurance [Member] \| Standard Poors NR Rating [Member] \| Private equity funds \| Recent Transaction Three [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
Average Share Price Used As Unobservable Input	0.13
Assets, Fair Value Disclosure	$ 15,800,000
Centrus [Member] \| Standard Poors NR Rating [Member] \| Mortgage-backed and asset-backed securities \| Discounted cash flows
Quantitative information for Level 3 Fair Value Measurements Assets
Unobservable Inputs \| input	0.10
Assets, Fair Value Disclosure	$ 5,600,000
Pari Passu Surplus Note [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
basis points	2.50%
Seller Priority Surplus Note [Member]
Quantitative information for Level 3 Fair Value Measurements Assets
basis points	2.50%

Debt and Standby Letter of Credit Facilities (Debt Outstanding) (Details) - USD ($) $ in Millions	Dec. 31, 2014	Oct. 10, 2014	Dec. 31, 2013	Mar. 31, 2007
Debt Instrument
Debt	$ 746.6		$ 676.4
SIG Senior Notes
Debt Instrument
Debt instrument at face value				$ 400.0
Other Debt [Member]
Debt Instrument
Debt	4.8		2.1
OneBeacon \| 2012 OBH Senior Notes
Debt Instrument
Debt instrument at face value	275.0		275.0
Unamortized original issue discount	(0.3)		(0.3)
Debt	274.7		274.7
Sirius Group \| SIG Senior Notes
Debt Instrument
Debt instrument at face value	400.0		400.0
Unamortized original issue discount	(0.3)		(0.4)
Debt	399.7		399.6
White Mountains \| WTM Bank Facility
Debt Instrument
Debt	0.0		0.0
Tranzact [Member] \| Tranzact Bank Facility [Member]
Debt Instrument
Line of Credit Facility, Fair Value of Amount Outstanding	67.4	$ 70.0	0.0
Line of Credit Facility, Amount Outstanding	68.7		0.0
Unamortized Debt Issuance Expense	$ (1.3)		$ 0.0

Goodwill and Other Intangible Assets (Goodwill and Intangible Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Oct. 10, 2014	Mar. 14, 2014	Feb. 19, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 213.5				$ 25.0
Amortization of Intangible Assets	16.0				4.3
Intangible Assets, Net (Excluding Goodwill)	197.5				20.7	$ 16.9
Goodwill	168.9				0.0	$ 0.0
Intangible Assets, Gross (Including Goodwill)	382.4				25.0
Goodwill and intangible assets	366.4				20.7
Tranzact [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	146.3				0.0
Amortization of Intangible Assets	3.5				0.0
Intangible Assets, Net (Excluding Goodwill)	142.8	$ 146.3			0.0
Goodwill	145.1	$ 145.1			0.0
QuoteLab [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	38.5				0.0
Amortization of Intangible Assets	6.0				0.0
Intangible Assets, Net (Excluding Goodwill)	32.5		$ 38.5		0.0
Goodwill	18.3		$ 18.3		0.0
WOBI [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	2.9				0.0
Amortization of Intangible Assets	0.4				0.0
Intangible Assets, Net (Excluding Goodwill)	2.5				0.0
Goodwill	5.5			$ 5.5	0.0
Developed Technology Rights [Member] \| Tranzact [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	12.7				0.0
Amortization of Intangible Assets	0.5				0.0
Intangible Assets, Net (Excluding Goodwill)	$ 12.2				0.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	5 years
Developed Technology Rights [Member] \| QuoteLab [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 32.0				0.0
Amortization of Intangible Assets	4.8				0.0
Intangible Assets, Net (Excluding Goodwill)	$ 27.2				0.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	5 years
Developed Technology Rights [Member] \| WOBI [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 0.8				0.0
Amortization of Intangible Assets	0.2				0.0
Intangible Assets, Net (Excluding Goodwill)	$ 0.6				0.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	3 years
Customer Relationships [Member]
Goodwill [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	3 years
Customer Relationships [Member] \| Tranzact [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 107.5				0.0
Amortization of Intangible Assets	2.1				0.0
Intangible Assets, Net (Excluding Goodwill)	$ 105.4				0.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	10 years
Customer Relationships [Member] \| QuoteLab [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 6.5				0.0
Amortization of Intangible Assets	1.2				0.0
Intangible Assets, Net (Excluding Goodwill)	$ 5.3				0.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	4 years
Customer Relationships [Member] \| Star & Shield Insurance Exchange [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 1.2				0.0
Amortization of Intangible Assets	0.4				0.0
Intangible Assets, Net (Excluding Goodwill)	0.8				0.0
Trademarks [Member] \| WOBI [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	2.1				0.0
Amortization of Intangible Assets	0.2				0.0
Intangible Assets, Net (Excluding Goodwill)	$ 1.9				0.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	8 years
Other Intangible Assets [Member] \| Tranzact [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 0.5				0.0
Amortization of Intangible Assets	0.0				0.0
Intangible Assets, Net (Excluding Goodwill)	$ 0.5				0.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	7 years
Other Intangible Assets [Member] \| OneBeacon
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 9.4				9.4
Amortization of Intangible Assets	5.7				4.3
Intangible Assets, Net (Excluding Goodwill)	$ 3.7				5.1
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	10 years
Trade Names [Member] \| Tranzact [Member]
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 25.6				0.0
Amortization of Intangible Assets	0.9				0.0
Intangible Assets, Net (Excluding Goodwill)	$ 24.7				0.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	6 years
Contract-Based Intangible Assets [Member] \| Sirius Group
Goodwill [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 15.2				15.6
Amortization of Intangible Assets	0.0				0.0
Intangible Assets, Net (Excluding Goodwill)	$ 15.2				$ 15.6

Debt and Standby Letter of Credit Facilities (Schedule of Contractual Repayments) (Details) $ in Millions	Dec. 31, 2014 USD ($)
Debt Disclosure [Abstract]
Due in one year or less	$ 6.0
Due in two to three years	424.6
Due in four to five years	42.9
Due after five years	275.0
Total	$ 748.5

Goodwill and Other Intangible Assets (Goodwill and Intangible Assets Rollforward) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill [Roll Forward]
Beginning balance	$ 0.0	$ 0.0
Acquisitions of businesses	168.9	0.0
Ending balance	168.9	0.0	$ 0.0
Finite-lived Intangible Assets [Roll Forward]
Beginning balance	20.7	16.9
Acquisitions of businesses	188.9	5.2
Goodwill and intangible assets	366.4	20.7
Dispositions of businesses	(0.4)
Amortization, including foreign currency translation	(11.7)	(1.4)	(1.2)
Ending balance	$ 197.5	$ 20.7	$ 16.9

Debt and Standby Letter of Credit Facilities (Narrative) (Details)	1 Months Ended		3 Months Ended		5 Months Ended	7 Months Ended	12 Months Ended
	Nov. 30, 2012 USD ($)	Mar. 31, 2007 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2013 USD ($)	Aug. 13, 2013 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Nov. 25, 2014 USD ($)	Oct. 10, 2014 USD ($)	Aug. 14, 2013 USD ($)	Aug. 12, 2011 USD ($)	May 31, 2003
Debt Instrument
Issuance of debt, net of debt issuance costs							$ 68,600,000	$ 0	$ 271,900,000
Aggregate purchase price of senior notes purchased and retired							(65,000,000)	0	275,900,000
Interest expense on debt							41,900,000	42,500,000	44,800,000
Draw down of revolving line of credit							0	200,000,000	150,000,000
Repayments of debt, principal							66,500,000	275,000,000	75,000,000
Interest Paid							42,000,000	42,600,000	44,600,000
Debt			$ 676,400,000		$ 676,400,000		746,600,000	676,400,000
SIG Senior Notes
Debt Instrument
Debt instrument at face value		$ 400,000,000
Percentage of par value at which debt was issued		99.715%
Issuance of debt, net of debt issuance costs		$ 392,000,000
Interest rate (as a percent)		6.375%
Debt issue costs		$ 3,600,000
Underwriting discount		$ 2,600,000
Effective yield (as a percent)		6.50%
Loss from interest rate hedge recorded in other comprehensive income		$ (2,400,000)
Unamortized loss remaining in accumulated other comprehensive income							1,000,000
Interest expense on debt							$ 26,200,000	$ 26,200,000	$ 26,200,000
Expenses related to issuance, including underwriting fees		$ 3,600,000
WTM Bank Facility
Debt Instrument
Effective yield (as a percent)			3.65%		3.65%		3.65%	3.65%
Interest expense on debt					$ 300,000		$ 300,000
Total commitment under revolving credit facility												$ 425,000,000
Draw down of revolving line of credit							65,000,000	$ 50,000,000
Repayments of lines of credit			$ 50,000,000
Prior W T M Bank Facility
Debt Instrument
Effective yield (as a percent)			2.83%	3.53%	2.83%			2.83%	3.53%
Interest expense on debt						$ 2,900,000			$ 1,700,000
Total commitment under revolving credit facility													$ 375,000,000
Draw down of revolving line of credit								$ 150,000,000	150,000,000
Repayments of debt, principal									75,000,000
Repayments of lines of credit								225,000,000
One Beacon US Holdings Inc. \| 2012 OBH Senior Notes
Debt Instrument
Debt instrument at face value	$ 275,000,000
Percentage of par value at which debt was issued	99.90%
Issuance of debt, net of debt issuance costs	$ 272,900,000
Interest rate (as a percent)	4.60%
Debt issue costs	$ 2,800,000
Underwriting discount	$ 1,800,000
Effective yield (as a percent)	4.70%
Interest Expense							13,000,000
Expenses related to issuance, including underwriting fees	$ 2,800,000
One Beacon US Holdings Inc. \| 2003 OBH Senior Notes
Debt Instrument
Interest Expense								13,000,000	$ 16,900,000
Guarantee fee basis points per annum on outstanding principal amount of debt (as a percent)														2.50%
One Beacon US Holdings Inc. \| Senior Notes \| 2003 OBH Senior Notes
Debt Instrument
Interest rate (as a percent)	5.875%
Debt Instrument, Repurchase Amount			$ 269,800,000		$ 269,800,000			269,800,000
Aggregate purchase price of senior notes purchased and retired				$ 275,900,000
Loss on retirement of debt				(6,300,000)
Write off of deferred issuance costs				$ 200,000
Tranzact [Member] \| Tranzact Bank Facility [Member]
Debt Instrument
Interest expense on debt							700,000
Line of Credit Facility, Fair Value of Amount Outstanding			0		0		67,400,000	0			$ 70,000,000
Line of Credit Facility, Amount Outstanding			$ 0		$ 0		68,700,000	$ 0
Line of Credit Facility, Remaining Borrowing Capacity							$ 4,500,000
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate							4.15575%
Sirius International \| Letter of Credit [Member]
Debt Instrument
Line of Credit Facility, Fair Value of Amount Outstanding										$ 200,000,000
number of Credit Lines										2
Minimum \| Tranzact [Member] \| Tranzact Bank Facility [Member]
Debt Instrument
LIBOR rate							2.50%
Maximum \| Tranzact [Member] \| Tranzact Bank Facility [Member]
Debt Instrument
LIBOR rate							4.50%
Nordea Bank Finland [Member]
Debt Instrument
Total commitment under revolving credit facility										$ 125,000,000
Lloyds Bank plc [Member]
Debt Instrument
Total commitment under revolving credit facility										75,000,000
Unsecured Debt [Member] \| Nordea Bank Finland [Member]
Debt Instrument
Total commitment under revolving credit facility										100,000,000
Unsecured Debt [Member] \| Lloyds Bank plc [Member]
Debt Instrument
Total commitment under revolving credit facility										$ 25,000,000

Goodwill and Other Intangible Assets (Amortization Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of Intangible Assets	$ 11.7	$ 1.4	$ 1.2
2015	27.1
2016	27.0
2017	26.4
2018	24.6
2019	16.5
Total	$ 121.6

Income Taxes (Income Tax (Benefit) Expense (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current tax expense (benefit):
U.S. federal									$ 6.2	$ 19.0	$ (8.2)
State									4.8	1.4	3.4
Non-U.S.									45.0	16.5	5.9
Total current tax expense									56.0	36.9	1.1
Deferred tax expense (benefit):
U.S. federal									(13.6)	24.4	55.5
State									0.0	0.0	0.0
Non-U.S.									10.9	15.3	(72.3)
Total deferred tax (benefit) expense									(2.7)	39.7	(16.8)
Total income tax expense (benefit)	$ (8.7)	$ 7.8	$ 23.9	$ 30.3	$ 27.4	$ 8.2	$ (0.6)	$ 41.6	$ 53.3	$ 76.6	$ (15.7)

Income Taxes (Effective Rate Reconciliation) (Details) - USD ($) $ in Millions		3 Months Ended									12 Months Ended
	Jan. 02, 2013	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Contingency [Line Items]
U.S. statutory rate (as a percent)										35.00%
Tax (expense) benefit at the U.S. statutory rate											$ (105.6)	$ (120.7)	$ (92.0)
Differences in taxes resulting from:
Non-U.S. earnings, net of foreign taxes											77.7	82.9	43.0
Change in valuation allowance											(18.1)	(33.6)	(14.1)
Effective Income Tax Rate Reconciliation, Deduction, Other, Amount											(5.6)	(1.7)	(2.9)
Tax exempt interest and dividends											4.4	3.2	3.1
Tax reserve adjustments											(2.2)	(10.2)	(1.3)
Purchase of subsidiaries											(0.3)	5.3	5.1
Other, net											(3.6)	(1.8)	2.2
Income tax (expense) benefit		$ 8.7	$ (7.8)	$ (23.9)	$ (30.3)	$ (27.4)	$ (8.2)	$ 0.6	$ (41.6)		(53.3)	(76.6)	15.7
Pre-tax loss		$ 46.2	$ 34.4	$ 109.0	$ 112.1	$ 134.2	$ 55.3	$ 3.6	$ 151.8		301.7	344.9	262.8
Tax Payments and Receipts
Net income tax payments to (receipts from) national governments, total											9.4	13.9	17.5
Non-US
Differences in taxes resulting from:
Pre-tax loss											338.5	294.3	250.0
SWEDEN
Differences in taxes resulting from:
Tax rate change enacted											0.0	0.0	65.4
Luxembourg
Differences in taxes resulting from:
Change in valuation allowance										$ 41.3	(1.2)	(1.4)
Tax rate change enacted											$ 0.0	$ 0.0	$ 7.2
Sirius Group \| SWEDEN
Differences in taxes resulting from:
Effective income tax	22.00%												26.30%
Increase (Decrease) in Deferred Income Taxes	$ 65.4

Income Taxes (Deferred Tax Inventory) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Contingency [Line Items]
Valuation allowance	$ 18.1	$ 33.6	$ 14.1
Deferred income tax assets related to:
Non-U.S. net operating loss carryforwards	427.4	520.6
U.S. federal net operating and capital loss carryforwards	213.4	148.6
Loss reserve discount	79.3	74.9
Unearned premiums	46.0	38.9
Incentive compensation	8.9	10.3
Tax credit carryforwards	25.8	23.1
Accrued interest	5.3	1.1
Fixed assets	3.6	4.9
Other items	8.4	6.9
Total gross deferred income tax assets	872.7	907.4
Less: valuation allowances	(274.6)	(289.8)
Total net deferred income tax assets	598.1	617.6
Deferred income tax liabilities related to:
Deferred Tax Liabilities, Gross, Noncurrent	0.0	3.4
Net unrealized investment gains	45.3	44.6
Deferred acquisition costs	40.5	33.0
Investment basis difference	22.9	3.0
Other items	3.1	7.9
Total deferred income tax liabilities	424.8	461.7
Net deferred tax asset	173.3	155.9
OneBeacon Runoff
Deferred income tax assets related to:
Runoff Transaction	12.6	24.2
Safety Reserve [Member]
Deferred income tax liabilities related to:
Deferred Tax Liabilities, Gross, Noncurrent	295.7	357.2
Purchase Accounting [Member]
Deferred income tax liabilities related to:
Deferred Tax Liabilities, Gross, Noncurrent	7.0	7.2
Members Surplus Contributions [Member]
Deferred income tax liabilities related to:
Deferred Tax Liabilities, Gross, Noncurrent	10.3	5.4
Incentive Compensation [Member]
Deferred income tax assets related to:
Incentive compensation	42.0	$ 53.9
UNITED STATES
Deferred income tax assets related to:
Tax credit carryforwards	11.1
Deferred income tax liabilities related to:
Net deferred tax asset	214.0
Luxembourg
Deferred income tax liabilities related to:
Net deferred tax asset	240.5
UNITED KINGDOM
Deferred income tax liabilities related to:
Net deferred tax asset	1.6
SWEDEN
Deferred income tax liabilities related to:
Total deferred income tax liabilities	$ 282.8

Income Taxes (Valuation Allowance) (Details) - USD ($)	3 Months Ended									12 Months Ended
Income Taxes (Valuation Allowance) (Details) - USD ($)	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Valuation Allowance [Line Items]
Valuation allowance	$ 274,600,000				$ 289,800,000					$ 274,600,000	$ 289,800,000
Valuation allowance										18,100,000	33,600,000	$ 14,100,000
Income Tax Expense (Benefit)	(8,700,000)	$ 7,800,000	$ 23,900,000	$ 30,300,000	27,400,000	$ 8,200,000	$ (600,000)	$ 41,600,000		53,300,000	76,600,000	$ (15,700,000)
Net operating losses in Luxembourg subsidiaries
Valuation Allowance [Line Items]
Valuation allowance	164,800,000				195,800,000					164,800,000	195,800,000
U.S. losses and other federal deferred tax benefits
Valuation Allowance [Line Items]
Valuation allowance	107,600,000				93,700,000					107,600,000	93,700,000
Net Operating Losses in Israel Subsidiaries [Member]
Valuation Allowance [Line Items]
Valuation allowance	1,900,000									1,900,000
Net Operating Losses in Netherlands Subsidiaries [Member] [Member]
Valuation Allowance [Line Items]
Valuation allowance	300,000				$ 300,000					300,000	300,000
Luxembourg
Valuation Allowance [Line Items]
Valuation allowance									$ (41,300,000)	1,200,000	1,400,000
Luxembourg \| Tax Benefit [Member]
Valuation Allowance [Line Items]
Valuation allowance										(14,300,000)	(16,700,000)
Luxembourg \| Tax Expense [Member]
Valuation Allowance [Line Items]
Valuation allowance										15,500,000	18,100,000
Sirius Re Holdings Inc.
Valuation Allowance [Line Items]
Valuation allowance	100,000									100,000
Foreign tax credit carryforwards, subject to expiration	$ 12,100,000									12,100,000
Sirius Re Holdings Inc. \| Tax Benefit [Member]
Valuation Allowance [Line Items]
Valuation allowance										(3,800,000)
Sirius Re Holdings Inc. \| Tax Expense [Member]
Valuation Allowance [Line Items]
Valuation allowance									$ 3,900,000
Guilford Holdings, Inc. \| UNITED STATES
Valuation Allowance [Line Items]
Valuation allowance										7,200,000	16,600,000
BAM
Valuation Allowance [Line Items]
Valuation allowance										8,500,000	21,300,000
Income Tax Expense (Benefit)										4,900,000	5,400,000
Houston General Insurance [Member]
Valuation Allowance [Line Items]
Valuation allowance										(100,000)	$ 6.0
Star & Shield Insurance Exchange [Member]
Valuation Allowance [Line Items]
Valuation allowance										$ (3,200,000)

