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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2011	Feb. 27, 2012	Jun. 30, 2011
Document and Entity Information
Entity Registrant Name	WHITE MOUNTAINS INSURANCE GROUP LTD
Entity Central Index Key	0000776867
Document Type	10-K
Document Period End Date	Dec. 31, 2011
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			$ 2,888,052,532
Entity Common Stock, Shares Outstanding		7,454,585
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	FY

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010
Assets
Fixed maturity investments, at fair value	$ 6,221.9	$ 5,786.1
Short-term investments, at amortized cost (which approximates fair value)	846.0	975.3
Common equity securities, at fair value	755.0	667.0
Convertible fixed maturity investments, at fair value	143.8	143.0
Other long-term investments	301.3	372.1
Total investments	8,268.0	7,943.5
Cash (restricted $453.5 and $286.7)	705.4	395.0
Reinsurance recoverable on unpaid losses	2,507.3	2,344.0
Reinsurance recoverable on paid losses	30.5	63.1
Insurance and reinsurance premiums receivable	489.2	532.5
Funds held by ceding companies	106.5	118.7
Investments in unconsolidated affiliates	275.3	389.7
Deferred acquisition costs	187.0	176.1
Deferred tax asset	536.9	431.9
Ceded unearned insurance and reinsurance premiums	87.3	184.0
Accrued investment income	51.4	63.3
Accounts receivable on unsettled investment sales	4.7	39.5
Other assets	681.9	730.0
Assets held for sale	132.6	1,122.8
Total assets	14,064.0	14,534.1
Liabilities
Loss and loss adjustment expense reserves	5,702.3	5,736.8
Unearned insurance and reinsurance premiums	846.9	938.7
Variable annuity benefit guarantee	768.5	610.2
Debt	671.2	818.8
Deferred tax liability	365.5	373.2
Accrued incentive compensation	187.9	157.4
Funds held under reinsurance treaties	42.9	85.8
Ceded reinsurance payable	134.6	221.1
Accounts payable on unsettled investment purchases	34.6	22.3
Other liabilities	534.1	557.5
Liabilities held for sale	107.6	751.5
Total liabilities	9,396.1	10,273.3
White Mountains' common shareholders' equity
White Mountains' common shares at $1 par value per share-authorized 50,000,000 shares; issued and outstanding 7,577,855 and 8,194,925 shares	7.6	8.2
Paid-in surplus	1,253.7	1,350.8
Retained earnings	2,789.7	2,175.6
Accumulated other comprehensive income (loss), after-tax:
Equity in unrealized gains (losses) from investments in unconsolidated affiliates		58.5
Net unrealized foreign currency translation gains	46.1	61.4
Pension liability and other	(9.4)	(1.5)
Total White Mountains' common shareholders' equity	4,087.7	3,653.0
Noncontrolling interests
Noncontrolling interest-OneBeacon, Ltd.	273.1	295.0
Noncontrolling interest-SIG Preference Shares	250.0	250.0
Noncontrolling interest-consolidated limited partnerships and A.W.G Dewar	57.1	62.8
Total noncontrolling interests	580.2	607.8
Total equity	4,667.9	4,260.8
Total liabilities and equity	$ 14,064.0	$ 14,534.1

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010
CONSOLIDATED BALANCE SHEETS
Cash restricted (in dollars)	$ 453.5	$ 286.7
Common shares, par value per share (in dollars per share)	$ 1	$ 1
Common shares, authorized shares	50,000,000	50,000,000
Common shares, issued shares	7,577,855	8,194,925
Common shares, outstanding shares	7,577,855	8,194,925

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues
Earned insurance and reinsurance premiums	$ 1,927.8	$ 2,251.8	$ 2,717.6
Net investment income	184.5	208.9	250.1
Net realized and unrealized investment gains	122.8	82.6	361.7
Other revenue	(57.0)	23.4	113.9
Total revenues	2,178.1	2,566.7	3,443.3
Expenses
Loss and loss adjustment expenses	1,206.9	1,389.2	1,424.1
Insurance and reinsurance acquisition expenses	400.0	479.1	547.2
Other underwriting expenses	279.1	332.9	406.6
General and administrative expenses	175.3	155.1	197.4
Interest expense on debt	55.2	57.3	70.8
Total expenses	2,116.5	2,413.6	2,646.1
Pre-tax income	61.6	153.1	797.2
Income tax benefit (expense)	122.7	(16.9)	(214.2)
Net income from continuing operations	184.3	136.2	583.0
Gain on sale of Esurance and AFI, net of tax	677.5
Loss on sale of AutoOne, net of tax	(19.2)
Net loss from discontinued operations, net of tax	(13.0)	(6.6)	(27.8)
Income before equity in earnings of unconsolidated affiliates	829.6	129.6	555.2
Equity in (losses) earnings of unconsolidated affiliates	(20.2)	9.9	24.3
Net income	809.4	139.5	579.5
Net income attributable to noncontrolling interests	(41.5)	(53.0)	(109.5)
Net income attributable to White Mountains' common shareholders	767.9	86.5	470.0
Change in equity in net unrealized (losses) gains from investments in unconsolidated affiliates, net of tax	(58.5)	73.5	192.4
Change in foreign currency translation, net of tax	(15.2)	49.8	73.0
Net change in pension liability and other, net of tax	(10.8)	6.3	19.1
Comprehensive income	683.4	216.1	754.5
Comprehensive loss (income) attributable to noncontrolling interests	2.8	(1.7)	(3.7)
Comprehensive income attributable to White Mountains' common shareholders	$ 686.2	$ 214.4	$ 750.8
Basic earnings (loss) per share
Continuing operations (in dollars per share)	$ 15.56	$ 10.89	$ 56.25
Discontinued operations (in dollars per share)	81.88	(0.77)	(3.14)
Total consolidated operations (in dollars per share)	97.44	10.12	53.11
Diluted earnings (loss) per share
Continuing operations (in dollars per share)	15.56	10.89	56.24
Discontinued operations (in dollars per share)	81.88	(0.77)	(3.14)
Total consolidated operations (in dollars per share)	97.44	10.12	53.10
Dividends declared and paid per White Mountains' common share (in dollars per share)	$ 1.00	$ 1.00	$ 1.00

CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY - USD ($) $ in Millions	Total	White Mountains' Common Shareholders' Equity	Common shares and paid-in surplus	Retained earnings	Accum. other comprehensive income (loss), after-tax	Noncontrolling interest
Balances at Dec. 31, 2008		$ 2,898.8	$ 1,428.2	$ 1,751.9	$ (281.3)	$ 613.7
Increase (Decrease) in Shareholders' Equity
Cumulative effect adjustment \| Symetra FAS115-2				2.9	(2.9)
Net income	$ 579.5	470.0		470.0		109.5
Net change in unrealized gains (losses) from investments in unconsolidated affiliates	192.4	192.4			192.4
Net change in foreign currency translation	73.0	73.0			73.0
Net change in pension liability and other accumulated comprehensive items	19.1	15.3			15.3	3.7
Dividends declared on common shares	(8.9)	(8.9)		(8.9)
Dividends/distributions to noncontrolling interests						(38.4)
Issuances of common shares		0.9	0.9
Repurchase and retirement of common shares		(0.4)	(0.4)
Distributions to noncontrolling interests in limited partnerships						(5.0)
Contributions from noncontrolling interests in OneBeacon						0.3
Amortization of restricted share and option awards		16.3	16.3			0.3
Balances at Dec. 31, 2009		3,657.4	1,445.0	2,215.9	(3.5)	684.1
Increase (Decrease) in Shareholders' Equity
Cumulative effect adjustment \| ASU 2009-17		(0.4)		(0.4)		(22.8)
Tax basis change due to intercompany transfer		(10.4)		(4.4)	(6.0)
Net income	139.5	86.5		86.5		53.0
Net change in unrealized gains (losses) from investments in unconsolidated affiliates	73.5	73.5			73.5
Net change in foreign currency translation	49.8	49.8			49.8
Net change in pension liability and other accumulated comprehensive items	6.3	4.6			4.6	1.7
Dividends declared on common shares	(8.8)	(8.8)		(8.8)
Dividends/distributions to noncontrolling interests						(94.7)
Issuances of common shares		0.7	0.7
Repurchase and retirement of common shares	(222.0)	(225.6)	(112.4)	(113.2)
Distributions to noncontrolling interests in limited partnerships						(13.6)
Amortization of restricted share and option awards		25.7	25.7			0.1
Balances at Dec. 31, 2010	4,260.8	3,653.0	1,359.0	2,175.6	118.4	607.8
Increase (Decrease) in Shareholders' Equity
Net income	809.4	767.9		767.9		41.5
Net change in unrealized gains (losses) from investments in unconsolidated affiliates	(58.5)	(58.5)			(58.5)
Net change in foreign currency translation	(15.2)	(15.2)			(15.2)
Net change in pension liability and other accumulated comprehensive items	(10.8)	(8.0)			(8.0)	(2.8)
Dividends declared on common shares		(8.0)		(8.0)
Dividends/distributions to noncontrolling interests						(61.5)
Issuances of common shares		0.9	0.9
Repurchase and retirement of common shares	(114.2)	(253.0)	(107.2)	(145.8)
Distributions to noncontrolling interests in limited partnerships						(8.6)
Amortization of restricted share and option awards		12.0	12.0			0.4
Noncontrolling interest attributable to intercompany sale of subsidiary		(3.4)	(3.4)			3.4
Balances at Dec. 31, 2011	$ 4,667.9	$ 4,087.7	$ 1,261.3	$ 2,789.7	$ 36.7	$ 580.2

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flows from operations:
Net income	$ 809.4	$ 139.5	$ 579.5
Charges (credits) to reconcile net income to net cash (used for) provided from operations:
Net realized and unrealized investment (gains) losses	(122.8)	(82.6)	(361.7)
Excess of fair value of acquired net assets over cost	(7.2)	(12.8)
Deferred income tax (benefit) expense	(80.6)	58.0	170.0
Undistributed equity in earnings from unconsolidated affiliates, after-tax	20.2	(9.9)	(24.3)
Net loss from discontinued operations	13.0	6.6	27.8
Net loss on sale of discontinued operation - AutoOne	19.2
Net gain on sale of discontinued operation - Esurance	(677.5)
Other operating items:
Net change in loss and loss adjustment expense reserves	35.2	(466.0)	(731.4)
Net change in reinsurance recoverable on paid and unpaid losses	(134.0)	361.8	306.2
Net change in unearned insurance and reinsurance premiums	(48.6)	(161.3)	(132.2)
Net change in ceded reinsurance premiums payable	(85.9)	120.1	(20.2)
Net change in ceded unearned insurance and reinsurance premiums	94.2	(89.8)	13.3
Net change in insurance and reinsurance premiums receivable	42.4	131.9	71.4
Net change in variable annuity benefit guarantee liabilities	158.3	229.5	(86.4)
Net change in deferred acquisition costs	(14.5)	57.9	25.4
Net change in funds held by ceding companies	11.6	53.7	62.9
Net change in funds held under reinsurance treaties	(42.3)	(85.1)	10.3
Net change in other assets and liabilities, net	(96.5)	(238.6)	27.5
Net cash (used for) provided from operations - continuing operations	(106.4)	12.9	(61.9)
Net cash (used for) provided from operations - discontinued operations	(8.1)	43.1	15.2
Net cash (used for) provided from operations	(114.5)	56.0	(46.7)
Cash flows from investing activities:
Net change in short-term investments	174.5	475.6	218.4
Sales of fixed maturity and convertible fixed maturity investments	3,481.9	2,447.8	2,121.9
Maturities, calls and paydowns of fixed maturity and convertible fixed maturity investments	1,163.6	1,744.1	1,206.9
Sales of common equity securities	237.8	167.5	300.8
Distributions and redemptions of other long-term investments	150.7	133.2	118.9
Sales of consolidated and unconsolidated affiliates, net of cash sold	1,010.6	188.3
Contributions to other long-term investments	(65.8)	(111.1)	(25.2)
Distributions from (contributions to) discontinued operations	28.7	(32.1)	(123.1)
Purchases of common equity securities	(297.8)	(273.6)	(190.1)
Purchases of fixed maturity and convertible fixed maturity investments	(5,200.6)	(4,217.7)	(3,296.5)
Purchases of consolidated and unconsolidated affiliates, net of cash acquired	(3.2)	(4.9)
Net change in unsettled investment purchases and sales	47.0	1.6	52.1
Net acquisitions of property and equipment	(5.5)	(5.8)	(7.6)
Net cash provided from investing activities - continuing operations	721.9	512.9	376.5
Net cash provided from (used for) investing activities - discontinued operations	77.7	(27.6)	(11.4)
Net cash provided from investing activities	799.6	485.3	365.1
Cash flows from financing activities:
Repayment of debt		(14.0)	(242.8)
Repurchase of debt	(161.6)	(197.3)	(63.1)
Settlement of interest rate swap associated with Mortgage Note			(7.5)
Capital lease obligation	23.1
Cash dividends paid to the Company's common shareholders	(8.0)	(8.8)	(8.9)
Cash dividends paid to OneBeacon Ltd.'s noncontrolling common shareholders	(42.8)	(75.9)	(19.6)
Cash dividends paid on SIG Preference Shares	(18.8)	(18.8)	(18.8)
Common shares repurchased	(253.0)	(225.6)	(0.4)
OneBeacon Ltd. common shares repurchased and retired		(10.5)
Proceeds from issuances of common shares	0.9	0.7	0.9
Net cash used for financing activities - continuing operations	(460.2)	(550.2)	(360.2)
Net cash provided from financing activities - discontinued operations	0.0
Net cash used for financing activities	(460.2)	(550.2)	(360.2)
Effect of exchange rate changes on cash	(1.5)	8.1	6.8
Net increase (decrease) in cash during year	223.4	(0.8)	(35.0)
Net decrease in cash from discontinued operations	(69.6)	(15.5)	(3.8)
Cash reclassified to assets held for sale	(5.5)
Cash balance at beginning of year (excludes restricted cash balances of $286.7, $217.1 and $225.7 and AutoOne cash of $4.7, $3.9 and $3.5)	103.6	119.9	158.7
Cash balance at end of year (excludes restricted cash balances of $453.5, $286.7and $217.1 and AutoOne cash of $0, $4.7 and $3.9)	$ 251.9	$ 103.6	$ 119.9

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
CONSOLIDATED STATEMENTS OF CASH FLOWS
Restricted cash balances, beginning of period	$ 286.7	$ 217.1	$ 225.7
Restricted cash balances, end of period	453.5	286.7	217.1
AutoOne Cash, beginning of period	4.7	3.9	3.5
AutoOne Cash, end of period	$ 0.0	$ 4.7	$ 3.9

- Definition

For the disposal group, including a component of the entity (discontinued operation), cash includes currency on hand as well as demand deposits with banks or financial institutions. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

+ References + Details

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2011

Summary of Significant Accounting Policies

Summary of Significant Accounting Policies

NOTE 1. Summary of Significant Accounting Policies

Basis of presentation

The accompanying consolidated financial statements include the accounts of White Mountains Insurance Group, Ltd. (the “Company” or the “Registrant”) and its subsidiaries (collectively with the Company, “White Mountains”) and have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”). The Company is an exempted Bermuda limited liability company whose principal businesses are conducted through its property and casualty insurance and reinsurance 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’ reportable segments are OneBeacon, Sirius Group and Other Operations. As discussed further in Note 2, on October 7, 2011 White Mountains completed its sale of Esurance Holdings, Inc. and its subsidiaries (“Esurance Insurance”) and Answer Financial Inc. and its subsidiaries (“AFI”) (collectively, “Esurance”). Esurance is presented as discontinued operations and assets and liabilities held for sale in the financial statements. Prior year amounts have been reclassified to conform to the current year’s presentation. (See Note 20 for discontinued operations and assets and liabilities held for sale).

The OneBeacon segment consists of OneBeacon Insurance Group, Ltd. (“OneBeacon Ltd.”), an exempted Bermuda limited liability company that owns a family of U.S. based property and casualty insurance companies (collectively “OneBeacon”), most of which operate in a multi-company pool. 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. During 2006, White Mountains sold 27.6 million, or 27.6%, of OneBeacon Ltd.’s common shares in an initial public offering (the “OneBeacon Offering”). As of December 31, 2011 and 2010, White Mountains owned 75.5% and 76.0% of OneBeacon Ltd.’s outstanding common shares. As discussed further in Note 2, OneBeacon entered into a definitive agreement on August 30, 2011 to sell the AutoOne business (“AutoOne”). Accordingly, effective as of December 31, 2011, AutoOne is presented as discontinued operations and assets and liabilities held for sale in the financial statements (see Note 20). Prior year income statement and cash flow amounts have been reclassified to conform to the current year’s presentation. The sale of AutoOne closed in February 2012.

The Sirius Group segment (previously defined as the White Mountains Re segment) consists of Sirius International Insurance Group, Ltd. (formerly White Mountains Re Ltd.), an exempted Bermuda limited liability company, and its subsidiaries (collectively, “Sirius Group”). During the fourth quarter of 2011, White Mountains completed a rebranding and reorganization (the “Reorganization”) of its reinsurance business. Under the Reorganization, White Mountains’ reinsurance businesses adopted the Sirius name globally and Sirius America Insurance Company (“Sirius America,” formerly WMRe America) became a wholly owned subsidiary of Sirius International Insurance Corporation (“Sirius International,” formerly WMRe Sirius).

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 subsidiaries, Sirius International and Sirius America, and Lloyds Syndicate 1945 (“Syndicate 1945”). Sirius Group also specializes in the acquisition and management of run-off insurance and reinsurance companies both in the United States and internationally through its White Mountains Solutions division. On December 30, 2011, Sirius Group completed a transaction led by White Mountains Solutions to acquire the run-off loss reserve portfolio of Old Lyme Insurance Company Ltd. (“Old Lyme”). Sirius Group also includes Scandinavian Reinsurance Company, Ltd. (“Scandinavian Re”), which is in run-off, and Central National Insurance Company of Omaha (“Central National”), which was acquired during the first quarter of 2010 and is in run-off.

White Mountains’ Other Operations segment consists of the Company and its intermediate holding companies, its wholly-owned investment management subsidiary, White Mountains Advisors LLC (“WM Advisors”), the consolidated results of the Tuckerman Capital, LP fund (“Tuckerman Fund I”), White Mountains’ variable annuity reinsurance business, White Mountains Life Reinsurance (Bermuda) Ltd. (“WM Life Re”), which is in run-off, as well as various other entities not included in other segments.

White Mountains’ discontinued operations consist of Esurance Insurance, AFI and AutoOne. Esurance Insurance wrote personal auto insurance directly to customers in 30 states through its website and over the phone and also sold other lines of personal insurance for unaffiliated insurance companies. Esurance Insurance also wrote personal auto policies through select online agents and provided other insurance products through partnerships with industry leading online providers. Esurance Insurance earned commissions and fees by referring to unaffiliated insurance companies those shoppers that it could not underwrite because of pricing or underwriting eligibility. AFI is one of the largest independent personal insurance agencies in the United States. AFI sold insurance online and through call centers for both Esurance Insurance and unaffiliated companies utilizing a comparison quoting platform. AutoOne was formed by OneBeacon in 2001 to provide products and services to automobile assigned risk markets primarily in New York and New Jersey.

All significant intercompany transactions have been eliminated in consolidation. 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. Certain amounts in the prior period financial statements have been reclassified to conform to the current presentation.

Significant Accounting Policies

Investment securities

At December 31, 2011, White Mountains’ invested assets consisted of securities and other investments held for general investment purposes. White Mountains’ 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 accreted to income over the anticipated life of the investment.

White Mountains’ invested assets that are measured at fair value include fixed maturity securities, common and preferred equity securities, convertible fixed maturity securities 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, 2011 and 2010, approximately 95% and 93% 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 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’ 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 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, matrix pricing, 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 a 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 million from the expected price based on these procedures are considered outliers. In circumstances where the results of White Mountains’ review process do not appear to support the market price provided by the pricing services, White Mountains challenges the price. During the past year, four securities fell outside White Mountains’ variance thresholds, 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’ 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, 2011 and December 31, 2010.

Other long-term investments

White Mountains’ other long-term investments comprise primarily of hedge funds and private equity funds. White Mountains made the fair value election for most of its investments in hedge funds and private equity interests. For the hedge fund and private equity investments for which White Mountains has made the fair value election, changes in fair value are reported in revenues on a pre-tax basis. For those hedge fund and private equity 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.

Warrants

White Mountains holds warrants to acquire common shares of Symetra which are included as investments in unconsolidated affiliates. 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. The Symetra warrants held by White Mountains are entitled to dividends declared to common shareholders. 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 has considered the effect of counterparty credit risk in determining the fair value of its derivative contracts and its GMAB and GMDB liabilities for the years ended December 31, 2011 and 2010.

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 8).

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 over the applicable premium recognition period as 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 adjustments resulting there from 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 (4.5% and 5.0% at December 31, 2011 and 2010). As of December 31, 2011 and 2010, the discount on OneBeacon’s workers compensation loss and LAE reserves amounted to $108.3 million and $119.4 million.

In connection with purchase accounting for the OneBeacon Acquisition, White Mountains was required to adjust to fair value OneBeacon’s loss and LAE reserves and the related reinsurance recoverables by $646.9 million and $346.9 million, respectively, on OneBeacon’s acquired balance sheet as of June 1, 2001. This net reduction to loss and LAE reserves of $300.0 million is being accreted through an income statement charge ratably with and over the period the claims are settled (See Note 3).

In connection with purchase accounting for Sirius International, White Mountains was required to adjust to fair value the loss and LAE reserves on Sirius International’s acquired balance sheet by $58.1 million. This fair value adjustment is being accreted through an income statement charge ratably with and over the period the claims are settled (See Note 3).

White Mountains’ 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 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 reinsurance treaties represent contractual payments due to the reinsurer that White Mountains has retained to secure obligations of the reinsurer. 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.

Mandatory Shared Market Mechanisms

As a condition to its licenses to do business in certain states, White Mountains’ 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’ insurance subsidiaries record 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. At December 31, 2011 and 2010, White Mountains had unamortized deferred software costs of $22.8 million and $18.1 million.

Federal and foreign income taxes

The majority of White Mountains’ 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’ 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 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, 2011 and 2010, White Mountains had unrealized foreign currency translation gains of $46.1 million and $61.4 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 2011	Closing Rate 2011	Opening Rate 2010	Closing Rate 2010
Swedish kronor	6.7030	6.8645	7.1280	6.7030
British pound	.6420	.6434	.6191	.6420
Canadian dollar	.9981	1.0193	1.0485	.9981

Noncontrolling Interest

Noncontrolling interests consist of the ownership interests of noncontrolling shareholders in consolidated subsidiaries, and are presented separately on the balance sheet. The portion of comprehensive income attributable to noncontrolling interests is presented net of related income taxes in the statement of operations and comprehensive income. The percentage of the noncontrolling shareholders’ ownership interest in OneBeacon Ltd. at December 31, 2011 and December 31, 2010 was 24.5% and 24.0%.

On May 24, 2007, Sirius International Group, Ltd. (“SIG”), an intermediate holding company of Sirius Group, 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 3.20% 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. 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 noncontrolling interest on the balance sheet and as noncontrolling interest expense on the statement of income and comprehensive income.

At December 31, 2011 and 2010, the noncontrolling equity interest in White Mountains, consolidated limited partnerships was $54.8 million and $59.7 million. At December 31, 2011 and 2010, the noncontrolling equity interest in A.W.G. Dewar Inc, a subsidiary of OneBeacon, was $2.3 million and $3.1 million.

Recently Adopted Changes in Accounting Principles

Transfers of Financial Assets and Amendments to FIN 46R

On June 12, 2009, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2009-16, Accounting for Transfers of Financial Assets, an amendment of FASB Statement No. 140 (included in ASC 860) and ASU 2009-17, Amendments to FIN46(R) (included in ASC 810). Both ASU 2009-16 and ASU 2009-17 became effective as of the beginning of the first annual reporting period that began after November 15, 2009. White Mountains adopted the new guidance on January 1, 2010.

ASU 2009-16 eliminates the concept of a qualifying special-purpose entity (“QSPE”). Under the new guidance, the appropriateness of de-recognition of assets held by an entity formerly considered a QSPE is evaluated based on whether or not the transferor has surrendered control of the transferred assets. The evaluation must consider any continuing involvement by the transferor. White Mountains did not have any entities that were considered a QSPE under guidance prior to the amendments to ASC 860 and there was no effect resulting from adoption.

ASU 2009-17 amends ASC 810-10 to clarify the application of consolidation accounting for entities for which the controlling financial interest might not be solely indentified through voting rights. Under the new guidance a variable interest represents a controlling financial interest in a variable interest entity (“VIE”) when it has both of the following: (1) the power to direct the activities of a variable interest entity that most significantly impact the entity’s economic performance and (2) the obligation to absorb losses of the entity that could potentially be significant to the VIE or the right to receive benefits from the entity that could potentially be significant to the VIE. A reporting entity must assess whether it has an implicit financial responsibility to ensure that a VIE operates as designed when determining if it has the power to direct the activities of the VIE that most significantly affect the entity’s economic performance. ASC 810-10 as amended requires ongoing reassessments of whether a reporting entity is the primary beneficiary of a VIE.

Upon adoption, White Mountains determined that its ownership interest in Tuckerman Fund II did not meet the criteria for consolidation under the revised guidance for variable interest entities and, accordingly, effective January 1, 2010, White Mountains deconsolidated its investment in Tuckerman Fund II. Upon deconsolidation, White Mountains made the fair value election for its investment in Tuckerman Fund II and recognized an adjustment to decrease opening retained earnings by $0.4 million.

Other-Than-Temporary Impairments

On June 30, 2009, White Mountains adopted FASB Staff Position (“FSP”) FSP FAS 115-2 and FAS 124-2, Recognition and Presentation of Other-Than-Temporary Impairments (included in ASC 320-10), which amends the guidance for other-than temporary impairments for debt securities classified as held-to-maturity (“HTM”) or available-for-sale (“AFS”). FSP FAS 115-2 and FAS 124-2 requires that, when evaluating whether an impairment of a debt security is other than temporary, the reporting entity is to assess whether it has the intent the sell the security or if it is more likely than not that it will be required to sell the security before the recovery of its amortized cost basis. In addition, if the present value of cash flows expected to be collected is less than the amortized cost of the security, a credit loss is deemed to exist and the security is considered to be other than temporarily impaired. The portion of the impairment loss related to a credit loss is to be recognized in earnings. The portion of the impairment loss related to factors other than credit loss is recognized as an unrealized loss.

White Mountains has made the fair value election for its investments in debt securities and, accordingly, all changes in the fair value of its debt securities are recognized in earnings regardless of whether such changes in fair value represent a temporary or other than temporary decline in value. As a result, adoption of FSP FAS 115-2 and FAS 124-2 did not impact White Mountains’ method of accounting for its portfolio of investment securities. However, White Mountains’ investment in Symetra Financial Corporation (“Symetra”) is accounted for under the equity method. Symetra adopted FSP FAS 115-2 and FAS 124-2 as of March 31, 2009. Upon adoption, Symetra recognized a cumulative effect adjustment to the opening balance of retained earnings with a corresponding adjustment to accumulated other comprehensive income. As a result, White Mountains recorded a $2.9 million cumulative effect adjustment to retained earnings and other comprehensive income, which represents its portion of the cumulative effect adjustment recorded by Symetra.

Recent Accounting Pronouncements

Policy Acquisition Costs

On October 13, 2010, the FASB issued ASU 2010-26, Accounting for Costs Associated with Acquiring or Renewing Insurance Contracts (ASC 944). The new standard changes the types of policy acquisition costs that are eligible for deferral. Specifically, the new guidance limits deferrable costs to those that are incremental direct costs of contract acquisition and certain costs related to acquisition activities performed by the insurer, such as underwriting, policy issuance and processing, medical and inspection costs and sales force contract selling. The ASU defines incremental direct costs as those costs that result directly from and were essential to the contract acquisition and would not have been incurred absent the acquisition. Accordingly, under the new guidance, deferrable acquisition costs are limited to costs related to successful contract acquisitions. Acquisition costs that are not eligible for deferral are to be charged to expense in the period incurred.

ASU 2010-26 is effective for interim periods and annual fiscal years beginning after December 15, 2011 and may be applied prospectively or retrospectively. White Mountains will adopt ASU 2010-26 prospectively. The adoption will not have a material effect on its financial position, results of operations or cash flows.

Fair Value Measurements

On May 12, 2011, the FASB issued ASU 2011-04, Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRS. The ASU clarifies existing guidance with respect to the concepts of highest and best use and valuation premise and measuring instruments classified within a reporting entity’s shareholders’ equity. The ASU also clarifies disclosure requirements, requiring disclosure of quantitative information about unobservable inputs used in Level 3 fair value measurements. The ASU also amends existing guidance. In circumstances where a reporting entity manages a portfolio of financial assets and liabilities based on the net market and counterparty credit risk exposures, the ASU permits determination of the fair value of those instruments to be based on the net risk exposure. In addition, the ASU permits the application of premiums or discounts to be applied in a fair value measurement to the extent that market participants would consider them in valuing the financial instruments. The ASU also expands the required disclosures for Level 3 measurements, requiring that reporting entities provide a narrative description of the sensitivity of Level 3 fair value measurements to changes in unobservable inputs and the interrelationships between those inputs, if any. ASU 2011-04 is effective for interim and annual periods beginning after December 15, 2011. White Mountains is currently evaluating the effect the adoption of ASU 2011-04 will have on its financial position and results of operations.

Offsetting Assets and Liabilities

On December 16, 2011, the FASB issued ASU 2011-11, Disclosures about Offsetting Assets and Liabilities (ASC 210).The new standard expands the required disclosures in circumstance where either balances have been offset or the right of offset exists. The required disclosures are intended to provide information to enable financial statement users to evaluate the effect or potential effect of netting arrangements on a reporting entity’s financial position. Disclosures required under the new standard include the gross amount of assets and liabilities recognized; the amounts that have been offset to arrive at the amounts presented in the statement of financial position; and any amounts subject to an enforceable master netting arrangement, whether or not such amounts have been offset. In addition, a description of the rights of set off should be disclosed. ASU 2011-11 is effective for periods beginning on or after January 1, 2013. White Mountains is party to master netting arrangements in connection with the derivative instruments held by WM Life Re and is currently evaluating the effect of adoption will have on its disclosures, but does not expect adoption to have a material effect on its financial position, results of operations or cash flows.

Comprehensive Income

On June 16, 2011, the FASB issued ASU 2011-05, Comprehensive Income which requires all components of comprehensive income to be reported in a continuous financial statement or in two consecutive statements displaying the components of net income and the components of other comprehensive income. The ASU also requires presentation of reclassification adjustments from other comprehensive income to net income on the face of the financial statements. ASU 2011-05 is effective for fiscal years beginning after December 15, 2011. On December 23, 2011, the FASB issued ASU 2011-12, Comprehensive Income which amends ASU 2011-05 to delay indefinitely the effective date of the guidance related to reclassification adjustments. White Mountains already presents comprehensive income in a continuous financial statement.

Significant Transactions

12 Months Ended

Dec. 31, 2011

Significant Transactions

Significant Transactions

NOTE 2. Significant Transactions

Sale of Esurance

On October 7, 2011, White Mountains completed the sale of Esurance Insurance and AFI to The Allstate Corporation (“Allstate”) for $700 million in excess of tangible book value. White Mountains recorded a gain on the sale of $677.5 million in discontinued operations. The transaction is subject to a true-up of the estimated tangible book value of the entities sold through the date of closing and certain other contingencies (see Note 19).

Tender Offers

During 2011, White Mountains completed two “modified Dutch auction” self-tender offers and repurchased 332,346 of its common shares at an average price of $418 per share. The total cost of the share repurchases was $138.8 million, including fees and expenses related to the tender offers.

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”). The transaction closed in February 2012. 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 business, and transferred substantially all of the AutoOne infrastructure including systems and office space as well as certain staff. As a result of entering into the Purchase Agreement, AutoOne is now reported as discontinued operations (see Note 20).

During the year ended 2011, OneBeacon recorded a loss of $19.2 million, net of a tax benefit of $10.4 million, reflecting the estimated loss on sale of the AutoOne business.

Acquisition of Old Lyme

On December 30, 2011, Sirius Group acquired the run-off loss reserve portfolio of Old Lyme, a Bermuda-based reinsurer in run-off, for $6.0 million in cash and a purchase note for $2.1 million (see Note 6). The transaction resulted in a gain of $7.2 million recorded in other revenues.

OneBeacon Personal Lines and Commercial Lines Sales

In July 2010, OneBeacon completed the sale of its traditional personal lines business (the “Personal Lines Transaction”) to Tower Group, Inc. (“Tower”). The Personal Lines Transaction included two insurance companies, York Insurance Company of Maine (“York”) and Massachusetts Homeland Insurance Company (“MHIC”), through which the majority of the traditional personal lines business was written on a direct basis. Subsequent to the transaction, OneBeacon cedes to Tower, on a 100% quota share basis, traditional personal lines business not directly written by York and MHIC; and OneBeacon assumes, on a 100% quota share basis, certain specialty lines business written directly by York. The Personal Lines Transaction also included two attorneys-in-fact managing the reciprocal insurance exchanges (“reciprocals”) that wrote the traditional personal lines business in New York and New Jersey, the surplus notes issued by the New York and New Jersey reciprocals, and the remaining renewal rights to certain other traditional personal lines insurance policies. The sale of the two attorneys-in-fact and the transfer of the surplus notes triggered deconsolidation of the reciprocals by White Mountains. OneBeacon and Tower also entered into a Transition Services Agreement (“TSA”), pursuant to which OneBeacon provides certain services to Tower during a three-year term.

OneBeacon received $166.6 million as consideration, which was based upon the carrying value of the traditional personal lines business as of July 1, 2010. For the year ended December 31, 2010, OneBeacon recorded an after-tax net gain of $24.6 million on the sale that is comprised of $8.5 million included in other revenues and a $16.1 million tax benefit. OneBeacon’s second quarter financial statements included $5.6 million of the tax benefit, which related to the difference between the tax basis of the companies sold as part of the Personal Lines Transaction and the net asset value of those entities under GAAP. Net written premiums for the business sold were approximately $420 million for the year ended December 31, 2009.

On December 3, 2009, OneBeacon sold the renewal rights to approximately $490 million in premiums from its non-specialty commercial lines business to The Hanover Insurance Group (“The Hanover”). The transaction includes small commercial accounts and the non-specialty portion of the middle-market business, beginning with January 1, 2010 effective dates (the “Commercial Lines Transaction”). As consideration for the Commercial Lines Transaction, OneBeacon received $23.2 million, reflected in other revenues. In accordance with the terms of the Commercial Lines Transaction, during the years ended December 31, 2011 and 2010, OneBeacon recognized additional consideration of $0.8 million and $10.2 million, reflected in other revenues, for aggregate premium renewals exceeding $200 million.

Acquisition of Central National

On February 26, 2010, Sirius Group acquired Central National for $5 million in cash. Central National ceased writing business in 1989 and has operated under the control of the Nebraska Department of Insurance since 1990. The transaction resulted in a gain of $12.8 million recorded in other revenues.

Share Repurchase Program

In 2006, White Mountains’ board of directors authorized the Company to repurchase up to 1 million of its common shares, from time to time, subject to market conditions. On August 26, 2010, White Mountains’ board of directors authorized the Company to repurchase an additional 600,000 common shares. Shares may be repurchased on the open market or through privately negotiated transactions. The repurchase authorization does not obligate the Company to acquire any specific number of shares, nor is there a stated expiration date. During 2011, the Company repurchased 313,967 common shares for $114.2 million exclusive of the two self tender offers described under “Tender Offers”. During 2010, the Company repurchased 677,125 common shares for $222.0 million. During 2009, the Company did not repurchase any common shares under the share repurchase plan.

Reserves for Unpaid Losses and Loss Adjustment Expenses

12 Months Ended

Dec. 31, 2011

Reserves for Unpaid Losses and Loss Adjustment Expenses

Reserves for Unpaid Losses and Loss Adjustment Expenses

NOTE 3. Reserves for Unpaid Losses and Loss Adjustment Expenses

Insurance

White Mountains’ insurance subsidiaries establish 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 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’ 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’ own experience, and can be especially useful for estimating costs of new business. For some lines of business, such as “long-tail” coverages discussed below, claims data reported in the most recent accident year is often too limited to provide a meaningful basis for analysis due to the typical delay in reporting of claims. For this type of business, White Mountains uses a selected 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 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, as applicable.

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’ 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 written 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’ 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.

The actuarial analysis is a primary consideration for management in determining its best estimate of loss and LAE reserves. In making its best estimate, management also considers other qualitative factors that may lead to a difference between its best estimate of loss and LAE reserves and the actuarial point estimate. Typically, these factors exist when management and the company’s 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. These factors may include, among others, changes in the techniques used to assess underwriting risk, more accurate and detailed levels of data submitted with reinsurance applications, the uncertainty of the current reinsurance pricing environment, the level of inflation in loss costs, changes in ceding company reserving practices, and legal and regulatory developments.

Reinsurance

Sirius Group establishes loss and LAE reserves that are estimates of amounts needed to pay claims and related expenses in the future for reinsured 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 being further extended because claims are first reported to the original primary insurance company and then through one or more intermediaries or reinsurers, (2) the diversity of loss development patterns among different types of reinsurance treaties or facultative contracts, (3) the necessary reliance on the ceding companies for information regarding reported claims and (4) the differing reserving practices among ceding companies.

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’ insurance and reinsurance subsidiaries for the years ended December 31, 2011, 2010 and 2009:

	Year Ended December 31,
Millions	2011			2010			2009
Gross beginning balance	$	5,736.8		$	6,379.2		$	7,029.4
Less beginning reinsurance recoverable on unpaid losses	(2,344.0		)	(2,771.5		)	(3,049.0		)
Net loss and LAE reserves	3,392.8			3,607.7			3,980.4

Less: Beginning net loss and LAE reserves for AutoOne (1)	(77.3		)	(95.8		)	(102.0		)

Loss and LAE reserves acquired—Old Lyme	21.0			—			—
Loss and LAE reserves acquired—Central National	—			17.6			—
Loss and LAE reserves sold—OneBeacon Personal Lines	—			(231.0		)	—

Losses and LAE incurred relating to:
Current year losses	1,256.7			1,503.4			1,571.2
Prior year losses	(49.8		)	(114.2		)	(147.1		)
Total incurred losses and LAE	1,206.9			1,389.2			1,424.1

Accretion of fair value adjustment to net loss and LAE reserves	8.3			8.5			12.2
Foreign currency translation adjustment to net loss and LAE reserves	.1			4.7			23.5

Loss and LAE paid relating to:
Current year losses	(404.0		)	(544.9		)	(591.6		)
Prior year losses	(952.8		)	(840.5		)	(1,234.7		)
Total loss and LAE payments	(1,356.8		)	(1,385.4		)	(1,826.3		)

Less: Beginning net loss and LAE reserves for AutoOne (1)	—			77.3			95.8

Net ending balance	3,195.0			3,392.8			3,607.7
Plus ending reinsurance recoverable on unpaid losses	2,507.3			2,344.0			2,771.5
Gross ending balance	$	5,702.3		$	5,736.8		$	6,379.2

(1)	Adjustment is to present loss and LAE reserve activities from continuing operations. At December 31, 2011, loss and LAE reserves for AutoOne have been reclassified as liabilities held for sale. Loss and LAE reserve balances for AutoOne prior to December 31, 2011 were not reclassified.

Loss and LAE development —2011

During the year ended December 31, 2011, White Mountains experienced $49.8 million of net favorable loss reserve development, which consisted of $2.9 million of net favorable loss reserve development at OneBeacon and $46.9 million of net favorable loss reserve development at Sirius Group.

During 2011, OneBeacon experienced $2.9 million of net favorable loss and LAE reserve development on prior accident year loss reserves, with $29.6 million of favorable development in its specialty insurance operations, substantially offset by $26.7 million of adverse loss reserve development in its other insurance operations. The favorable loss reserve development in specialty insurance operations was primarily due to lower than expected severity on non-catastrophe losses related to professional liability lines, multiple peril liability lines and other general liability lines. The adverse loss reserve development in other insurance operations resulted from a detailed review of run-off expenses, principally other adjusting expenses (“ULAE”), completed during the fourth quarter of 2011.

With respect to the favorable loss reserve development in specialty insurance operations, at December 31, 2010, management had revised its expectations downward for future loss emergence in the professional liability business, which had initially been based on market analysis when this business was initiated in 2002 and 2003. However, during 2011, losses continued to be significantly lower than these revised expectations. As a result, management lowered its reserves on the earliest years which affected more recent years as total loss expectations for those years are based in part on prior years’ results. The impact of this revised estimate was a decrease to professional liability reserves of $11.5 million.

During 2010, management began separately reviewing loss reserves for some business which had been previously managed as a part of OneBeacon’s former commercial lines underwriting unit. As of December 31, 2010, the reserves for these businesses had been selected based on expected emergence that was based on the historic loss development of former commercial lines underwriting unit. However, during 2011 the actual emerged experience for these businesses was significantly lower than the expected emergence. As a result of this favorable emergence, management lowered the loss reserves for these businesses by $14.0 million during 2011.

With respect to the $26.7 million of adverse loss reserve development in other insurance operations, management completed a detailed review of loss and defense and cost containment expenses (“ALAE”) and ULAE during the fourth quarter of 2011. The analysis considered costs, based on current non-staff expenses and staffing projections for the run-off business, as management continues efforts to segregate its claims operations between ongoing claims and run-off claims. The analysis also factored in the revised definition of run-off operations to include the non-specialty commercial lines business that was exited via the Commercial Lines Transaction.

In addition to the development described for the lines of business above, OneBeacon also recorded a $4.1 million net decrease in reserves in other lines of business as a result of its review of loss reserves at December 31, 2011.

The net favorable loss reserve development at Sirius Group was primarily attributable to $41.2 million of favorable development on property lines including, $13.1 million of loss reserve reductions for the 2010 Chile earthquake, partially offset by asbestos and environmental increases of $12.3 million.

Loss and LAE development —2010

During the year ended December 31, 2010, White Mountains experienced $114.2 million of net favorable loss reserve development, which consisted of $57.1 million of net favorable loss reserve development at OneBeacon and $57.1 million of net favorable loss reserve development at Sirius Group.

OneBeacon’s net favorable loss reserve development was primarily due to lower than expected severity on losses related to professional liability business, multiple peril liability and other general liability lines. The favorable development also included a $7.5 million release of commercial catastrophe reserves associated with storms occurring in 2004 and 2005.

Specifically, at December 31, 2009, management had revised its expectations downward with respect to future loss emergence in the professional liability business, which had initially been based on market analysis when this business was initiated in 2002 and 2003. However, during 2010, losses continued to be significantly lower than these revised expectations. As a result, management lowered its selected reserves on the earliest years which affected more recent years as total loss expectations for those years are based in part on prior years’ results. The impact of this revised estimate was a decrease to professional liability reserves of $19.3 million.

At December 31, 2009, management had recorded $7.5 million of reserves for certain claims related to catastrophes from accident years 2004 and 2005 related to OneBeacon’s excess property business. During 2010, these claims were resolved for amounts below OneBeacon’s policy coverage therefore the reserves were no longer necessary.

At December 31, 2009, based on actuarial techniques described above, management estimated that IBNR related to multiple peril liability was $170.5 million, or approximately 93% of case reserves of $184.1 million for accident years 2004 through 2009. During 2010, case incurred loss and ALAE was $65.8 million, which was less than expected for this business. As a result of the lower than expected case incurred loss and ALAE during 2010, the actuarial methods based on case incurred losses produced lower estimated ultimate losses for these accident years. As a result, at December 31, 2010, the IBNR was determined to be $86.2 million, or approximately 57% of the remaining case reserves. The impact of this revised estimate was a decrease to multiple peril liability reserves of $18.4 million.

At December 31, 2009, based on actuarial techniques described above, management estimated that IBNR related to general liability occurrence was $107.1 million, or approximately 265% of case reserves of $40.4 million for accident years 2004 through 2009. During 2010, case incurred loss and ALAE was $33.1 million, which was less than expected for this business. As a result of the lower than expected case incurred loss and ALAE during 2010, the actuarial methods based on case incurred losses produced lower estimated ultimate losses for these accident years. As a result, at December 31, 2010, the IBNR was determined to be $61.7 million, or approximately 164% of the remaining case reserves. The impact of this revised estimate was a decrease to general liability occurrence reserves of $12.3 million.

In addition to the development described for the lines of business above, management also recorded a $6.4 million net increase in IBNR in other lines of business as a result of its review of loss reserves at December 31, 2010. The change in IBNR for each other line of business was not individually significant.

The net favorable loss reserve development at Sirius Group was primarily related to short-tailed lines, such as property, accident and health and marine, in recent underwriting years. Included in the $57.1 million favorable loss reserve development was the recognition of $16.3 million in deferred gains from a retrocessional reinsurance contract that incepted in 2000 and was fully collected in 2010.

Loss and LAE development—2009

During the year ended December 31, 2009, White Mountains experienced $147.1 million of net favorable loss reserve development, which consisted of $116.7 million of net favorable loss reserve development at OneBeacon and $30.4 million of net favorable loss reserve development at Sirius Group.

OneBeacon’s net favorable loss reserve development in 2009 was primarily related to lower than expected severity on losses. The favorable loss reserve development was primarily related to professional liability business, multiple peril liability and other general liability lines and was partially offset by adverse loss reserve development at AutoOne.

Specifically, at December 31, 2008, management had revised its expectations downward with respect to future loss emergence in the professional liability business. The original expectations had initially been based on market analysis when this business was initiated in 2002 and 2003. However, during 2009, losses continued to be significantly lower than these revised expectations. As a result, management lowered its selected reserves on the earliest years of this business. Loss estimates in more recent years were also affected as total loss expectations for later years are based in part on prior years’ results. The impact of this revised estimate was a decrease to professional liability reserves of $60.0 million.

At December 31, 2008, based on actuarial techniques described above, OneBeacon estimated that IBNR related to multiple peril liability was $173.9 million, or approximately 85% of case reserves of $204.9 million for 2002 and subsequent accident years. During 2009, ALAE was $36.8 million, which was less than expected for this line of business. As a result of the lower than expected case incurred loss and ALAE during 2009, the actuarial methods based on case incurred losses produced lower estimated ultimate losses for these accident years. As a result, at December 31, 2009, the IBNR was determined to be $95.4 million, or approximately 73% of the remaining case reserves. The impact of this revised estimate was a decrease to multiple peril liability reserves of $42.6 million.

At December 31, 2008, based on actuarial techniques described above, OneBeacon estimated that IBNR related to general liability occurrence was $93.9 million, or approximately 275% of case reserves of $34.2 million for 2002 and subsequent accident years. During 2009, case incurred loss and ALAE was $15.6 million, which was less than expected for this line of business. As a result of the lower than expected case incurred loss and ALAE during 2009, the actuarial methods based on case incurred losses produced lower estimated ultimate losses for these accident years. As a result, at December 31, 2009, the IBNR was determined to be $61.6 million, or approximately 214% of the remaining case reserves. The impact of this revised estimate was a decrease to general liability occurrence reserves of $14.1 million.

In addition to the development described for the lines of business above, OneBeacon also recorded changes in IBNR in other lines of business as a result of its review of loss reserves at December 31, 2009 that essentially offset. The change in IBNR for each other line of business was not individually significant.

Sirius Group’s net favorable loss reserve development in 2009 is due mainly to a cession under a retrocessional contract related to the 2001 accident year and favorable commutation activity on certain old casualty treaties, partially offset by $17.7 million of additional losses related to A&E exposures.

Sirius Group’s cession of $20.0 million of losses under a retrocessional reinsurance contract related to the 2001 accident year. These retroceded losses were substantially offset in pre-tax income by $10.0 million of ceded premiums and $7.2 million of interest charges on funds held under the contract.

Fair value adjustment to loss and LAE reserves

In connection with purchase accounting for the acquisitions of OneBeacon, Scandinavian Re and Stockbridge Insurance Company, White Mountains was 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 $8.3 million, $8.5 million and $12.2 million of such charges, recorded as loss and LAE during 2011, 2010 and 2009. As of December 31, 2011, the pre-tax un-accreted adjustment was $12.7 million.