Income Taxes (ASC 740-10) (Details) - USD ($) $ in Millions	12 Months Ended
Income Taxes (ASC 740-10) (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2014
Income Tax Contingency [Line Items]
Percentage of likelihood for realization of benefit upon ultimate settlement		50.00%
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns
Balance at beginning	$ 50.0	$ 46.6	$ 65.5
Changes in prior year tax positions	(4.8)	(4.8)	1.9
Tax positions taken during the current year	13.7
Lapse in statute of limitations	(1.1)		0.0
Settlements with tax authorities	(0.9)	(0.4)	(0.6)
Tax positions taken during the current year		8.6	(20.2)
Balance at year end	56.9	50.0	46.6
Unrecognized tax benefit recognition including interest and penalties, if recognized, would effect income tax expense	27.1			$ 5.0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	(2.6)	1.3	1.2
Permanent Differences [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns
Balance at beginning	18.2	9.7	9.6
Changes in prior year tax positions	(2.0)	0.6	0.5
Tax positions taken during the current year	5.6
Lapse in statute of limitations	(0.8)		0.0
Settlements with tax authorities	(0.6)	0.0	(0.4)
Tax positions taken during the current year		7.9	0.0
Balance at year end	20.4	18.2	9.7
Temporary Differences [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns
Balance at beginning	22.5	28.9	49.1
Changes in prior year tax positions	(0.8)	(7.1)	0.0
Tax positions taken during the current year	8.1
Lapse in statute of limitations	0.0		0.0
Settlements with tax authorities	0.0	0.0	0.0
Tax positions taken during the current year		0.7	(20.2)
Balance at year end	29.8	22.5	28.9
Interest and Penalties Net of Tax Benefit [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns
Balance at beginning	9.3	8.0	6.8
Changes in prior year tax positions	(2.0)	1.7	1.4
Tax positions taken during the current year	0.0
Lapse in statute of limitations	(0.3)		0.0
Settlements with tax authorities	(0.3)	(0.4)	(0.2)
Tax positions taken during the current year		0.0	0.0
Balance at year end	$ 6.7	$ 9.3	$ 8.0

Income Taxes (Tax Examinations) (Details) - USD ($) $ in Millions	Dec. 31, 2014	Mar. 31, 2014
Income Tax Examination [Line Items]
Unrecognized tax benefit recognition including interest and penalties, if recognized, would effect income tax expense	$ 27.1	$ 5.0
Tax Assessment Year 2005 to 2006 [Member] \| IRS
Income Tax Examination [Line Items]
Tax Examination	3.3
Tax Assessment Year 2007 to 2009 [Member] \| IRS
Income Tax Examination [Line Items]
Tax Examination	72.9
Income Tax Examination, Increase (Decrease) in Liability from Prior Year, Dissallowed	$ 60.2

Derivatives (Details) ¥ in Billions, $ in Billions	Dec. 31, 2014 USD ($)	Dec. 31, 2014 JPY (¥)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Notional amount	$ 1.1	¥ 134.2
Collective account values of underlying variable annuities as a percentage of the guarantee value	113.00%	113.00%

Derivatives (Pre-Tax Operating Results of WM Life Re) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pre-tax operating results of WM Life Re
Total revenues	$ 689.7	$ 589.4	$ 652.8	$ 578.3	$ 626.6	$ 574.1	$ 489.3	$ 627.4	$ 2,510.2	$ 2,317.4	$ 2,435.7
General and administrative expenses									(288.2)	(181.3)	(182.2)
Pre-tax income	$ 46.2	$ 34.4	$ 109.0	$ 112.1	$ 134.2	$ 55.3	$ 3.6	$ 151.8	301.7	344.9	262.8
White Mountains Life Re
Pre-tax operating results of WM Life Re
Fees, included in other revenue									18.6	25.0	31.8
Change in Fair Value of Variable Annuity Liability, included in other revenues									52.9	378.5	312.8
Change in fair value of derivatives, included in other revenue									(72.4)	(402.0)	(339.0)
Foreign exchange, included in other revenue									(3.2)	(14.5)	(30.3)
Other investment income and (losses) gains									(1.4)	(7.1)	2.5
Total revenues									(5.5)	(20.1)	(22.2)
Change in fair value of variable annuity death benefit liabilities, included in general and administrative expenses									0.6	10.2	14.2
Death benefit claims paid, included in general and administrative expenses									(0.1)	(1.9)	(5.7)
General and administrative expenses									(4.3)	(4.9)	(5.2)
Pre-tax income									(9.3)	(16.7)	$ (18.9)
Level 3 \| Projected Surrender Assumption [Member] \| White Mountains Life Re
Pre-tax operating results of WM Life Re
Change in fair value of derivatives, included in other revenue									$ (0.2)	$ 7.2

Derivatives (Realized and Unrealized Gains (Losses)) (Details) - White Mountains Life Re - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values of instruments
Change in fair value of derivatives, included in other revenue	$ (72.4)	$ (402.0)	$ (339.0)
Derivative, Fair Value, Net	56.4	69.2	98.3	$ 290.4
Fixed income/interest rate
Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values of instruments
Change in fair value of derivatives, included in other revenue	(33.7)	(108.7)	(149.5)
Derivative, Fair Value, Net	(1.7)	(9.7)
Foreign exchange
Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values of instruments
Change in fair value of derivatives, included in other revenue	(1.3)	(96.7)	(102.3)
Derivative, Fair Value, Net	44.1	58.0
Equity
Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values of instruments
Change in fair value of derivatives, included in other revenue	(37.4)	(196.6)	$ (87.2)
Derivative, Fair Value, Net	14.0	20.9
Level 3 \| Projected Surrender Assumption [Member]
Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values of instruments
Change in fair value of derivatives, included in other revenue	$ (0.2)	$ 7.2

Derivatives (Variable Annuity Reinsurance Liabilities and Derivative Instruments) (Details) - White Mountains Life Re - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Variable Annuity Reinsurance [Line Items]
Fair Value Derivatives Measured on Recurring Basis, Asset Purchases	$ 0.0	$ 59.4
Changes in derivative instruments
Beginning of period	69.2	98.3	$ 290.4
Purchases			6.1
Realized and unrealized gains (losses)	72.4	402.0	339.0
Transfers in (out)	0.0	0.0	0.0
Sales/settlements	59.6	313.5	140.8
Ending balance	56.4	69.2	98.3
Collateral Cash and Investments	33.2	81.3	393.6
Change in fair value of variable annuity death benefit liabilities, included in general and administrative expenses	0.6	10.2	14.2
Level 3
Variable Annuity Reinsurance [Line Items]
Fair Value Derivatives Measured on Recurring Basis, Asset Purchases		0.0
Changes in variable annuity (liabilities)
Purchases			0.0
Level 2
Variable Annuity Reinsurance [Line Items]
Fair Value Derivatives Measured on Recurring Basis, Asset Purchases	0.0	0.0
Changes in derivative instruments
Beginning of period	4.7	(20.5)	39.2
Purchases			0.0
Realized and unrealized gains (losses)	71.0	196.1	186.9
Transfers in (out)	0.0	0.0	0.0
Sales/settlements	100.1	221.3	127.2
Ending balance	33.8	4.7	(20.5)
Level 1
Variable Annuity Reinsurance [Line Items]
Fair Value Derivatives Measured on Recurring Basis, Asset Purchases	0.0	0.0
Changes in derivative instruments
Beginning of period	1.1	(21.7)	4.1
Purchases			0.0
Realized and unrealized gains (losses)	(37.2)	69.4	68.1
Transfers in (out)	0.0	0.0	0.0
Sales/settlements	(34.6)	92.2	42.3
Ending balance	3.7	1.1	(21.7)
Variable Annuity [Member] \| Level 3
Variable Annuity Reinsurance [Line Items]
Fair Value Derivatives Measured on Recurring Basis, Asset Purchases	0.0
Changes in variable annuity (liabilities)
Beginning balance	(52.8)	(441.5)	(768.5)
Realized and unrealized gains (losses)	(53.5)	(388.7)	(327.0)
Transfers in (out)	0.0	0.0	0.0
Sales/settlements	0.0	0.0	0.0
Ending balance	0.7	(52.8)	(441.5)
Derivative [Member] \| Level 3
Variable Annuity Reinsurance [Line Items]
Fair Value Derivatives Measured on Recurring Basis, Asset Purchases	0.0	59.4
Changes in derivative instruments
Beginning of period	63.4	140.5	247.1
Purchases			6.1
Realized and unrealized gains (losses)	38.6	136.5	84.0
Transfers in (out)	0.0	0.0	0.0
Sales/settlements	(5.9)	0.0	(28.7)
Ending balance	$ 18.9	$ 63.4	$ 140.5

Derivatives (Additional Collateral) (Details) - White Mountains Life Re - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Credit risk on derivative instruments
Collateral Cash and Investments	$ 33.2	$ 81.3	$ 393.6
Cash
Credit risk on derivative instruments
Derivative Collateral Right to Reclaim	23.7	56.1
Short-term investments
Credit risk on derivative instruments
Derivative Collateral Right to Reclaim	0.0	2.0
Fixed maturity investments
Credit risk on derivative instruments
Derivative Collateral Right to Reclaim	$ 9.5	$ 23.2

Derivatives (Level 3 Derivative Instruments) (Details) - White Mountains Life Re $ in Millions	12 Months Ended
	Dec. 31, 2014 USD ($)
Discounted cash flows
Quantitative information for Level 3 Fair Value Measurements Liabilities
Fair value Liabilities	$ 0.7
Equity Index Options \| Counterparty valuations [Member]
Quantitative information for Level 3 Fair Value Measurements Liabilities
Fair value Liabilities	$ 11.7
Equity Index Options \| Counterparty valuations [Member] \| Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Adjustment to counterparty valuations	0.70%
Equity Index Options \| Counterparty valuations [Member] \| Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Adjustment to counterparty valuations	6.50%
Equity Index Options \| Counterparty valuations [Member] \| Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Adjustment to counterparty valuations	2.00%
Variable annuity benefit guarantee liabilities \| Discounted cash flows \| Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Mortality	0.00%
Variable annuity benefit guarantee liabilities \| Discounted cash flows \| Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Mortality	5.90%
Variable annuity benefit guarantee liabilities \| Discounted cash flows \| Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Mortality	1.00%
Foreign Exchange Option [Member] \| Counterparty valuations [Member]
Quantitative information for Level 3 Fair Value Measurements Liabilities
Fair value Liabilities	$ 7.2
Foreign Exchange Option [Member] \| Counterparty valuations [Member] \| Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Foreign exchange volatilities	(0.50%)
Foreign Exchange Option [Member] \| Counterparty valuations [Member] \| Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Foreign exchange volatilities	11.60%
Foreign Exchange Option [Member] \| Counterparty valuations [Member] \| Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Foreign exchange volatilities	3.60%
Year Two [Member] \| Variable annuity benefit guarantee liabilities \| Discounted cash flows \| Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders	0.10%
Foreign exchange volatilities	11.70%
Index volatilities	19.40%
Year Two [Member] \| Variable annuity benefit guarantee liabilities \| Discounted cash flows \| Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders	40.00%
Foreign exchange volatilities	13.80%
Index volatilities	23.10%
Year Two [Member] \| Variable annuity benefit guarantee liabilities \| Discounted cash flows \| Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders	32.10%
Foreign exchange volatilities	12.60%
Index volatilities	21.80%
Year One [Member] \| Variable annuity benefit guarantee liabilities \| Discounted cash flows \| Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders	0.20%
Foreign exchange volatilities	12.60%
Index volatilities	24.00%
Year One [Member] \| Variable annuity benefit guarantee liabilities \| Discounted cash flows \| Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders	40.00%
Foreign exchange volatilities	15.10%
Index volatilities	26.60%
Year One [Member] \| Variable annuity benefit guarantee liabilities \| Discounted cash flows \| Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Surrenders	40.00%
Foreign exchange volatilities	13.30%
Index volatilities	25.60%

Derivatives Derivatives (Gross Asset (Gross liability) Amounts Offset Under Master Netting Agreements) (Details) - White Mountains Life Re - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Derivative Asset	$ 64.4	$ 106.0
Derivative Liability	(8.0)	(36.8)
Net amounts recognized in Other Assets	56.4	69.2
Interest Rate Contract \| Over the Counter [Member]
Derivative [Line Items]
Derivative Asset	1.0	2.4
Derivative Liability	(5.4)	(11.7)
Net amounts recognized in Other Assets	(4.4)	(9.3)
Interest Rate Contract \| Exchange Traded [Member]
Derivative [Line Items]
Derivative Asset	2.8	1.0
Derivative Liability	(0.1)	(1.6)
Net amounts recognized in Other Assets	2.7	(0.6)
Foreign Exchange Contract \| Over the Counter [Member]
Derivative [Line Items]
Derivative Asset	45.5	67.8
Derivative Liability	0.0	(12.0)
Net amounts recognized in Other Assets	45.5	55.8
Foreign Exchange Contract \| Exchange Traded [Member]
Derivative [Line Items]
Derivative Asset	0.0	2.3
Derivative Liability	(1.4)	0.0
Net amounts recognized in Other Assets	(1.4)	2.3
Equity Contract \| Over the Counter [Member]
Derivative [Line Items]
Derivative Asset	11.7	30.7
Derivative Liability	(0.2)	(9.2)
Net amounts recognized in Other Assets	11.5	21.5
Equity Contract \| Exchange Traded [Member]
Derivative [Line Items]
Derivative Asset	3.4	1.8
Derivative Liability	(0.9)	(2.3)
Net amounts recognized in Other Assets	$ 2.5	$ (0.5)

Derivatives (Uncollateralized Amounts Due Under WM Life Re's OTC Derivative Contracts) (Details) $ in Thousands	Dec. 31, 2014 USD ($) Rating	Dec. 31, 2013 USD ($)
White Mountains Life Re
Variable Annuity Reinsurance [Line Items]
Net amounts recognized in Other Assets	$ 56,400	$ 69,200
Credit risk on derivative instruments
Net exposure on fair value of OTC instruments	77,200	135,700
Derivative, Collateral, Right to Reclaim Cash	3,500	0
Derivative, Collateral, Right to Reclaim Securities	0	400
Derivative Asset, Fair Value, Amount Offset Against Collateral	59,900	69,600
Excess collateral provided to counterparty in cash	17,700	44,100
Excess collateral providedto counterparty in financial instruments	9,500	22,800
Derivative, Collateral, Obligation to Return Cash	$ 9,900	800
Forward contracts
Credit risk on derivative instruments
S&P Credit Ratings \| Rating	21
A \| Citigroup OTC [Member] \| White Mountains Life Re
Variable Annuity Reinsurance [Line Items]
Net amounts recognized in Other Assets	$ 22,200	19,400
Credit risk on derivative instruments
Net exposure on fair value of OTC instruments	21,100	21,700
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	22,200	19,400
Excess collateral provided to counterparty in cash	0	2,300
Excess collateral providedto counterparty in financial instruments	0	0
Derivative, Collateral, Obligation to Return Cash	1,100	0
A \| Barclays [Member] \| White Mountains Life Re
Variable Annuity Reinsurance [Line Items]
Net amounts recognized in Other Assets	100	1,400
Credit risk on derivative instruments
Net exposure on fair value of OTC instruments	100	1,400
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	100	1,400
Excess collateral provided to counterparty in cash	0	0
Excess collateral providedto counterparty in financial instruments	0	0
Derivative, Collateral, Obligation to Return Cash	0	0
A \| Bank of America [Member] \| White Mountains Life Re
Variable Annuity Reinsurance [Line Items]
Net amounts recognized in Other Assets	5,600	27,200
Credit risk on derivative instruments
Net exposure on fair value of OTC instruments	5,600	27,200
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	5,600	27,200
Excess collateral provided to counterparty in cash	0	0
Excess collateral providedto counterparty in financial instruments	0	0
Derivative, Collateral, Obligation to Return Cash	0	0
A \| Citigroup Exchange Traded [Member] \| White Mountains Life Re
Variable Annuity Reinsurance [Line Items]
Net amounts recognized in Other Assets	3,700	1,200
Credit risk on derivative instruments
Net exposure on fair value of OTC instruments	19,700	21,000
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	3,700	1,200
Excess collateral provided to counterparty in cash	16,000	19,800
Excess collateral providedto counterparty in financial instruments	0	0
Derivative, Collateral, Obligation to Return Cash	0	0
BBB plus \| Nomura [Member] \| White Mountains Life Re
Variable Annuity Reinsurance [Line Items]
Net amounts recognized in Other Assets	(3,500)	(400)
Credit risk on derivative instruments
Net exposure on fair value of OTC instruments	11,200	22,000
Derivative, Collateral, Right to Reclaim Cash	3,500	0
Derivative, Collateral, Right to Reclaim Securities	0	400
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Excess collateral provided to counterparty in cash	1,700	0
Excess collateral providedto counterparty in financial instruments	9,500	22,800
Derivative, Collateral, Obligation to Return Cash	0	800
Standard & Poor's, A+ Rating [Member] \| J P Morgan Chase [Member] \| White Mountains Life Re
Variable Annuity Reinsurance [Line Items]
Net amounts recognized in Other Assets	24,300	9,100
Credit risk on derivative instruments
Net exposure on fair value of OTC instruments	15,500	31,100
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	24,300	9,100
Excess collateral provided to counterparty in cash	0	22,000
Excess collateral providedto counterparty in financial instruments	0	0
Derivative, Collateral, Obligation to Return Cash	8,800	0
Standard & Poor's, A- Rating [Member] \| Royal Bank of Scotland [Member] \| White Mountains Life Re
Variable Annuity Reinsurance [Line Items]
Net amounts recognized in Other Assets	4,000	11,300
Credit risk on derivative instruments
Net exposure on fair value of OTC instruments	4,000	11,300
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	4,000	11,300
Excess collateral provided to counterparty in cash	0	0
Excess collateral providedto counterparty in financial instruments	0	0
Derivative, Collateral, Obligation to Return Cash	$ 0	$ 0

Derivatives (Forward Contracts) (Details) kr in Millions, $ in Millions, ¥ in Billions	3 Months Ended	12 Months Ended
	Mar. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2014 JPY (¥)	Dec. 31, 2014 SEK (kr)
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount			$ 1,100.0	¥ 134.2
Forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount		$ 20.4	$ 33.1		kr 257.5
Realized and unrealized gains (losses)	$ (0.3)	0.1
Derivative Liability		$ (0.1)

Derivatives Derivatives (Forward Contracts Collateral) (Details) kr in Millions, $ in Millions, ¥ in Billions	Dec. 31, 2014 USD ($) Rating	Dec. 31, 2014 JPY (¥) Rating	Dec. 31, 2014 SEK (kr) Rating	Dec. 31, 2013 USD ($)
Derivative [Line Items]
Notional amount	$ 1,100.0	¥ 134.2
Forward contracts
Derivative [Line Items]
S&P Credit Ratings \| Rating	21	21	21
Notional amount	$ 33.1		kr 257.5	$ 20.4
Uncollaterailized Balance of Forward Currency Derivatives	$ 0.0			(0.1)
Interest Rate Cap
Derivative [Line Items]
S&P Credit Ratings \| Rating	21	21	21
Barclays [Member] \| A \| Forward contracts
Derivative [Line Items]
Notional amount	$ 2.1			5.8
Uncollaterailized Balance of Forward Currency Derivatives	0.0			0.0
Deutsche Bank [Member] \| A \| Forward contracts
Derivative [Line Items]
Notional amount	0.0			7.7
Uncollaterailized Balance of Forward Currency Derivatives	0.0			0.0
Goldman Sachs [Member] \| A \| Forward contracts
Derivative [Line Items]
Notional amount	8.7			2.1
Uncollaterailized Balance of Forward Currency Derivatives	0.0			0.0
HSBC Bank plc [Member] \| Standard & Poor's, AA- Rating [Member] \| Forward contracts
Derivative [Line Items]
Notional amount	11.2			3.3
Uncollaterailized Balance of Forward Currency Derivatives	0.0			(0.1)
J P Morgan Chase [Member] \| Standard & Poor's, A+ Rating [Member] \| Forward contracts
Derivative [Line Items]
Notional amount	5.7			1.3
Uncollaterailized Balance of Forward Currency Derivatives	0.0			0.0
Royal Bank of Canada [Member] \| Standard & Poor's, AA- Rating [Member] \| Forward contracts
Derivative [Line Items]
Notional amount	5.4			0.2
Uncollaterailized Balance of Forward Currency Derivatives	$ 0.0			$ 0.0

Derivatives Derivatives (Interest Rate Cap) (Details) $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2007 shares	Dec. 31, 2014 USD ($) Rating	Dec. 31, 2013 USD ($)
Interest Rate Cap
Derivative [Line Items]
Derivative Collateral Right to Reclaim		$ 4.3
Beginning of period		11.1	$ 0.0
Purchases		0.0	9.9
Change in fair value of derivatives, included in other revenue		7.0	(1.2)
Ending balance		4.1	11.1
Fair Value Derivatives Measured on Recurring Basis, Asset Sales and Settlements		$ 0.0	$ 0.0
S&P Credit Ratings \| Rating		21
Barclays [Member] \| A \| Interest Rate Cap
Derivative [Line Items]
Derivative Collateral Right to Reclaim		$ 3.0
Nordea Bank Finland [Member] \| Standard & Poor's, AA- Rating [Member] \| Interest Rate Cap
Derivative [Line Items]
Derivative Collateral Right to Reclaim		$ 1.3
Sirius Internation Group Ltd \| Interest Rate Cap
Derivative [Line Items]
basis points		3.95%
years of interest rate cap		5 years	5 years
Derivative, Cap Interest Rate		8.30%	8.30%
Derivative, Cost of Hedge		$ 9.9
Sirius Internation Group Ltd \| Preferred stocks
Derivative [Line Items]
Non-cumulative perpetual preference shares issued \| shares	250,000,000
Sirius Internation Group Ltd \| Preferred stocks \| Interest Rate Cap
Derivative [Line Items]
Preferred stock dividend rate	7.506%
Preference shares reference rate for dividend	3
Non-cumulative perpetual preference shares issued \| shares	250,000,000.0

Derivatives Derivatives (Weather) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
weather derivatives [Member] \| Sirius Group
Derivative [Line Items]
Realized and unrealized gains (losses)	$ 0.2	$ 0.6

Derivatives Derivative (Tranzact Interest Rate Swap) (Details) (Details) - Tranzact [Member] - USD ($) $ in Millions	Dec. 31, 2014	Oct. 10, 2014	Mar. 31, 2014	Dec. 31, 2013
Tranzact Bank Facility [Member]
Derivative [Line Items]
Line of Credit Facility, Fair Value of Amount Outstanding	$ 67.4	$ 70.0		$ 0.0
Line of Credit Facility, Amount Outstanding	$ 68.7			$ 0.0
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	4.15575%
Minimum \| Tranzact Bank Facility [Member]
Derivative [Line Items]
LIBOR rate	2.50%
Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate	1.34%
Derivative, Variable Interest Rate	0.1558%	0.1518%
Derivative, Fair Value, Net			$ 0.1

Municipal Bond Guarantee Insurance (Details) $ in Millions	3 Months Ended								12 Months Ended
Municipal Bond Guarantee Insurance (Details) $ in Millions	Dec. 31, 2014 USD ($) Contract	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2013 USD ($) Contract	Sep. 30, 2013 USD ($)	Jun. 30, 2013 USD ($)	Mar. 31, 2013 USD ($)	Dec. 31, 2014 USD ($) Contract	Dec. 31, 2013 USD ($) Contract	Dec. 31, 2012 USD ($)
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Percentage of par value of policy reinsured	15.00%								15.00%
Pre-tax loss	$ 46.2	$ 34.4	$ 109.0	$ 112.1	$ 134.2	$ 55.3	$ 3.6	$ 151.8	$ 301.7	$ 344.9	$ 262.8
Net investment income (loss) - surplus note interest									$ 0.0	$ 0.0	0.0
BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Municipal bond contract \| Contract	1,750				701				1,750	701
Insured Financial Obligations with Credit Deterioration, Remaining Weighted Average Contract Period									12 years 10 months	13 years 9 months 21 days
Municipal bond outstanding principal	$ 12,362.5				$ 4,703.7				$ 12,362.5	$ 4,703.7
Municipal bond outstanding interest	7,086.9				3,264.4				7,086.9	3,264.4
Financial Guarantee Insurance Contracts, Unearned Premium Revenue	27.6				13.2				27.6	13.2
White Mountains
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Capital contributions										594.5	594.5
HG Global
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Surplus notes	$ 503.0				$ 503.0				$ 503.0	503.0
Percentage of par value of policy reinsured	15.00%								15.00%
BAM Management
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Capital contributions										$ 14.5	14.5
Preferred stocks \| HG Global
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Ownership interest (as a percent)	96.90%				97.30%				96.90%	97.30%
Common Stock \| HG Global
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Ownership interest (as a percent)	88.40%				88.70%				88.40%	88.70%
BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Surplus notes	$ 503.0								$ 503.0
Pre-tax loss									(40.5)	$ (78.6)	(36.3)
Net investment income (loss) - surplus note interest									(15.7)	(40.2)	(18.4)
HG Re
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Statutory capital and surplus	$ 449.1				$ 436.9				$ 449.1	$ 436.9
Collateral Held in Supplement Trust	120,000,000				105,400,000				120,000,000	105,400,000
HG Global
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Percentage of par value of policy reinsured	15.00%								15.00%
Pre-tax loss									$ 18.3	$ 38.1	14.2
Net investment income (loss) - surplus note interest									15.7	$ 40.2	$ 18.4
Surplus Note \| HG Global
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Interest Receivable	$ 74.4								$ 74.4

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Net income (loss) attributable to White Mountains’ common shareholders									$ 316.1	$ 317.3	$ 322.4
Basic and diluted earnings per share numerators (in millions):
Allocation of income for unvested restricted common shares(1)									(4.1)	(4.7)	(4.3)
Dividends declared on participating restricted common shares(1)									(0.1)	(0.1)	(0.1)
Total allocation to restricted common shares									(4.2)	(4.8)	(4.4)
Net income attributable to White Mountains’s common shareholders, net of restricted common share amounts									311.9	312.5	318.0
Undistributed net earnings (in millions):
Net income attributable to White Mountains’s common shareholders, net of restricted common share amounts									311.9	312.5	318.0
Dividends declared net of restricted common share amounts(1)									(6.1)	(6.1)	(6.5)
Total undistributed net earnings, net of restricted common share amounts									$ 305.8	$ 306.4	$ 311.5
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period									6,104,900	6,200,400	6,799,800
Average unvested restricted common shares									(78,900)	(91,400)	(91,100)
Basic earnings per share denominator									6,026,000	6,109,000	6,708,700
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period									6,104,900	6,200,400	6,799,800
Average unvested restricted common shares									(78,900)	(91,400)	(91,100)
Average outstanding dilutive options to acquire common shares									0	0	0
Diluted earnings (loss) per share denominator									6,026,000	6,109,000	6,708,700
Basic earnings per share (in dollars):
Net income attributable to White Mountains’s common shareholders	$ 13.71	$ 7.35	$ 15.10	$ 15.56	$ 19.14	$ 9.20	$ 3.62	$ 19.10	$ 51.77	$ 51.15	$ 47.41
Dividends declared and paid									(1.00)	(1.00)	(1.00)
Undistributed earnings									50.77	50.15	46.41
Diluted earnings per share (in dollars)
Net income attributable to White Mountains’s common shareholders	$ 13.71	$ 7.35	$ 15.10	$ 15.56	$ 19.14	$ 9.20	$ 3.62	$ 19.10	51.77	51.15	47.41
Dividends declared and paid									(1.00)	(1.00)	(1.00)
Undistributed earnings									$ 50.77	$ 50.15	$ 46.41
Incremental common shares attributable to share-based payment arrangements									125,000

Retirement and Postretirement Plans (Benefit Obligations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 102.9	$ 119.5
Service cost	0.6	0.8	$ 0.7
Interest cost	4.7	4.2	4.7
Special termination benefits expense	0.3	0.3	0.6
Assumption changes	17.5	(13.0)
Actuarial loss (gain)	1.1	(0.5)
Benefits and expenses paid with plan assets	(5.2)	(6.2)
Benefits paid directly by OneBeacon	(2.2)	(2.2)
Projected benefit obligation at end of year	119.7	102.9	119.5
Change in plan assets:
Fair value of plan assets at beginning of year	142.8	124.7
Actual return on plan assets	8.4	24.3
Benefits and expenses paid with plan assets	(5.2)	(6.2)
Fair value of plan assets at end of year	146.0	142.8	$ 124.7
Funded status at end of year	26.3	39.9
Amounts recognized in the financial statements
Net assets of the Qualified Plan recorded in other assets	53.4	64.1
Net liabilities of the Non-qualified Plan recorded in other liabilities	(27.1)	(24.2)
Defined Benefit Plan, Amounts Recognized in Balance Sheet	26.3	39.9
Qualified Plan [Member]
Change in plan assets:
Fair value of plan assets at beginning of year	142.1
Fair value of plan assets at end of year	143.2	$ 142.1
Amounts recognized in the financial statements
Net assets of the Qualified Plan recorded in other assets	53.4
Other Postretirement Benefit Plan, Defined Benefit [Member]
Amounts recognized in the financial statements
Net liabilities of the Non-qualified Plan recorded in other liabilities	(27.1)
Other Postretirement Benefit Plan, Defined Benefit [Member] \| OneBeacon Ltd.
Change in plan assets:
Amount set aside in irrevocable rabbi trust	$ 18.2

Retirement and Postretirement Plans (Qualifed, Non-qualified, and Accumulated Benefit Obligations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Amounts recognized in accumulated other comprehensive income (loss) on a pre-tax basis noncontrolling interest
Accumulated other comprehensive income (loss) beginning balance	$ (8.0)	$ 10.5	$ (21.2)
Increase (decrease) in accumulated other comprehensive income (loss):
Amortization of net actuarial losses recognized during the year		0.3	0.9
Net actuarial (losses) gains occurring during the year		(18.8)	30.8
Accumulated other comprehensive (loss) income ending balance		(8.0)	10.5
Other Postretirement Benefit Plan, Defined Benefit [Member]
Information for the Non-qualified Plan, which had accumulated benefit obligations in excess of plan assets
Projected benefit obligation		27.1	24.2
Accumulated benefit obligation		27.1	24.2
Fair value of plan assets		0.0	0.0
Qualified Plan [Member]
Information for the Qualified Plan, which had accumulated benefit obligations less than plan assets
Projected benefit obligation		92.6	78.7
Accumulated benefit obligation		92.6	78.7
Fair value of plan net assets		$ 146.0	$ 142.8
Scenario, Forecast [Member] \| OneBeacon Ltd.
Increase (decrease) in accumulated other comprehensive income (loss):
Amount expected to be amortized from accumulated other comprehensive income (loss) into net periodic benefit cost during 2012	$ 1.2

Retirement and Postretirement Plans (Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Components of net periodic benefit cost (income)
Service cost	$ 0.6	$ 0.8	$ 0.7
Interest cost	4.7	4.2	4.7
Expected return on plan assets	(8.5)	(7.1)	(6.9)
Amortization of unrecognized loss	0.3	0.9	0.8
Net periodic pension income before settlements, curtailments and special termination benefits	(2.9)	(1.2)	(0.7)
Settlement loss	0.0	0.0	0.6
Special termination benefits expense	(0.3)	(0.3)	(0.6)
Total net periodic (income) benefit cost	$ (2.6)	$ (0.9)	$ 0.5
Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount Yield (as a percent)	3.91%	4.66%
Weighted average discount rate assumptions used to determine benefit obligations
Discount rate (as a percent)	4.66%
Pension Costs [Member]
Weighted average discount rate assumptions used to determine benefit obligations
Discount rate (as a percent)		3.64%
Long-Duration Contracts, Assumptions by Product and Guarantee, Estimated Average Investment Yield	6.00%	5.75%

Retirement and Postretirement Plans (Qualified Plan's Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Plan Assets
Fair value	$ 146.0	$ 142.8	$ 124.7
Qualified Plan [Member]
Plan Assets
Fair value	$ 143.2	$ 142.1
Asset allocations (as a percent)	100.00%	100.00%
Qualified Plan [Member] \| Level 1 Inputs
Plan Assets
Fair value	$ 105.8	$ 112.1
Qualified Plan [Member] \| Level 2 Inputs
Plan Assets
Fair value	37.4	30.0
Qualified Plan [Member] \| Level 3 Inputs
Plan Assets
Fair value	0.0	0.0
Qualified Plan [Member] \| Fixed maturity investments
Plan Assets
Fair value	$ 24.2	$ 0.0
Asset allocations (as a percent)	16.90%	0.00%
Qualified Plan [Member] \| Fixed maturity investments \| Level 1 Inputs
Plan Assets
Fair value	$ 0.0	$ 0.0
Qualified Plan [Member] \| Fixed maturity investments \| Level 2 Inputs
Plan Assets
Fair value	24.2	0.0
Qualified Plan [Member] \| Fixed maturity investments \| Level 3 Inputs
Plan Assets
Fair value	0.0	0.0
Qualified Plan [Member] \| Common equity securities
Plan Assets
Fair value	$ 101.0	$ 103.3
Asset allocations (as a percent)	70.60%	72.70%
Qualified Plan [Member] \| Common equity securities \| Level 1 Inputs
Plan Assets
Fair value	$ 101.0	$ 103.3
Qualified Plan [Member] \| Common equity securities \| Level 2 Inputs
Plan Assets
Fair value	0.0	0.0
Qualified Plan [Member] \| Common equity securities \| Level 3 Inputs
Plan Assets
Fair value	0.0	0.0
Qualified Plan [Member] \| Convertible fixed maturity investments
Plan Assets
Fair value	$ 12.8	$ 29.9
Asset allocations (as a percent)	8.90%	21.10%
Qualified Plan [Member] \| Convertible fixed maturity investments \| Level 1 Inputs
Plan Assets
Fair value	$ 0.0	$ 0.0
Qualified Plan [Member] \| Convertible fixed maturity investments \| Level 2 Inputs
Plan Assets
Fair value	12.8	29.9
Qualified Plan [Member] \| Convertible fixed maturity investments \| Level 3 Inputs
Plan Assets
Fair value	0.0	0.0
Qualified Plan [Member] \| Cash
Plan Assets
Fair value	$ 5.2	$ 8.9
Asset allocations (as a percent)	3.60%	6.20%
Qualified Plan [Member] \| Cash \| Level 1 Inputs
Plan Assets
Fair value	$ 4.8	$ 8.8
Qualified Plan [Member] \| Cash \| Level 2 Inputs
Plan Assets
Fair value	0.4	0.1
Qualified Plan [Member] \| Cash \| Level 3 Inputs
Plan Assets
Fair value	$ 0.0	$ 0.0

Retirement and Postretirement Plans Retirement and Postretirment Plans (Assumptions) (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Qualified Plan [Member]
Discount Yield (as a percent)	3.91%	4.66%
Discount rate (as a percent)	4.66%
Pension Costs [Member]
Discount rate (as a percent)		3.64%
Long-Duration Contracts, Assumptions by Product and Guarantee, Estimated Average Investment Yield	6.00%	5.75%

Retirement and Postretirement Plans (Cash Flow) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee savings plan
Defined Benefit Plan, Benefit Obligation	$ 119,700,000	$ 102,900,000	$ 119,500,000
Funded status at end of year	26,300,000	39,900,000
OneBeacon Ltd.
Expected Benefit Payments
2015	4,900,000
2016	5,300,000
2017	5,600,000
2018	5,900,000
2019	6,100,000
2020-2024	34,400,000
Employee savings plan
Anticipated contribution to plan	2,200,000
OneBeacon
Employee savings plan
Post-employment benefit liability	4,800,000	5,800,000
Sirius Group
Employee savings plan
Defined Contribution Plan, Cost Recognized	500,000	700,000	400,000
Government Pension Plans [Member] \| Sirius Group
Employee savings plan
Defined Contribution Plan, Cost Recognized	10,300,000	9,700,000	7,500,000
Defined Benefit Plan, Benefit Obligation	14,100,000	13,100,000
Funded status at end of year	(1,800,000)	(1,000,000)
Qualified Plan [Member] \| Sirius Group
Employee savings plan
Defined Contribution Plan, Cost Recognized	$ 700,000	600,000	600,000
Combination One [Member] \| Sirius Group
Employee savings plan
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	2.00%
Combination Two [Member] \| Sirius Group
Employee savings plan
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	4.00%
Maximum \| Sirius Group
Employee savings plan
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	100.00%
Employer matching contribution variable contributions	7.00%
Minimum \| Sirius Group
Employee savings plan
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	50.00%
One Beacon Employee Stock Ownership Plan
Employee savings plan
Defined Contribution Plan, Cost Recognized	$ 4,400,000	6,300,000	4,800,000
Annual base contribution provided to participants expressed as percentage of salary	3.00%
Social security wage base amount maximum	$ 117,000
Variable contribution provided to participants (as percentage)	6.00%
One Beacon Employee Stock Ownership Plan \| OneBeacon
Employee savings plan
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	50.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	6.00%
Defined Contribution Plan, Cost Recognized	$ 2,700,000	$ 2,300,000	$ 2,800,000
IRS \| OneBeacon
Employee savings plan
Defined Benefit Plan Compensation LImits	260,000
IRS \| Sirius Group
Employee savings plan
Defined Benefit Plan Compensation LImits	$ 260,000

Employee Share-Based Incentive Compensation Plans (Details)	12 Months Ended
	Dec. 31, 2014 USD ($)
Performance Shares
Share-based compensation arrangement by share-based payment award
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
One Beacon Employee Stock Ownership Plan
Share-based compensation arrangement by share-based payment award
Annual base contribution provided to participants expressed as percentage of salary	3.00%
Social security wage base amount maximum	$ 117,000
Variable contribution provided to participants (as percentage)	6.00%
OneBeacon \| IRS
Share-based compensation arrangement by share-based payment award
Defined Benefit Plan Compensation LImits	$ 260,000