The fair values of OneBeacon’s loss and LAE reserves and related reinsurance recoverables acquired on June 1, 2001, Scandinavian Re’s loss and LAE reserves and related reinsurance recoverables acquired on April 16, 2004, and Stockbridge Insurance Company’s loss and LAE reserves and related reinsurance recoverables acquired on December 22, 2006 were based on the present value of their expected cash flows with consideration for the uncertainty inherent in both the timing of, and the ultimate amount of, future payments for losses and receipts of amounts recoverable from reinsurers. In estimating fair value, management discounted the nominal loss reserves of OneBeacon (net of the effects of reinsurance obtained from the NICO Cover, as defined below and the GRC Cover, as defined below), Scandinavian Re and Stockbridge Insurance Company to their present value using an applicable risk-free discount rate. The series of future cash flows related to such loss payments and reinsurance recoveries were developed using OneBeacon’s, Scandinavian Re’s and Stockbridge Insurance Company’s historical loss data. The resulting discount was reduced by the “price” for bearing the uncertainty inherent in OneBeacon’s, Scandinavian Re’s and Stockbridge Insurance Company’s net loss reserves in order to estimate fair value. This was approximately 11%, 12% and 2% of the present value of the expected underlying cash flows of the loss reserves and reinsurance recoverables of OneBeacon, Scandinavian Re and Stockbridge Insurance Company, respectively, which is believed to be reflective of the cost OneBeacon, Scandinavian Re and Stockbridge Insurance Company would incur if they had attempted to reinsure the full amount of its net loss and LAE reserves with a third-party reinsurer.

Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity

White Mountains’ 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.

Immediately prior to White Mountains’ acquisition of OneBeacon, Aviva caused OneBeacon to purchase a reinsurance contract with National Indemnity Company (“NICO”) under which OneBeacon is entitled to recover from NICO up to $2.5 billion in the future for asbestos claims arising from business written by OneBeacon in 1992 and prior, environmental claims arising from business written by OneBeacon in 1987 and prior, and certain other exposures (the “NICO Cover”). Under the terms of the NICO Cover, NICO receives the economic benefit of reinsurance recoverables from certain of OneBeacon’s third-party reinsurers in existence at the time the NICO Cover was executed (“Third-Party Recoverables”). As a result, the Third-Party Recoverables serve to protect the $2.5 billion limit of NICO coverage for the benefit of OneBeacon. Any amounts uncollectible from third-party reinsurers due to dispute or the reinsurers’ financial inability to pay are covered by NICO under its agreement with OneBeacon. Third-Party Recoverables are typically for the amount of loss in excess of a stated level each year. Of claim payments in the past 11 years, approximately 47% of asbestos and environmental losses have been recovered under the historical third-party reinsurance.

During 2011, OneBeacon completed a new study of its legacy A&E exposures. Reasonable estimates of potential adverse scenarios continue to be within the $2.5 billion reinsurance cover issued by NICO. Based on the results of the study, OneBeacon increased the point estimate of incurred losses ceded to NICO from $2.2 billion to $2.3 billion, an increase of $122 million, net of underlying reinsurance. Due to the NICO Cover, there was no impact to income or equity from the change in the estimate.

As noted above, OneBeacon estimates that on an incurred basis it has used approximately $2.3 billion of the coverage provided by NICO at December 31, 2011. Since entering into the NICO Cover, approximately 8% of the $2.3 billion of utilized coverage relates to uncollectible Third-Party Recoverables and settlements on Third-Party Recoverables through December 31, 2011. Net losses paid by NICO totaled approximately $1.4 billion as of December 31, 2011. Asbestos payments during 2011 reflect payments resulting from intensified efforts by claimants to resolve asbestos claims prior to enactment of potential U.S. federal asbestos legislation.

In 2010, Sirius Group completed an in-depth analysis of Sirius America’s asbestos exposure. The main focus of the analysis was on the internal claims analysis of all treaty and facultative contracts likely to have asbestos exposure at June 30, 2010. This analysis entailed examining total expected asbestos losses and LAE from a variety of information sources, including asbestos studies, reported data, and external benchmarking scenarios. Since the 2010 study, management has monitored quarterly activity against established metrics.

In 2010, Sirius Group also reviewed Sirius America’s exposure to environmental losses using industry benchmarks such as “survival ratios”, IBNR to case reserve ratios, and reported and paid environmental claim activity.

As a result of monitoring the asbestos and environmental claims activity in 2011 against established benchmarks, Sirius Group increased net asbestos reserves and net environmental reserves $10.3 million and $2.0 million, respectively. Sirius Group’s A&E three year survival ratio was 11.1 years at December 31, 2011 and 12.5 years at December 31, 2010.

White Mountains’ reserves for A&E losses at December 31, 2011 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.

The following tables summarize reported asbestos and environmental loss and LAE reserve activities (gross and net of reinsurance) for OneBeacon and Sirius Group, for the years ended December 31, 2011, 2010 and 2009, respectively:

OneBeacon

Net A&E Loss	Year Ended December 31,
Reserve Activity	2011									2010									2009
				Pre-NICO									Pre-NICO									Pre-NICO
Millions	Gross			Net(1)			Net			Gross			Net(1)			Net			Gross			Net(1)			Net
Asbestos:
Beginning balance	$	904.0		$	647.3		$	6.4		$	985.6		$	688.8		$	6.5		$	1,098.4		$	741.5		$	6.5
Incurred losses and LAE	256.8			32.2			(4.0		)	—			—			—			1.0			—			—
Paid losses and LAE	(86.5		)	1.7			(.2		)	(81.6		)	(41.5		)	(.1		)	(113.8		)	(52.7		)	—
Ending balance	1,074.3			681.2			2.2			904.0			647.3			6.4			985.6			688.8			6.5
Environmental:
Beginning balance	119.0			93.8			9.2			350.7			218.6			7.6			470.3			261.2			5.5
Incurred losses and LAE	231.8			62.2			10.0			6.2			6.0			6.0			4.9			5.0			5.0
Paid losses and LAE	(71.0		)	(4.4		)	(10.2		)	(237.9		)	(130.8		)	(4.4		)	(124.5		)	(47.6		)	(2.9		)
Ending balance	279.8			151.6			9.0			119.0			93.8			9.2			350.7			218.6			7.6
Total asbestos and environmental:
Beginning balance	1,023.0			741.1			15.6			1,336.3			907.4			14.1			1,568.7			1,002.7			12.0
Incurred losses and LAE	488.6			94.4			6.0			6.2			6.0			6.0			5.9			5.0			5.0
Paid losses and LAE	(157.5		)	(2.7		)	(10.4		)	(319.5		)	(172.3		)	(4.5		)	(238.3		)	(100.3		)	(2.9		)
Ending balance	$	1,354.1		$	832.8		$	11.2		$	1,023.0		$	741.1		$	15.6		$	1,336.3		$	907.4		$	14.1

(1)	Represents A&E reserve activity, net of third-party reinsurance, but prior to the NICO Cover.

Sirius Group

Net A&E Loss Reserve Activity	Year Ended December 31,
	2011						2010						2009
Millions	Gross			Net			Gross			Net			Gross			Net
Asbestos:
Beginning balance	$	191.9		$	151.5		$	187.0		$	146.6		$	173.7		$	138.5
Losses and LAE acquired — Central National	—			—			10.4			9.7			—			—
Incurred losses and LAE	13.6			10.3			9.0			7.3			24.7			18.4
Paid losses and LAE	(20.4		)	(15.6		)	(14.5		)	(12.1		)	(11.4		)	(10.3		)
Ending balance	185.1			146.2			191.9			151.5			187.0			146.6
Environmental:
Beginning balance	22.4			18.1			22.2			17.9			24.5			20.1
Losses and LAE acquired — Central National	—			—			3.5			2.4			—			—
Incurred losses and LAE	2.9			2.0			(2.5		)	(1.3		)	(.8		)	(.7		)
Paid losses and LAE	(3.2		)	(3.6		)	(.8		)	(.9		)	(1.5		)	(1.5		)
Ending balance	22.1			16.5			22.4			18.1			22.2			17.9
Total asbestos and environmental:
Beginning balance	214.3			169.6			209.2			164.5			198.2			158.6
Losses and LAE acquired — Central National	—			—			13.9			12.1			—			—
Incurred losses and LAE	16.5			12.3			6.5			6.0			23.9			17.7
Paid losses and LAE	(23.6		)	(19.2		)	(15.3		)	(13.0		)	(12.9		)	(11.8		)
Ending balance	$	207.2		$	162.7		$	214.3		$	169.6		$	209.2		$	164.5

- Definition

Disclosure of accounting policy for the various components of the reserve for future policy benefits and guaranteed minimum benefits, and for claims and claims adjustment expenses; the significant assumptions for estimating claims losses; causes of significant variances from prior periods (such as catastrophes, asbestos and environmental claims reserve losses); and reconciliations of beginning to ending reserve balances.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 7
-Section 03
-Paragraph 13

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 60
-Paragraph 60
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Statement of Position (SOP)
-Number 94-5
-Paragraph 11
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6482852&loc=d3e14931-158439

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14754-158437

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.13(a)(1),(b))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

Third-Party Reinsurance

12 Months Ended

Dec. 31, 2011

Third-Party Reinsurance

Third-Party Reinsurance

NOTE 4. Third-Party Reinsurance

In the normal course of business, White Mountains’ insurance and reinsurance subsidiaries may 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’ insurance and reinsurance subsidiaries’ written and earned premiums and on losses and LAE were as follows:

	Year ended December 31, 2011
Millions	OneBeacon			Sirius Group			Other Operations		Total
Written premiums:
Direct	$	1,077.6		$	139.5		$	—	$	1,217.1
Assumed	48.2			988.6			—		1,036.8
Gross written premiums	1,125.8			1,128.1			—		2,253.9
Ceded	(62.9		)	(212.4		)	—		(275.3		)
Net written premiums	$	1,062.9		$	915.7		$	—	$	1,978.6
Earned premiums:
Direct	$	1,138.5		$	128.5		$	—	$	1,267.0
Assumed	43.1			989.8			—		1,032.9
Gross earned premiums	1,181.6			1,118.3			—		2,299.9
Ceded	(166.1		)	(206.0		)	—		(372.1		)
Net earned premiums	$	1, 015.5		$	912.3		$	—	$	1,927.8
Losses and LAE:
Direct	$	1,151.1		$	80.0		$	—	$	1,231.1
Assumed	36.1			627.8			—		663.9
Gross losses and LAE	1,187.2			707.8			—		1,895.0
Ceded	(606.3		)	(81.8		)	—		(688.1		)
Net losses and LAE	$	580.9		$	626.0		$	—	$	1,206.9

	Year ended December 31, 2010
Millions	OneBeacon			Sirius Group			Other Operations		Total
Written premiums:
Direct	$	1,501.5		$	121.6		$	—	$	1,623.1
Assumed	57.7			957.5			—		1,015.2
Gross written premiums	1,559.2			1,079.1			—		2,638.3
Ceded (1)	(400.2		)	(213.3		)	—		(613.5		)
Net written premiums	$	1,159.0		$	865.8		$	—	$	2,024.8
Earned premiums:
Direct	$	1,648.7		$	117.9		$	—	$	1,766.6
Assumed	64.2			929.7			—		993.9
Gross earned premiums	1,712.9			1,047.6			—		2,760.5
Ceded (1)	(309.0		)	(199.7		)	—		(508.7		)
Net earned premiums	$	1,403.9		$	847.9		$	—	$	2,251.8
Losses and LAE:
Direct	$	877.1		$	59.4		$	—	$	936.5
Assumed	138.4			684.4			—		822.8
Gross losses and LAE	1,015.5			743.8			—		1,759.3
Ceded (1)	(157.3		)	(212.8		)	—		(370.1		)
Net losses and LAE	$	858.2		$	531.0		$	—	$	1,389.2

(1)	During 2010, OneBeacon ceded written premiums of $262.2, earned premiums of $165.0 and loss and LAE of $86.5 pursuant to the Commercial Lines Transaction.

	Year ended December 31, 2009
Millions	OneBeacon			Sirius Group			Other Operations		Total
Written premiums:
Direct	$	1,972.4		$	107.3		$	—	$	2,079.7
Assumed	58.6			889.2			—		947.8
Gross written premiums	2,031.0			996.5			—		3,027.5
Ceded	(213.2		)	(189.7		)	—		(402.9		)
Net written premiums	$	1,817.8		$	806.8		$	—	$	2,624.6
Earned premiums:
Direct	$	2,021.7		$	107.2		$	—	$	2,128.9
Assumed	66.8			927.5			—		994.3
Gross earned premiums	2,088.5			1,034.7			—		3,123.2
Ceded	(229.7		)	(175.9		)	—		(405.6		)
Net earned premiums	$	1,858.8		$	858.8		$	—	$	2,717.6
Losses and LAE:
Direct	$	1,020.7		$	68.8		$	—	$	1,089.5
Assumed	40.8			492.2			—		533.0
Gross losses and LAE	1,061.5			561.0			—		1,622.5
Ceded	(56.2		)	(142.2		)	—		(198.4		)
Net losses and LAE	$	1,005.3		$	418.8		$	—	$	1,424.1

OneBeacon

In the normal course of its business, OneBeacon purchases reinsurance from highly rated third-party reinsurers in order to minimize loss from large risks or catastrophic events.

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 position. Examples of catastrophes include losses caused by earthquakes, wildfires, hurricanes and other types of storms and terrorist acts. The extent of losses caused by catastrophes is a function of the amount and type of insured exposure in the area affected by the event as well as the severity of the event. OneBeacon uses models (primarily AIR Worldwide (“AIR”) Version 12) to estimate the probability of the occurrence of a catastrophic event as well as potential losses under various scenarios. OneBeacon uses this model output in conjunction with other data to manage its exposure to catastrophe losses through individual risk selection and by limiting its concentration of insurance written in catastrophe-prone areas such as coastal regions. In addition, OneBeacon imposes wind deductibles on existing coastal windstorm exposures.

Since the terrorist attacks of September 11, 2001, OneBeacon has sought to mitigate the risk associated with any future terrorist attacks by limiting the aggregate insured value of policies in geographic areas with exposure to losses from terrorist attacks. This is accomplished by either limiting the total insured values exposed, or, where applicable, through the use of terrorism exclusions.

In December 2007, the U.S. government extended the Terrorism Risk Insurance Act of 2002 (the “Terrorism Act” or “TRIA”) until December 31, 2014. The Terrorism Act established a federal “backstop” for commercial property and casualty losses, including workers compensation, resulting from acts of terrorism by or on behalf of any foreign person or foreign interest. As extended, the law now also covers domestic acts of terrorism. The law limits the industry’s aggregate liability by requiring the federal government to share 85% of certified losses once a company meets a specific retention or deductible as determined by its prior year’s direct written premiums and limits the aggregate liability to be paid by the government and industry without further action by Congress at $100 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.

OneBeacon estimates its individual retention level for commercial policies subject to the Terrorism Act to be approximately $100 million in 2012, which is based on 2011 net written premiums. The federal government will pay 85% of covered terrorism losses that exceed OneBeacon’s or the industry’s retention levels in 2012 up to a total of $100 billion.

OneBeacon seeks to further reduce its potential loss from catastrophe exposures through the purchase of catastrophe reinsurance. Effective May 1, 2011, OneBeacon renewed its property catastrophe reinsurance program through April 30, 2012. The program provides coverage for OneBeacon’s property business for losses resulting from natural catastrophes, as well as certain acts of terrorism. Under the program, the first $50.0 million of losses resulting from any single catastrophe are retained and the next $175.0 million of losses resulting from the catastrophe are reinsured, although OneBeacon retains a co-participation of 26% of losses from $50.0 million to $100.0 million and 10% of the losses from $100.0 million to $175.0 million. Losses from $175.0 million to $225.0 million are fully reinsured. Any loss above $225.0 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 had entered into a 30% quota share agreement with a group of reinsurers that ran from January 1, 2009 through December 31, 2009, and had renewed the agreement effective January 1, 2010. Through June 30, 2010 OneBeacon ceded $25.6 million of written premiums from its Northeast homeowners business written through OneBeacon Insurance Company (“OBIC”) and its subsidiary companies, along with Adirondack and New Jersey Skylands Insurance Association. Effective July 1, 2010, the closing date of the Personal Lines Transaction, the agreement was amended to remove OneBeacon as a signatory. During the year ended December 31, 2009, OneBeacon ceded $59.9 million under this quota share agreement.

OneBeacon’s property catastrophe reinsurance program does not cover property losses resulting from any nuclear events or biological, chemical or radiological terrorist attacks or losses resulting from acts of terrorism as defined under the Terrorism Act, as amended, committed by an individual or individuals acting on behalf of any foreign person or foreign interest, as well as domestic acts of terrorism. Such losses are subject to coverage provided to insurance companies by TRIA.

OneBeacon also purchases property-per-risk reinsurance coverage to reduce large loss volatility. The property-per-risk reinsurance program reinsures losses in excess of $10.0 million up to $100.0 million. Individual risk facultative reinsurance may be purchased above $100.0 million where OneBeacon deems it appropriate. The property-per-risk treaty also provides one limit of reinsurance protection for losses in excess of $10.0 million up to $100.0 million on an individual risk basis for terrorism losses. 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 workers compensation, general liability, automobile liability, professional liability or umbrella liability in excess of $5.0 million up to $21.0 million ($20.0 million for healthcare professional liability). Casualty losses involving more than one insured are covered by a dedicated treaty up to $40.0 million in excess of a retention of $10.0 million.

In addition, OneBeacon has reinsurance contracts with two reinsurance companies rated “AA+” (Very Strong, the second highest of twenty-one financial strength ratings) by Standard & Poor’s and “A++” (Superior, the highest of fifteen financial strength ratings) by A.M. Best. One contract is the reinsurance cover with NICO, which entitles OneBeacon to recover up to $2.5 billion in ultimate loss and LAE incurred related primarily to claims arising from business written by OneBeacon prior to 1992 for asbestos claims and prior to 1987 for environmental claims and certain other exposures. As of December 31, 2011, OneBeacon has ceded estimated incurred losses of approximately $2.3 billion to the NICO Cover. Net losses paid totaled $1.4 billion as of December 31, 2011. Since entering into the NICO Cover, approximately 8% ($184 million) of the $2.3 billion of utilized coverage relates to uncollectible Third-Party Recoverables and settlements on Third-Party Recoverables through December 31, 2011. The other contract is a reinsurance cover with General Reinsurance Corporation (“GRC”) for up to $570 million of additional losses on all claims arising from accident years 2000 and prior (the “GRC Cover”). Through December 31, 2011, OneBeacon had ceded estimated incurred losses of $562.0 million to the GRC Cover. Pursuant to the GRC Cover, OneBeacon is not entitled to recover losses to the full contract limit if such losses are reimbursed by GRC more quickly than anticipated at the time the contract was signed. OneBeacon intends to only seek reimbursement from GRC for claims which result in payment patterns similar to those supporting OneBeacon’s recoverables recorded pursuant to the GRC Cover. The economic cost of not submitting certain other eligible claims to GRC is primarily the investment spread between the rate credited by GRC and the rate achieved by OneBeacon on its own investments. This cost, if any, is expected to be nominal. During the years ended December 31, 2011 and 2010, OneBeacon collected $73.5 million and $61.3 million, respectively, under the GRC Cover.

At December 31, 2011, OneBeacon had $16.5 million of reinsurance recoverables on paid losses and $2,330.8 million (gross of $163.3 million in purchase accounting adjustments, as described in Note 3) that will become recoverable if claims are paid in accordance with current reserve estimates. Reinsurance contracts do not relieve OneBeacon of its obligation to its policyholders. Therefore, collectability of balances due from reinsurers is critical to its financial strength.

The following table provides a listing of OneBeacon’s top reinsurers, excluding industry pools and associations and affiliates of White Mountains, based upon recoverable amounts, the percentage of total reinsurance recoverables and the reinsurer’s A.M. Best rating.

Top Reinsurers ($ in millions)	Balance at December 31, 2011		% of Total		A.M. Best Rating(1)
National Indemnity Company and General Reinsurance Corporation (2)	$	1,540.6	66	%		A++
Hanover Insurance Group Ltd.	90.9		4	%		A
Tokio Marine and Nichido Fire (3)	57.1		2	%		A++
Tower Group Inc.	35.1		1	%		A-
Munich Reinsurance America	26.4		1	%		A+

(1)	A.M. Best ratings as detailed above are: “A++” (Superior, which is the highest of fifteen financial strength ratings), “A+” (Superior, which is the second highest of fifteen financial strength ratings), “A” (Excellent, which is the third highest of fifteen financial strength ratings), and “A-” (Excellent, which is the fourth highest of fifteen financial strength ratings). Ratings are as of December 31, 2011.
(2)	Includes $198.3 of Third-Party Recoverables, which NICO would pay under the terms of the NICO Cover if they are unable to collect from third-party reinsurers.
(3)	Includes $30.5 of reinsurance recoverables from various third-party reinsurers that are guaranteed by Tokio Marine and Nichido Fire under the terms of a 100% quota share reinsurance agreement between Houston General Insurance Company and Tokio Marine and Nichido Fire.

Sirius Group

Sirius Group’s reinsurance protection primarily consists of pro-rata and excess of loss protections to cover aviation, trade credit, and certain property exposures. Sirius Group’s property reinsurance provides both proportional and non-proportional protections for Europe, the Americas, Asia, the Middle East, and Australia. This reinsurance is designed to increase underwriting capacity where appropriate, and to reduce exposure both to large catastrophe losses and to a frequency of smaller loss events. Attachment points and coverage limits vary by region around the world. Reinsurance contracts do not relieve Sirius Group of its obligation to its ceding companies. Therefore, collectability of balances due from its retrocessional reinsurers is critical to Sirius Group’s financial strength.

In 2011, 2010 and 2009, Sirius Group purchased group excess of loss retrocessional coverage for its non-U.S. and non-Japan earthquake-related exposures. The non-U.S. and non-Japan earthquake cover was renewed for one year at April 1, 2011, providing $61.0 million of reinsurance protection through partially placed coverage layers in excess of Sirius Group’s retention of $35.0 million. Sirius Group will recognize the full $61.0 million recovery if a covered earthquake loss reaches $110.0 million. At April 1, 2010, Sirius Group purchased coverage for $65.0 million in excess of $45.0 million. At December 31, 2011, losses incurred for the February 2011 New Zealand earthquake totaled $44.4 million, which is less than the $45.0 million retention; accordingly, Sirius Group has not recovered any losses from this coverage. At April 1, 2009, Sirius Group purchased coverage for $65.0 million in excess of $35.0 million, and this coverage applied to losses incurred from the Chile earthquake. During 2010, Sirius Group recovered the full $65.0 million limit under this earthquake cover as a result of the Chile Earthquake in February 2010.

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. In 2012, for the proportional and facultative aviation portfolios, reinsurance protection was purchased on average in excess of a market loss of $150.0 million up to a full airline policy limit of $2.25 billion. For the non-proportional aviation portfolio, reinsurance protection includes a 15% quota share treaty and several excess of loss covers with varying attachment points and limits. In addition, the non-proportional portfolio is protected by $30.0 million in the form of first event industry loss warranties (“ILW”), and $6.0 million of available limit in the form of second event ILWs. The first event ILWs attach at industry event levels between $400.0 million and $900.0 million. The second event ILWs attach at industry event levels between $300.0 million and $600.0 million.

For accident and health, Sirius Group has excess of loss protection covering personal accident and life of €10 million ($13 million based on the December 31, 2011 EUR to USD exchange rate) of protection in excess of a €5 million ($7 million based on the December 31, 2011 EUR to USD exchange rate) retention for the Stockholm, Hamburg, Liege and Singapore branches.

For 2011, Sirius Group ceded 19% of its trade credit business under a quota share retrocession, which supported growth in this line. The treaty was renewed for 2012 at a 20% cession percentage for credit business and 50% for bond business.

All of Sirius Group’s excess of loss reinsurance protections include provisions that reinstate coverage at a cost of 100% or more of the original reinsurance premium.