Employee Share-Based Incentive Compensation Plans (WTM Performance Shares) (Details)	3 Months Ended	12 Months Ended
	Dec. 31, 2014 USD ($) shares	Dec. 31, 2014 USD ($) multiplier shares	Dec. 31, 2013 USD ($) shares	Dec. 31, 2012 USD ($) shares
Unamortized grant date fair value
Beginning of period		$ 218,300,000
Ending December 31,	$ 184,600,000	$ 184,600,000	$ 218,300,000
Performance Shares \| Range of Performance Cycle from 2011 to 2013 [Member]
Unamortized grant date fair value
Vested (in shares) \| shares		3,570
Performance Shares \| Range of Performance Cycle from 2009 to 2011 [Member]
Unamortized grant date fair value
Vested (in shares) \| shares			9,577
Performance Shares \| White Mountains
Share-based compensation arrangement by share-based payment award
Multiplier for determining payout, low end of range \| multiplier		0
Multiplier for determining payout, high end of range \| multiplier		2
Performance cycle period		3 years
Performance Shares \| W T M Incentive and Phantom Plan [Member] \| Range Of Performance Cycle From 2014-2016 [Member]
Target Performance Share activity
Assumed forfeitures and cancellations(2)(3) \| shares	3,040
Performance Shares \| W T M Incentive and Phantom Plan [Member] \| Range of Performance Cycle from 2011 to 2013 [Member]
Unamortized grant date fair value
Performance goal percentage for minimum payout		88.00%
Payout for maximum growth target percentage		131.50%
Performance Shares \| W T M Incentive and Phantom Plan [Member] \| Range of Performance Cycle from 2010 to 2012 [Member]
Unamortized grant date fair value
Performance goal percentage for minimum payout			33.00%
Payout for maximum growth target percentage			98.00%
Partial Payout for 2010 - 2012 cycle				$ 9.9
Performance Shares \| W T M Incentive and Phantom Plan [Member] \| Range of Performance Cycle from 2009 to 2011 [Member]
Unamortized grant date fair value
Performance goal percentage for minimum payout				147.00%
Payout for maximum growth target percentage				155.00%
Performance Shares \| W T M Incentive Plan \| Range Of Performance Cycle From 2014-2016 [Member]
Unamortized grant date fair value
Payout for maximum growth target percentage		200.00%
Performance Shares \| W T M Incentive Plan \| White Mountains
Target Performance Share activity
Beginning of period \| shares		119,220	119,357	150,064
Shares paid or expired(1) \| shares		(37,130)	(47,310)	(68,357)
New grants \| shares		45,660	47,170	38,432
Assumed forfeitures and cancellations(2)(3) \| shares		4,201	(3)	782
Ending December 31, \| shares	123,549	123,549	119,220	119,357
Unamortized grant date fair value
Beginning of period		$ 60,200,000	$ 29,400,000	$ 66,100,000
Shares paid or expired(1)		(26,700,000)	(11,000,000)	(58,300,000)
Assumed forfeitures and cancellations(2)(3)		(700,000)	(600,000)	600,000
Expense recognized		15,300,000	42,400,000	21,000,000
Ending December 31,	$ 48,100,000	48,100,000	$ 60,200,000	$ 29,400,000
Unamortized grant date fair value	$ 16,900,000	$ 16,900,000

Employee Share-Based Incentive Compensation Plans (WTM Performance Shares Granted Under the WTM Incentive Plan) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based compensation arrangement by share-based payment award
Accrued incentive compensation	$ 184.6	$ 218.3
Range Of Performance Cycle From 2014-2016 [Member] \| W T M Incentive Plan \| Performance Shares
Share-based compensation arrangement by share-based payment award
Targeted performance goal for personnel expressed as percentage of growth in intrinsic business value per share	9.00%
Share-based Compensation Arrangement by Share-based Payment Award, Payout for Maximum Growth Target Percentage	200.00%
Performance Cycle From 2013 to 2015 \| W T M Incentive Plan \| Performance Shares
Share-based compensation arrangement by share-based payment award
Targeted performance goal for personnel expressed as percentage of growth in intrinsic business value per share	8.00%
Share-based Compensation Arrangement by Share-based Payment Award, Payout for Maximum Growth Target Percentage	200.00%
Performance Cycle From 2012 to 2014 \| W T M Incentive Plan \| Performance Shares
Share-based compensation arrangement by share-based payment award
Targeted performance goal for personnel expressed as percentage of growth in intrinsic business value per share	8.00%
Share-based Compensation Arrangement by Share-based Payment Award, Payout for Maximum Growth Target Percentage	200.00%
White Mountains \| W T M Incentive Plan \| Performance Shares
Share-based compensation arrangement by share-based payment award
Options nonvested, number before forfeitures (in shares)	126,717
Incentive compensation payable before forfeitures	$ 49.4
forfeitures	(3,168)
Assumed forfeitures in period amount	(1.3)
Shares outstanding (in shares)	123,549	119,220	119,357	150,064
Accrued incentive compensation	$ 48.1	$ 60.2	$ 29.4	$ 66.1
White Mountains \| Range Of Performance Cycle From 2014-2016 [Member] \| W T M Incentive Plan \| Performance Shares
Share-based compensation arrangement by share-based payment award
Options nonvested, number before forfeitures (in shares)	41,937
Incentive compensation payable before forfeitures	$ 4.1
White Mountains \| Performance Cycle From 2013 to 2015 \| W T M Incentive Plan \| Performance Shares
Share-based compensation arrangement by share-based payment award
Options nonvested, number before forfeitures (in shares)	46,803
Incentive compensation payable before forfeitures	$ 18.9
White Mountains \| Performance Cycle From 2012 to 2014 \| W T M Incentive Plan \| Performance Shares
Share-based compensation arrangement by share-based payment award
Options nonvested, number before forfeitures (in shares)	37,977
Incentive compensation payable before forfeitures	$ 26.4
Minimum \| Range Of Performance Cycle From 2014-2016 [Member] \| W T M Incentive Plan \| Performance Shares
Share-based compensation arrangement by share-based payment award
Performance goal percentage for minimum payout	3.00%
Minimum \| Performance Cycle From 2013 to 2015 \| W T M Incentive Plan \| Performance Shares
Share-based compensation arrangement by share-based payment award
Performance goal percentage for minimum payout	2.00%
Minimum \| Performance Cycle From 2012 to 2014 \| W T M Incentive Plan \| Performance Shares
Share-based compensation arrangement by share-based payment award
Performance goal percentage for minimum payout	2.00%
Maximum \| Range Of Performance Cycle From 2014-2016 [Member] \| W T M Incentive Plan \| Performance Shares
Share-based compensation arrangement by share-based payment award
Performance goal percentage for minimum payout	15.00%
Maximum \| Performance Cycle From 2013 to 2015 \| W T M Incentive Plan \| Performance Shares
Share-based compensation arrangement by share-based payment award
Performance goal percentage for minimum payout	14.00%
Maximum \| Performance Cycle From 2012 to 2014 \| W T M Incentive Plan \| Performance Shares
Share-based compensation arrangement by share-based payment award
Performance goal percentage for minimum payout	14.00%

Employee Share-Based Incentive Compensation Plans (WTM Restricted Shares) (Details) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2014 USD ($) shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($) Installment shares	Dec. 31, 2012 USD ($) shares
Restricted Share Cliff Vesting in January 2016 [Member]
Target Performance Share activity
Issued (in shares)			25,720
Restricted Share Cliff Vesting in January 2015 [Member]
Target Performance Share activity
Issued (in shares)			27,960
Restricted Share Vesting Beginning in February 2014 [Member]
Target Performance Share activity
Issued (in shares)			3,000
Unamortized grant date fair value
Number of restricted shares installments \| Installment			2
Restricted Share Cliff Vesting in July 2015 [Member]
Target Performance Share activity
Issued (in shares)			1,200
W T M Incentive and Phantom Plan [Member] \| Restricted Share Cliff Vesting in January 2017 [Member]
Target Performance Share activity
Issued (in shares)		23,440
Restricted Share Vested in December 2012 [Member] \| Restricted Stock
Unamortized grant date fair value
Number of restricted shares installments				5,000
White Mountains \| W T M Incentive Plan \| Restricted Stock
Target Performance Share activity
Beginning of period		94,130	69,910	72,000
Issued (in shares)		23,440	25,720	32,160
Vested (in shares)		(33,205)	(1,500)	(32,945)
Assumed forfeitures and cancellations (in shares)		(1,051)	0	(1,305)
Ending December 31,	83,314	83,314	94,130	69,910
Unamortized grant date fair value
Beginning balance \| $		$ 17.0	$ 16.8	$ 13.3
Issued \| $		13.1	14.4	15.7
Assumed forfeitures and cancellations \| $		(0.5)	0.0	(0.2)
Expense recognized \| $		15.3	14.2	(12.0)
Ending balance \| $	$ 14.3	$ 14.3	$ 17.0	$ 16.8
White Mountains \| W T M Incentive Plan \| Performance Shares
Target Performance Share activity
Beginning of period		119,220	119,357	150,064
Assumed forfeitures and cancellations (in shares)		(4,201)	3	(782)
Ending December 31,	123,549	123,549	119,220	119,357
Unamortized grant date fair value
Assumed forfeitures and cancellations \| $		$ (0.7)	$ (0.6)	$ 0.6
Expense recognized \| $		(15.3)	$ (42.4)	$ (21.0)
Ending balance \| $	$ 16.9	$ 16.9
Range Of Performance Cycle From 2014-2016 [Member] \| W T M Incentive and Phantom Plan [Member] \| Restricted Stock
Target Performance Share activity
Issued (in shares)	3,040
Assumed forfeitures and cancellations (in shares)	(3,040)
Range Of Performance Cycle From 2014-2016 [Member] \| W T M Incentive and Phantom Plan [Member] \| Performance Shares
Target Performance Share activity
Assumed forfeitures and cancellations (in shares)	(3,040)

Employee Share-Based Incentive Compensation Plans (WTM Non-Qualified and Qualified Options) (Details) - shares	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Performance Shares
Share-based compensation arrangement by share-based payment award
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	125,000
Qualified Plan [Member]
Share-based compensation arrangement by share-based payment award
Percentage of common shares outstanding	3.00%	3.00%
Eligible contribution percentage	2.00%	4.00%	3.00%

Employee Share-Based Incentive Compensation Plans (OneBeason Peformance Shares) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Expense Amortized
Beginning of period	$ 218.3
Ending December 31,	$ 184.6	$ 218.3
Long Term Incentive Plan
Expense Amortized
Percentage of payout for minimum growth target percentage			138.60%
Performance Shares
Share-based compensation arrangement by share-based payment award
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	125,000
Share-based Compensation Arrangement by Share-based Payment Award, Options Outstanding Amended, Exercise Price	$ 742
OneBeacon \| Performance Shares \| Long Term Incentive Plan
Target options outstanding
Beginning of period	493,421	563,190	642,667
Shares paid or expired (in shares)	(142,138)	(238,658)	(258,901)
New grants	165,800	179,000	181,290
Assumed forfeitures and cancellations (in shares)	387	(10,111)	(1,866)
Ending December 31,	517,470	493,421	563,190
Expense Amortized
Beginning of period	$ 4.0	$ 1.2	$ 9.7
Payments and deferrals	(1.0)	0.0	(7.7)
Assumed forfeitures and cancellations	0.0	(0.1)	0.0
Expense recognized	0.4	2.9	(0.8)
Ending December 31,	$ 3.4	$ 4.0	$ 1.2
Range of Performance Cycle from 2011 to 2013 [Member] \| Long Term Incentive Plan
Expense Amortized
Percentage of payout for minimum growth target percentage	37.10%

Employee Share-Based Incentive Compensation Plans (OneBeacon Performance Shares Outstanding) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based compensation arrangement by share-based payment award
Accrued incentive compensation	$ 184.6	$ 218.3
OneBeacon \| Performance Shares \| Long Term Incentive Plan
Share-based compensation arrangement by share-based payment award
Options nonvested, number before forfeitures (in shares)	526,090
Incentive compensation payable before forfeitures	$ 3.4
forfeitures	(8,620)
Assumed forfeitures in period amount	0.0
Shares outstanding (in shares)	517,470	493,421	563,190	642,667
Accrued incentive compensation	$ 3.4	$ 4.0	$ 1.2	$ 9.7
Unamortized grant date fair value	$ 1.6
Targeted performance goal for personnel expressed as percentage of growth in intrinsic business value per share	14.00%	13.00%	10.00%
Range Of Performance Cycle From 2014-2016 [Member] \| OneBeacon \| Performance Shares \| Long Term Incentive Plan
Share-based compensation arrangement by share-based payment award
Options nonvested, number before forfeitures (in shares)	165,800
Incentive compensation payable before forfeitures	$ 0.5
Performance Cycle From 2013 to 2015 \| OneBeacon \| Performance Shares \| Long Term Incentive Plan
Share-based compensation arrangement by share-based payment award
Options nonvested, number before forfeitures (in shares)	179,000
Incentive compensation payable before forfeitures	$ 1.4
Performance Cycle From 2012 to 2014 \| OneBeacon \| Performance Shares \| Long Term Incentive Plan
Share-based compensation arrangement by share-based payment award
Options nonvested, number before forfeitures (in shares)	181,290
Incentive compensation payable before forfeitures	$ 1.5
Maximum \| OneBeacon \| Performance Shares \| Long Term Incentive Plan
Share-based compensation arrangement by share-based payment award
Performance goal percentage for minimum payout	21.00%	20.00%	17.00%
Percentage of performance shares earned	200.00%	200.00%	200.00%
Minimum \| OneBeacon \| Performance Shares \| Long Term Incentive Plan
Share-based compensation arrangement by share-based payment award
Performance goal percentage for minimum payout	7.00%	6.00%	3.00%

Employee Share-Based Incentive Compensation Plans (OneBeacon Restricted Shares) (Details) - Restricted Stock - Long Term Incentive Plan $ in Millions		1 Months Ended	12 Months Ended
	Mar. 01, 2012 Installment shares	May 31, 2011 shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($) shares	Dec. 31, 2012 USD ($) shares	May 25, 2011 Installment
One Beacon Insurance Company
Unamortized grant date fair value
Forfeited shares		35,000
One Beacon Insurance Company \| Chief Executive Officer
Target Performance Share activity
Issued (in shares)	300,000	630,000
Unamortized grant date fair value
Number of installments in which the shares vest \| Installment	2					4
Forfeited shares		35,000
Years performance shares will be forfeited		5 years
OneBeacon
Target Performance Share activity
Beginning of period			915,000	927,000	630,000
Issued (in shares)			0	0	300,000
Vested (in shares)			(300,000)	(9,000)	(667)
Assumed forfeitures and cancellations (in shares)			(2,500)	(3,000)	(2,333)
Ending December 31,			612,500	915,000	927,000
Unamortized grant date fair value
Beginning balance \| $			$ 6.5	$ 9.6	$ 7.7
Issued \| $			0.0	0.0	4.5
Vested \| $			0.0		0.0
Assumed forfeitures and cancellations \| $			0.0	0.0	0.0
Expense recognized \| $			(3.0)	(3.1)	(2.6)
Ending balance \| $			$ 3.5	$ 6.5	$ 9.6

Employee Share-Based Incentive Compensation Plans (Under Qualified Retirement Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
One Beacon Employee Stock Ownership Plan
Share-based compensation arrangement by share-based payment award
Defined Contribution Plan, Cost Recognized	$ 4.4	$ 6.3	$ 4.8
Qualified Plan [Member]
Share-based compensation arrangement by share-based payment award
Eligible contribution percentage	2.00%	4.00%	3.00%
Percentage of common shares outstanding	3.00%	3.00%

Common Shareholders’ Equity and Non-controlling Interests (Details) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended			61 Months Ended
	May 31, 2007 USD ($) Period quarter shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / shares shares	Dec. 31, 2012 USD ($) $ / shares shares	Jun. 30, 2022	May 24, 2007 $ / shares
Common Shares Repurchased and Retired [Abstract]
Common shares repurchased and retired during the period \| shares			1,329,640
Value of common shares repurchased and retired during the period		$ 134.5	$ 79.8	$ 669.1
Value of each common share repurchased and retired during the period (in dollars per share) \| $ / shares		$ 617	$ 564	$ 503
Common Shares Issued [Abstract]
Stock Issued During Period, Shares, New Issues \| shares		28,405	27,310	44,054
Shares issued to directors (in shares) \| shares		1,395	1,590
Dividends, Common Stock [Abstract]
Cash dividends declared and paid		$ 6.2	$ 6.2	$ 6.6
Dividends delared and paid (in dollars per share) \| $ / shares		$ 1.00	$ 1.00	$ 1.00
Non-controlling interests		$ 543.0	$ 491.9
Non-controlling Interests
Common Shares Repurchased and Retired [Abstract]
Value of common shares repurchased and retired during the period		0.0	0.0	$ 0.0
Total Non-Controlling Excluding Reciprocals [Member]
Dividends, Common Stock [Abstract]
Non-controlling interests		$ 168.6	$ 65.8
Common Stock
Common Shares Repurchased and Retired [Abstract]
Value of common shares repurchased and retired during the period				669.1
Dividends, Common Stock [Abstract]
Allocation of fair value of net assets acquired to non-controlling interests				$ (2.2)
Restricted Stock
Common Shares Issued [Abstract]
Stock Issued During Period, Shares, New Issues \| shares		23,440	25,720
Performance Shares
Common Shares Issued [Abstract]
Stock Issued During Period, Shares, New Issues \| shares		3,570
Common Stock
Common Shares Repurchased and Retired [Abstract]
Common shares repurchased and retired during the period \| shares		217,879	141,535	1,329,640
Combination Three [Member] \| Performance Shares
Common Shares Issued [Abstract]
Stock Issued During Period, Shares, New Issues \| shares				9,577
Combination One [Member] \| Restricted Stock
Common Shares Issued [Abstract]
Stock Issued During Period, Shares, New Issues \| shares				32,160
Combination Two [Member]
Common Shares Issued [Abstract]
Shares issued to directors (in shares) \| shares				700
Combination Four [Member]
Common Shares Issued [Abstract]
Shares issued to directors (in shares) \| shares				1,617
General Board Authorization [Member]
Common Shares Repurchased and Retired [Abstract]
Additional authorized repurchase of common shares \| shares		338,092
Common shares repurchased and retired during the period \| shares		207,404	140,000	502,801
Value of common shares repurchased and retired during the period		$ 128.2	$ 78.9	$ 256.0
Value of each common share repurchased and retired during the period (in dollars per share) \| $ / shares		$ 618	$ 564	$ 508
Repurchased for Employee Benefit Plans [Member]
Common Shares Repurchased and Retired [Abstract]
Common shares repurchased and retired during the period \| shares		10,475
Repurchased for Employee Benefit Plans [Member] \| Combination Three [Member]
Common Shares Repurchased and Retired [Abstract]
Common shares repurchased and retired during the period \| shares			1,535	10,010
Tender Offer [Member] \| Combination Two [Member]
Common Shares Repurchased and Retired [Abstract]
Value of common shares repurchased and retired during the period				$ 408.6
Value of each common share repurchased and retired during the period (in dollars per share) \| $ / shares				$ 500
Tender Offer [Member] \| Combination Two [Member] \| Common Stock
Common Shares Repurchased and Retired [Abstract]
Common shares repurchased and retired during the period \| shares				816,829
White Mountains
Dividends, Common Stock [Abstract]
Capital contributions			$ 594.5	$ 594.5
Sirius Internation Group Ltd \| Preferred stocks
Dividends, Common Stock [Abstract]
Non-cumulative perpetual preference shares issued \| shares	250,000,000
Preferred Stock, Liquidation Preference Per Share \| $ / shares						$ 1,000
Proceeds from Preference Shares	$ 245.7
Payments of Stock Issuance Costs	$ 4.3
Right to elect directors on board number	2
Number of Quarterly Period for Non Payment of Dividend which Give Right to Elect Directors on Board \| Period	6
Minimum Required Payment Period for Dividend to Cease Right to Elect Directors on Board \| quarter	4
Preference shares floating rate of dividend amount in excess of libor	3.20%
Preferred Stock Redemption Basis Spread on Treasury Issue Rate	45.00%
OneBeacon Ltd.
Dividends, Common Stock [Abstract]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		24.70%	24.80%
Non-controlling interests		$ 258.7	$ 273.7
HG/BAM [Member]
Dividends, Common Stock [Abstract]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		100.00%	100.00%
Non-controlling interests		$ (121.9)	$ (97.6)
Star & Shield Insurance Exchange [Member]
Dividends, Common Stock [Abstract]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		100.00%	0.00%
Non-controlling interests		$ (12.4)	$ 0.0
HG Global
Dividends, Common Stock [Abstract]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		3.10%	2.70%
Non-controlling interests		$ 17.9	$ 16.6
QuoteLab [Member]
Dividends, Common Stock [Abstract]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		40.00%	0.00%
Non-controlling interests		$ 22.6	$ 0.0
Tranzact [Member]
Dividends, Common Stock [Abstract]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		36.80%	0.00%
Non-controlling interests		$ 88.2	$ 0.0
WOBI [Member]
Dividends, Common Stock [Abstract]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		36.70%	0.00%
Non-controlling interests		$ 5.4	$ 0.0
Prospector Offshore Fund Ltd [Member]
Dividends, Common Stock [Abstract]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		23.40%	28.30%
Non-controlling interests		$ 31.1	$ 32.1
Prospector Turtle Fund [Member]
Dividends, Common Stock [Abstract]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		0.00%	31.10%
Non-controlling interests		$ 0.0	$ 14.1
A W G Dewar Inc [Member]
Dividends, Common Stock [Abstract]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		18.00%	18.00%
Non-controlling interests		$ 3.4	$ 3.0
SIG Preference Shares
Dividends, Common Stock [Abstract]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		100.00%	100.00%
Non-controlling interests		$ 250.0	$ 250.0
BAM Management
Dividends, Common Stock [Abstract]
Capital contributions			$ 14.5	14.5
BAM Management \| Non-controlling Interests
Dividends, Common Stock [Abstract]
Allocation of fair value of net assets acquired to non-controlling interests				$ 2.2
Interest Rate Cap \| Sirius Internation Group Ltd
Dividends, Common Stock [Abstract]
years of interest rate cap		5 years	5 years
Derivative, Cap Interest Rate		8.30%	8.30%
Interest Rate Cap \| Sirius Internation Group Ltd \| Preferred stocks
Dividends, Common Stock [Abstract]
Non-cumulative perpetual preference shares issued \| shares	250,000,000.0
Preference shares reference rate for dividend	3
Preferred stock dividend rate	7.506%
OneBeacon
Dividends, Common Stock [Abstract]
Non-controlling interests		$ 262.1	$ 276.8
OneBeacon \| Scenario, Forecast [Member]
Dividends, Common Stock [Abstract]
years of interest rate cap					5 years