In 2000, Sirius America purchased a reinsurance contract from Imagine Re (the “Imagine Cover”) to reduce its statutory operating leverage and protect its statutory surplus from adverse development relating to A&E exposures as well as the reserves assumed in certain recent acquisitions. In accordance with ASC 944, the amounts related to reserves transferred to Imagine Re for liabilities incurred as a result of past insurable events were accounted for as retroactive reinsurance. During 2010, Sirius America determined that the full reinsurance recoverable under the Imagine Cover was due. Accordingly, Sirius America billed Imagine Re for the remaining balance due under the Imagine Cover and withdrew this amount from a trust that included invested assets that fully collateralized the reinsurance recoverable balance. As of December 31, 2010, Sirius America had collected all amounts due from Imagine Re. At December 31, 2009, Sirius America had $16.3 million of unamortized deferred gains related to the Imagine Cover. During 2010, as a result of the collection of the reinsurance recoverable balance due under the Imagine Cover, Sirius America recognized the remaining $16.3 million of unamortized deferred gains. Sirius Group recognized $4.6 million of deferred gains during 2009.

At December 31, 2011, Sirius Group had $13.9 million of reinsurance recoverables on paid losses and $339.7 million of reinsurance that will become recoverable if claims are paid in accordance with current reserve estimates. The following table provides a listing of Sirius Group’s top reinsurers based upon recoverable amounts, the percentage of total recoverables and the reinsurer’s A.M. Best Rating.

Top Reinsurers ($ in millions)	Balance at December 31, 2011		% of Total		A.M. Best Rating(1)		% Collateralized
General Reinsurance Corporation	$	42.7	12	%		A++	1	%
Swiss Re Group	40.2		11	%		A+	20	%
Olympus (2)	35.5		10	%		NR-5	100	%
Lloyds of London(3)	27.2		8	%		A	8	%
Michigan Catastrophic Claims Association	14.6		4	%		N/A(4)	—	%

(1)	A.M. Best ratings as detailed above are: “NR-5” (Not formally followed), “A++” (Superior, which is the highest of fifteen financial strength ratings), “A+” (Superior, which is the second highest of fifteen financial strength ratings), and “A” (Excellent, which is the third highest of fifteen financial strength ratings).
(2)	Non-U.S. insurance entities. Balances are fully collateralized through funds held, letters of credit or trust agreements.
(3)	Represents the total of reinsurance recoverables due to Sirius Group from all Lloyds Syndicates.
(4)	Michigan Catastrophic Claims Association (“MCCA”) is a non-profit unincorporated association of which every insurance company that sells automobile coverage in Michigan is required to be a member. A.M. Best does not rate MCCA. Sirius Group acquired its recoverable from MCCA as a result of its acquisition of Stockbridge Insurance Company.

- 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 Statement of Financial Accounting Standard (FAS)
-Number 113
-Paragraph 27
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 7
-Section 03
-Paragraph 13

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Statement of Position (SOP)
-Number 92-5
-Paragraph 19
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 7
-Section 03
-Paragraph 6

Reference 5: 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 6: 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 7: 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 8: 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 9: 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 10: 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 11: 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 12: 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 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 113
-Paragraph 120
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Investment Securities

12 Months Ended

Dec. 31, 2011

Investment Securities

Investment Securities

NOTE 5. Investment Securities

Net Investment Income

White Mountains’ net investment income is comprised primarily of interest income associated with White Mountains’ fixed maturity investments, dividend income from its equity investments and interest income from its short-term investments. Pre-tax net investment income for 2011, 2010 and 2009 consisted of the following:

	Year Ended December 31,
Millions	2011			2010			2009
Investment income:
Fixed maturity investments	$	166.2		$	194.7		$	243.3
Short-term investments	4.5			3.0			5.5
Common equity securities	15.4			10.2			4.9
Convertible fixed maturity investments	5.5			5.6			8.0
Other long-term investments	4.2			6.0			4.2
Interest on funds held under reinsurance treaties	(.4		)	(1.7		)	(7.3		)
Total investment income	195.4			217.8			258.6
Third-party investment expenses	(10.9		)	(8.9		)	(8.5		)
Net investment income, pre-tax	$	184.5		$	208.9		$	250.1

Net Realized and Unrealized Investment Gains and Losses

	Year ended December 31,
Millions	2011			2010			2009
Net realized investment gains (losses), pre-tax	$	117.0		$	136.4		$	(69.9	)
Net unrealized investment gains (losses), pre-tax	5.8			(53.8		)	431.6
Net realized and unrealized investment gains (losses), pre-tax	122.8			82.6			361.7
Income taxes attributable to realized and unrealized investment gains (losses)	(30.9		)	(22.8		)	(124.4		)
Net realized and unrealized investment gains (losses), after-tax	$	91.9		$	59.8		$	237.3

Net realized investment gains (losses)

Net realized investment gains (losses) for 2011, 2010, and 2009 consisted of the following:

	Year Ended December 31,
Millions	2011			2010			2009
Fixed maturity investments	$	49.4		$	96.9		$	(7.4	)
Short-term investments	—			—			.2
Common equity securities	34.6			6.9			(46.4		)
Convertible fixed maturity investments	(2.2		)	16.7			15.6
Other long-term investments	35.2			15.9			(31.9		)
Net realized investment gains (losses), pre-tax	117.0			136.4			(69.9		)
Income taxes attributable to realized investment gains and (losses)	(37.0		)	(42.1		)	14.9
Net realized investment gains (losses), after-tax	$	80.0		$	94.3		$	(55.0	)

White Mountains recognized gross realized investment gains of $191.6 million, $205.0 million and $157.3 million and gross realized investment losses of $74.6 million, $68.6 million and $227.2 million on sales of investment securities during 2011, 2010, and 2009.

As of December 31, 2011 and 2010, White Mountains reported $34.6 million and $22.3 million in accounts payable on unsettled investment purchases and $4.7 million and $39.5 million in accounts receivable on unsettled investment sales.

Net unrealized investment gains (losses)

The following table summarizes changes in the carrying value of investments measured at fair value:

	Year Ended December 31, 2011
Millions	Net unrealized gains (losses)			Net foreign currency gains (losses)			Total changes in fair value reflected in earnings
Fixed maturities	$	7.6		$	68.9		$	76.5
Short-term investments	—			(1.1		)	(1.1		)
Common equity securities	(40.6		)	(1.8		)	(42.4		)
Convertible fixed maturity investments	(11.5		)	—			(11.5		)
Other long-term investments	(19.1		)	3.4			(15.7		)
Net unrealized investment gains (losses), pre-tax	(63.6		)	69.4			5.8
Income taxes attributable to unrealized investment gains (losses)	24.0			(17.9		)	6.1
Net unrealized investment gains (losses), after-tax	$	(39.6	)	$	51.5		$	11.9

	Year Ended December 31, 2010
Millions	Net unrealized gains (losses)			Net foreign currency gains (losses)			Total changes in fair value reflected in earnings
Fixed maturities	$	(67.4	)	$	(53.8	)	$	(121.2	)
Short-term investments	—			.2			.2
Common equity securities	72.4			(9.6		)	62.8
Convertible fixed maturity investments	(5.4		)	—			(5.4		)
Other long-term investments	17.6			(7.8		)	9.8
Net unrealized investment gains (losses), pre-tax	17.2			(71.0		)	(53.8		)
Income taxes attributable to unrealized investment gains (losses)	.5			18.8			19.3
Net unrealized investment gains (losses), after-tax	$	17.7		$	(52.2	)	$	(34.5	)

	Year Ended December 31, 2009
Millions	Net unrealized gains (losses)			Net foreign currency gains (losses)			Total changes in fair value reflected in earnings
Fixed maturities	$	333.9		$	(53.6	)	$	280.3
Short-term investments	(.3		)	1.6			1.3
Common equity securities	57.9			(9.9		)	48.0
Convertible fixed maturity investments	39.8			—			39.8
Other long-term investments	67.2			(5.0		)	62.2
Net unrealized investment gains (losses), pre-tax	498.5			(66.9		)	431.6
Income taxes attributable to unrealized investment gains (losses)	(154.3		)	15.0			(139.3		)
Net unrealized investment gains (losses), after-tax	$	344.2		$	(51.9	)	$	292.3

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, 2011, 2010, and 2009.

	Year Ended December 31,
Millions	2011			2010			2009
Fixed maturities	$	(12.2	)	$	10.2		$	47.3
Common equity securities	(16.6		)	(19.2		)	14.7
Convertible fixed maturities	—			—			.1
Other long-term investments	(16.8		)	39.0			65.0
Total unrealized investment gains (losses), pre-tax - Level 3 investments	$	(45.6	)	$	30.0		$	127.1

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

	Year Ended December 31,
Millions	2011			2010			2009
Net change in pre-tax unrealized gains (losses) on investments in unconsolidated affiliates	$	(63.6	)	$	72.7		$	192.7
Income taxes	5.1			.8			(.3		)
Net change in unrealized gains (losses) on investments in unconsolidated affiliates, after tax	(58.5		)	73.5			192.4
Net unrealized foreign currency gains (losses) on investments	(90.1		)	102.9			185.1
Total investments gains (losses) through accumulated other comprehensive income	(148.6		)	176.4			377.5
Change in net unrealized investment gains (losses), after-tax	11.9			(34.5		)	292.3
Net realized investment gains (losses), after-tax	80.0			94.3			(55.0		)
Total investment gains (losses) recorded during the period, after-tax	$	(56.7	)	$	236.2		$	614.8

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’ fixed maturity investments as of December 31, 2011 and 2010, were as follows:

	December 31, 2011
Millions	Cost or amortized cost		Gross unrealized gains		Gross unrealized losses			Net foreign currency gains(losses)			Carrying value
US Government and agency obligations	$	299.4	$	5.3	$	(.1	)	$	.4		$	305.0
Debt securities issued by industrial corporations	2,072.1		73.7		(7.8		)	(2.9		)	2,135.1
Municipal obligations	2.7		—		—			—			2.7
Mortgage-backed and asset-backed securities	3,190.5		25.9		(3.9		)	10.4			3,222.9
Foreign government, agency and provincial obligations	581.2		11.0		(.1		)	(2.9		)	589.2
Preferred stocks	82.3		3.2		(6.7		)	—			78.8
Total fixed maturity investments including assets held for sale	$	6,228.2	$	119.1	$	(18.6	)	$	5.0		$	6,333.7
Fixed maturity investments reclassified to assets held for sale related to AutoOne											(111.8		)
Total fixed maturity investments											$	6,221.9

	December 31, 2010
Millions	Cost or amortized cost		Gross unrealized gains		Gross unrealized losses			Net foreign currency gains (losses)			Carrying value
US Government and agency obligations	$	385.9	$	13.6	$	(.8	)	$	—		$	398.7
Debt securities issued by industrial corporations	2,149.2		87.9		(21.1		)	(37.9		)	2,178.1
Municipal obligations	3.3		.1		(.1		)	—			3.3
Mortgage-backed and asset-backed securities	2,082.0		18.2		(15.6		)	(12.9		)	2,071.7
Foreign government, agency and provincial obligations	1,053.6		7.7		(6.6		)	(8.3		)	1,046.4
Preferred stocks	81.9		6.1		—			(.1		)	87.9
Total fixed maturity investments	$	5,755.9	$	133.6	$	(44.2	)	$	(59.2	)	$	5,786.1

The cost or amortized cost and carrying value of White Mountains’ fixed maturity investments and convertible fixed maturity investments, at December 31, 2011 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, 2011
Millions	Cost or amortized cost		Carrying value
Due in one year or less	$	669.6	$	681.0
Due after one year through five years	1,809.1		1,857.5
Due after five years through ten years	563.1		582.8
Due after ten years	52.8		54.5
Mortgage-backed and asset-backed securities	3,190.5		3,222.9
Preferred stocks	82.3		78.8
Total	$	6,367.4	$	6,477.5

The cost or amortized cost, gross unrealized investment gains and losses, net foreign currency gains and losses, and carrying values of White Mountains’ common equity securities, convertible fixed maturities and other long-term investments as of December 31, 2011 and 2010, were as follows:

	December 31, 2011
Millions	Cost or amortized cost		Gross unrealized gains		Gross unrealized losses			Net foreign currency gains (losses)			Carrying value
Common equity securities	$	691.7	$	72.0	$	(8.7	)	$	—		$	755.0
Convertible fixed maturities	$	139.2	$	6.2	$	(1.6	)	$	—		$	143.8
Other long-term investments	$	274.4	$	55.5	$	(25.2	)	$	(3.4	)	$	301.3

	December 31, 2010
Millions	Cost or amortized cost		Gross unrealized gains		Gross unrealized losses			Net foreign currency gains (losses)			Carrying value
Common equity securities	$	561.2	$	105.5	$	(1.5	)	$	1.8		$	667.0
Convertible fixed maturities	$	126.9	$	16.2	$	(.1	)	$	—		$	143.0
Other long-term investments	$	329.5	$	62.4	$	(13.0	)	$	(6.8	)	$	372.1

Sales and maturities of investments, excluding short-term investments, totaled $5,044.5 million, $4,492.6 million and $3,748.5 million for the years ended December 31, 2011, 2010, and 2009. There were no non-cash exchanges or involuntary sales of investment securities during 2011, 2010, and 2009.

Investments Held on Deposit or as Collateral

As of December 31, 2011 and 2010, investments of $100.2 million and $314.1 million, respectively, were held in trusts required to be maintained in relation to various reinsurance agreements. White Mountains’ 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 $313.4 million and $352.6 million as of December 31, 2011 and 2010.

Fair value measurements at December 31, 2011

White Mountains’ invested assets measured at fair value include fixed maturity securities, common and preferred equity securities, convertible fixed maturity securities and other long-term investments which primarily consist of hedge funds and private equity funds. Fair value measurements reflect management’s best estimate of the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Fair value measurements fall into a hierarchy with three levels based on the nature of the inputs. Fair value measurements based on quoted prices in active markets for identical assets are at the top of the hierarchy (“Level 1”), followed by fair value measurements based on observable inputs that do not meet the criteria for Level 1, including quoted prices in inactive markets and quoted prices in active markets for similar, but not identical instruments (“Level 2”). Measurements based on unobservable inputs, including a reporting entity’s estimates of the assumptions that market participants would use are at the bottom of the hierarchy (“Level 3”).

White Mountains uses quoted market prices or other observable inputs to estimate fair value for the vast majority of its investment portfolio. Investments valued using Level 1 inputs include fixed maturities, primarily U.S. Treasury securities, publicly-traded common equities and short-term investments, which include U.S. Treasury Bills. Investments valued using Level 2 inputs consist of fixed maturities, including corporate debt, state and other government debt, convertible fixed maturity securities and mortgage-backed and asset-backed securities. Fair value estimates for investments classified as Level 3 measurements include investments in hedge funds, private equity funds and certain investments in fixed maturities and common equity securities. Fair value measurements for securities for which observable inputs are unavailable are estimated using industry standard pricing models and observable inputs such as benchmark interest rates, matrix pricing, market comparables, broker quotes, issuer spreads, bids, offers, credit ratings, prepayment speeds and other relevant inputs. In circumstances where quoted prices or observable inputs are adjusted to reflect management’s best estimate of fair value, such fair value measurements are considered a lower level measurement in the fair value hierarchy.

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 each hedge fund’s and private equity fund’s audited annual financial statements 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 values of White Mountains’ investments in hedge funds and private equity funds have been classified as Level 3 measurements. The fair value of White Mountains’ 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 $68.1 million and $77.8 million of investment-related liabilities recorded at fair value and included in other liabilities as of December 31, 2011 and 2010. 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’ fair value measurements for investments at December 31, 2011 and 2010, by level. The fair value measurements for derivative assets associated with White Mountains’ variable annuity business are presented in Note 8.

	December 31, 2011
Millions	Fair value		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs

Fixed maturities:
US Government and agency obligations	$	305.0	$	296.2	$	8.8	$	—

Debt securities issued by corporations:
Consumer	790.7		—		790.7		—
Industrial	359.4		—		359.4		—
Financials	239.6		3.8		235.8		—
Communications	225.8		—		225.8		—
Basic materials	195.7		—		195.7		—
Utilities	140.1		—		140.1		—
Energy	155.8		—		155.8		—
Technology	24.5		—		24.5		—
Diversified	3.5		—		3.5		—
Total debt securities issued by corporations:	2,135.1		3.8		2,131.3		—

Municipal obligations	2.7		—		2.7		—
Mortgage-backed and asset-backed securities	3,222.9		—		3,207.8		15.1
Foreign government, agency and provincial obligations	589.2		65.7		523.5		—
Preferred stocks	78.8		—		15.0		63.8
Total fixed maturities(1)	6,333.7		365.7		5,889.1		78.9

Short-term investments	846.0		846.0		—		—

Common equity securities:
Financials	219.2		185.8		1.5		31.9
Consumer	188.8		188.5		.3		—
Basic materials	121.0		119.9		1.1		—
Energy	72.6		72.6		—		—
Utilities	42.0		41.8		.2		—
Technology	25.8		25.8		—		—
Other	85.6		33.0		52.2		.4
Total common equity securities	755.0		667.4		55.3		32.3

Convertible fixed maturity investments	143.8		—		143.8		—
Other long-term investments(2)	268.3		—		—		268.3
Total investments	$	8,346.8	$	1,879.1	$	6,088.2	$	379.5

(1) Carrying value includes $111.8 that is classified as assets held for sale relating to AutoOne discontinued operations.

(2) Excludes carrying value of $33.0 associated with other long-term investments accounted for using the equity method.

	December 31, 2010
Millions	Fair value		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs

Fixed maturities:
US Government and agency obligations	$	398.7	$	388.9	$	9.8	$	—

Debt securities issued by corporations:
Consumer	769.0		—		769.0		—
Industrial	511.3		—		511.3		—
Financials	265.8		6.3		259.5		—
Communications	226.3		—		226.3		—
Basic materials	125.3		—		125.3		—
Utilities	106.7		—		106.7		—
Energy	151.5		—		151.5		—
Technology	22.1		—		22.1		—
Total debt securities issued by corporations:	2,178.0		6.3		2,171.7		—

Municipal obligations	3.3		—		3.3
Mortgage-backed and asset-backed securities	2,071.7		—		2,014.7		57.0
Foreign government, agency and provincial obligations	1,046.5		82.6		963.9		—
Preferred stocks	87.9		—		16.5		71.4
Total fixed maturities	5,786.1		477.8		5,179.9		128.4

Short-term investments	975.3		878.7		96.6		—

Common equity securities:
Financials	221.6		152.6		1.2		67.8
Consumer	123.3		122.5		.8		—
Basic materials	98.8		97.1		1.7		—
Energy	60.2		60.2		—		—
Utilities	47.6		44.6		—		3.0
Technology	31.8		30.4		1.4		—
Other	83.7		30.5		52.8		.4
Total common equity securities	667.0		537.9		57.9		71.2

Convertible fixed maturity investments	143.0		—		143.0		—
Other long-term investments(1)	330.2		—		—		330.2
Total investments	$	7,901.6	$	1,894.4	$	5,477.4	$	529.8

(1) Excludes carrying value of $41.9 associated with other long-term investments accounted for using the equity method.

Debt securities issued by corporations

The following table summarizes the ratings of the corporate debt securities held in White Mountains’ investment portfolio as of December 31, 2011 and 2010:

Millions	December 31, 2011		December 31, 2010
AAA	$	—	$	—
AA	206.8		210.0
A	802.8		833.7
BBB	1,110.8		1,109.1
BB	6.2		24.5
Other	8.5		.7
Debt securities issued by corporations	$	2,135.1	$	2,178.0

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’ non-agency commercial mortgage-backed portfolio (“CMBS”) is generally short tenor and structurally senior, with more than 20 points of subordination on average for fixed rate CMBS and more than 45 points of subordination on average for floating rate CMBS as of December 31, 2011. 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. White Mountains believes these levels of protection will mitigate the risk of loss tied to the refinancing challenges facing the commercial real estate market. As of December 31, 2011, on average less than 2% of the underlying loans were reported as non-performing for all non-agency CMBS held by White Mountains. White Mountains is not an originator of residential mortgage loans and did not hold any residential mortgage-backed securities (“RMBS”) categorized as sub-prime as of December 31, 2011. White Mountains’ investments in hedge funds and private equities contain negligible amounts of sub-prime mortgage-backed securities at December 31, 2011. 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’ review of the characteristics of their underlying mortgage loan pools, such as credit scores and financial ratios. White Mountains’ non-agency residential mortgage-backed portfolio is generally of moderate average life and structurally senior. White Mountains does not own any collateralized debt obligations, including residential mortgage-backed collateralized debt obligations.

	December 31, 2011						December 31, 2010
Millions	Fair Value		Level 2		Level 3		Fair Value		Level 2		Level 3
Mortgage-backed securities:
Agency:
GNMA	$	1,365.8	$	1,365.8	$	—	$	1,143.6	$	1,102.7	$	40.9
FNMA	712.6		712.6		—		234.9		234.9		—
FHLMC	35.9		35.9		—		39.1		39.1		—
Total Agency(1)	2,114.3		2,114.3		—		1,417.6		1,376.7		40.9
Non-agency:
Residential	83.1		68.0		15.1		90.6		74.5		16.1
Commercial	276.7		276.7		—		87.0		87.0		—
Total Non-agency	359.8		344.7		15.1		177.6		161.5		16.1

Total mortgage-backed securities	2,474.1		2,459.0		15.1		1,595.2		1,538.2		57.0
Other asset-backed securities:
Credit card receivables	380.6		380.6		—		248.3		248.3		—
Vehicle receivables	345.6		345.6		—		228.1		228.1		—
Other	22.6		22.6		—		.1		.1		—
Total other asset-backed securities	748.8		748.8		—		476.5		476.5		—
Total mortgage and asset-backed securities	$	3,222.9	$	3,207.8	$	15.1	$	2,071.7	$	2,014.7	$	57.0

(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’ investments in non-agency RMBS and non-agency CMBS securities as of December 31, 2011 are as follows:

			Security Issuance Year
Millions	Fair Value		2003		2006		2007		2009		2010		2011
Non-agency RMBS	$	83.1	$	3.3	$	23.0	$	26.4	$	—	$	10.5	$	19.9
Non-agency CMBS	276.7		—		—		17.4		11.2		2.3		245.8
Total	$	359.8	$	3.3	$	23.0	$	43.8	$	11.2	$	12.8	$	265.7

Non-agency Residential Mortgage-backed Securities

The classification of the underlying collateral quality and the tranche levels of White Mountains’ non-agency RMBS securities are as follows as of December 31, 2011:

Millions	Fair Value		Super Senior (1)		Senior (2)		Subordinate(3)
Prime	$	67.2	$	20.5	$	46.7	$	—
Non-prime	15.9		15.2		.7		—
Sub-prime	—		—		—		—
Total	$	83.1	$	35.7	$	47.4	$	—

(1) At issuance, Super Senior 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 were rated AAA by Standard & Poor’s or Aaa by Moody’s and were senior to non-AAA or non-Aaa bonds.

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

Non-agency Commercial Mortgage-backed Securities

The amount of fixed and floating rate securities and their tranche levels of White Mountains’ non-agency CMBS securities are as follows as of December 31, 2011:

Millions	Fair Value		Super Senior (1)		Senior(2)		Subordinate(3)
Fixed rate CMBS	$	249.3	$	46.7	$	202.6	$	—
Floating rate CMBS	27.4		17.4		10.0		—
Total	$	276.7	$	64.1	$	212.6	$	—

(1) At issuance, Super Senior were rated AAA by Standard & Poor’s or Aaa by Moody’s and were senior to other AAA or Aaa bonds.

(2) At issuance, Senior were rated AAA by Standard & Poor’s or Aaa by Moody’s and were senior to non-AAA or non-Aaa bonds.

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

Other long-term investments

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. At December 31, 2011, White Mountains held investments in 16 hedge funds and 32 private equity funds. The decrease in fair value of hedge funds and private equity funds is due to net redemptions during the period. The largest investment in a single fund was $27.4 million and $49.2 million at December 31, 2011 and 2010.

The following table summarizes investments in hedge funds and private equity interests by investment objective and sector at December 31, 2011 and December 31, 2010:

	December 31, 2011				December 31, 2010
Millions	Fair Value		Unfunded Commitments		Fair Value		Unfunded Commitments
Hedge funds
Long/short equity	$	48.8	$	—	$	50.4	$	—
Long/short credit & distressed	32.3		—		34.1		—
Long diversified strategies	16.9		—		25.2		—
Long/short equity REIT	14.5		—		24.0		—
Long/short equity activist	12.3		—		16.9		—
Long bank loan	.5		—		5.1		—
Total hedge funds	125.3		—		155.7		—

Private equity funds
Energy infrastructure & services	28.0		9.9		24.2		10.8
Distressed residential real estate	27.4		—		49.2		—
Multi-sector	26.9		8.2		26.0		10.6
Private equity secondaries	11.3		4.0		10.4		4.4
Real estate	9.5		3.3		9.1		4.6
International multi-sector, Europe	7.8		4.7		10.5		5.3
Manufacturing/Industrial	6.2		—		17.9		—
International multi-sector, Asia	3.6		2.6		4.9		2.7
Insurance	3.5		41.3		3.9		41.3
Venture capital	2.4		.5		2.2		1.0
Healthcare	2.3		7.0		1.5		8.0
Total private equity funds	128.9		81.5		159.8		88.7

Total hedge and private equity funds included in other long-term investments	$	254.2	$	81.5	$	315.5	$	88.7

At December 31, 2011, other long-term investments also include $21.8 million of an investment in a tax advantaged federal affordable housing development fund. White Mountains has unfunded commitments to this fund of $10.1 million at December 31, 2011.

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, 2011 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	$	—	$	—	$	—	$	6.5	$	6.5
Quarterly	27.5		27.0		20.1		—		74.6
Semi-annual	—		5.1		—		14.5		19.6
Annual	16.9		—		7.2		.5		24.6
Total	$	44.4	$	32.1	$	27.3	$	21.5	$	125.3

Certain of the hedge fund investments in which White Mountains is invested are no longer active and are in process of disposing of their underlying investments. Distributions from such funds are remitted to investors as the fund’s underlying investments are liquidated. At December 31, 2011, distributions of $3.3 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 at December 31, 2011.

White Mountains has also submitted redemption requests for certain of its investments in active hedge funds. At December 31, 2011 redemptions of $2.2 million are outstanding. The date at which such remittances will be received is not determinable at December 31, 2011. Redemptions are recorded as receivables when approved by the hedge funds and when 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. At December 31, 2011, 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	$	42.9	$	—	$	79.8	$	6.2	$	128.9

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 maturities, common equity securities, convertible fixed maturities and other long-term investments at December 31, 2011 are comprised 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 table summarizes the changes in White Mountains’ fair value measurements by level for the year ended December 31, 2011:

							Level 3 Investments
Millions	Level 1 Investments			Level 2 Investments			Fixed Maturities			Common equity securities			Convertible fixed maturities		Other long-term investments			Total
Balance at January 1, 2011	$	1,894.4		$	5,477.4		$	128.4		$	71.2		$	—	$	330.2	(1)	$	7,901.6	(1)
Total realized and unrealized gains (losses) (1) (2)	(1.4		)	113.2			(8.1		)	(4.7		)	—		19.5			118.5
Foreign currency gains (losses) through OCI and other revenue	4.6			(76.1		)	(4.4		)	1.6			—		(5.0		)	(79.3		)
Amortization/Accretion	2.3			(54.2		)	.3			—			—		—			(51.6		)
Purchases	10,653.6			8,905.6			213.7			19.7			—		58.4			19,851.0
Sales	(10,674.4		)	(8,528.7		)	—			(55.5		)	—		(134.8		)	(19,393.4		)
Transfers in	—			269.2			18.2			—			—		—			287.4
Transfers out	—			(18.2		)	(269.2		)	—			—		—			(287.4		)
Balance at December 31, 2011	$	1,879.1		$	6,088.2	(2)	$	78.9		$	32.3		$	—	$	268.3	(1)	$	8,346.8	(1)

(1) Excludes carrying value of $41.9 and $33.0 at January 1, 2011 and December 31, 2011 associated with other long-term investments accounted for using the equity method.

(2) Carrying value includes $111.8 that is classified as assets held for sale relating to AutoOne discontinued operations.

Fair Value Measurements — transfers between levels

Transfers between levels are recorded using the fair value measurement as of the end of the quarterly period in which the event or change in circumstance giving rise to the transfer occurred.

During 2011, 10 securities which had been classified as Level 3 measurements at January 1, 2011 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 at December 31, 2011. These measurements comprise “Transfers out” of Level 3 and “Transfers in” to Level 2 of $269.2 million in fixed maturities for the period ended December 31, 2011. Two securities that were classified as Level 2 investments at January 1, 2011 were priced with unobservable inputs during the current period and represent the “Transfers in” of $18.2 million in Level 3 investments. The fair value of these securities were estimated using industry standard pricing models, in which management selected inputs using its best judgment. These securities are considered to be Level 3 because the measurements are not directly observable. At December 31, 2011, the estimated fair value for these securities determined using the industry standard pricing models was $1.6 million less than the estimated fair value based upon quoted prices provided by a third party.

- Definition

Tabular disclosure of investments in certain debt and equity securities (and certain other trading assets) which include all debt and equity securities (other than those equity securities accounted for under the equity or cost methods of accounting) with readily determinable fair values. Other trading assets include assets that are carried on the balance sheet at fair value and held for trading purposes. A debt security represents a creditor relationship with an enterprise that is in the form of a security. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities (and other trading assets).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 3, 19, 20, 21, 22, 137
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27161-111563

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 320
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27357-111563

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27290-111563

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27405-111563

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27232-111563

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Debt Security
-URI http://asc.fasb.org/extlink&oid=6509901
-Topic 320

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Equity Security
-URI http://asc.fasb.org/extlink&oid=6511694
-Topic 320

+ Details

Debt

12 Months Ended

Dec. 31, 2011

Debt

Debt

NOTE 6. Debt

White Mountains’ debt outstanding as of December 31, 2011 and 2010 consisted of the following:

	December 31,
Millions	2011			2010
OBH Senior Notes, at face value	$	269.9		$	419.9
Unamortized original issue discount	(.1		)	(.3		)
OBH Senior Notes, carrying value	269.8			419.6

SIG Senior Notes, at face value	400.0			400.0
Unamortized original issue discount	(.7		)	(.8		)
SIG Senior Notes, carrying value	399.3			399.2
WTM Bank Facility	—			—
Old Lyme	2.1			—
Total debt	$	671.2		$	818.8

A schedule of contractual repayments of White Mountains’ debt as of December 31, 2011 follows:

Millions	December 31, 2011
Due in one year or less	$	—
Due in two to three years	269.9
Due in four to five years	2.1
Due after five years	400.0
Total	$	672.0

OBH Senior Notes

In May 2003, OneBeacon U.S. Holdings, Inc. (“OBH”), formerly Fund American Companies, Inc., a wholly-owned subsidiary of OneBeacon Ltd., issued $700.0 million face value of senior unsecured debt through a public offering, at an issue price of 99.7% (the “OBH Senior Notes”) and received $693.4 million of proceeds, net of a $4.5 million underwriting discount. The OBH Senior Notes bear an annual interest rate of 5.875%, payable semi-annually in arrears on May 15 and November 15, until maturity in May 2013. White Mountains fully and unconditionally guarantees the payment of principal and interest on the OBH Senior Notes. OneBeacon Ltd. pays White Mountains a guarantee fee equal to 25 basis points per annum on the outstanding principal amount of the OBH Senior Notes. If White Mountains’ voting interest in OneBeacon Ltd.’s common shares ceases to represent more than 50% of all their voting securities, OneBeacon Ltd. is obligated to seek to redeem, exchange or otherwise modify the senior notes in order to fully and permanently eliminate White Mountains’ obligations under the guarantee. In the event that White Mountains’ guarantee is not eliminated, the guarantee fee will increase over time up to a maximum guarantee fee of 425 basis points.

OBH incurred $7.3 million in expenses related to the issuance of the OBH Senior Notes (including $4.5 million in underwriting fees), which have been deferred and are being recognized into 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 6.0% per annum. OBH recorded $20.5 million, $29.5 million, and $38.1 million in interest expense, inclusive of amortization of issuance costs, on the OBH Senior Notes for the years ended December 31, 2011, 2010, and 2009.

On June 1, 2010, through a cash tender offer, OBH repurchased and retired $156.4 million aggregate principal amount of OBH Senior Notes for an aggregate purchase price of $165.4 million, which resulted in a $9.6 million loss, including transaction fees.

In addition to the cash tender offer, during 2010 OBH repurchased and retired $29.7 million of outstanding OBH Senior Notes for $30.8 million, which resulted in a $1.2 million loss and OBIC purchased $1.1 million of outstanding OBH Senior Notes for $1.1 million.

On April 6, 2011, through a cash tender offer, OBH purchased and retired $150.0 million aggregate principal amount of OBH Senior Notes for $161.6 million, which resulted in a $12.0 million loss, including transaction fees.

At December 31, 2011, White Mountains was in compliance with all of the covenants under the OBH Senior Notes.

SIG Senior Notes

In March 2007, SIG 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. At December 31, 2011, the unamortized balance of the loss remaining in accumulated other comprehensive income was $1.2 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 6.49% per annum. White Mountains recorded $26.1 million of interest expense, inclusive of amortization of issuance costs and the interest rate lock agreement, on the SIG Senior Notes for the years ended December 31, 2011, 2010, and 2009.

At December 31, 2011, White Mountains was in compliance with all of the covenants under the SIG Senior Notes.

Bank Facility

On August 12, 2011, White Mountains entered into a revolving credit facility with a total commitment of $375.0 million (the “WTM Bank Facility”) with a syndicate of lenders administered by Bank of America, N.A. The WTM Bank Facility replaces the previous revolving credit facility which had a total commitment of $475.0 million. As of December 31, 2011, the WTM Bank Facility was undrawn.

The WTM Bank Facility contains various affirmative, negative and financial covenants which White Mountains considers to be customary for such borrowings, including certain minimum net worth and maximum debt to capitalization standards. 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. At December 31, 2011, White Mountains was in compliance with all of the covenants under the WTM Bank Facility.

Old Lyme

On December 30, 2011 Sirius Group acquired the run-off loss reserve portfolio of Old Lyme (see Note 2). As part of the acquisition, Sirius Group entered into a five-year $2.1 million purchase note. The principal amount of the purchase note is subject to upward adjustments for favorable loss reserve development (up to 50% of $6.0 million) and downward adjustments for any adverse loss reserve development.

Mortgage Note

In December 2005, OneBeacon entered into a $40.8 million, 18-year mortgage note, which has a variable interest rate based upon the lender’s 30-day LIBOR rate, to purchase land and a building in Canton, Massachusetts. In 2009, OneBeacon repaid the entire outstanding principal balance on the Mortgage Note.

Concurrent with entering into the Mortgage Note, OneBeacon also entered into an interest rate swap to hedge its exposure to variability in the interest rate on the Mortgage Note. Interest paid or received on the swap was reported in interest expense. Changes in the fair value of the interest rate swap were reported as a component of other comprehensive income. At the time of repayment of the outstanding balance on the Mortgage Note, OneBeacon paid $7.4 million to settle the related interest rate swap that had been used to fix the rate of interest on the Mortgage Note. The interest rate swap settlement was recorded as a reduction of other revenues on a pre-tax basis with a corresponding $7.4 million increase in other comprehensive income on a pre-tax basis ($4.8 million after-tax). The after-tax change in the fair value of the interest rate swap was a gain of $2.0 million for the year ended December 31, 2009.

Sierra Note

In connection with its acquisition of the Sierra Insurance Group Companies (“Sierra Group”) on March 31, 2004, Sirius Group entered into a $62.0 million purchase note (the “Sierra Note”), $58.0 million of which may be adjusted over its six-year term to reflect favorable or adverse loss reserve development on the acquired reserve portfolio and run-off of remaining policies in force (mainly workers compensation business), as well as certain other balance sheet protections. Since inception the principal of the Sierra Note had been reduced by $29.0 million as a result of adverse development on the acquired reserves and run-off of unearned premium, which includes $5.2 million and $22.8 million of adverse development which occurred during 2008 and 2005 and $1.9 million and $9.1 million of favorable development in 2010 and 2007. Interest accrued on the unpaid balance of the Sierra Note at a rate of 4.0% per annum, compounded quarterly, and was payable at its maturity.

On October 31, 2008, White Mountains disposed of its remaining interest in the Sierra Group as part of the Berkshire Exchange transaction. White Mountains was still obligated to repay the Sierra Note, but Berkshire provided White Mountains an indemnity, whereby Berkshire reimbursed White Mountains all amounts due under the Sierra Note at its maturity, as adjusted for future reserve development, except for the portion of interest on the Sierra Note that accrued from its issue date through December 31, 2007, plus interest on this accrued amount through the date of repayment.

The Sierra Note matured on March 31, 2010. However, the final amount due was in dispute with respect to the amount of loss reserve development. On September 15, 2010, White Mountains paid Sierra the undisputed amounts owed of $42.8 million on the Sierra Note which consisted of $33.0 million for the principal repayment and $9.8 million for accrued interest. Berkshire reimbursed White Mountains $36.7 million, which was consisted of the $33.0 million principal balance and $3.7 million for accrued interest.

During the fourth quarter of 2011, the dispute was settled through arbitration. White Mountains paid the interest accrued on the Sierra Note and recognized $5.5 million of interest expense.

Atlantic Specialty Note

In connection with its acquisition of Atlantic Specialty Insurance Company on March 31, 2004, OneBeacon issued a $20.0 million ten-year note to the seller (the “Atlantic Specialty Note”). The note accrued interest at a rate of 5.2%, except that the outstanding principal amount in excess of $15.0 million accrued interest at a rate of 3.6%. In 2010, OneBeacon repaid the remaining $14.0 million outstanding principal on the note.

Interest

Total interest expense incurred by White Mountains for its indebtedness was $55.2 million, $57.3 million and $70.8 million in 2011, 2010 and 2009. Total interest paid by White Mountains for its indebtedness was $59.0 million, $64.1 million and $69.8 million in 2011, 2010 and 2009.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References + Details

Income Taxes

12 Months Ended

Dec. 31, 2011

Income Taxes

Income Taxes

NOTE 7. 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, Germany, Gibraltar, Luxembourg, the Netherlands, Singapore, Sweden, Switzerland, the United Kingdom and the United States.

The total income tax benefit (expense) for the years ended December 31, 2011, 2010 and 2009 consisted of the following:

	Year Ended December 31,
Millions	2011			2010			2009
Current tax benefit (expense):
U.S. federal	$	39.5		$	52.4		$	(40.0	)
State	(2.5		)	(2.2		)	(1.5		)
Non-U.S.	5.1			(9.1		)	(2.7		)
Total current tax benefit (expense)	42.1			41.1			(44.2		)
Deferred tax benefit (expense):
U.S. federal	(34.1		)	(61.6		)	(139.0		)
State	—			—			—
Non-U.S.	114.7			3.6			(31.0		)
Total deferred tax benefit (expense)	80.6			(58.0		)	(170.0		)
Total income tax benefit (expense)	$	122.7		$	(16.9	)	$	(214.2	)

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’ worldwide operations are taxed) to the income tax (expense) benefit on pre-tax income follows:

	Year Ended December 31,
Millions	2011			2010			2009
Tax (expense) benefit at the U.S. statutory rate	$	(21.5	)	$	(53.6	)	$	(279.1	)
Differences in taxes resulting from:
Change in valuation allowance	128.2			2.6			53.7
Non-U.S. earnings, net of foreign taxes	6.2			22.8			(1.2		)
Tax reserve adjustments	4.3			(2.8		)	8.8
Tax exempt interest and dividends	2.9			2.3			1.7
Tax rate change enacted in Luxembourg	1.2			2.8			—
Withholding tax	.2			(.2		)	(.7		)
Purchase of subsidiaries	—			4.5			—
Sale of subsidiaries	—			4.3			—
Other, net	1.2			.4			2.6
Total income tax benefit (expense) on pre-tax income	$	122.7		$	(16.9	)	$	(214.2	)

The non-U.S. component of pre-tax income was $65.4 million, $74.4 million and $221.0 million for the years ended December 31, 2011, 2010 and 2009.

Tax Payments and Receipts

Net income tax payments to (receipts from) national governments (primarily the United States) totaled $12.5 million, $(47.0) million and $(17.5) million for the years ended December 31, 2011, 2010 and 2009.

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’ deferred tax assets and liabilities follows:

	December 31,
Millions	2011			2010
Deferred income tax assets related to:
Non-U.S. net operating loss carryforwards	$	504.0		$	545.4
Loss reserve discount	114.2			142.4
U.S. federal and state net operating loss carryforwards	102.7			103.6
Incentive compensation	43.4			36.9
Unearned premiums	41.2			37.3
U.S. tax credit carryforwards	13.5			12.0
Deferred compensation	11.4			13.1
Loss on sale of AutoOne	10.4			—
Pension and benefit accruals	8.0			4.3
Accrued interest	3.5			.5
Investment basis differences	1.6			7.3
Fixed assets	(.1		)	4.8
Other items	9.5			14.1
Total gross deferred income tax assets	863.3			921.7
Less: valuation allowances	(232.7		)	(385.8		)
Total net deferred income tax assets	630.6			535.9
Deferred income tax liabilities related to:
Safety reserve	369.6			378.5
Deferred acquisition costs	48.8			41.5
Net unrealized investment gains	34.8			55.8
Purchase accounting	.7			2.1
Intangible assets	(.1		)	.1
Other items	5.4			(.8		)
Total deferred income tax liabilities	459.2			477.2
Net deferred tax asset (liability)	$	171.4		$	58.7

White Mountains’ 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.

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. During the next twelve months, it is possible that certain planning strategies will no longer be sufficient to utilize the entire deferred tax asset, which could result in material changes to White Mountains’ deferred tax assets and tax expense.

Of the $232.7 million valuation allowance at December 31, 2011, $225.5 million relates to deferred tax assets on net operating losses in Luxembourg subsidiaries (discussed below under “Net Operating Loss Carryforwards”) that are not expected to have significant income in the future, $6.9 million relates to deferred tax assets on U.S. losses and other federal deferred tax benefits. Of the $385.8 million valuation allowance at December 31, 2010, $379.6 million relates to deferred tax assets on net operating losses in Luxembourg subsidiaries (discussed below under “Net Operating Loss Carryforwards”) that are not expected to have significant income in the future, $6.2 million relates to deferred tax assets on U.S. losses and other federal deferred tax benefits.

Release of Valuation Allowance in Luxembourg

During the fourth quarter of 2011, White Mountains recorded a $129.5 million tax benefit from the release of valuation allowances against deferred tax assets in two Luxembourg domiciled subsidiaries, White Sands Holdings (Luxembourg) S.à r.l. (“Sands”) and OneBeacon Holdings (Luxembourg) S.à r.l. (“Holdings”). These companies had built up substantial deferred tax assets due to net operating loss carryforwards (“NOLs”). There were full valuation allowances on these deferred tax assets in periods prior to the fourth quarter of 2011 because neither company expected future taxable income to utilize them.

During the fourth quarter, Sirius Group reorganized its corporate structure to optimize operational and capital efficiency. As part of the Reorganization, additional internal debt instruments were added to Sirius International Holdings Sweden AB. These additional internal debt instruments were initially contributed to Sands and later some were contributed to Holdings after Sirius Group acquired Holdings from OneBeacon on January 24, 2012. As the plan for the Sirius Group to acquire 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. The valuation allowance released at Sands and Holdings is equal to the expected future tax-effected income from the notes. The notes have staggered maturity dates with the longest dated note being 30 years. The remaining deferred tax asset for the unutilized NOLs at both companies still carries a full valuation allowance as no additional taxable income is expected.

Net Operating Loss and Capital Loss Carryforwards

Net operating loss and capital loss carryforwards as of December 31, 2011, the expiration dates and the deferred tax assets thereon are as follows:

	December 31, 2011
Millions	United States			Luxembourg			Sweden			Total
2012	$	—		$	—		$	—		$	—
2013-2017	2.4			—			—			2.4
2018-2022	18.7			—			—			18.7
2023-2032	305.7			—			—			305.7
No expiration date	—			1,740.3			10.7			1,751.0
Total	$	326.8		$	1,740.3		$	10.7		$	2,077.8

Gross deferred tax asset	$	102.7		$	501.2		$	2.8		$	606.7
Valuation allowance	(1.8		)	(225.5		)	(.3		)	(227.6		)
Net deferred tax asset	$	100.9		$	275.7		$	2.5		$	379.1

White Mountains expects to utilize net operating loss carryforwards in Luxembourg of $999.7 million but does not expect to utilize the remainder as they belong to companies that are not expected to have significant 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 $29.1 million subject to an annual limitation on utilization under Internal Revenue Code Section 382. At December 31, 2011, there were U.S. foreign tax credit carryforwards available of $8.8 million, which begin to expire in 2016. At December 31, 2011, there were U.S. low-income housing tax credit carryforwards available of $2.0 million, which begin to expire in 2031. Also, at December 31, 2011, there were U.S. alternative minimum tax credit carryforwards of $2.7 million which do not expire.

During 2010, White Mountains International S.à r.l. (“WMI”) received a tax ruling in Luxembourg which allowed it to change its tax functional currency in Luxembourg to the Swedish krona from the euro. Pursuant to the ruling, WMI revalued its NOL carryforwards in Luxembourg using the December 31, 2008 euro/krona exchange rate. This resulted in WMI recording an $11.9 million deferred tax benefit in 2010 for the increase in its NOLs in Luxembourg.

ASC 740-10

Under ASC 740-10, recognition of the benefit of a given tax position is based upon whether or not 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, 2009	$	61.4		$	17.1		$	8.3		$	86.8
Changes in prior year tax positions	7.2			46.1			3.1			56.4
Tax positions taken during the current year	—			16.4			—			16.4
Lapse in statute of limitations	(1.0		)	—			(.2		)	(1.2		)
Settlements with tax authorities	(53.7		)	(.9		)	(6.9		)	(61.5		)
Balance at December 31, 2009	13.9			78.7			4.3			96.9
Changes in prior year tax positions	.5			(8.5		)	1.9			(6.1		)
Tax positions taken during the current year	.4			5.0			—			5.4
Lapse in statute of limitations	—			—			—			—
Settlements with tax authorities	(.3		)	(.1		)	—			(.4		)
Balance at December 31, 2010	14.5			75.1			6.2			95.8
Changes in prior year tax positions	(.9		)	.1			2.0			1.2
Tax positions taken during the current year	—			(20.4		)	—			(20.4		)
Lapse in statute of limitations	(3.4		)	(5.7		)	(1.4		)	(10.5		)
Settlements with tax authorities	(.6		)	—			—			(.6		)
Balance at December 31, 2011	$	9.6		$	49.1		$	6.8		$	65.5

(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 recognized, $16.4 million (tax plus interest and penalties) would be recorded as a reduction to income tax expense. Also included in the balance at December 31, 2011, are $49.1 million of tax positions for which ultimate deductibility is highly certain but the timing of deductibility is uncertain. Because of the impact of deferred tax accounting, other than interest and penalties, the disallowance of the shorter deductibility period would not affect the effective tax rate but would accelerate the payment of cash to the taxing authority to an earlier period. On November 18, 2009, the Internal Revenue Service (“IRS”) released a coordinated issue paper outlining their position with respect to loss reserves. The vast majority of the increase during 2009 and decrease during 2011 relates to deductions for loss reserves in which 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, 2011, 2010 and 2009 White Mountains recognized $0.6 million, $1.9 million, $(4.0) million in interest (benefit) expense, net of any tax benefit. The balance of accrued interest at December 31, 2011 and 2010 is $6.8 million and $6.2 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.

On October 14, 2009, a settlement was reached with the IRS on the 2003 through 2004 federal tax examination for certain U.S. subsidiaries of OneBeacon, Sirius Group and Esurance. The settlement resulted in an assessment of $24.9 million of additional tax or a total assessment of $51.9 million including interest, withholding tax and utilization of credits. White Mountains recorded a tax benefit of $17.8 million in the fourth quarter of 2009 from the settlement of the 2003 through 2004 tax examination.

The IRS is conducting an examination of income tax returns for 2005 and 2006 for certain U.S. subsidiaries of OneBeacon. On January 5, 2011, White Mountains received Form 4549-A (Income Tax Discrepancy Adjustments) from the IRS relating to the examination of tax years 2005 and 2006. The estimated total assessment, including interest and utilization of alternative minimum and foreign tax credit carryovers, is $19.6 million. White Mountains disagrees with the adjustments proposed by the IRS and intends to defend its position. The timing of the resolution of these issues is uncertain, however, 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.