Statutory Capital and Surplus (Details) $ in Millions		3 Months Ended	12 Months Ended
Statutory Capital and Surplus (Details) $ in Millions	Jan. 02, 2013	Mar. 31, 2014 USD ($)	Dec. 31, 2014 USD ($) yr	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)
Statutory Accounting Practices [Line Items]
Stockholders' Equity Attributable to Parent			$ 3,996.6	$ 3,905.5
Amount available for dividend distributions without prior approval from regulatory authorities			$ 500.0
Equity held in insurance and reinsurance subsidiaries			2,100.0
Distributions made			$ 6.2
Fair value investments			5,991.4	6,766.5	$ 6,950.7
Trading Securities			4,796.5
Dividend Capacity
Other long-term investments			408.2	288.9
Sirius Group
Statutory Accounting Practices [Line Items]
Stockholders' Equity Attributable to Parent			1,604.1	1,459.6
Unrestricted cash			20.4
Cash Dividends Paid to Parent Company			50.0
OneBeacon
Statutory Accounting Practices [Line Items]
Statutory net income (loss)			(14.2)	100.1	82.0
Stockholders' Equity Attributable to Parent			788.4	830.6
Distributions made			80.0
Unrestricted cash			107.0
Other Operations
Statutory Accounting Practices [Line Items]
Stockholders' Equity Attributable to Parent			1,038.6	1,025.8
Unrestricted cash			275.1
Dividend Capacity
Other long-term investments			106.4
Unregulated Operation \| OneBeacon
Statutory Accounting Practices [Line Items]
Distributions made			4.8	17.3
Surplus notes			101.0
Unrestricted cash			78.1
Star & Shield Insurance Exchange [Member]
Statutory Accounting Practices [Line Items]
Surplus notes			17.0
Star & Shield Insurance Exchange [Member] \| Other Operations
Statutory Accounting Practices [Line Items]
Statutory capital and surplus			6.5
Statutory net income (loss)			(9.5)
Surplus required			2.8
Alstead [Member] \| Sirius Group
Statutory Accounting Practices [Line Items]
Statutory capital and surplus			25.5
Surplus required			1.1
Central National [Member] \| Sirius Group
Statutory Accounting Practices [Line Items]
Statutory capital and surplus				9.3
Sirius Bermuda [Member] \| Sirius Group
Statutory Accounting Practices [Line Items]
Statutory capital and surplus			2,400.0
Surplus required			1.0
Amount available for dividend distributions without prior approval from regulatory authorities			$ 350.0
Percentage of prior year statutory surplus that may be paid as dividends without prior approval of regulatory authorities			15.00%
Woodridge [Domain] \| Sirius Group
Statutory Accounting Practices [Line Items]
Statutory capital and surplus			$ 8.3	8.4
Statutory net income (loss)			(0.2)	(0.1)	0.1
Surplus required			2.0
OneBeacon
Statutory Accounting Practices [Line Items]
Dividends available, net of noncontrolling interest			199.0
Sirius International \| Sirius Group
Statutory Accounting Practices [Line Items]
Statutory capital and surplus			2,300.0
Surplus required			158.2
Restricted equity			1,400.0
Cash Dividends Paid to Parent Company			$ 220.9
Statutory capital and surplus required, percent			125.00%
Maximum contributions per bankruptcy agreement			$ 200.0
Ratio limitation			70.00%
Expense limitation			$ 90.0
Dividend Capacity
Amount of safety reserve			$ 1,300.0
Exchange rate			7.77
Deferred Tax Liabilities, Safety Reserve			$ 295.7
Sirius International \| Regulated Operation \| Sirius Group
Statutory Accounting Practices [Line Items]
Unrestricted statutory surplus available for distribution			467.0
HG Global
Statutory Accounting Practices [Line Items]
Surplus notes			503.0	503.0
HG Global \| HG Global-BAM
Dividend Capacity
Preferred stock, value			$ 613.0
Ownership interest (as a percent)			96.90%
Preferred stock dividend rate			6.00%
HG Re \| HG Global-BAM
Statutory Accounting Practices [Line Items]
Statutory capital and surplus			$ 444.5
Collateral Held in Supplement Trust			402.6
Dividend Capacity
Accrued interest on surplus notes			$ 44.3
BAM \| HG Global-BAM
Statutory Accounting Practices [Line Items]
Statutory capital and surplus			448.7
Surplus required			66.0
Subsidiaries
Statutory Accounting Practices [Line Items]
Stockholders' Equity Attributable to Parent			2,600.0
One Beacon Insurance Company \| OneBeacon
Statutory Accounting Practices [Line Items]
Distributions made			700.5
Noncash distribution received			151.2
Payments of Capital Distribution				190.0
Proceeds from Contributions from Affiliates				35.0
Split Rock [Member] \| OneBeacon
Statutory Accounting Practices [Line Items]
Statutory capital and surplus			122.6	96.4
Statutory net income (loss)			46.2	(38.7)
Distributions made			10.0
Payments of Capital Distribution		$ 10.0
Proceeds from Contributions from Affiliates			135.1
White Mountains \| OneBeacon
Statutory Accounting Practices [Line Items]
Distributions made				60.3
White Mountains \| Other Operations
Statutory Accounting Practices [Line Items]
Proceeds from Contributions from Affiliates			15.0
Unrestricted cash			25.7
Atlantic Speciality Insurance Company (ASIC) [Member] \| OneBeacon
Statutory Accounting Practices [Line Items]
Surplus required			136.0
Payments of Capital Distribution			67.0	190.0
Atlantic Speciality Insurance Company (ASIC) [Member] \| Regulated Operation \| OneBeacon
Statutory Accounting Practices [Line Items]
Statutory capital and surplus			721.5
Amount available for dividend distributions without prior approval from regulatory authorities			44.9
Statutory accounting practices earned surplus			87.8
Sirius America \| Sirius Group
Statutory Accounting Practices [Line Items]
Statutory capital and surplus			620.6	548.4
Statutory net income (loss)			56.1	$ 55.9	26.2
Surplus required			106.5
Statutory accounting practices earned surplus			81.9
Percentage of prior year statutory surplus that may be paid as dividends without prior approval of regulatory authorities				10.00%
Oakwood \| Sirius Group
Statutory Accounting Practices [Line Items]
Statutory capital and surplus			29.4	$ 20.7
Statutory net income (loss)			(0.8)	(0.9)	$ 3.9
Surplus required			8.1
Ashmere [Member] \| Sirius Group
Statutory Accounting Practices [Line Items]
Statutory capital and surplus			12.5	12.7
Statutory net income (loss)			(0.5)	(0.4)
Surplus required			2.0
Empire [Member] \| Sirius Group
Statutory Accounting Practices [Line Items]
Statutory capital and surplus			10.5	10.7
Statutory net income (loss)			(0.6)	(10.4)
Surplus required			3.4
White Shoals Reinsurance Company \| Sirius Group
Statutory Accounting Practices [Line Items]
Statutory capital and surplus			22.4	14.6
Surplus required			8.2	6.2
White Mountains Life Re \| Other Operations
Statutory Accounting Practices [Line Items]
Statutory capital and surplus			76.0	$ 85.9
Surplus required			0.4
Olympus [Member] \| Sirius Group
Statutory Accounting Practices [Line Items]
Statutory capital and surplus			12.3
Surplus required			$ 2.6
Surplus Note \| BAM \| HG Global-BAM
Dividend Capacity
Interest rate (as a percent)			8.00%
basis points			3.00%
SWEDEN \| Sirius Group
Dividend Capacity
Effective income tax	22.00%				26.30%
Preferred stocks \| HG Global \| HG Global-BAM
Dividend Capacity
Dividends Payable			$ 96.2
Preferred stocks \| White Mountains \| HG Global \| HG Global-BAM
Dividend Capacity
Dividends Payable			$ 93.3
SEK
Dividend Capacity
Exchange rate			7.7737	6.4339	6.4973
SEK \| Sirius International \| Sirius Group
Dividend Capacity
Amount of safety reserve			$ 10,400.0
Common Stock [Member] \| OneBeacon
Statutory Accounting Practices [Line Items]
Trading Securities			89.4
Common Equities [Member] \| Other Operations
Statutory Accounting Practices [Line Items]
Trading Securities			172.7
Retained earnings
Statutory Accounting Practices [Line Items]
Stockholders' Equity Attributable to Parent			3,011.4	$ 2,802.3	$ 2,542.7	$ 2,789.7
Amount available for dividend distributions without prior approval from regulatory authorities			958.0
Retained earnings \| Split Rock [Member] \| OneBeacon
Statutory Accounting Practices [Line Items]
Amount available for dividend distributions without prior approval from regulatory authorities			$ 18.8
Statutory Accounting Practices, Statutory Capital, Percent			15.00%
Retained earnings \| Atlantic Speciality Insurance Company (ASIC) [Member] \| OneBeacon
Statutory Accounting Practices [Line Items]
Statutory Accounting Practices, Statutory Capital, Percent			10.00%
U.S and Bermuda [Member] \| OneBeacon
Statutory Accounting Practices [Line Items]
Statutory capital and surplus			$ 721.5	$ 866.2
NAIC Risk-Based Capital [Member] \| Ashmere [Member] \| Sirius Group
Statutory Accounting Practices [Line Items]
Surplus required			0.1
NAIC Risk-Based Capital [Member] \| Empire [Member] \| Sirius Group
Statutory Accounting Practices [Line Items]
Surplus required			1.2
Surplus Note \| Unregulated Operation \| OneBeacon
Statutory Accounting Practices [Line Items]
Fair value investments			$ 65.1
Combination One [Member] \| Surplus Note \| BAM \| HG Global-BAM
Dividend Capacity
Number of years of change in interest rate			5
Combination Two [Member] \| Surplus Note \| BAM \| HG Global-BAM
Dividend Capacity
Number of years of change in interest rate \| yr			3
US Treasury Rate [Member] \| Surplus Note \| BAM \| HG Global-BAM
Dividend Capacity
Interest rate (as a percent)			3.13%
Fixed interest rate [Member] \| Surplus Note \| BAM \| HG Global-BAM
Dividend Capacity
Interest rate (as a percent)			8.00%

Segment Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
Segment Information (Details) - USD ($) $ in Millions	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment reporting information
Percentage of par value of policy reinsured	15.00%								15.00%
Earned insurance and reinsurance premiums									$ 2,058.9	$ 1,987.3	$ 2,063.6
Net investment income									105.0	110.9	153.6
Net investment income (loss) - surplus note interest									0.0	0.0	0.0
Net realized and unrealized investment gains									283.9	161.7	118.2
Other revenue									62.4	57.5	100.3
Total revenues	$ 689.7	$ 589.4	$ 652.8	$ 578.3	$ 626.6	$ 574.1	$ 489.3	$ 627.4	2,510.2	2,317.4	2,435.7
Loss and loss adjustment expenses									1,169.3	1,040.5	1,193.9
Insurance and reinsurance acquisition expenses									399.8	376.9	430.2
Other underwriting expenses									309.3	331.3	321.8
General and administrative expenses									288.2	181.3	182.2
Interest expense on debt									41.9	42.5	44.8
Expenses	643.5	555.0	543.8	466.2	492.4	518.8	485.7	475.6	2,208.5	1,972.5	2,172.9
Pre-tax loss	$ 46.2	$ 34.4	$ 109.0	$ 112.1	$ 134.2	$ 55.3	$ 3.6	$ 151.8	301.7	344.9	262.8
OneBeacon
Segment reporting information
Earned insurance and reinsurance premiums									1,177.1	1,120.4	1,132.0
Net investment income									41.7	41.1	53.6
Net investment income (loss) - surplus note interest									0.0	0.0	0.0
Net realized and unrealized investment gains									40.4	49.4	55.7
Other revenue									5.8	31.2	(0.5)
Total revenues									1,265.0	1,242.1	1,240.8
Loss and loss adjustment expenses									815.1	622.1	650.0
Insurance and reinsurance acquisition expenses									203.3	208.9	249.4
Other underwriting expenses									179.2	204.8	205.2
General and administrative expenses									13.8	12.0	13.4
Interest expense on debt									13.0	13.0	16.9
Expenses									1,224.4	1,060.8	1,134.9
Pre-tax loss									40.6	181.3	105.9
Sirius Group
Segment reporting information
Earned insurance and reinsurance premiums									873.9	866.4	931.6
Net investment income									41.1	48.8	65.0
Net investment income (loss) - surplus note interest									0.0	0.0	0.0
Net realized and unrealized investment gains									209.2	26.7	17.3
Other revenue									(62.4)	16.8	70.6
Total revenues									1,061.8	958.7	1,084.5
Loss and loss adjustment expenses									345.3	418.4	543.9
Insurance and reinsurance acquisition expenses									193.6	166.5	180.8
Other underwriting expenses									129.7	126.1	116.4
General and administrative expenses									30.5	32.2	45.9
Interest expense on debt									26.3	26.3	26.2
Expenses									725.4	769.5	913.2
Pre-tax loss									336.4	189.2	171.3
BAM
Segment reporting information
Earned insurance and reinsurance premiums									0.4	0.1	0.0
Net investment income									5.7	4.7	1.9
Net investment income (loss) - surplus note interest									(15.7)	(40.2)	(18.4)
Net realized and unrealized investment gains									6.6	(9.3)	0.0
Other revenue									0.6	0.4	0.0
Total revenues									(2.4)	(44.3)	(16.5)
Loss and loss adjustment expenses									0.0	0.0	0.0
Insurance and reinsurance acquisition expenses									1.8	1.4	0.0
Other underwriting expenses									0.4	0.4	0.2
General and administrative expenses									35.9	32.5	19.6
Interest expense on debt									0.0	0.0	0.0
Expenses									38.1	34.3	19.8
Pre-tax loss									(40.5)	(78.6)	(36.3)
Other Segments
Segment reporting information
Earned insurance and reinsurance premiums									6.1	0.0	0.0
Net investment income									15.1	15.3	32.8
Net investment income (loss) - surplus note interest									0.0	0.0	0.0
Net realized and unrealized investment gains									26.0	96.9	45.2
Other revenue									118.4	9.1	30.2
Total revenues									165.6	121.3	108.2
Loss and loss adjustment expenses									8.9	0.0	0.0
Insurance and reinsurance acquisition expenses									0.8	0.0	0.0
Other underwriting expenses									0.0	0.0	0.0
General and administrative expenses									206.4	103.2	98.8
Interest expense on debt									2.6	3.2	1.7
Expenses									218.7	106.4	100.5
Pre-tax loss									$ (53.1)	14.9	7.7
HG Global
Segment reporting information
Percentage of par value of policy reinsured	15.00%								15.00%
Earned insurance and reinsurance premiums									$ 1.4	0.4	0.0
Net investment income									1.4	1.0	0.3
Net investment income (loss) - surplus note interest									15.7	40.2	18.4
Net realized and unrealized investment gains									1.7	(2.0)	0.0
Other revenue									0.0	0.0	0.0
Total revenues									20.2	39.6	18.7
Loss and loss adjustment expenses									0.0	0.0	0.0
Insurance and reinsurance acquisition expenses									0.3	0.1	0.0
Other underwriting expenses									0.0	0.0	0.0
General and administrative expenses									1.6	1.4	4.5
Interest expense on debt									0.0	0.0	0.0
Expenses									1.9	1.5	4.5
Pre-tax loss									$ 18.3	$ 38.1	$ 14.2

Segment Information (Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment reporting information
Total investments	$ 6,886.3	$ 7,192.6
Reinsurance recoverable on paid and unpaid losses	507.5	453.5
Assets held for sale	58.1	1,880.1
Assets	10,456.9	12,144.3
Loss and loss adjustment expense reserves	3,159.8	3,079.3	$ 3,168.9	$ 5,702.3
Liabilities held for sale	0.0	1,880.1
Liabilities	5,917.3	7,746.9
Non-controlling interests	543.0	491.9
White Mountains’ common shareholders’ equity	3,996.6	3,905.5
OneBeacon
Segment reporting information
Total investments	2,527.0	2,364.9
Reinsurance recoverable on paid and unpaid losses	173.8	89.9
Assets held for sale	58.1	1,880.1
Assets	3,561.0	5,191.3
Loss and loss adjustment expense reserves	1,342.2	1,054.3
Liabilities held for sale		1,880.1
Liabilities	2,510.5	4,083.9
Non-controlling interests	262.1	276.8
White Mountains’ common shareholders’ equity	788.4	830.6
Sirius Group
Segment reporting information
Total investments	3,178.4	3,251.4
Reinsurance recoverable on paid and unpaid losses	333.6	363.6
Assets held for sale	0.0	0.0
Assets	5,034.7	5,124.1
Loss and loss adjustment expense reserves	1,809.8	2,025.0
Liabilities held for sale		0.0
Liabilities	3,180.6	3,414.5
Non-controlling interests	250.0	250.0
White Mountains’ common shareholders’ equity	1,604.1	1,459.6
HG Global
Segment reporting information
Total investments	121.0	107.9
Reinsurance recoverable on paid and unpaid losses	0.0	0.0
Assets held for sale	0.0	0.0
Assets	704.4	675.0
Loss and loss adjustment expense reserves	0.0	0.0
Liabilities held for sale		0.0
Liabilities	120.9	68.9
Non-controlling interests	17.9	16.6
White Mountains’ common shareholders’ equity	565.5	589.5
BAM
Segment reporting information
Total investments	454.2	468.6
Reinsurance recoverable on paid and unpaid losses	0.0	0.0
Assets held for sale	0.0	0.0
Assets	(89.4)	(77.9)
Loss and loss adjustment expense reserves	0.0	0.0
Liabilities held for sale		0.0
Liabilities	32.5	19.7
Non-controlling interests	(121.9)	(97.6)
White Mountains’ common shareholders’ equity	0.0	0.0
Surplus notes	503.0
Accrued interest on surplus notes	74.4	58.6
Other Operations
Segment reporting information
Total investments	605.7	999.8
Reinsurance recoverable on paid and unpaid losses	0.1	0.0
Assets held for sale	0.0	0.0
Assets	1,246.2	1,231.8
Loss and loss adjustment expense reserves	7.8	0.0
Liabilities held for sale		0.0
Liabilities	72.8	159.9
Non-controlling interests	134.9	46.1
White Mountains’ common shareholders’ equity	$ 1,038.6	$ 1,025.8

Investments in Unconsolidated Affiliates (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investments in unconsolidated affiliates
Investments in unconsolidated affiliates	$ 414.4	$ 321.4
Symetra
Investments in unconsolidated affiliates
Unrealized gains (losses) from Symetra’s fixed maturity portfolio	37.6	(43.6)
Investments in unconsolidated affiliates	411.4	317.3	$ 381.5	$ 273.6
Symetra \| Common Stock
Investments in unconsolidated affiliates
Symetra common shares	373.8	360.9
Investments in unconsolidated affiliates	411.4	317.3	351.2	261.0
Symetra \| Warrants
Investments in unconsolidated affiliates
Investments in unconsolidated affiliates	0.0	0.0	$ 30.3	$ 12.6
Hamer, LLC
Investments in unconsolidated affiliates
Investments in unconsolidated affiliates	$ 3.0	$ 4.1

Investments in Unconsolidated Affiliates (Symetra Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended	12 Months Ended
	Jun. 20, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investments in unconsolidated affiliates
Common shares repurchased and retired during the period			1,329,640
Treasury Stock Acquired, Average Cost Per Share		$ 617	$ 564	$ 503
Symetra
Investments in unconsolidated affiliates
Shares of symetra financial corporation owned (in shares)		20,050,000
Ownership interest (as a percent)		17.31%	17.03%
Dividends received		$ (34.1)	$ (6.4)	$ (4.9)
Investments in unconsolidated affiliates on conversion of warrants	2,650,000			9,490,000
Gain (Loss) on Warrants			10.8	$ 17.7
Fair value of investment					$ 261.0
Estimated fair value of investment per share					$ 15
After-tax equity in losses of unconsolidated affiliates					$ 45.9
Equity in net unrealized losses increase relating to amortization of common share impairment					$ 136.6
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 19.3	2.4
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity, Attributable to Equity Earnings in Affiliates		0.5
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity, Net Unrealized Gains and Losses of Affiliate		$ 1.9
Term of amortization (in years)				30 years
Weight Average Years Remaining		28 years
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity, Unamortized Basis Difference Attributable to Equity Earnings		$ 36.4
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity, Unamortized Basis Difference Attributable to Unrealized Gains in Affiliates		134.0
Common Stock \| Symetra
Investments in unconsolidated affiliates
Dividends received		$ (34.1)	(6.4)	$ (4.9)
Per share price, class of warrant (in dollars per share)		$ 23.05
Gain (Loss) on Warrants			0.0	0.0
Warrants
Investments in unconsolidated affiliates
Gain (Loss) on Warrants	10.8
Warrants \| Symetra
Investments in unconsolidated affiliates
Dividends received		$ 0.0	0.0	$ 0.0
Per share price, class of warrant (in dollars per share)				$ 11.49
Gain (Loss) on Warrants			$ 10.8	$ 17.7
Cash dividends received on warrants	$ 1.5
Symetra \| Common Stock
Investments in unconsolidated affiliates
Common shares repurchased and retired during the period	6,600,000
Treasury Stock Acquired, Average Cost Per Share	$ 13.44
equity in earnings of unconsolidated affiliates [Member] \| Symetra
Investments in unconsolidated affiliates
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 0.4	170.4
After tax amortization through equity in earnings		2.8
Net unrealized gains (losses) of unconsolidated affiliates [Member] \| Symetra
Investments in unconsolidated affiliates
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 18.9
After tax amortization through equity in net unrealized losses		$ 11.7

Investments in Unconsolidated Affiliates (Investments in Symetra) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								6 Months Ended	12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Jun. 20, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Changes in carrying value of investment in Symetra
Carrying value at the beginning of the period				$ 321.4						$ 321.4
Equity in earnings of unconsolidated affiliates, net of tax	$ 12.3	$ 7.0	$ 12.5	13.8	$ 11.7	$ 8.6	$ 7.1	$ 9.2		45.6	$ 36.6	$ 29.9
Net change in pre-tax unrealized gains (losses) on investments in unconsolidated affiliates										81.2	(106.4)	62.8
Carrying value at the end of the period	414.4				321.4					414.4	321.4
Income Tax Expense (Benefit)	(8.7)	$ 7.8	$ 23.9	30.3	27.4	$ 8.2	$ (0.6)	41.6		53.3	76.6	(15.7)
Symetra
Changes in carrying value of investment in Symetra
Carrying value at the beginning of the period				317.3				381.5	$ 381.5	317.3	381.5	273.6
Equity in earnings of unconsolidated affiliates, net of tax										47.0	37.8	32.3
Net change in pre-tax unrealized gains (losses) on investments in unconsolidated affiliates										81.2	(106.4)	62.8
Dividends received										(34.1)	(6.4)	(4.9)
Increase (decrease) in value of warrants											10.8	17.7
Carrying value at the end of the period	411.4				317.3					411.4	317.3	381.5	$ 273.6
Unrealized gains (losses) from Symetra’s fixed maturity portfolio	37.6				(43.6)					37.6	(43.6)
Equity in net unrealized losses increase relating to amortization of common share impairment													136.6
Exercise of warrants											0.0
Common Stock \| Symetra
Changes in carrying value of investment in Symetra
Carrying value at the beginning of the period				317.3				351.2	351.2	317.3	351.2	261.0
Equity in earnings of unconsolidated affiliates, net of tax										47.0	37.8	32.3
Net change in pre-tax unrealized gains (losses) on investments in unconsolidated affiliates										81.2	(106.4)	62.8
Dividends received										(34.1)	(6.4)	(4.9)
Increase (decrease) in value of warrants											0.0	0.0
Carrying value at the end of the period	411.4				317.3					411.4	317.3	351.2	261.0
Loss from dilutive effect resulting from dividend and issuance of restricted shares										(0.1)	0.2	1.3
Aggregate value of White Mountains common shares of Symetra at quoted market price	$ 462.1									$ 462.1
Share Price	$ 23.05									$ 23.05
Exercise of warrants											41.1
Common Stock \| White Mountains
Changes in carrying value of investment in Symetra
Net change in pre-tax unrealized gains (losses) on investments in unconsolidated affiliates										$ 37.6	(43.6)	62.8
Warrants
Changes in carrying value of investment in Symetra
Increase (decrease) in value of warrants									10.8
Warrants \| Symetra
Changes in carrying value of investment in Symetra
Carrying value at the beginning of the period				$ 0.0				$ 30.3	$ 30.3	0.0	30.3	12.6
Equity in earnings of unconsolidated affiliates, net of tax										0.0	0.0	0.0
Net change in pre-tax unrealized gains (losses) on investments in unconsolidated affiliates										0.0	0.0	0.0
Dividends received										0.0	0.0	0.0
Increase (decrease) in value of warrants											10.8	17.7
Carrying value at the end of the period	$ 0.0				$ 0.0					0.0	0.0	$ 30.3	$ 12.6
Share Price												$ 11.49
Exercise of warrants											(41.1)
equity in earnings of unconsolidated affiliates [Member] \| Common Stock \| Symetra
Changes in carrying value of investment in Symetra
Income Tax Expense (Benefit)										3.3	2.8	$ 2.6
Net unrealized gains (losses) of unconsolidated affiliates [Member] \| Common Stock \| Symetra
Changes in carrying value of investment in Symetra
Income Tax Expense (Benefit)										5.9	(8.3)	5.1
Net unrealized gains (losses) of unconsolidated affiliates [Member] \| Common Stock \| White Mountains
Changes in carrying value of investment in Symetra
Income Tax Expense (Benefit)										(2.7)	3.2	(5.1)
impairment of equity in earnings [Member] \| equity in earnings of unconsolidated affiliates [Member] \| Common Stock \| Symetra
Changes in carrying value of investment in Symetra
Equity in earnings of unconsolidated affiliates, net of tax												3.5
impairment of net unrealized gains (losses) [Member] \| Net unrealized gains (losses) of unconsolidated affiliates [Member] \| Common Stock \| Symetra
Changes in carrying value of investment in Symetra
Net change in pre-tax unrealized gains (losses) on investments in unconsolidated affiliates										12.7	11.8	$ 13.1
Amortization of common share basis difference [Member] \| Common Stock \| Symetra
Changes in carrying value of investment in Symetra
Equity in earnings of unconsolidated affiliates, net of tax										$ 3.0	$ 3.0

Investments in Unconsolidated Affiliates (Financial Information) (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended								9 Months Ended	12 Months Ended
	Apr. 30, 2007	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Symetra income statement data: [Abstract]
Equity in earnings of unconsolidated affiliates, net of tax		$ 12.3	$ 7.0	$ 12.5	$ 13.8	$ 11.7	$ 8.6	$ 7.1	$ 9.2		$ 45.6	$ 36.6	$ 29.9
Investments in unconsolidated affiliates		414.4				321.4					414.4	321.4
Symetra
Symetra balance sheet data; [Abstract]
Total investments		30,634.3				27,901.1					30,634.3	27,901.1
Separate account assets		949.8				978.4					949.8	978.4
Total assets		32,994.2				30,129.5					32,994.2	30,129.5
Policyholder liabilities		27,276.0				25,328.8					27,276.0	25,328.8
Long-term debt		697.2				449.5					697.2	449.5
Separate account liabilities		949.8				978.4					949.8	978.4
Total liabilities		29,633.6				27,187.6					29,633.6	27,187.6
Common shareholders’ equity		$ 3,360.6				$ 2,941.9					3,360.6	2,941.9
Symetra income statement data: [Abstract]
Net premiums earned											629.1	627.2	605.0
Net investment income											1,320.5	1,285.0	1,275.2
Total revenues											2,182.3	2,103.9	2,101.2
Policy benefits											1,399.6	1,394.9	1,371.8
Total expenses											1,882.4	1,865.3	1,831.1
Net income											254.4	220.7	205.4
Comprehensive net income (loss)											$ 397.0	$ (777.6)	549.3
Ownership interest (as a percent)		17.31%				17.03%					17.31%	17.03%
Equity in earnings of unconsolidated affiliates, net of tax											$ 47.0	$ 37.8	32.3
Dividends received											(34.1)	(6.4)	(4.9)
Investments in unconsolidated affiliates		$ 411.4				$ 317.3					411.4	317.3	381.5	$ 273.6
Pentelia Capital Management
Symetra income statement data: [Abstract]
Ownership interest (as a percent)	33.00%
Payments to acquire investment	$ 1.6
Equity in earnings of unconsolidated affiliates, net of tax											0.1	(1.3)
Dividends received											(0.4)
Hamer, LLC
Symetra income statement data: [Abstract]
Equity in earnings of unconsolidated affiliates, net of tax											1.9	0.9	0.4
Dividends received											(3.0)	(0.8)
Investments in unconsolidated affiliates		3.0				4.1					3.0	4.1
Bri-Mar Manufacturing, LLC
Symetra income statement data: [Abstract]
Equity in earnings of unconsolidated affiliates, net of tax										$ 0.9
Proceeds from Sale of Equity Method Investments												1.1
Equity Method Investment, Realized Gain (Loss) on Disposal												1.7
Total \| Symetra
Symetra income statement data: [Abstract]
Equity in earnings of unconsolidated affiliates, net of tax											47.0	37.8	32.3
Dividends received											(34.1)	(6.4)	(4.9)
Investments in unconsolidated affiliates		$ 411.4				$ 317.3					$ 411.4	317.3	$ 351.2	$ 261.0
Per share price, class of warrant (in dollars per share)		$ 23.05									$ 23.05
Total \| Amortization of common share basis difference [Member] \| Symetra
Symetra income statement data: [Abstract]
Equity in earnings of unconsolidated affiliates, net of tax											$ 3.0	$ 3.0

Variable Interest Entities (Details) $ in Millions	3 Months Ended								6 Months Ended	12 Months Ended
Variable Interest Entities (Details) $ in Millions	Dec. 31, 2014 USD ($) trust	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Sep. 30, 2013 USD ($)	Jun. 30, 2013 USD ($)	Mar. 31, 2013 USD ($) company	Jun. 30, 2014	Dec. 31, 2014 USD ($) trust	Dec. 31, 2013 USD ($) director	Dec. 31, 2012 USD ($)	Dec. 31, 2011
Variable Interest Entity [Line Items]
Percentage of par value of policy reinsured	15.00%									15.00%
Accumulated losses	$ 3,011.4				$ 2,802.3					$ 3,011.4	$ 2,802.3
Noncontrolling interest in VIE	543.0				491.9					543.0	491.9
Non-controlling interest in consolidated subsidiaries	$ (15.0)	$ (11.2)	$ 4.6	$ (0.5)	0.3	$ (1.1)	$ (11.1)	$ (0.5)		(22.1)	(12.4)	$ (14.0)
Payments to Acquire Other Investments										$ 137.0	36.3	96.7
HG Global
Variable Interest Entity [Line Items]
Percentage of par value of policy reinsured	15.00%									15.00%
Noncontrolling interest in VIE	$ 17.9				16.6					$ 17.9	16.6
Star & Shield Insurance Exchange [Member]
Variable Interest Entity [Line Items]
Surplus notes	17.0									17.0
Total assets related to consolidated VIE's	13.5									13.5
Total liabilities related to consolidated VIE's	25.9									25.9
Accumulated losses	12.4									12.4
Prospector
Variable Interest Entity [Line Items]
Total assets related to consolidated VIE's	135.8				249.2					135.8	249.2
Total liabilities related to consolidated VIE's	39.8				90.6					39.8	90.6
Noncontrolling interest in VIE	31.1				46.2					31.1	46.2
Net Income (Loss) Attributable to Parent										5.6	14.5	9.3
Non-controlling interest in consolidated subsidiaries										1.9	$ 4.0	$ 2.7
Captial at risk, investment in the fund	64.9									64.9
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage											67.60%
Houston General Insurance [Member]
Variable Interest Entity [Line Items]
Surplus notes	4.0									4.0
Total assets related to consolidated VIE's	2.4				2.6					2.4	$ 2.6
Total liabilities related to consolidated VIE's	4.0				4.2					4.0	$ 4.2
Accumulated losses	1.8									1.8
Accrued interest on surplus notes	0.2									0.2
TaClaro [Member]
Variable Interest Entity [Line Items]
Payments to Acquire Other Investments	2.0		$ 1.5							$ 3.0
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage									39.00%	49.00%	27.00%
Notes Issued	1.7
Tranzutary Holdings LLC [Member]
Variable Interest Entity [Line Items]
Total assets related to consolidated VIE's	29.6									$ 29.6
Total liabilities related to consolidated VIE's	$ 4.1									$ 4.1
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage										36.00%
Entities Owned by Tuckerman Fund I [Member]
Variable Interest Entity [Line Items]
Number Of Manufacturing Companies From Whom Shares Received \| company								2
Common Stock \| BAM
Variable Interest Entity [Line Items]
Issuance of notes											$ 503.0
Common Stock \| Tuckerman Fund I [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage													94.00%
BAM
Variable Interest Entity [Line Items]
Right to elect directors on board number \| director											2
HG Global
Variable Interest Entity [Line Items]
Percentage of par value of policy reinsured	15.00%									15.00%
Surplus notes	$ 503.0				503.0					$ 503.0	$ 503.0
Noncontrolling interest in VIE	$ 17.9				$ 16.6					$ 17.9	$ 16.6
First Loss Reinsurance Treaty [Member] \| HG Global
Variable Interest Entity [Line Items]
Percentage of par value of policy reinsured	15.00%									15.00%
First Loss Reinsurance Treaty [Member] \| BAM
Variable Interest Entity [Line Items]
Percentage of Premiums	60.00%									60.00%
First Loss Reinsurance Treaty [Member] \| HG Global
Variable Interest Entity [Line Items]
Number of Trust \| trust	2									2
Amendment [Member] \| Houston General Insurance [Member]
Variable Interest Entity [Line Items]
Surplus notes	$ 4.0									$ 4.0
Common Stock \| TaClaro [Member]
Variable Interest Entity [Line Items]
Stock Issued	0.3
Other Intangible Assets [Member] \| Tranzutary Holdings LLC [Member]
Variable Interest Entity [Line Items]
Total assets related to consolidated VIE's	$ 28.9									$ 28.9

Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Senior notes	$ 746.6	$ 676.4
Fair value \| 2012 OBH Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Senior notes	286.0	269.8
Fair value \| SIG Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Senior notes	437.8	438.1
Fair value \| SIG Preference Shares
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Senior notes	260.0	260.0
Carrying Value \| 2012 OBH Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Senior notes	274.7	274.7
Carrying Value \| SIG Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Senior notes	399.7	399.6
Carrying Value \| SIG Preference Shares
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Senior notes	$ 250.0	$ 250.0