On July 28, 2011, the IRS commenced an examination of the income tax returns for 2007, 2008 and 2009 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.

On December 15, 2011, the IRS commenced an examination of the income tax returns for 2010 for certain U.S. subsidiaries of AFI. Pursuant to a Stock Purchase Agreement dated as of May 17, 2011 between White Mountains and Allstate, White Mountains is required to indemnify Allstate for any changes in pre-closing taxes. White Mountains does not expect the resolution of this examination to result in a material change to its financial position.

The IRS conducted an examination of income tax returns for 2006 and 2007 for certain U.S. subsidiaries of Sirius Group. On October 26, 2011, the Sirius Group received and signed the IRS Revenue Agent’s Report, which contained no proposed adjustments. The IRS also examined the U.S. income tax return filed by WM Belvaux S.à r.l., a Luxembourg subsidiary, for tax year 2007. On May 3, 2011, the exam was completed with no proposed adjustments.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph h
-Article 4

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 136, 172
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 43, 44, 45, 46, 47, 48, 49
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319

Reference 6: 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.(h))
-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32537-109319

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32559-109319

+ Details

Variable Annuity Reinsurance and Weather Derivatives

12 Months Ended

Dec. 31, 2011

Variable Annuity Reinsurance and Weather Derivatives

Variable Annuity Reinsurance and Weather Derivatives

NOTE 8. Variable Annuity Reinsurance and Weather Derivatives

White Mountains has entered into agreements to reinsure death and living benefit guarantees associated with certain variable annuities in Japan. At December 31, 2011, the total guarantee value was approximately ¥233.7 billion (approximately $3.0 billion at exchange rates on that date). The collective account values of the underlying variable annuities were approximately 78% of the guarantee value at December 31, 2011. The following table summarizes the pre-tax operating results of WM Life Re for the years ended December 31, 2011, 2010 and 2009:

	Year Ended December 31,
Millions	2011			2010			2009
Fees, included in other revenues	$	32.5		$	30.2		$	28.5
Change in fair value of variable annuity liability, included in other revenues	(156.5		)	(223.5		)	77.1
Change in fair value of derivatives, included in other revenues	92.9			127.0			(158.4		)
Foreign exchange, included in other revenues	15.1			21.4			(3.9		)
Other investment income and gains (losses)	(.9		)	(.9		)	(1.4		)
Total revenues	(16.9		)	(45.8		)	(58.1		)
Change in fair value of variable annuity death benefit liabilities, included in other expenses	(1.8		)	(6.0		)	9.3
Death benefit claims paid, included in other expenses	(3.8		)	(2.7		)	(2.2		)
General and administrative expenses	(4.7		)	(6.3		)	(5.6		)
Pre-tax loss	$	(27.2	)	$	(60.8	)	$	(56.6	)

For the years ended December 31, 2011, 2010 and 2009 the change in the fair value of the variable annuity liability included $7.2 million, $47.7 million and $22.4 million of losses associated with changes in projected surrender assumptions.

All of White Mountains’ variable annuity reinsurance liabilities were classified as Level 3 measurements at December 31, 2011. The following table summarizes the changes in White Mountains’ variable annuity reinsurance liabilities and derivative instruments for the year ended December 31, 2011:

	Variable Annuity (Liabilities)			Derivative Instruments
Millions	Level 3			Level 3 (1)			Level 2 (1)(2)			Level 1 (3)			Total(4)
Balance at January 1, 2011	$	(610.2	)	$	275.3		$	72.2		$	—		$	347.5
Purchases	—			5.0			—			—			5.0
Realized and unrealized gains (losses)	(158.3		)	14.5			67.7			10.7			92.9
Transfers in (out)	—			—			—			—			—
Sales/settlements	—			(47.7		)	(100.7		)	(6.6		)	(155.0		)
Balance at December 31, 2011	$	(768.5	)	$	247.1		$	39.2		$	4.1		$	290.4

(1) Comprises over-the-counter instruments.

(2) Comprises interest rate swaps, total return swaps and foreign currency forward contracts. 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) Comprises 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 $485.3 at December 31, 2011 posted as collateral to its counterparties.

The following summarizes realized and unrealized derivative gains (losses) recognized in other revenues for the years ended December 31, 2011, 2010, and 2009 and the carrying values at December 31, 2011 and 2010 by type of instrument:

									Carrying Value
	Year Ended December 31,								December 31,
Millions	2011		2010			2009			2011		2010
Fixed income/interest rate	$	8.9	$	17.6		$	8.0		$	31.1	$	43.9
Foreign exchange	29.5		144.6			(69.5		)	161.3		225.3
Equity	54.5		(35.2		)	(96.9		)	98.0		78.3
Total	$	92.9	$	127.0		$	(158.4	)	$	290.4	$	347.5

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 over-the-counter counterparties’ credit ratings. 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 collateral provided to WM Life Re from counterparties:

	Year Ended December 31,
Millions	2011		2010
Short term investments	$	73.2	$	52.4
Fixed maturity securities	—		48.6
Total	$	73.2	$	101.0

Collateral held by or provided by WM Life Re in the form of fixed maturity securities comprise U.S. Treasury securities, 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. The following summarizes the value of collateral provided (held) by WM Life Re and net exposure on OTC derivative instruments recorded within other assets:

Millions	December 31, 2011			December 31, 2010
OTC derivative instruments(1)	$	295.4		$	351.5
Collateral held	(73.2		)	(101.0		)
Collateral provided	83.0			25.3
Net exposure on fair value of OTC instruments	$	305.2		$	275.8

(1) Value of OTC derivative instruments as of December 31, 2011 and 2010 excludes adjustments for counterparty credit risk of $(9.1) and $(4.0) included in fair value under GAAP.

The following table summarizes uncollateralized amounts due under WM Life Re’s OTC derivative contracts as of December 31, 2011 by counterparty:

Millions	Uncollateralized balance as of December 31, 2011		Standard & Poor’s Rating(1)
Royal Bank of Scotland	$	82.5	A-
Citigroup (2)	67.7		A-
Bank of America	54.2		A-
JP Morgan Chase(2)	34.2		A
Nomura(2)	31.9		BBB+
Barclays	25.1		A
Goldman Sachs	9.6		A-
Total	$	305.2

(1) Standard & Poor’s ratings as detailed above are: “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).

(2) Collateral provided (held) calculated under master netting agreement.

The OTC derivative contracts are subject to restrictions on liquidation of the instruments and distribution of proceeds under collateral agreements. In addition, WM Life Re held cash and short-term investments posted as collateral to its reinsurance counterparties. The total collateral comprises the following:

	Year Ended December 31,
Millions	2011		2010
Cash	$	453.5	$	291.1
Short-term investments	.6		31.6
Fixed maturity investments	31.2		3.3
Total	$	485.3	$	326.0

Weather Derivatives

During 2009, White Mountains sold Galileo Weather Risk Management Advisors LLC, Galileo Weather Risk Management Ltd and Galileo Weather Risks Advisors Limited for nominal consideration. White Mountains retained the outstanding weather derivative contracts and stopped writing any new contracts. Effective December 2009, White Mountains entered into an agreement to novate the remaining outstanding weather derivative contracts to an unrelated third party. White Mountains was released from any liability related to the weather derivative contracts and all guaranties related to the weather business were terminated. For the year ended December 31, 2009, $2.6 million of net losses were recognized on the weather and weather contingent derivatives portfolio.

Earnings Per Share

12 Months Ended

Dec. 31, 2011

Earnings Per Share

Earnings Per Share

NOTE 9. 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 for the years ended December 31, 2011, 2010 and 2009:

	Year Ended December 31,
	2011			2010			2009
Basic and diluted earnings per share numerators (in millions):
Net income attributable to White Mountains’ common shareholders	$	122.6		$	93.1		$	497.8

Allocation of income for participating unvested restricted common shares	(1.1		)	(1.1		)	(4.8		)
Dividends paid on participating restricted common shares	(.1		)	(.1		)	(.6		)
Total allocation to restricted common shares	(1.2		)	(1.2		)	(5.4		)
Net income attributable to White Mountains’ common shareholders, net of restricted share amounts	$	121.4		$	91.9		$	492.4
Undistributed net earnings:
Net income attributable to White Mountains’ common shareholders, net of restricted common share amounts	$	121.4		$	91.9		$	492.4
Dividends paid net of restricted common share amounts	(7.9		)	(8.7		)	(8.3		)
Total undistributed net earnings, net of restricted common share amounts	$	113.5		$	83.2		$	484.1
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period	7,881.0			8,548.4			8,849.4
Average unvested restricted common shares (1)	(69.4		)	(97.3		)	(85.3		)
Basic earnings per share denominator	7,811.6			8,451.1			8,764.1
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period	7,881.0			8,548.4			8,849.4
Average unvested restricted common shares (1)	(69.4		)	(97.3		)	(85.3		)
Average outstanding dilutive options to acquire common shares (2)	—			.5			1.5
Diluted earnings per share denominator	7,811.6			8,451.6			8,765.6
Basic earnings per share (in dollars):
Net income attributable to White Mountains’ common shareholders	$	15.56		$	10.89		$	56.25
Dividends declared and paid	(1.00		)	(1.00		)	(1.00		)
Undistributed earnings	$	14.56		$	9.89		$	55.25
Diluted earnings per share (in dollars)
Net income attributable to White Mountains’ common shareholders	$	15.56		$	10.89		$	56.24
Dividends declared and paid	(1.00		)	(1.00		)	(1.00		)
Undistributed earnings	$	14.56		$	9.89		$	55.24

(1) Restricted common shares outstanding vest either in equal annual installments or upon a stated date (see Note 11).

(2) The diluted earnings per share denominator for the year ended December 31, 2010 includes 1,200 common shares issuable upon exercise of incentive options at an average strike price of $189.31 per common share. The diluted earnings per share denominator for the year ended December 31, 2009 includes 5,280 common shares issuable upon exercise of incentive options at an average strike price of $183.03 per common share. The non-qualified options were not included in the diluted earnings per share denominator for any of the periods presented as their inclusion would be anti-dilutive (See Note 11).

Retirement and Postretirement Plans

12 Months Ended

Dec. 31, 2011

Retirement and Postretirement Plans

Retirement and Postretirement Plans

NOTE 10. 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, as well as former employees that had met the eligibility requirements and 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. Participants generally vest after five years of continuous service. 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 various pension plans at December 31, 2011 and 2010:

	Pension Benefits
Millions	2011			2010
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$	110.2		$	117.1
Service cost	.8			.8
Interest cost	5.2			6.0
Settlement gain	(.6		)	(2.2		)
Special termination benefit cost	.8			1.9
Assumption changes	7.7			6.6
Actuarial (gain) loss	(.3		)	(1.5		)
Benefits and expenses paid with plan assets, net of participant contributions	(8.4		)	(15.9		)
Benefits paid directly by OneBeacon	(2.4		)	(2.6		)
Projected benefit obligation at end of year	$	113.0		$	110.2
Change in plan assets:
Fair value of plan assets at beginning of year	$	133.0		$	130.2
Actual return on plan assets	(3.8		)	18.7
Benefits and expenses paid, net of participant contributions	(8.4		)	(15.9		)
Fair value of plan assets at end of year	$	120.8		$	133.0
Funded status at end of year	$	7.8		$	22.8

The funded status of the consolidated pension plans at December 31, 2011 was $7.8 million, which represents an over-funding of $34.3 million related to the Qualified Plan and an under-funding of $26.5 million related to the Non-qualified Plan. The Non-qualified Plan, which is unfunded, does not hold any assets. OneBeacon has set aside $12.2 million in an irrevocable rabbi trust for the benefit of Non-qualified Plan participants. In accordance with GAAP, the 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, 2011 and 2010 consist of:

	Pension Benefits
Millions	2011			2010
Net balance recorded in other assets	$	34.3		$	50.3
Net balance recorded in other liabilities	(26.5		)	(27.5		)
Net amount accrued in the financial statements	$	7.8		$	22.8

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

	December 31,
Millions	2011		2010
Projected benefit obligation	$	26.5	$	27.5
Accumulated benefit obligation	$	26.5	$	27.5
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	2011		2010
Projected benefit obligation	$	86.5	$	82.7
Accumulated benefit obligation	$	86.5	$	82.7
Fair value of plan net assets (1)	$	120.8	$	133.0

(1) Includes receivables related to securities sold, interest and dividends as well as payables related to securities purchased.

The amounts recognized in accumulated other comprehensive income (loss) on a pre-tax basis and before noncontrolling interest for the years ended December 31, 2011 and 2010 were as follows:

	December 31,
Millions	2011			2010
Accumulated other comprehensive income (loss) beginning balance	$	.5		$	(8.5	)
Increase (decrease) in accumulated other comprehensive income (loss):
Amortization of net actuarial losses recognized during the year	.5			.6
Net actuarial (losses) gains occurring during the year(1)	(18.2		)	8.4
Other adjustments	.5			—
Accumulated other comprehensive (loss) income ending balance	$	(16.7	)	$	.5

(1) Primarily relates to investment results relating to the overfunded status of the Plans.

The amount in accumulated other comprehensive loss, on a pre-tax basis and before noncontrolling interest, that has not yet been recognized as a component of net periodic benefit cost for the year ended December 31, 2011 is attributable to net losses. During 2012, OneBeacon expects $0.7 million will be amortized from accumulated other comprehensive income (loss) into net periodic benefit cost.

The components of net periodic benefit cost (income) for the years ended December 31, 2011, 2010 and 2009 were as follows:

	Year Ended December 31,
Millions	2011			2010			2009
Service cost	$	.8		$	.8		$	.5
Interest cost	5.2			6.0			6.5
Expected return on plan assets	(7.6		)	(7.3		)	(6.3		)
Amortization of unrecognized loss	.5			.6			1.6
Net periodic pension cost (income) before settlements, curtailments and special termination benefits	(1.1		)	.1			2.3
Settlement gain	.5			(.1		)	—
Special termination benefits expense(1)	.8			1.9			1.2
Total net periodic benefit cost	$	.2		$	1.9		$	3.5

(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 4.38% and 4.94% at December 31, 2011 and 2010. The weighted average assumptions used to determine net periodic benefit cost included a 4.94% discount rate and 5.75% expected long-term rate of return on plan assets for the year ended December 31, 2011. The weighted average assumptions used to determine net periodic benefit cost included a 5.16% discount rate and 5.75% expected long-term rate of return on plan assets for the year ended December 31, 2010.

OneBeacon’s discount rate assumptions used to account for the Plans reflect the rates at which the benefit obligations could be effectively settled. For 2011 and 2010, in addition to consideration of published yields for high quality long-term corporate bonds, U.S. Treasuries and insurance company annuity contract pricing, consideration was given to a cash flow matching analysis.

OneBeacon performed an analysis of expected long-term rates of return based on the allocation of its Qualified Plan assets at December 31, 2010 and 2009 to develop expected rates of return for 2011 and 2010 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’ assets are managed by Prospector Partners, LLC (“Prospector”), a related party (see Note 18). 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 include fixed maturity, equity, convertible fixed maturities, and cash and short-term investments. Fixed maturity and convertible fixed maturities include bonds, convertible fixed maturities and convertible preferred stocks of companies from diversified industries. Equity securities primarily include investments in large-cap and mid-cap companies primarily located in the United States. Cash and short-term investments include registered investment companies and common/collective trust funds.

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 maturities 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 at December 31, 2011 by asset category were as follows:

	December 31, 2011								December 31, 2010
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	$	2.4	$	—	$	2.4	$	—	$	.5	$	—	$	.5	$	—
Common equity securities	72.2		72.2		—		—		74.5		74.5		—		—
Convertible fixed maturities	42.8		—		42.8		—		55.7		—		55.7		—
Cash and short-term investments	3.1		3.1		—		—		2.0		2.0		—		—
Total	$	120.5	$	75.3	$	45.2	$	—	$	132.7	$	76.5	$	56.2	$	—

There were no transfers between Levels 1, 2 or 3 during the years ended December 31, 2011 or 2010.

The Qualified Plan’s asset allocations at December 31, 2011 and 2010, by asset category were as follows:

	Plan Assets at December 31,
Asset Category	2011		2010
Fixed maturity investments	2.0	%	.4	%
Common equity securities	59.9		56.1
Convertible fixed maturities	35.5		42.0
Cash and short-term investments	2.6		1.5
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 2012. OneBeacon anticipates contributing $2.4 million to the Non-qualified Plan, 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
2012	$	4.6
2013	5.0
2014	5.3
2015	5.7
2016	6.0
2017—2021	34.0

Other Benefit Plans

OneBeacon sponsors an employee savings plan (defined contribution plan) 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 the plan was $3.0 million, $3.8 million and $4.6 million in 2011, 2010 and 2009.

OneBeacon had a post-employment benefit liability of $6.7 million and $7.9 million at December 31, 2011 and 2010.

- Definition

The entire disclosure for pension and other postretirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph a
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph h
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 8
-Subparagraph m
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 106
-Paragraph 518
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 87
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Emerging Issues Task Force (EITF)
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-Paragraph 8
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-Name Accounting Principles Board Opinion (APB)
-Number 30
-Paragraph 26
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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
-Name Statement of Financial Accounting Standard (FAS)
-Number 158
-Paragraph 7, 21, 22
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5, 6, 7, 8
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Implementation Guide (Q and A)
-Number FAS88
-Paragraph 63
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+ Details

Employee Share-Based Incentive Compensation Plans

12 Months Ended

Dec. 31, 2011

Employee Share-Based Incentive Compensation Plans

Employee Share-Based Incentive Compensation Plans

NOTE 11. Employee Share-Based Incentive Compensation Plans

White Mountains’ 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’ calculation of its owners’ returns includes the expense of all outstanding share-based compensation awards.

Incentive Compensation Plans

White Mountains’ 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 and 2010. Share-based incentive awards that may be granted under the plan include performance shares, restricted shares, Incentive 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 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.

The OneBeacon Long-Term Incentive Plan (the “OneBeacon Incentive Plan”) provides for granting to key employees of OneBeacon Ltd., and certain of its subsidiaries, 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 participants the ability to invest their balances in several different investment options, including the Company’s or OneBeacon’s common shares. OneBeacon’s employee stock ownership plan (“ESOP”) is a OneBeacon-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 ($106,800 for 2011). 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 Social Security wage base and contingent upon OneBeacon’s performance. In April 2007, the ESOP was merged into the 401(k) Plan to form the OneBeacon 401(k) Savings and ESOP Plan (“KSOP”). Sirius Group’s profit sharing plan is a Sirius Group-funded benefit plan that provides all of its participants with a variable contribution up to 7% of their salary, contingent upon Sirius Group’s performance.

Performance Shares

White Mountains’ share-based compensation expense consists primarily of performance share expense. 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’ 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’ 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’ 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, 2011, 2010 and 2009 for performance shares granted under the WTM Incentive Plan and the WTM Phantom Share Plan:

	Year Ended December 31,
	2011					2010					2009
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	163,184		$	29.4		172,454		$	12.2		156,373		$	4.2
Shares expired (1)	(51,131	)	—			(49,127	)	—			(48,573	)	—
New grants	37,675		—			47,880		—			69,092		—
Assumed forfeitures and cancellations (2)	336		(.9		)	(8,023	)	(.7		)	(4,438	)	(.3		)
Expense recognized	—		37.6			—		17.9			—		8.3
Ending December 31,	150,064		$	66.1		163,184		$	29.4		172,454		$	12.2

(1) There were no payments made in 2011, 2010 and 2009 for the 2008-2010, 2007-2009 and 2006-2008 performance cycles; those performance shares did not meet the threshold performance goals and expired.

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

If 100% of the outstanding performance shares had vested on December 31, 2011, the total additional compensation cost to be recognized would have been $19.3 million, based on accrual factors at December 31, 2011 (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 at December 31, 2011 for each performance cycle:

Millions, except share amounts	Target WTM Performance Shares Outstanding		Accrued Expense
Performance cycle:
2009-2011	60,410		$	42.6
2010-2012	42,890		10.9
2011-2013	37,675		6.8
Sub-total	140,975		60.3
Assumed forfeitures	(3,524	)	(1.6		)
Total at December 31, 2011	137,451		$	58.7

The targeted performance goal for full payment of outstanding performance shares granted under the WTM Incentive Plan to non-investment personnel for the 2011-2013 performance cycles is a 10% growth in intrinsic business value per share. Growth of 3% or less would result in no payout and growth of 17% 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 2010-2012 performance cycles is an 11% growth in intrinsic business value per share. Growth of 4% or less would result in no payout and growth of 18% 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 2009-2011 performance cycles is a 10% growth in intrinsic business value per share. Growth of 3% or less would result in no payout and growth of 17% 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 in part on growth in intrinsic business value per share (as described above) and in part on achieving a total return on invested assets as measured against metrics based on U.S. Treasury Note and/or industry benchmark returns.

Phantom Performance Shares granted under the WTM Phantom Share Plan

The following summarizes phantom performance shares outstanding and accrued expense for awards made under the WTM Phantom Share Plan at December 31, 2011 for each performance cycle:

Millions, except share amounts	Target WTM Phantom Performance Shares Outstanding		Accrued Expense
Performance cycle:
2009-2011	7,947		$	6.0
2010-2012	4,990		1.5
2011-2013(1)	—		—
Sub-total	12,937		7.5
Assumed forfeitures	(324	)	(.1		)
Total at December 31, 2011	12,613		$	7.4

(1) All performance shares for the 2011-2013 performance cycle were granted from the WTM Incentive Plan.

The performance goals for full payment of performance shares issued under the WTM Phantom Share Plan are identical to those of the WTM Incentive Plan.

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, 2011, 2010 and 2009:

	Year Ended December 31,
	2011					2010					2009
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 at beginning of year	46,250		$	14.1		91,900		$	23.7		53,200		$	24.2
Issued	27,250		9.9			19,750		6.7			47,100		9.6
Vested	(1,500	)	—			(65,150	)	—			(8,400	)	—
Forfeited	—		—			(250	)	(.1		)	—		—
Modified(1)	—		—			—		(3.3		)	—		—
Expense recognized	—		(10.7		)	—		(12.9		)	—		(10.1		)
Non-vested at end of year	72,000		$	13.3		46,250		$	14.1		91,900		$	23.7

(1) During the first quarter of 2007, White Mountains issued 15,000 restricted shares to the Company’s Chairman and CEO in connection with his hiring that would vest in the event of a change in control of the Company before January 20, 2012. During 2010, the Compensation Committee modified the vesting terms so that the 15,000 restricted shares time vest in three equal annual installments beginning on January 20, 2013.

During the second quarter of 2011, White Mountains issued 250 restricted shares that vest on January 1, 2014. During the first quarter of 2011, White Mountains issued 27,000 restricted shares that vest on January 1, 2014. During the first quarter of 2010, White Mountains issued 19,750 restricted shares that vest on December 31, 2012. During 2009, White Mountains issued 2,500 restricted shares that cliff vested in November 2010, 40,100 restricted shares that cliff vested on December 31, 2010 and 4,500 restricted shares that vest in equal installments at December 31, 2011, 2012 and 2013.

The unrecognized compensation cost at December 31, 2011 is expected to be recognized ratably over the remaining vesting periods.

Stock Options

Non-Qualified Options

In January 2007, the Company issued 200,000 seven-year Non-Qualified Options to the Company’s Chairman and CEO (the “original grant”) that vest in equal annual installments over five years and that had an initial exercise price of $650 per common share that escalated at an annual rate of 5% less the annual regular dividend rate (the “Escalator”). The fair value of the Non-Qualified Options was $27.2 million at the grant date. The fair value of the Non-Qualified Options at the grant date was estimated using a closed-form option model using an expected volatility assumption of 29.7%, a risk-free interest rate assumption of 1.1% (or 4.7% less the Escalator), a forfeiture assumption of 0%, an expected dividend rate assumption of 1.4% and a term assumption of seven years.