Transactions with Related Persons (Details) - USD ($)		12 Months Ended
Transactions with Related Persons (Details) - USD ($)	Jul. 16, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Mar. 15, 2013
Related Party Transaction [Line Items]
Purchases		$ 5,602,100,000	$ 4,635,500,000
Sales of common equity securities		660,900,000	$ 521,100,000	$ 192,400,000
Beneficial Owner
Related Party Transaction [Line Items]
Per share price, class of warrant (in dollars per share)						$ 563.57
Shares purchased			140,000
Prospector
Related Party Transaction [Line Items]
Asset Management Fees		$ 6,500,000	$ 6,500,000	6,400,000
Performance shares granted at the beginning of each performance cycle			4,500,000
Percentage of fees in excess of $500,000 revenue chargeable		6.00%
Amount of revenue over which 6% of fees chargeable			500,000
Invested in limited partnership investment interests		$ 82,400,000
Management Fees, Base Revenue		1,100,000	1,300,000		$ 1,100,000
Incentive fees incurred		700,000	3,200,000		$ 1,300,000
OneBeacon \| Prospector
Related Party Transaction [Line Items]
Assets under management		431,200,000
ERISA Assets		202,900,000
Invested in limited partnership investment interests		15,800,000
White Mountains Advisors LLC \| Symetra
Related Party Transaction [Line Items]
Assets under management		30,900,000,000	27,800,000,000
Asset Management Fees		18,400,000	16,500,000	15,900,000
White Mountains Advisors LLC \| Prospector
Related Party Transaction [Line Items]
Assets under management		$ 195,700,000
Oakum Bay Capital
Related Party Transaction [Line Items]
Ownerhsip percentage	7.50%
Sales of common equity securities			$ 500,000
Number of years to receive portion of revenue			10 years
Oakum Bay Capital \| Director
Related Party Transaction [Line Items]
Related party ownerhship percentage			67.50%
Maximum \| Prospector
Related Party Transaction [Line Items]
Target number of performance shares granted (as a percent)		200.00%
Minimum \| Prospector
Related Party Transaction [Line Items]
Target number of performance shares granted (as a percent)		0.00%
Preferred Equity Securities \| Oakum Bay Capital
Related Party Transaction [Line Items]
Purchases	$ 2,000,000
revenue sharing agreement \| Prospector
Related Party Transaction [Line Items]
Fees from Revenue Sharing Agreement with Related Party		$ 400,000	$ 900,000	$ 500,000
Trimarc Capital Fund \| Oakum Bay Capital
Related Party Transaction [Line Items]
Management fees			$ 100,000
Trimarc Capital Fund \| Hedge funds \| Oakum Bay Capital
Related Party Transaction [Line Items]
Trading Securities, Other		7,800,000
First Threshold Limit \| White Mountains Advisors LLC \| Prospector
Related Party Transaction [Line Items]
Assets under management		$ 200,000,000
basis points		100.00%
Second Threshold Limit \| White Mountains Advisors LLC \| Prospector
Related Party Transaction [Line Items]
Assets under management		$ 200,000,000
basis points		50.00%
Third Threshold Limit \| White Mountains Advisors LLC \| Prospector
Related Party Transaction [Line Items]
Assets under management		$ 400,000,000
basis points		25.00%
Range Of Performance Cycle From 2015 to 2017 [Member] \| Prospector
Related Party Transaction [Line Items]
Number of performance shares granted		6,250
Range Of Performance Cycle From 2014-2016 [Member] \| Prospector
Related Party Transaction [Line Items]
Number of performance shares granted		6,250
Performance Cycle From 2013 to 2015 \| Prospector
Related Party Transaction [Line Items]
Number of performance shares granted		7,000
Performance Cycle From 2011 to 2013 \| Prospector
Related Party Transaction [Line Items]
Number of performance shares granted		7,750
Percentage of target number granted actually received by prospector		145.50%
Payment made with respect to the performance shares granted to the related party		$ 7,500,000

Commitments and Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Loss Contingencies [Line Items]
Rent expense	$ 19.4	$ 20.2	$ 18.8
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Capital lease payments due next year	16.5
Capital lease payments due in two years	15.2
Capital lease payments due in three years	13.6
Capital Lease payments due in four years and thereafter	54.7
Commitments to fund other-long term investments	81.7
Reserve for probable liability from mandatory shared market mechanisms	11.9
OB Services
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Capital lease payments due next year	5.3
Capital lease payments due in two years	5.3
Capital lease payments due in three years	1.8
Cash proceeds received a result of entering into the sale-leaseback transactions	23.1
Capital lease obligation	7.1	12.5
Capital lease asset	$ 7.0	$ 10.9
Furniture and equipment \| OB Services
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Capital lease term (in years)	5 years
Capitalized software \| OB Services
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Capital lease term (in years)	4 years

Commitments and Contingencies (Legal Contingencies) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Jun. 30, 2007
Legal Contingency [Abstract]
Period for which company has indemnified Allstate for breaches of representations and warranties (in months)	18 months
Period for which the entity has agreed not to solicit certain employees of transferred subsidiaries (in years)	3 years
Percentage of positive or negative development in the loss reserves of the Transferred Subsidiaries retained	90.00%
Tribune Company Litigation
Legal Contingency [Abstract]
Proceeds in connection with Tribune leveraged buyout		$ 39.0

Discontinued Operations (Details) - USD ($) $ in Millions		3 Months Ended								6 Months Ended	12 Months Ended
Discontinued Operations (Details) - USD ($) $ in Millions	Dec. 23, 2014	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Discontinued Operations
(Loss) gain on sale of discontinued operations, net of tax											$ (1.6)	$ 46.6	$ (91.0)
Loss and loss adjustment expense reserves		$ 3,159.8				$ 3,079.3					3,159.8	3,079.3	3,168.9	$ 5,702.3
Loss and loss adjustment expenses											1,169.3	1,040.5	1,193.9
Other revenue											62.4	57.5	100.3
Net loss from discontinued operations, net of tax		(12.2)	$ 6.7	$ 2.6	$ (0.5)	(0.3)	$ 0.4	$ 3.9	$ 0.5		(1.8)	(42.1)	(24.0)
Reinsurance recoverable on paid losses		23.6				25.4					23.6	25.4
Prior Accident Year											(6.0)	(48.4)	(41.9)
Discontinued Operations
Discontinued Operations
(Loss) gain on sale of discontinued operations, net of tax											(1.6)	46.6	(91.0)
Loss and loss adjustment expense reserves						1,793.1						1,793.1
Net (loss) income from discontinued operations											(3.4)	4.5	(115.0)
Loss and loss adjustment expenses											(0.7)	78.9	48.4
Other revenue											0.0	10.8	0.0
Net loss from discontinued operations, net of tax											(1.8)	(42.1)	(24.0)
Reinsurance recoverable on paid losses						$ 10.7						10.7
Runoff Entities [Member] \| Discontinued Operations
Discontinued Operations
(Loss) gain on sale of discontinued operations, net of tax											(18.8)
Esurance [Member] \| White Mountains
Discontinued Operations
(Loss) gain on sale of discontinued operations, net of tax											3.2
OneBeacon Runoff
Discontinued Operations
Surplus notes	$ 101.0
OneBeacon Runoff \| Discontinued Operations
Discontinued Operations
(Loss) gain on sale of discontinued operations, net of tax											(35.9)		91.5
Transfer of assets		7.4									7.4
Surplus notes		101.0									101.0
Net loss from discontinued operations, net of tax													24.0
Prior Accident Year												(71.5)
liability for unpaid claims and claims adjustment expenses, incurred claims, prior years, after-tax												$ 46.5
AutoOne \| Discontinued Operations
Discontinued Operations
(Loss) gain on sale of discontinued operations, net of tax													$ 0.5
Fireman's Fund Insurance Company [Member] \| White Mountains
Discontinued Operations
(Loss) gain on sale of discontinued operations, net of tax											13.9
Surplus Note \| OneBeacon Runoff \| Discontinued Operations
Discontinued Operations
(Loss) gain on sale of discontinued operations, net of tax											(23.5)
Reserve Charge [Member] \| OneBeacon Runoff \| Discontinued Operations
Discontinued Operations
(Loss) gain on sale of discontinued operations, net of tax											4.8
Reserve charge under the SPA, before tax										$ 7.4
Fair Value [Member] \| OneBeacon Runoff \| Discontinued Operations
Discontinued Operations
Surplus notes		$ 65.1									65.1
Fair Value [Member] \| Other long-term investments \| OneBeacon Runoff
Discontinued Operations
Surplus notes	64.9
Safeco v. American International Group, Inc. [Member] \| OneBeacon Runoff \| Discontinued Operations
Discontinued Operations
Other revenue								$ 7.8
Surplus Note \| OneBeacon Runoff \| Discontinued Operations
Discontinued Operations
(Loss) gain on sale of discontinued operations, net of tax	$ 36.1										36.1
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax											$ 23.5

Discontinued Operations (Assets and Liabilities Classified as Held for Sale) (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Assets held for sale
Fixed maturity investments, at fair value	$ 4,784.3	$ 5,030.5
Insurance and reinsurance premiums receivable	547.7	518.9
Deferred tax asset	173.3	155.9
Other assets	356.1	437.4
Total assets	10,456.9	12,144.3
Liabilities held for sale
Loss and loss adjustment expense reserves	3,159.8	3,079.3	$ 3,168.9	$ 5,702.3
Unearned insurance premiums	955.3	901.4
Ceded reinsurance payable	105.7	71.9
Other liabilities	341.0	415.7
Total liabilities	5,917.3	7,746.9
Reinsurance recoverable on unpaid losses	483.9	428.1
Reinsurance recoverable on paid losses	$ 23.6	25.4
Discontinued Operations
Assets held for sale
Fixed maturity investments, at fair value		236.3
Insurance and reinsurance premiums receivable		9.1
Deferred tax asset		3.3
Other assets		16.0
Total assets		1,880.1
Liabilities held for sale
Loss and loss adjustment expense reserves		1,793.1
Unearned insurance premiums		0.2
Ceded reinsurance payable		12.3
Other liabilities		74.5
Total liabilities		1,880.1
Net assets held for sale		0.0
Reinsurance recoverable on unpaid losses		1,604.7
Reinsurance recoverable on paid losses		$ 10.7

Discontinued Operations (Loss from Discontinued Operations) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues
Earned insurance premiums									$ 2,058.9	$ 1,987.3	$ 2,063.6
Other revenue									62.4	57.5	100.3
Revenues (including realized gains and losses)	$ 689.7	$ 589.4	$ 652.8	$ 578.3	$ 626.6	$ 574.1	$ 489.3	$ 627.4	2,510.2	2,317.4	2,435.7
Expenses
Loss and loss adjustment expenses									1,169.3	1,040.5	1,193.9
Insurance and reinsurance acquisition expenses									399.8	376.9	430.2
Other underwriting expenses									309.3	331.3	321.8
Total expenses	643.5	555.0	543.8	466.2	492.4	518.8	485.7	475.6	2,208.5	1,972.5	2,172.9
Net loss from discontinued operations, net of tax	$ (12.2)	$ 6.7	$ 2.6	$ (0.5)	$ (0.3)	$ 0.4	$ 3.9	$ 0.5	(1.8)	(42.1)	(24.0)
(Loss) gain on sale of discontinued operations, net of tax									(1.6)	46.6	(91.0)
Discontinued Operations
Revenues
Earned insurance premiums									0.1	0.8	10.6
Other revenue									0.0	10.8	0.0
Revenues (including realized gains and losses)									0.1	11.6	10.6
Expenses
Loss and loss adjustment expenses									(0.7)	78.9	48.4
Insurance and reinsurance acquisition expenses									0.1	0.0	(2.1)
Other underwriting expenses									3.5	(0.2)	1.7
Total expenses									2.9	78.7	48.0
Loss from discontinued operations									(2.8)	(67.1)	(37.4)
Income tax benefit									1.0	25.0	13.4
Net loss from discontinued operations, net of tax									(1.8)	(42.1)	(24.0)
(Loss) gain on sale of discontinued operations, net of tax									(1.6)	46.6	(91.0)
Net (loss) income from discontinued operations									$ (3.4)	$ 4.5	$ (115.0)

Discontinued Operations (Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Basic and diluted earnings (loss) per share numerators (in millions):
Allocation of income for participating unvested restricted common shares									$ (4.1)	$ (4.7)	$ (4.3)
Net income attributable to White Mountains’s common shareholders	$ 70.0	$ 51.5	$ 95.6	$ 95.6	$ 117.9	$ 57.2	$ 26.3	$ 120.4	$ 312.7	$ 321.8	$ 207.4
Basic earnings (loss) per share denominators (in thousands):
Total average common shares outstanding during the period									6,104,900	6,200,400	6,799,800
Average unvested restricted common shares									(78,900)	(91,400)	(91,100)
Basic earnings (loss) per share denominator									6,026,000	6,109,000	6,708,700
Diluted earnings (loss) per share denominator (in thousands):
Total average common shares outstanding during the period									6,104,900	6,200,400	6,799,800
Average unvested restricted common shares									(78,900)	(91,400)	(91,100)
Average outstanding dilutive options to acquire common shares									0	0	0
Diluted earnings (loss) per share denominator									6,026,000	6,109,000	6,708,700
Incremental common shares attributable to share-based payment arrangements									125,000
Discontinued Operations
Discontinued Operations
Net (loss) income from discontinued operations									$ (3.4)	$ 4.5	$ (115.0)
Basic and diluted earnings (loss) per share numerators (in millions):
Allocation of income for participating unvested restricted common shares									0.0	0.0	1.5
Net income attributable to White Mountains’s common shareholders									$ (3.4)	$ 4.5	$ (113.5)
Basic earnings (loss) per share denominators (in thousands):
Total average common shares outstanding during the period									6,104,900	6,200,400	6,799,800
Average unvested restricted common shares									(78,900)	(91,400)	(91,100)
Basic earnings (loss) per share denominator									6,026,000	6,109,000	6,708,700
Diluted earnings (loss) per share denominator (in thousands):
Total average common shares outstanding during the period									6,104,900	6,200,400	6,799,800
Average unvested restricted common shares									(78,900)	(91,400)	(91,100)
Average outstanding dilutive options to acquire common shares									0	0	0
Diluted earnings (loss) per share denominator									6,026,000	6,109,000	6,708,700
Basic and diluted earnings (loss) per share (in dollars):									$ (0.56)	$ 0.74	$ (16.91)
Incremental common shares attributable to share-based payment arrangements										125,000

Discontinued Operations Discontinued Operations (Surplus Note Table) (Details) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 23, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions
(Loss) gain on sale of discontinued operations, net of tax	$ (1.6)	$ 46.6	$ (91.0)
OneBeacon Runoff
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Surplus notes				$ 101.0
OneBeacon Runoff \| Other long-term investments \| Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Surplus notes				$ 64.9
OneBeacon Runoff \| Surplus Note
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Percentage of Total Adjusted Capital	200.00%
OneBeacon Runoff \| Surplus Note \| Other long-term investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Interest rate (as a percent)				6.00%
Discontinued Operations
Fair Value, Balance Sheet Grouping, Financial Statement Captions
(Loss) gain on sale of discontinued operations, net of tax	$ (1.6)	$ 46.6	(91.0)
Discontinued Operations \| OneBeacon Runoff
Fair Value, Balance Sheet Grouping, Financial Statement Captions
RBC Score	250.00%
Current Market Rate	$ (6.6)
Regulatory Approval Payment	(12.6)
Liquidity Adjustments	(16.7)
(Loss) gain on sale of discontinued operations, net of tax	(35.9)		$ 91.5
Surplus notes	101.0
Discontinued Operations \| OneBeacon Runoff \| Seller Priority Surplus Note [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Current Market Rate	1.6
Regulatory Approval Payment	(4.6)
Liquidity Adjustments	(11.0)
(Loss) gain on sale of discontinued operations, net of tax	(14.0)
Surplus notes	57.9
Discontinued Operations \| OneBeacon Runoff \| Pari Passu Surplus Note [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Current Market Rate	(8.2)
Regulatory Approval Payment	(8.0)
Liquidity Adjustments	(5.7)
(Loss) gain on sale of discontinued operations, net of tax	(21.9)
Surplus notes	43.1
Discontinued Operations \| OneBeacon Runoff \| Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Surplus notes	65.1
Discontinued Operations \| OneBeacon Runoff \| Fair Value [Member] \| Seller Priority Surplus Note [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Surplus notes	43.9
Discontinued Operations \| OneBeacon Runoff \| Fair Value [Member] \| Pari Passu Surplus Note [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Surplus notes	21.2
Discontinued Operations \| OneBeacon Runoff \| Surplus Note
Fair Value, Balance Sheet Grouping, Financial Statement Captions
(Loss) gain on sale of discontinued operations, net of tax	$ (23.5)

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Revenues (including realized gains and losses)	$ 689.7	$ 589.4	$ 652.8	$ 578.3	$ 626.6	$ 574.1	$ 489.3	$ 627.4	$ 2,510.2	$ 2,317.4	$ 2,435.7
Total expenses	643.5	555.0	543.8	466.2	492.4	518.8	485.7	475.6	2,208.5	1,972.5	2,172.9
Pre-tax loss	46.2	34.4	109.0	112.1	134.2	55.3	3.6	151.8	301.7	344.9	262.8
Tax benefit (expense)	8.7	(7.8)	(23.9)	(30.3)	(27.4)	(8.2)	0.6	(41.6)	(53.3)	(76.6)	15.7
Net income from continuing operations	54.9	26.6	85.1	81.8	106.8	47.1	4.2	110.2	248.4	268.3	278.5
Net loss from discontinued operations, net of tax	(12.2)	6.7	2.6	(0.5)	(0.3)	0.4	3.9	0.5	(1.8)	(42.1)	(24.0)
Non-controlling interest in consolidated subsidiaries	15.0	11.2	(4.6)	0.5	(0.3)	1.1	11.1	0.5	22.1	12.4	14.0
Equity in earnings of unconsolidated affiliates, net of tax	12.3	7.0	12.5	13.8	11.7	8.6	7.1	9.2	45.6	36.6	29.9
Net income attributable to White Mountains’s common shareholders	$ 70.0	$ 51.5	$ 95.6	$ 95.6	$ 117.9	$ 57.2	$ 26.3	$ 120.4	$ 312.7	$ 321.8	$ 207.4
Basic earnings (loss) per share
Continuing operations	$ 13.71	$ 7.35	$ 15.10	$ 15.56	$ 19.14	$ 9.20	$ 3.62	$ 19.10	$ 51.77	$ 51.15	$ 47.41
Discontinued operations	(2.03)	1.10	0.43	(0.08)	(0.05)	0.06	0.64	0.07	(0.56)	0.74	(16.91)
Total consolidated operations	11.68	8.45	15.53	15.48	19.09	9.26	4.26	19.17	51.21	51.89	30.50
Diluted earnings (loss) per share
Continuing operations	13.71	7.35	15.10	15.56	19.14	9.20	3.62	19.10	51.77	51.15	47.41
Discontinued operations	(2.03)	1.10	0.43	(0.08)	(0.05)	0.06	0.64	0.07	(0.56)	0.74	(16.91)
Total consolidated operations	$ 11.68	$ 8.45	$ 15.53	$ 15.48	$ 19.09	$ 9.26	$ 4.26	$ 19.17	$ 51.21	$ 51.89	$ 30.50