At the 2010 Annual General Meeting of Members held on May 26, 2010 (the “modification date”), the Company’s shareholders approved the following amendments to the Non-Qualified Options (the “amended grant”): (1) extend the term of the Non-Qualified Options by three years to January 20, 2017; (2) freeze the exercise price at $742 per common share, the exercise price on February 24, 2010; (3) extinguish 75,000 of the 200,000 Non-Qualified Options; and (4) limit the potential in-the-money value of the Non-Qualified Options in excess of $100 million to 50% of the amount in excess of $100 million. The fair value of the amended grant was $4.4 million at the modification date, while the fair value of the original grant as of the modification date was $3.5 million. The fair value of the amended grant was estimated using a closed-form option model using an expected volatility assumption of 34.0%, a risk-free interest rate assumption of 2.43%, a forfeiture assumption of 0%, an expected dividend rate assumption of 0.32% and a term assumption of 6.67 years. The fair value of the original grant as of the modification date was estimated using a closed-form option model using an expected volatility assumption of 41.0%, a risk-free interest rate assumption of 1.57%, a forfeiture assumption of 0%, an expected dividend rate assumption of 0.32% and a term assumption of 3.67 years.

Prior to the modification, $18.2 million of the original grant fair value had been amortized into income. In connection with the modification, White Mountains recognized $8.7 million of the remaining $9.0 million of unamortized option expense related to the original grant. As of the first quarter in 2011, the Non-Qualified Options have been fully amortized.

For the years ended December 31, 2011, 2010, and 2009 White Mountains recognized a total of $0.1 million, $11.9 million, and $5.4 million of expense related to amortizing the Non-Qualified Options.

Incentive Options

The Company had 2,400 Incentive Options outstanding at December 31, 2009, which were granted to certain key employees on February 28, 2000 (the grant date) under the WTM Incentive Plan. The 81,000 Incentive Options originally granted were issued at an exercise price equal to the market price of the Company’s underlying common shares on February 27, 2000. The exercise price escalated by 6% per annum over the life of the Incentive Options. The Incentive Options vested ratably over a ten-year service period. The grant date fair value of the awards as originally disclosed, adjusted for estimated future forfeitures, became the basis for recognition of compensation expense for the Incentive Options. The fair value of each Incentive Option award at the grant date was estimated using a closed-form option model using an expected volatility assumption of 18.5%, a risk-free interest rate assumption of 6.4% and an expected term of ten years.

The following table summarizes the Company’s Incentive Options activity for the years ended December 31, 2010 and 2009. There were no Incentive Options issued and outstanding in 2011.

	Year ended December 31,
Millions, except share and per share amounts	2010			2009
Opening balance—outstanding Incentive Options	2,400			6,000
Forfeited	—			—
Exercised	(2,400		)	(3,600		)
Ending balance—outstanding Incentive Options	—			2,400
Opening balance—exercisable Incentive Options	2,400			3,000
Vested	—			3,000
Exercised	(2,400		)	(3,600		)
Ending balance—exercisable Incentive Options	—			2,400
Intrinsic value of Incentive Options exercised (1)	$	.3		$	.5
Exercise price—beginning of year	$	188.43		$	177.76
Exercise price—end of year	$	—		$	188.43
Compensation expense (income)	$	—		$	—

(1) Amount is equal to the number of options exercised multiplied by amount the ending market value exceeds the strike price on the date of exercise.

Share-Based Compensation Based on OneBeacon Ltd. Common Shares

OneBeacon Performance Shares

The following summarizes activity for the years ended December 31, 2011, 2010, and 2009 for OneBeacon performance shares granted under the OneBeacon Incentive Plan:

	Year Ended December 31,
	2011					2010					2009
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	1,464,295		$	18.5		2,224,215		$	15.1		2,212,313		$	4.6
Payments and deferrals (1)(2)	(936,150	)	(10.5		)	(889,594	)	(4.6		)	(137,400	)	—
New awards	194,900		—			270,691		—			379,085		—
Forfeitures and cancellations	(80,378	)	(.5		)	(141,017	)	(2.2		)	(229,783	)	(.5		)
Expense recognized	—		2.2			—		10.2			—		11.0
End of period	642,667		$	9.7		1,464,295		$	18.5		2,224,215		$	15.1

(1) OneBeacon performance share payments in 2011 for the 2008-2010 performance cycle were at 68.5% of target. OneBeacon performance shares payments in 2010 for the 2007-2009 performance cycle were at 14.2% of target. OneBeacon performance share payments in 2009 for the 2007-2008 performance cycle were at 1.4% of target.

(2) As a result of the Commercial Lines Transaction and the Personal Lines Transaction, payments were made to certain former employees of OneBeacon prior to the end of the performance cycle (2008-2010, 2009-2011, and 2010-2012 performance cycles) on a pro rata basis based upon a performance factor of 100%.

The following summarizes OneBeacon performance shares outstanding awarded under the OneBeacon Incentive Plan at December 31, 2011 for each performance cycle:

Millions, except share amounts	Target OneBeacon Performance Shares Outstanding		Accrued Expense
Performance cycle:
2009-2011	256,751		$	7.7
2010-2012	244,248		1.2
2011-2013	151,563		.9
Sub-total	652,562		9.8
Assumed forfeitures	(9,895	)	(.1		)
Total at December 31, 2011	642,667		$	9.7

If 100% of the outstanding OneBeacon performance shares had been vested on December 31, 2011, the total additional compensation cost to be recognized would have been $2.3 million, based on December 31, 2011 accrual factors (common share price and payout assumptions).

The targeted performance goal for full payment of the outstanding OneBeacon performance shares granted during 2011 is growth in intrinsic business value per share of 11%. At a growth in intrinsic business value per share of 4% or less, no performance shares would be earned and at a growth in intrinsic business value per share of 18% or more, 200% of performance shares would be earned. The targeted performance goal for full payment of the outstanding OneBeacon performance shares granted during 2010 is growth in intrinsic business value per share of 12%. At a growth in intrinsic business value per share of 5% or less, no performance shares would be earned and at a growth in intrinsic business value per share of 19% or more, 200% of performance shares would be earned.

Non-Qualified Options

In November 2006, in connection with its initial public offering, OneBeacon Ltd. issued to its key employees 1,420,000 fixed price OneBeacon Non-Qualified Options to acquire OneBeacon Ltd. common shares at an above-market fixed exercise price. The options vest in equal installments on each of the third, fourth and fifth anniversaries of their issuance and expire 5.5 years from the date of issuance. The fair value of each option award at grant was estimated using a Black-Scholes option pricing model using an expected volatility assumption of 30%, a risk-free interest rate assumption of 4.6%, a forfeiture assumption of 5%, an expected dividend rate assumption of 3.4% and an expected term assumption of 5.5 years. The options originally had a per share exercise price of $30.00. On May 27, 2008, the OneBeacon Compensation Committee of the Board of Directors (the “OB Compensation Committee”) amended the exercise price to $27.97 as a result of the $2.03 per share special dividend paid in the first quarter of 2008. On November 16, 2010, the OB Compensation Committee adjusted the exercise price to $25.47 as a result of the $2.50 per share special dividend paid in the third quarter of 2010.

The compensation expense associated with the options and the incremental fair value of the award modifications is being recognized ratably over the remaining period.

The following table summarizes option activity for the years ended December 31, 2011, 2010 and 2009:

	Year ended December 31,
	2011				2010				2009
Millions	Target Outstanding Options		Expense Amortized		Target Outstanding Options		Expense Amortized		Target Outstanding Options		Expense Amortized
Beginning of period	768,652		$	4.5	1,015,610		$	3.6	1,237,872		$	2.5
New awards	—		—		—		—		—		—
Forfeitures	(27,782	)	—		(37,044	)	—		(222,262	)	—
Vested and expired(1)	—		—		(209,914	)	—		—		—
Exercised	—		—		—		—		—		—
Expense recognized	—		.5		—		.9		—		1.1
End of period	740,870		$	5.0	768,652		$	4.5	1,015,610		$	3.6

(1) During the year ended December 31, 2010, as a result of the Commercial Lines Transaction and Personal Lines Transaction, 209,914 options vested that were unexercised and expired.

OneBeacon Restricted Shares

On May 25, 2011, OneBeacon issued 630,000 restricted shares to its CEO that vest one-fourth on each of 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 each of the next 5 years will also be reduced by 35,000 shares. The restricted shares contain dividend participation features, and therefore, are considered participating securities. As of December 31, 2011, there were 630,000 unvested restricted shares. For the year ended December 31, 2011, OneBeacon recognized $0.9 million of expense. As of December 31, 2011, $7.7 million is expected to be recognized ratably over the remaining vesting period.

Restricted Stock Units

The Non-Qualified Options granted by OneBeacon Ltd., in connection with its initial public offering, did not include a mechanism in the options to reflect the contribution to total return from the regular quarterly dividend. As a result, during the first quarter of 2008, OneBeacon granted 116,270 Restricted Stock Units (“RSUs”) to actively employed option holders. The RSUs were scheduled to vest one-third on each of November 9, 2009, 2010 and 2011 subject to, for each vesting tranche of units, the attainment of 4% growth in OneBeacon’s book value per share from January 1, 2008 through the end of the calendar year immediately following the applicable vesting date.

Consistent with the terms of the RSU plan, all three tranches of RSUs vested and were deferred into a OneBeacon non-qualified deferred compensation plan that will be paid out in May 2012 in cash or shares at the discretion of the OB Compensation Committee.

The expense associated with the RSUs was recognized ratably over the vesting period. For the years ended December 31, 2011, 2010 and 2009, OneBeacon recognized expense of $0.1 million, $0.5 million and $0.6 million.

Share-based Compensation Under Qualified Retirement Plans

The variable contribution amounts earned by eligible participants of the KSOP constituted approximately 2%, 0% and 4% of salary for the years ended 2011, 2010 and 2009. White Mountains recorded $6.3 million, $3.0 million and $11.0 million in compensation expense to pay benefits and allocate common shares to participant’s accounts for the years ended 2011, 2010 and 2009. The contributions made to the KSOP with respect to the years ended 2011, 2010 and 2009 were made with either the Company’s or OneBeacon Ltd.’s common shares, dependent on the employer. As of December 31, 2011 and 2010, 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.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph 64, 65, A240
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Statement of Position (SOP)
-Number 93-6
-Paragraph 53
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 14

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 50
-Section 50
-Paragraph 1
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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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
-Topic 718
-SubTopic 40
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-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

+ Details

Common Shareholders' Equity

12 Months Ended

Dec. 31, 2011

Common Shareholders' Equity

Common Shareholders' Equity

NOTE 12. Common Shareholders’ Equity

Common Shares Repurchased and Retired

On November 17, 2006, White Mountains’ Board of Directors authorized the Company to repurchase up to 1 million of its common shares, from time to time, subject to market conditions. On August 26, 2010, White Mountains’ board of directors authorized the Company to repurchase up to an additional 600,000 common shares under the share repurchase program. Shares may be repurchased on the open market or through privately negotiated transactions. This program does not have a stated expiration date. As of December 31, 2011, the Company had 188,297 shares remaining under its share repurchase authorization. Since the inception of the program, the Company has repurchased and retired 1,411,703 common shares for $537.5 million. During 2011, the Company repurchased 313,967 common shares for $114.2 million. During 2010, the Company repurchased 677,125 common shares for $222.0 million. During 2009, the Company did not repurchase any common shares under the Share Repurchase Plan.

In addition to the shares repurchased under the share repurchase program, during 2011, White Mountains completed two “modified Dutch auction” self-tender offers and repurchased 332,346 of its common shares at an average price of $417.55 per share. The total cost of the share repurchases was $138.8 million, including fees and expenses related to the tender offers.

The Company also repurchases its common shares, from time to time, that relate to the administration of its various incentive compensation and deferred compensation programs. For the years ended December 31, 2011, 2010 and 2009 the Company repurchased 189 common shares, 10,186 common shares and 1,113 common shares that were not subject to the Share Repurchase Plan.

Common Shares Issued

During 2011, the Company issued a total of 29,432 common shares, which consisted of 27,250 restricted shares issued to key management personnel and 2,182 shares issued to directors of the Company. During 2010, the Company issued a total of 23,050 common shares, which consisted of 2,400 shares issued in satisfaction of options exercised, 19,750 restricted shares issued to key management personnel and 900 shares issued to directors of the Company. During 2009, the Company issued a total of 52,420 common shares, which consisted of 3,600 shares issued in satisfaction of options exercised, 47,820 restricted shares issued to key management personnel and 1,000 shares issued to directors of the Company.

Dividends on Common Shares

For the years ended December 31, 2011, 2010, and 2009, the Company declared and paid cash dividends totaling $8.0 million, $8.8 million, and $8.9 million (or $1.00 per common share).

- Definition

The entire disclosure for shareholders' equity, comprised of portions attributable to the parent entity and noncontrolling interest, if any, including other comprehensive income (as applicable). Including, but not limited to: (1) balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings; (2) accumulated balance for each classification of other comprehensive income and total amount of comprehensive income; (3) amount and nature of changes in separate accounts, including the number of shares authorized and outstanding, number of shares issued upon exercise and conversion, and for other comprehensive income, the adjustments for reclassifications to net income; (4) rights and privileges of each class of stock authorized; (5) basis of treasury stock, if other than cost, and amounts paid and accounting treatment for treasury stock purchased significantly in excess of market; (6) dividends paid or payable per share and in the aggregate for each class of stock for each period presented; (7) dividend restrictions and accumulated preferred dividends in arrears (in aggregate and per share amount); (8) retained earnings appropriations or restrictions, such as dividend restrictions; (9) impact of change in accounting principle, initial adoption of new accounting principle and correction of an error in previously issued financial statements; (10) shares held in trust for Employee Stock Ownership Plan (ESOP); (11) deferred compensation related to issuance of capital stock; (12) note received for issuance of stock; (13) unamortized discount on shares; (14) description, terms, and number of warrants or rights outstanding; (15) shares under subscription and subscription receivables, effective date of new retained earnings after quasi-reorganization and deficit eliminated by quasi-reorganization and, for a period of at least ten years after the effective date, the point in time from which the new retained dates; and (16) retroactive effective of subsequent change in capital structure.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 12
-Paragraph 10
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 4
-Section 08
-Paragraph d

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 43
-Chapter 1
-Section B
-Paragraph 7, 11A
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 129
-Paragraph 2, 3, 4, 5, 6, 7, 8
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
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-Number 210
-Section 08
-Article 4

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
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-Paragraph 29, 30, 31
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
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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
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-Paragraph 1
-Subparagraph (SX 210.3-04)
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Reference 22: http://www.xbrl.org/2003/role/presentationRef
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+ Details

Statutory Capital and Surplus

12 Months Ended

Dec. 31, 2011

Statutory Capital and Surplus

Statutory Capital and Surplus

NOTE 13. Statutory Capital and Surplus

White Mountains’ 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. In addition, the NAIC uses risk-based capital (“RBC”) standards for property and casualty insurers as a means of monitoring certain aspects affecting the overall financial condition of insurance companies. At December 31, 2011, White Mountains’ active insurance and reinsurance operating subsidiaries exceeded their respective RBC requirements.

OneBeacon’s consolidated combined policyholders’ surplus of its insurance operating subsidiaries as reported to various regulatory authorities as of December 31, 2011 and 2010 was $1.0 billion and $1.1 billion. OneBeacon’s consolidated combined statutory net income (loss) for the years ended December 31, 2011, 2010 and 2009 was $119.6 million, $257.2 million and $210.5 million. The principal differences between OneBeacon’s combined statutory amounts and the amounts reported in accordance with GAAP include deferred acquisition costs, deferred taxes, market value adjustments for debt securities and recognition of pension plans. OneBeacon’s insurance operating subsidiaries’ statutory policyholders’ surplus at December 31, 2011 was in excess of the minimum requirements of relevant state insurance regulations.

Sirius International’s total regulatory capital at December 31, 2011 was $2.1 billion. In accordance with Swedish regulations, Sirius International holds restricted equity of $1.6 billion as a component of Swedish statutory regulatory capital. This restricted equity cannot be paid as dividends.

Sirius America’s policyholders’ surplus, as reported to various regulatory authorities as of December 31, 2011 and 2010, was $533.7 million and $742.6 million. Sirius America’s statutory net income (loss) for the years ended December 31, 2011, 2010 and 2009 was $101.4 million, $70.2 million and $46.9 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. Sirius America’s statutory policyholders’ surplus at December 31, 2011 was in excess of the minimum requirements of relevant state insurance regulations.

Central National’s policyholders’ surplus, as reported to various regulatory authorities as of December 31, 2011 and 2010, was $13.4 million and $15.0 million. Central National’s statutory net income (loss) for the years ended December 31, 2011 and 2010 was $0.1 million and $1.6 million.

Scandinavian Re and White Shoals Re are also subject to regulation and supervision by the Bermuda Monetary Authority (“BMA”). Generally, the 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. In general, such regulation is for the protection of policyholders rather than shareholders. As of December 31, 2011, Scandinavian Re and White Shoals Re had statutory capital and surplus of $27.6 million and $15.4 million, which was in excess of the minimum requirements of the BMA.

WM Life Re is subject to regulation and supervision by the BMA. As of December 31, 2011, WM Life Re had statutory capital and surplus of $26.4 million, which was in excess of the minimum requirement of the BMA.

Dividend Capacity

Under the insurance laws of the states and jurisdictions under which White Mountains’ 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. 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’ insurance and reinsurance operating subsidiaries:

OneBeacon:

Generally, OneBeacon’s regulated insurance operating subsidiaries have the ability to pay dividends during any 12-month period without the prior approval of regulatory authorities in an amount set by formula based on the greater of prior year statutory net income or 10% of prior year end statutory surplus, subject to the availability of unassigned funds. Based upon OneBeacon’s top tier regulated insurance operating subsidiaries have the ability to pay $103 million of dividends during 2012 without prior approval of regulatory authorities, subject to the availability of unassigned funds. At December 31, 2011, OneBeacon’s top tier regulated insurance operating subsidiaries had $0.7 billion of unassigned funds. During 2011, OneBeacon’s top tier regulated insurance operating subsidiaries distributed $150.0 million in extraordinary dividends to their immediate parent.

During 2011, OneBeacon Ltd. paid $79.7 million of regular quarterly dividends and a $95.1 million special dividend to its common shareholders. White Mountains received $132.0 million of these dividends. At December 31, 2011, OneBeacon Ltd. and its intermediate holding companies had $16.9 million of net unrestricted cash, short-term investments and fixed maturity investments outside of its regulated and unregulated insurance operating subsidiaries.

During 2011, OneBeacon’s unregulated insurance operating subsidiaries paid $4.3 million of dividends to their immediate parent. At December 31, 2011, OneBeacon’s unregulated insurance operating subsidiaries had approximately $183.0 million of net unrestricted cash, short-term investments and fixed maturity investments and approximately $30.0 million of common equity securities and convertible fixed maturities.

Sirius Group:

Subject to certain limitations under Swedish law, Sirius International is permitted to transfer all or a portion of its pre-tax income to its Swedish parent companies to minimize taxes (referred to as a group contribution). In 2011, Sirius International transferred $74.0 million of its 2010 pre-tax income to its Swedish parent companies as a group contribution. In 2012, Sirius International intends to transfer approximately $80.0 million (based on December 31, 2011 SEK to USD exchange rate) of its 2011 pre-tax income to its Swedish parent companies as a group contribution.

Sirius International has the ability to pay dividends subject to the availability of unrestricted statutory surplus. Historically, Sirius International has allocated the majority of its pre-tax income, after group contributions to its Swedish parent companies, to the Safety Reserve (see “Safety Reserve” below). At December 31, 2011, Sirius International had $514.9 million (based on December 31, 2011 SEK to USD exchange rate) of unrestricted statutory surplus, which is available for distribution in 2012. During 2011, Sirius International paid $177 million of dividends to its immediate parent. In connection with the Reorganization, Sirius International’s unrestricted statutory surplus increased by $436.3 million due to the contribution of the remaining shares of Sirius America.

Sirius America has the ability to pay dividends to its intermediate parent, which is an indirect subsidiary wholly-owned subsidiary of Sirius International, during any 12-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. Based upon December 31, 2011 statutory surplus of $533.7 million, Sirius America has the ability to pay $53.4 million of dividends during 2012 without prior approval of regulatory authorities, subject to the availability of earned surplus. At December 31, 2011, Sirius America had $75.5 million of earned surplus.

During 2011, Sirius Group distributed a total of $169.0 million to its immediate parent in addition to the $425.0 million distribution that was made as part of the Reorganization for a total of $594.0 million

At December 31, 2011, Sirius Group and its intermediate holding companies had $75.1 million of net unrestricted cash, short-term investments and fixed maturity investments and $16.3 million of other long-term investments outside of its regulated and unregulated insurance and reinsurance operating subsidiaries.

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. At December 31, 2011, Sirius International’s safety reserve amounted to SEK 9.6 billion or $1.4 billion at the December 31, 2011 exchange rate of 6.86 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 26.3%, is classified as common shareholders’ equity. Generally, this deferred tax liability is only required to be paid by Sirius International if it fails to maintain predetermined levels of premium writings and loss reserves in future years. As a result of the indefinite deferral of these taxes, Swedish regulatory authorities do not apply any 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 ($369.6 million at December 31, 2011) is included in solvency capital. Access to the safety reserve is restricted to coverage of insurance 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 $1.4 billion balance of the safety reserve, without any provision for deferred taxes, in Sirius International’s capital when assessing Sirius International’s financial strength.

Other Operations:

During 2011, WM Advisors paid a $5.0 million dividend to its immediate parent. At December 31, 2011, WM Advisors had $25.8 million of net unrestricted cash, short-term investments and fixed maturity investments.

At December 31, 2011, the Company and its intermediate holding companies had $1,554.3 million of net unrestricted cash, short-term investments and fixed maturity investments, $316.6 million of common equity securities and $33.4 million of other long-term investments included in its Other Operations segment.

Segment Information

12 Months Ended

Dec. 31, 2011

Segment Information

Segment Information

NOTE 14. Segment Information

White Mountains has determined that its reportable segments are OneBeacon, Sirius Group, and Other Operations. As a result of the Esurance Sale, the results of operations for Esurance 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 20).

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.

Historically, OneBeacon offered a range of specialty, commercial and personal products and services. However, OneBeacon has completed two transactions that have transformed it into a specialty insurance company. On December 3, 2009, OneBeacon sold the renewal rights to its non-specialty commercial lines (the “Commercial Lines Transaction”) business and on July 1, 2010, OneBeacon completed the sale of its traditional personal lines business (the “Personal Lines Transaction”). OneBeacon specialty lines coverage is comprised of a collection of niche insurance business lines including professional liability products, marine insurance, collector cars and boats, property and inland marine, tuition reimbursement, excess property and accident and health products as well as property and casualty insurance coverages tailored to industry groups such as technology, financial services, entertainment, sports and leisure industries and government entities.

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.

Other Operations consists of the Company, the Company’s intermediate holding companies, WM Advisors and WM Life Re as well as and various other entities not included in other segments.

Significant intercompany transactions among White Mountains’ segments have been eliminated herein.