SCHEDULE I SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES (Details) $ in Millions	Dec. 31, 2014 USD ($)
Summary of investments other than investments in related parties
Cost	$ 6,499.7
Carrying Value	6,863.1
Fair Value	6,863.1
Fixed maturity investments
Summary of investments other than investments in related parties
Cost	4,653.3
Carrying Value	4,784.3
Fair Value	4,784.3
US Government and agency obligations
Summary of investments other than investments in related parties
Cost	184.7
Carrying Value	188.1
Fair Value	188.1
Debt securities issued by corporations
Summary of investments other than investments in related parties
Cost	2,221.3
Carrying Value	2,311.2
Fair Value	2,311.2
Municipal obligations
Summary of investments other than investments in related parties
Cost	1,811.1
Carrying Value	1,840.9
Fair Value	1,840.9
Mortgage-backed and asset-backed securities
Summary of investments other than investments in related parties
Cost	82.0
Carrying Value	83.2
Fair Value	83.2
Foreign government, agency and provincial obligations
Summary of investments other than investments in related parties
Cost	274.6
Carrying Value	275.1
Fair Value	275.1
Redeemable preferred stocks
Summary of investments other than investments in related parties
Cost	79.6
Carrying Value	85.8
Fair Value	85.8
Short-term investments
Summary of investments other than investments in related parties
Cost	871.7
Carrying Value	871.7
Fair Value	871.7
Common equity securities
Summary of investments other than investments in related parties
Cost	633.6
Carrying Value	801.6
Fair Value	801.6
Banks, trust and insurance companies
Summary of investments other than investments in related parties
Cost	167.0
Carrying Value	233.9
Fair Value	233.9
Public utilities
Summary of investments other than investments in related parties
Cost	7.9
Carrying Value	9.5
Fair Value	9.5
Industrial, miscellaneous and other
Summary of investments other than investments in related parties
Cost	458.7
Carrying Value	558.2
Fair Value	558.2
Convertible fixed maturity and preferred investments
Summary of investments other than investments in related parties
Cost	19.1
Carrying Value	20.5
Fair Value	20.5
Other long-term investments
Summary of investments other than investments in related parties
Cost	322.0
Carrying Value	385.0
Fair Value	385.0
Other long-term investments
Summary of investments other than investments in related parties
Equity Method Investment, Carrying Value	22.5
Carrying value of investment accounted for using the equity method	$ 23.2

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013
Assets
Cash	$ 373.2	$ 382.8
Fixed maturity investments, at fair value	4,784.3	5,030.5
Short-term investments, at amortized cost	871.7	635.9
Other assets	356.1	437.4
Total assets	10,456.9	12,144.3
Liabilities
Debt	746.6	676.4
Other liabilities	341.0	415.7
Total liabilities	5,917.3	7,746.9
White Mountains’s common shareholders’ equity	4,539.6	4,397.4
Total liabilities and equity	10,456.9	12,144.3
White Mountains Insurance Group Ltd.
Assets
Cash	0.2	0.2
Fixed maturity investments, at fair value	0.0	31.8
Short-term investments, at amortized cost	31.0	1.4
Other assets	0.2	0.4
Investments in consolidated and unconsolidated affiliates	4,119.4	3,919.1
Total assets	4,150.8	3,952.9
Liabilities
Debt	0.0	0.0
Payable to subsidiary	161.6	47.0
Other liabilities	(7.4)	0.4
Total liabilities	154.2	47.4
White Mountains’s common shareholders’ equity	3,996.6	3,905.5
Total liabilities and equity	$ 4,150.8	$ 3,952.9

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT (Details 2) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Revenues (including realized gains and losses)	$ 689.7	$ 589.4	$ 652.8	$ 578.3	$ 626.6	$ 574.1	$ 489.3	$ 627.4	$ 2,510.2	$ 2,317.4	$ 2,435.7
Expenses	643.5	555.0	543.8	466.2	492.4	518.8	485.7	475.6	2,208.5	1,972.5	2,172.9
Pre-tax loss	46.2	34.4	109.0	112.1	134.2	55.3	3.6	151.8	301.7	344.9	262.8
Income tax (expense) benefit	8.7	(7.8)	(23.9)	(30.3)	(27.4)	(8.2)	0.6	(41.6)	(53.3)	(76.6)	15.7
Net income from continuing operations	54.9	26.6	85.1	81.8	106.8	47.1	4.2	110.2	248.4	268.3	278.5
Net loss from discontinued operations, net of tax	(12.2)	6.7	2.6	(0.5)	(0.3)	0.4	3.9	0.5	(1.8)	(42.1)	(24.0)
Net income attributable to White Mountains’s common shareholders	70.0	51.5	95.6	95.6	117.9	57.2	26.3	120.4	312.7	321.8	207.4
Comprehensive income attributable to White Mountains’ common shareholders									211.1	242.0	302.6
Computation of net income (loss) available to common shareholders:
Net income attributable to White Mountains’s common shareholders	$ 70.0	$ 51.5	$ 95.6	$ 95.6	$ 117.9	$ 57.2	$ 26.3	$ 120.4	312.7	321.8	207.4
White Mountains Insurance Group Ltd.
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Revenues (including realized gains and losses)									0.3	1.2	20.8
Expenses									32.3	39.0	32.4
Pre-tax loss									(32.0)	(37.8)	(11.6)
Income tax (expense) benefit									0.9	(0.1)	(0.3)
Net income from continuing operations									(31.1)	(37.9)	(11.9)
Net loss from discontinued operations, net of tax									13.9	0.0	0.0
Equity in earnings (losses) from consolidated and unconsolidated affiliates									329.9	359.7	219.3
Net income attributable to White Mountains’s common shareholders									312.7	321.8	207.4
Other comprehensive income (loss), after-tax									(101.6)	(79.8)	95.2
Comprehensive income attributable to White Mountains’ common shareholders									211.1	242.0	302.6
Computation of net income (loss) available to common shareholders:
Net income attributable to White Mountains’s common shareholders									$ 312.7	$ 321.8	$ 207.4

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT (Details 3) - USD ($) $ in Millions	1 Months Ended	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Net income attributable to White Mountains’s common shareholders		$ 70.0	$ 51.5	$ 95.6	$ 95.6	$ 117.9	$ 57.2	$ 26.3	$ 120.4	$ 312.7	$ 321.8	$ 207.4
Charges (credits) to reconcile net income to net cash (used for) provided from operations:
Net realized and unrealized investment gains										(283.9)	(161.7)	(118.2)
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest		12.2	$ (6.7)	$ (2.6)	$ 0.5	0.3	$ (0.4)	$ (3.9)	$ (0.5)	1.8	42.1	24.0
Net change in other assets and liabilities, net										57.1	2.6	(103.5)
Net Cash Provided by (Used in) Operating Activities, Continuing Operations										206.9	(28.7)	(29.6)
Net cash used for discontinued operations										(88.1)	(72.3)	(196.2)
Net cash provided from (used for) operations										118.8	(101.0)	(225.8)
Cash flows from investing activities:
Net decrease in short-term investments										(351.5)	34.8	145.3
Purchases of investment securities										(5,602.1)	(4,635.5)
Sales and maturities of investment securities										6,387.5	4,979.8
Receipt of cash flow from discontinued operations										(88.1)	(72.3)	(196.2)
Net Cash Provided by (Used in) Investing Activities, Continuing Operations										(40.2)	329.5	633.4
Net cash provided from investing activities — discontinued operations										88.1	72.3	196.2
Net cash provided from investing activities										47.9	401.8	829.6
Cash flows from financing activities:
Draw down of revolving line of credit										0.0	200.0	150.0
Repayment of revolving line of credit										(66.5)	(275.0)	(75.0)
Repurchases and retirement of common shares										(128.2)	(79.8)	(669.1)
Dividends paid on common shares										(6.2)	(6.2)	(6.6)
Net cash used for financing activities										(129.6)	(186.5)	(648.2)
Net change in cash during the period										22.8	114.1	(41.3)
Cash balance at beginning of year	$ 326.7	349.5				326.7				349.5	326.7	212.6	$ 251.9
Cash balance at end of year	326.7	349.5				326.7				349.5	326.7	212.6	251.9
Interest Paid										(42.0)	$ (42.6)	(44.6)
Common shares repurchased and retired during the period											1,329,640
OneBeacon Ltd. common shares repurchased and retired										(1.7)	$ 0.0	0.0
Lone Tree Insurance Group Ltd
Cash flows from financing activities:
Cash dividends received on warrants	28.0									29.7
Noncash distribution received	27.9
White Mountains Insurance Group Ltd.
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Net income attributable to White Mountains’s common shareholders										312.7	321.8	207.4
Charges (credits) to reconcile net income to net cash (used for) provided from operations:
Net realized and unrealized investment gains										(0.2)	(0.2)	(11.0)
Undistributed current earnings from subsidiaries										(329.9)	(359.7)	(219.3)
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest										(13.9)	0.0	0.0
Other non-cash reconciling items including restricted share and option amortization										12.9	15.6	22.1
Net change in other assets and liabilities, net										(7.6)	(2.9)	(10.0)
Net Cash Provided by (Used in) Operating Activities, Continuing Operations										(26.0)	(25.4)	(10.8)
Net cash used for discontinued operations										13.9	0.0	0.0
Net cash provided from (used for) operations										(12.1)	(25.4)	(10.8)
Cash flows from investing activities:
Net decrease in short-term investments										(29.6)	7.5	63.3
Purchases of investment securities										(7.6)	(26.2)	(706.2)
Sales and maturities of investment securities										39.4	61.1	2,009.7
Issuance of debt (to) from subsidiaries										144.6	153.9	(121.0)
Repayment of debt (to) from subsidiaries										(30.0)	(10.3)	28.5
Receipt of cash flow from discontinued operations										13.9	0.0	0.0
Payments to subsidiaries										0.0	0.0	(663.0)
Distributions from subsidiaries										29.7	0.1	0.0
Net Cash Provided by (Used in) Investing Activities, Continuing Operations										160.4	186.1	611.3
Net cash provided from investing activities — discontinued operations										(13.9)	0.0	0.0
Net cash provided from investing activities										146.5	186.1	611.3
Cash flows from financing activities:
Draw down of revolving line of credit										65.0	200.0	150.0
Repayment of revolving line of credit										(65.0)	(275.0)	(75.0)
Proceeds from issuances of common shares										0.0	0.0	0.0
Repurchases and retirement of common shares										(128.2)	(79.8)	(669.1)
Dividends paid on common shares										(6.2)	(6.2)	(6.6)
Net Cash Provided by (Used in) Financing Activities, Continuing Operations										(134.4)	(161.0)	(600.7)
Cash Provided by (Used in) Financing Activities, Discontinued Operations										0.0	0.0	0.0
Net cash used for financing activities										(134.4)	(161.0)	(600.7)
Net change in cash during the period										0.0	(0.3)	(0.2)
Cash balance at beginning of year	0.2	0.2				0.2				0.2	0.2	0.5	0.7
Cash balance at end of year	0.2	$ 0.2				$ 0.2				0.2	0.2	0.5	$ 0.7
Interest Paid										$ (0.3)	(2.0)	(12.4)
OneBeacon Ltd. common shares repurchased and retired												$ (663.0)
Fixed maturity investments \| Lone Tree Insurance Group Ltd
Cash flows from financing activities:
Cash dividends received on warrants	27.9
Cash \| Lone Tree Insurance Group Ltd
Cash flows from financing activities:
Cash dividends received on warrants	$ 0.1
Revolving Credit Facility [Member] \| White Mountains Insurance Group Ltd.
Cash flows from financing activities:
Repayment of revolving line of credit											$ (75.0)

SCHEDULE III SUPPLEMENTARY INSURANCE INFORMATION (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
SUPPLEMENTARY INSURANCE INFORMATION
Net investment income	$ 105.0	$ 110.9	$ 153.6
OneBeacon
SUPPLEMENTARY INSURANCE INFORMATION
Deferred acquisition costs	103.2	103.7	123.9
Future policy benefits, losses, claims and loss expenses	1,342.2	1,054.3	1,000.0
Unearned premiums	588.3	544.9	573.8
Other policy claims and benefits payable	0.0	0.0	0.0
Premiums earned	1,177.1	1,120.4	1,132.0
Net investment income	41.7	41.1	53.6
Benefits, claims, losses, and settlement expenses	815.1	622.1	650.0
Amortization of deferred policy acquisition costs	203.3	208.9	249.4
Other operating expenses	179.2	204.8	205.2
Premiums written	1,216.9	1,088.6	1,179.2
Net investment income	41.7	41.1	53.6
Sirius Group
SUPPLEMENTARY INSURANCE INFORMATION
Deferred acquisition costs	69.9	69.3	71.4
Future policy benefits, losses, claims and loss expenses	1,809.8	2,025.0	2,168.9
Unearned premiums	338.6	343.3	350.2
Other policy claims and benefits payable	0.0	0.0	0.0
Premiums earned	873.9	866.4	931.6
Net investment income	41.1	30.3	65.0
Benefits, claims, losses, and settlement expenses	345.3	418.4	543.9
Amortization of deferred policy acquisition costs	193.6	166.5	180.8
Other operating expenses	129.7	126.1	116.4
Premiums written	882.5	876.6	947.7
HG Global-BAM
SUPPLEMENTARY INSURANCE INFORMATION
Deferred acquisition costs	4.0	1.7
Future policy benefits, losses, claims and loss expenses	0.0	0.0
Unearned premiums	27.6	13.2
Other policy claims and benefits payable	0.0	0.0
Premiums earned	1.8	0.5
Net investment income	7.1	5.7
Benefits, claims, losses, and settlement expenses	0.0	0.0
Amortization of deferred policy acquisition costs	2.1	1.5
Other operating expenses	0.4	0.4
Premiums written	16.2	13.6
Other Operations
SUPPLEMENTARY INSURANCE INFORMATION
Deferred acquisition costs	0.0	0.0	0.0
Future policy benefits, losses, claims and loss expenses	7.8	0.0	0.0
Unearned premiums	0.8	0.0	0.0
Other policy claims and benefits payable	0.0	0.0	0.0
Premiums earned	6.1	0.0	0.0
Net investment income	0.2	0.1	0.5
Benefits, claims, losses, and settlement expenses	8.9	0.0	0.0
Amortization of deferred policy acquisition costs	0.8	0.0	0.0
Other operating expenses	0.0	0.0	0.0
Premiums written	5.9	0.0	0.0
Non-insurance [Member] \| Operating Segments
SUPPLEMENTARY INSURANCE INFORMATION
Net investment income	$ 14.9	$ 33.7	$ 32.3

SCHEDULE IV REINSURANCE (Details) - USD ($) $ in Millions	12 Months Ended
SCHEDULE IV REINSURANCE (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Premiums earned
Gross amount	$ 1,433.7
Ceded to other companies	(371.1)
Assumed from other companies	996.3
Net earned premiums	2,058.9	$ 1,987.3	$ 2,063.6
OneBeacon
Premiums earned
Gross amount	1,209.1	1,043.3	1,158.3
Ceded to other companies	(102.9)	(71.4)	(79.1)
Assumed from other companies	70.9	148.5	52.8
Net earned premiums	$ 1,177.1	$ 1,120.4	$ 1,132.0
Percentage of amount assumed to net	6.00%	13.30%	4.70%
Sirius Group
Premiums earned
Gross amount	$ 200.2	$ 174.0	$ 169.9
Ceded to other companies	(251.7)	(246.2)	(226.6)
Assumed from other companies	925.4	938.6	988.3
Net earned premiums	$ 873.9	$ 866.4	$ 931.6
Percentage of amount assumed to net	105.90%	108.30%	106.10%
HG/BAM
Premiums earned
Gross amount	$ 1.8
Ceded to other companies	0.0
Assumed from other companies	0.0
Net earned premiums	$ 1.8
Percentage of amount assumed to net	0.00%
Other Segments
Premiums earned
Gross amount	$ 22.6
Ceded to other companies	(16.5)
Assumed from other companies	0.0
Net earned premiums	$ 6.1	$ 0.0	$ 0.0
Percentage of amount assumed to net	0.00%

SCHEDULE V VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reinsurance recoverable on paid losses: Allowance for reinsurance balances
VALUATION AND QUALIFYING ACCOUNTS
Balance at beginning of period	$ 23.7	$ 35.5	$ 34.4
Charged to costs and expenses	(1.1)	(0.6)	(0.6)
Charged to other accounts	0.0	0.0	0.0
Deductions described	(11.2)	(11.2)	1.7
Balance at end of period	11.4	23.7	35.5
Property and casualty insurance and reinsurance premiums receivable: Allowance for uncollectible accounts
VALUATION AND QUALIFYING ACCOUNTS
Balance at beginning of period	4.0	4.4	3.4
Charged to costs and expenses	(0.2)	1.0	1.1
Charged to other accounts	(1.0)	0.0	0.0
Deductions described	0.1	(1.4)	(0.1)
Balance at end of period	2.9	4.0	$ 4.4
Allowance for Doubtful Accounts [Member]
VALUATION AND QUALIFYING ACCOUNTS
Balance at beginning of period	0.0
Charged to costs and expenses	3.6
Charged to other accounts	0.0
Deductions described	(0.3)
Balance at end of period	$ 3.3	$ 0.0

SCHEDULE VI SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS
Rate at which reserves are discounted (as a percent)	2.50%	3.50%	3.50%
OneBeacon
SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS
Deferred acquisition costs	$ 103.2	$ 103.7	$ 123.9
Reserves for Unpaid Claims and Claims Adjustment Expenses	1,342.2	1,054.3	1,000.0
Discount, if any, deducted in Column C	1.0	3.0	4.6
Unearned Premiums	588.3	544.9	573.8
Earned Premiums	1,177.1	1,120.4	1,132.0
Net investment income	41.7	41.1	53.6
Claims and ClaimsAdjustment ExpensesIncurred Related to, Current Year	725.3	622.1	657.4
Claims and ClaimsAdjustment ExpensesIncurred Related to, Prior Year	89.8	0.0	(7.4)
Amortization of deferred policy acquisition	203.3	208.9	249.4
Paid Claims and Claims Adjustment Expenses	608.6	540.7	565.1
Premiums written	1,216.9	1,088.6	1,179.2
Sirius Group
SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS
Deferred acquisition costs	69.9	69.3	71.4
Reserves for Unpaid Claims and Claims Adjustment Expenses	1,809.8	2,025.0	2,168.9
Discount, if any, deducted in Column C	0.7	1.7	2.4
Unearned Premiums	338.6	343.3	350.2
Earned Premiums	873.9	866.4	931.6
Net investment income	41.1	30.3	65.0
Claims and ClaimsAdjustment ExpensesIncurred Related to, Current Year	443.2	466.8	578.4
Claims and ClaimsAdjustment ExpensesIncurred Related to, Prior Year	(98.0)	(48.4)	(34.5)
Amortization of deferred policy acquisition	193.6	166.5	180.8
Paid Claims and Claims Adjustment Expenses	544.9	628.1	741.2
Premiums written	882.5	876.6	947.7
Other Operations
SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS
Deferred acquisition costs	0.0	0.0	0.0
Reserves for Unpaid Claims and Claims Adjustment Expenses	7.8	0.0	0.0
Discount, if any, deducted in Column C	0.0	0.0	0.0
Unearned Premiums	0.0	0.0	0.0
Earned Premiums	0.8	0.0	0.0
Net investment income	0.2	0.0	0.0
Claims and ClaimsAdjustment ExpensesIncurred Related to, Current Year	6.7	0.0	0.0
Claims and ClaimsAdjustment ExpensesIncurred Related to, Prior Year	2.2	0.0	0.0
Amortization of deferred policy acquisition	0.0	0.0	0.0
Paid Claims and Claims Adjustment Expenses	14.8	0.0	0.0
Premiums written	$ 5.9	$ 0.0	$ 0.0

Label	Element	Value
Auto One [Member]
Liability for Unpaid Claims and Claims Adjustment Expense, Net	us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	$ (383,300,000)