Financial information for White Mountains’ segments follows:

Millions	OneBeacon			Sirius Group			Other Operations			Total
Year ended December 31, 2011:
Earned insurance and reinsurance premiums	$	1,015.5		$	912.3		$	—		$	1,927.8
Net investment income	71.4			89.9			23.2			184.5
Net realized and unrealized investment gains (losses)	10.6			101.9			10.3			122.8
Other revenue	(10.7		)	(44.6		)	(1.7		)	(57.0		)
Total revenues	1,086.8			1,059.5			31.8			2,178.1
Losses and LAE	580.9			626.0			—			1,206.9
Insurance and reinsurance acquisition expenses	219.0			181.0			—			400.0
Other underwriting expenses	173.3			105.8			—			279.1
General and administrative expenses	9.8			34.1			131.4			175.3
Interest expense on debt	20.5			31.6			3.1			55.2
Total expenses	1,003.5			978.5			134.5			2,116.5
Pre-tax income (loss)	$	83.3		$	81.0		$	(102.7	)	$	61.6

Millions	OneBeacon		Sirius Group			Other Operations			Total
Year ended December 31, 2010:
Earned insurance and reinsurance premiums	$	1,403.9	$	847.9		$	—		$	2,251.8
Net investment income	96.6		96.5			15.8			208.9
Net realized and unrealized investment gains (losses)	74.6		(9.8		)	17.8			82.6
Other revenue	9.6		35.9			(22.1		)	23.4
Total revenues	1,584.7		970.5			11.5			2,566.7
Losses and LAE	858.2		531.0			—			1,389.2
Insurance and reinsurance acquisition expenses	311.6		167.5			—			479.1
Other underwriting expenses	233.1		99.8			—			332.9
General and administrative expenses	13.0		31.6			110.5			155.1
Interest expense on debt	29.6		26.6			1.1			57.3
Total expenses	1,445.5		856.5			111.6			2,413.6
Pre-tax income (loss)	$	139.2	$	114.0		$	(100.1	)	$	153.1

Millions	OneBeacon		Sirius Group		Other Operations			Total
Year ended December 31, 2009:
Earned insurance and reinsurance premiums	$	1,858.8	$	858.8	$	—		$	2,717.6
Net investment income	125.5		110.3		14.3			250.1
Net realized and unrealized investment gains	248.6		112.6		.5			361.7
Other revenue	23.1		106.5		(15.7		)	113.9
Total revenues	2,256.0		1,188.2		(.9		)	3,443.3
Losses and LAE	1,005.3		418.8		—			1,424.1
Insurance and reinsurance acquisition expenses	376.3		170.9		—			547.2
Other underwriting expenses	308.5		98.1		—			406.6
General and administrative expenses	18.5		74.4		104.5			197.4
Interest expense on debt	39.7		26.3		4.8			70.8
Total expenses	1,748.3		788.5		109.3			2,646.1
Pre-tax income (loss)	$	507.7	$	399.7	$	(110.2	)	$	797.2

Selected Balance Sheet Data Millions	OneBeacon		Sirius Group		Other Operations		Discontinued Operations		Total
December 31, 2011:
Total investments	$	2,707.6	$	3,640.5	$	1,919.9	$	—	$	8,268.0
Reinsurance recoverable on paid and unpaid losses	2,184.1		353.7		—		—		2,537.8
Assets held for sale	132.6		—		—		—		132.6
Total assets	5,792.4		5,337.9		2,933.7		—		14,064.0
Loss and LAE reserves	3,358.6		2,343.7		—		—		5,702.3
Liabilities held for sale	107.6		—		—		—		107.6
Total liabilities	4,678.5		3,784.1		933.5		—		9,396.1
Noncontrolling interest	287.2		289.5		3.5		—		580.2
Total White Mountains’ common shareholders’ equity	826.7		1,264.3		1,996.7		—		4,087.7
December 31, 2010:
Total investments	$	3,266.0	$	4,116.2	$	561.3	$	—	$	7,943.5
Reinsurance recoverable on paid and unpaid losses	1,937.7		469.4		—		—		2,407.1
Assets held for sale	—		—		—		1,122.8		1,122.8
Total assets	6,138.3		5,618.7		1,654.3		1,122.8		14,534.1
Loss and LAE reserves	3,295.5		2,441.3		—		—		5,736.8
Liabilities held for sale	—		—		—		751.5		751.5
Total liabilities	4,889.4		3,863.0		769.4		751.5		10,273.3
Noncontrolling interest	314.9		290.6		2.3		—		607.8
Total White Mountains’ common shareholders’ equity	934.0		1,465.1		882.6		371.3		3,653.0

- 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 Statement of Financial Accounting Standard (FAS)
-Number 131
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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-Section 50
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
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-Paragraph 10
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-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=d3e9038-108599

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Publisher FASB
-Name Accounting Standards Codification
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-Publisher FASB
-Name Accounting Standards Codification
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Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8933-108599

+ Details

Investments in Unconsolidated Affiliates

12 Months Ended

Dec. 31, 2011

Investments in Unconsolidated Affiliates

Investments in Unconsolidated Affiliates

NOTE 15. Investments in Unconsolidated Affiliates

White Mountains’ 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.

Millions	December 31, 2011		December 31, 2010
Symetra common shares	$	261.0	$	350.4
Symetra warrants	12.6		37.1
Total investment in Symetra	273.6		387.5

Pentelia Capital Management	1.7		2.2
Total investments in unconsolidated affiliates	$	275.3	$	389.7

Symetra

At December 31, 2011, White Mountains owned 17.4 million common shares of Symetra and warrants to acquire an additional 9.5 million common shares. In January 2010, Symetra completed an initial public offering at a price of $12.00 per share, with 25.3 million shares sold by Symetra and 9.7 million shares sold by existing shareholders. White Mountains did not sell any of its shares in the offering. As a result of the offering, White Mountains’ fully converted ownership in Symetra decreased from 24% to approximately 20% during the first quarter of 2010. The issuance of the new Symetra shares at a price below its adjusted book value per share diluted White Mountains’ investment in Symetra’s common shares, resulting in a $16.0 million decrease to White Mountains’ carrying value in Symetra.

White Mountains accounts for its investment in common shares of Symetra using the equity method. Under the equity method, the GAAP carrying value of White Mountains’ investment in Symetra common shares is normally equal to the percentage of Symetra’s GAAP book value represented by White Mountains’ common share ownership, which was 15% at December 31, 2011. Under GAAP, a decline in the fair value of an investment is considered to be other-than-temporary when the fair value of the investment is not expected to recover to its GAAP carrying value in the near term. Declines in the fair value of an investment that are considered to be other-than-temporary are recognized as a write-down to the GAAP carrying value of the investment. At December 31, 2011, due to the prolonged low interest rate environment in which life insurance companies currently operate, 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 at December 31, 2011. 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. The GAAP fair value of an investment is the price that would be paid by a market participant to acquire it in the investment’s principal (or most advantageous) market. For investments that are publicly traded, quoted market prices generally provide the best measurement of GAAP fair value. However, a decline in the quoted market price of an investment below its GAAP carrying value is not necessarily indicative of a loss in value that is other-than-temporary, and in circumstances where the characteristics of the investment being measured are not the same as those for which quoted market prices are available, unadjusted quoted market prices do not represent GAAP fair value. White Mountains’ investment in Symetra common shares is different than the shares that are traded on the public stock exchange, principally due to the size of its position and its representation on Symetra’s Board of Directors. In circumstances like this, GAAP requires that fair value be determined giving consideration to multiple valuation techniques. Management considered three different valuation techniques to determine the GAAP fair value of White Mountains’ investment in Symetra common shares at December 31, 2011.

Valuation techniques based on actuarial appraisal

When determining the value of life insurance holding companies that are acquisition targets, market participants commonly utilize an approach that values the company as the sum of (A) adjusted statutory net worth of any regulated life insurance companies (i.e. statutory surplus plus asset valuation reserve) plus the GAAP net assets of any non-life businesses, less holding company debt and (B) the present value of future earnings related to business in force as of the valuation date plus the present value of future earnings related to business written after the valuation date. Part A of the calculation can be performed using observable inputs from the statutory and GAAP financial statements. Part B of the calculation requires a large number of actuarial calculations including assumptions such as discount rates, mortality, persistency and future investment results that, while based on historical data and are supportable, are nonetheless judgmental and largely unobservable. For Symetra, part A is approximately $15 per share as of December 31, 2011. Symetra management provided its Board of Directors (of which White Mountains has 2 representatives) with an internal actuarial appraisal that demonstrates that part B would be a meaningful positive value in most reasonable scenarios. When determining the GAAP fair value of White Mountains’ investment in Symetra common shares at December 31, 2011, management ascribed the greatest weight to part A, as it is observable and less subjective.

Valuation techniques based on multiples from recent transactions

White Mountains uses growth in adjusted book value to assess Symetra’s financial performance. Adjusted book value excludes unrealized gains and losses from Symetra’s fixed maturity investment portfolio. Life insurance industry analysts and market participants commonly use multiples of adjusted book value per share to determine relative values of companies in the life insurance industry. Applying this approach to Symetra at December 31, 2011, utilizing multiples which were observed in a recently announced transaction within the life insurance industry provides an estimated fair value range from $16 to $30 per share. However, the range of fair value estimates generated by applying the adjusted book value per share multiple and market premium observed in the recently announced transaction is wide, and there have been no other significant acquisitions of life insurance companies in 2011. Therefore, management did not ascribe significant weight to valuations determined using the adjusted book value per share multiple or market price premium observed in recent acquisition activity when determining the GAAP fair value of White Mountains’ investment in Symetra common shares at December 31, 2011.

Valuation techniques based on quoted market prices

White Mountains’ representation on Symetra’s Board of Directors gives it the ability to exercise significant influence over Symetra’s operations and policies. Generally, market participants are willing to pay a premium to obtain the ability to exert influence over the operations and policies of an investee, which is not reflected in the quoted market price of Symetra’s common shares. There is no reliable means to calculate the value of this premium for an investment in a life insurance company. The actuarial appraisals used by market participants described above implicitly consider the ability to influence an investee’s operations and policies in the actuarial assumptions underlying projected future earnings, but the value associated with the ability to exert influence is not explicitly calculated separately from other components of value. As a result, management did not ascribe significant weight to valuations based on quoted market prices when determining the GAAP fair value of White Mountains’ investment in Symetra common shares at December 31, 2011, as the premium associated with the ability to exert influence over the operations and policies of Symetra is unobservable and highly subjective.

After considering these valuation techniques, management determined that the best estimate of the GAAP fair value of White Mountains’ investment in Symetra’s common shares at December 31, 2011 was $15 per share. Given the scarcity of relevant observable inputs and the wide range of estimates developed under the approaches used, the estimated GAAP fair value of White Mountains’ investment in Symetra’s common shares involved a significant degree of judgment, is very subjective in nature and, accordingly, is considered a Level 3 fair value measurement.

White Mountains accounts for its Symetra warrants as derivatives with changes in fair value recognized through the income statement as a gain or loss recognized through other revenues. White Mountains uses a Black Scholes valuation model to determine the fair value of the Symetra warrants. The major assumptions used in valuing the Symetra warrants at December 31, 2011 were a risk free rate of 0.31%, volatility of 36%, an expected life of 2.58 years, a strike price of $11.49 per share and a share price of $9.07 per share.

During 2011, White Mountains received cash dividends from Symetra of $4.0 million on its common share investment which is accounted for as a reduction of White Mountains’ investment in Symetra in accordance with equity accounting. During 2011, White Mountains also received cash dividends from Symetra of $2.2 million on its investment in Symetra warrants that was recorded as net investment income.

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 January 1, 2009	$	54.0		$	27.3		$	81.3
Equity in earnings of Symetra(1)(8)	23.9			—			23.9
Net unrealized losses from Symetra’s fixed maturity portfolio(5)	191.3			—			191.3
Increase in value of warrants	—			11.2			11.2
Carrying value of investment in Symetra as of December 31, 2009(2)	269.2			38.5			307.7
Equity in earnings of Symetra(1)(3)(8)	11.1			—			11.1
Net unrealized gains from Symetra’s fixed maturity portfolio(6)(7)	72.7			—			72.7
Dividends received	(2.6		)	—			(2.6		)
Decrease in value of warrants	—			(1.4		)	(1.4		)
Carrying value of investment in Symetra as of December 31, 2010(2)	350.4			37.1			387.5
Equity in earnings of Symetra(1)(8)	28.2			—			28.2
Impairment of equity in earnings of Symetra(4)	(50.0		)	—			(50.0		)
Net unrealized gains from Symetra’s fixed maturity portfolio(7)	85.0			—			85.0
Impairment of net unrealized gains from Symetra’s fixed maturity portfolio (5)	(148.6		)	—			(148.6		)
Dividends received	(4.0		)	—			(4.0		)
Decrease in value of warrants	—			(24.5		)	(24.5		)
Carrying value of investment in Symetra as of December 31, 2011(2)	$	261.0		$	12.6		$	273.6

(1) Equity in earnings for the years end December 31, 2011, 2010, and 2009 excludes tax expense of $2.3, $1.4, and $0.

(2) Includes White Mountains’ equity in net unrealized gains (losses) from Symetra’s fixed maturity portfolio of $0, $63.7, and $(9.0) as of December 31, 2011, 2010, and 2009, which excludes tax expense of $0, $5.2 and $0.

(3) Includes a $17.9 loss from the dilutive effect of Symetra’s public offering

(4) Impairment of equity in earnings of Symetra excludes tax benefit of $4.1

(5) Impairment of net unrealized gains from Symetra’s fixed maturity portfolio excludes tax benefit of $12.0

(6) Includes a $1.9 gain from the dilutive effect of Symetra’s public offering.

(7) Net unrealized gains (losses) from Symetra’s fixed maturity portfolio excludes tax (expense) benefit of $(6.9), $0.8, and $0 for the years ended December 31, 2011, 2010, and 2009.

(8) Equity in earnings for the years end December 31, 2011, 2010, and 2009 includes $1.0, $0.8, and $0 loss from the dilutive effect of Symetra’s yearly dividend and the issuance of restricted shares by Symetra

The following table summarizes financial information for Symetra as of December 31, 2011 and 2010:

	December 31,
Millions	2011		2010
Symetra balance sheet data:
Total investments	$	26,171.7	$	23,500.2
Separate account assets	795.8		881.7
Total assets	28,212.7		25,636.9
Policyholder liabilities	23,140.6		21,591.5
Long-term debt	449.2		449.0
Separate account liabilities	795.8		881.7
Total liabilities	25,078.7		23,256.3
Common shareholders’ equity	3,134.0		2,380.6

The following table summarizes financial information for Symetra for the years ended December 31, 2011, 2010 and 2009:

	Year Ended December 31,
Millions	2011		2010		2009
Symetra income statement data:
Net premiums earned	$	540.5	$	473.0	$	470.1
Net investment income	1,270.9		1,199.4		1,113.6
Total revenues	1,999.0		1,878.5		1,714.3
Policy benefits	1,307.3		1,234.6		1,197.3
Total expenses	1,720.0		1,589.4		1,533.2
Net income	199.6		200.9		128.3
Comprehensive net income	780.6		683.1		1,018.6

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. For the year ended December 31, 2011, 2010, and 2009, White Mountains recorded $(0.2) million, $0.5 million, and $0.1 million of equity in earnings in PCM. As of December 31, 2011 and 2010, White Mountains investment in PCM was $1.7 million and $2.2 million.

Delos

In August 2006, Sirius Group sold a wholly-owned subsidiary to an investor group led by Lightyear Capital for $138.8 million in cash and recognized a pre-tax gain of $14.0 million in other revenue. As part of this transaction, White Mountains acquired an equity interest of approximately 18% for $32.0 million in the acquiring entity, Delos, and accounted for its investment in Delos under the equity method. In December 2010, White Mountains sold its investment in Delos for $21.7 million and recognized a pre-tax loss of $10.9 million in other revenue.

- Definition

The entire disclosure for equity investment, or group of investments, for which combined disclosure is appropriate, including: (a) the name of each investee and percentage of ownership of common stock, (b) accounting policies for investments in common stock, (c) difference between the amount at which the investment is carried and the amount of underlying equity in net assets and the accounting treatment of the difference, (d) the total fair value of each identified investment for which a market value is available, (e) summarized information as to assets, liabilities, and results of operations of the investees (for investments in unconsolidated subsidiaries, common stock of joint ventures, or other investments using the equity method), and (f) material effects of possible conversions, exercises, or contingent issuances of the investee. Other disclosures include (a) the names of any investee in which the investor owns 20 percent or more of the voting stock and investment is not accounted for using the equity method, and the reasons why not, and (b) the names of any investee in which the investor owns less than 20 percent of the voting stock and the investment is accounted for using the equity method, and the reasons why it is.

+ References + Details

Variable Interest Entities

12 Months Ended

Dec. 31, 2011

Variable Interest Entities

Variable Interest Entities

NOTE 16. Variable Interest Entities

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.

OneBeacon had capitalized three reciprocals by loaning funds to them in exchange for surplus notes. In 2002, OneBeacon formed New Jersey Skylands Management LLC (“NJSM”) to provide management services for a fee to New Jersey Skylands Insurance Association, a reciprocal, and its wholly-owned subsidiary New Jersey Skylands Insurance Company (together, “New Jersey Skylands Insurance”). In 2004, OneBeacon formed Houston General Management Company to provide management services for a fee to another reciprocal, Houston General Insurance Exchange. In 2006, Adirondack AIF, LLC (“AAIF”), a wholly-owned subsidiary of OneBeacon, entered into an agreement to provide management services for a fee to Adirondack Insurance, a reciprocal. OneBeacon has no ownership interest in the reciprocals. Under the provisions of ASC 810, OneBeacon had determined that each of the reciprocals qualifies as a VIE. Further, OneBeacon had determined that it is the primary beneficiary as it has both the power to direct the activities of the VIE that most significantly impact the entity’s economic performance and the obligation to absorb losses or receive benefits of the entity that could potentially be significant to the VIE as a result of the management services provided to the reciprocal and the funds loaned to it. Accordingly, OneBeacon consolidates Houston General Insurance and, until the completion of the Personal Lines Transaction on July 1, 2010, consolidated New Jersey Skylands Insurance and Adirondack Insurance.

As described in Note 2, the Personal Lines Transaction, which was completed on July 1, 2010, included the sale of NJSM and AAIF and the transfer of the surplus notes issued by New Jersey Skylands Insurance and Adirondack Insurance. Completion of the Personal Lines Transaction triggered deconsolidation of New Jersey Skylands Insurance and Adirondack Insurance.

Subsequent to the Personal Lines Transaction, Houston General Insurance is OneBeacon’s only reciprocal. At December 31, 2011 and December 31, 2010, consolidated amounts related to Houston General Insurance included total assets of $105.9 million and $118.0 million, respectively, and total liabilities of $126.2 million and $136.2 million, respectively. At December 31, 2011, the net amount of capital at risk is equal to the surplus note of $23.7 million less the accumulated losses of $20.3 million which includes accrued interest on the surplus note of $17.0 million which eliminates in consolidation.

Prospector Offshore Fund

White Mountains has determined that the Prospector Offshore Fund, Ltd. (“the Prospector Fund”) is a VIE for which White Mountains is the primary beneficiary and is required to consolidate the Prospector Fund. At December 31, 2011 and 2010, White Mountains consolidated total assets of $135.8 million and $145.3 million and total liabilities of $31.6 million and $39.1 million of the Prospector Fund. In addition, at December 31, 2011 and 2010, White Mountains recorded noncontrolling interest of $38.9 million and $40.6 million in the Prospector Fund. For the years ended December 31, 2011, 2010 and 2009 White Mountains recorded $0.2 million, $(3.2) million and $(5.0) million of noncontrolling interest income (expense) related to the Fund. At December 31, 2011, the net amount of capital at risk is equal to White Mountains’ investment in the Fund of $65.3 million, which represents White Mountains’ ownership interest of 62.65% in the Prospector Fund.

Tuckerman Fund I

On December 31, 2011, Tuckerman Capital, LP fund (the “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 common shares of the two small manufacturing companies that were owned by Tuckerman Fund I. At December 31, 2011, White Mountains consolidated assets of $17.6 million, liabilities of $9.9 million, noncontrolling interests of $3.5 million and $2.2 million of noncontrolling interest expense related to the companies distributed by Tuckerman Fund I.

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. At December 31, 2010, White Mountains consolidated total assets of $19.4 million and total liabilities of $12.3 million of Tuckerman Fund I. In addition, at December 31, 2010, White Mountains recorded noncontrolling interest of $2.4 million in Tuckerman Fund I. For the years ended December 31, 2010 and 2009 White Mountains recorded $1.0 million and $0.7 million of noncontrolling interest expense related to Tuckerman Fund I.

Fair Value of Financial Instruments

12 Months Ended

Dec. 31, 2011

Fair Value of Financial Instruments

Fair Value of Financial Instruments

NOTE 17. Fair Value of Financial Instruments

White Mountains carries its financial instruments on its balance sheet at fair value with the exception of its fixed-rate, long-term indebtedness and the SIG Preference Shares, which are recorded as noncontrolling interest. For certain financial instruments where quoted market prices are not available, the fair values of these financial instruments were estimated using quoted market prices. Because considerable judgment is used, these estimates are not necessarily indicative of amounts that could be realized in a current market exchange. The following summarizes the carrying value and fair value of financial instruments that are not accounted for at fair value.

	December 31, 2011				December 31, 2010
Millions	Fair Value		Carrying Value		Fair Value		Carrying Value
OBH Senior Notes	$	277.4	$	269.8	$	435.1	$	419.6
SIG Senior Notes	418.6		399.3		390.9		399.2
SIG Preference Shares	217.5		250.0		212.5		250.0

- 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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 44A, 44B
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 15C, 15D
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 15A
-Subparagraph a-d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 15B
-Subparagraph a, b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 3, 10, 14, 15
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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-Paragraph 32, 33, 34
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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-Name Statement of Financial Accounting Standard (FAS)
-Number 159
-Paragraph 17-22, 27, 28
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+ Details

Transactions with Related Persons

12 Months Ended

Dec. 31, 2011

Transactions with Related Persons

Transactions with Related Persons

NOTE 18. Transactions with Related Persons

Prospector

Mr. John Gillespie is the founder and Managing Member of Prospector. Prospector serves as a discretionary adviser with respect to specified assets, primarily equity securities, managed by 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 million of assets under management; 50 basis points on the next $200 million; and 25 basis points on amounts over $400 million. At December 31, 2011, Prospector managed a total of $408.2 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 equity securities, 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. At December 31, 2011, Prospector managed $558.2 million of assets for OneBeacon under this arrangement, including $216.6 million of ERISA Assets.

During 2011, 2010, and 2009, Prospector earned $6.0 million, $6.6 million, and $6.5 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 7,750 performance shares for the 2012-2014 cycle, 8,500 performance shares for the 2011-2013 performance cycle and 9,200 performance shares for the 2010-2012 performance 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 151% of the 10,800 performance shares granted for the 2009-2011 performance cycle for a total payout of $7.7 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 2011, 2010, and 2009, White Mountains earned $0.2 million, $0.7 million, and $0.2 million under this arrangement.

At December 31, 2011, White Mountains had $109.1 million invested in limited partnership investment interests managed by Prospector (the “Funds”). This total includes $42.9 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 year ended December 31, 2011, White Mountains and OneBeacon incurred $1.1 million in management fees and $0 in incentive fees. In addition, Messrs. Barrette, Davis, Gillespie and Waters, each a director of the Company, and Mr. Campbell, an executive officer of the Company, owned limited partnership investment interests managed by Prospector as of such date.

Other Relationships and Transactions

WMA provides investment advisory and management services to Symetra. At December 31, 2011 and 2010, WMA had $26.3 billion and $23.6 billion of assets under management from Symetra. During 2011, 2010 and 2009, WMA earned $15.2 million, $13.8 million and $13.7 million in fees from Symetra.

On January 7, 2011, the Company agreed to repurchase 140,000 WTM common shares from mutual funds managed by Franklin Mutual Advisers, a beneficial owner of the Company. The price per share was $342.50, which was $2.50 less than the market price at the time the agreement was reached.

Mr. Clark, a director of the Company, was the Vice Chairman of Barclays Capital from 2008 until his retirement in 2011. Barclays has, from time to time, provided various services to White Mountains including investment banking services, brokerage services, underwriting of debt and equity securities and financial consulting services.

Mr. Gillespie, a director of the Company, indirectly through general and limited partnership interests holds a 33% interest in Dowling & Partners Connecticut Fund III, LP (“Fund III”). Two of the Company’s indirect subsidiaries, OneBeacon Professional Insurance (“OBPI”) and White Mountains Specialty Underwriting, Inc. (“WMSUI”), had previously borrowed approximately $8 million and $7 million, respectively, from Fund III in connection with an incentive program sponsored by the State of Connecticut known as the Connecticut Insurance Reinvestment Act (the “CIR Act”). The CIR Act provides for Connecticut income tax credits to be granted for qualifying investments made by approved fund managers. Both loans were repaid in full during 2006. The loans were qualifying investments which generated tax credits to be shared equally between Fund III on the one hand and OBPI and WMSUI on the other. As a result of his interest in Fund III, during 2009, Mr. Gillespie generated approximately $0.5 million in such tax credits.

Until November, 2009, White Mountains leased a building partially owned by Mr. Gillespie and trusts for the benefit of members of his family (the “Gillespie Trusts”).

- Definition

The entire disclosure for related party transactions, including the nature of the relationship(s), a description of the transactions, the amount of the transactions, the effects of any change in the method of establishing the terms of the transaction from the previous period, stated interest rate, expiration date, terms and manner of settlement per the agreement with the related party, and amounts due to or from related parties. If the entity and one or more other entities are under common ownership or management control and this control affects the operating results or financial position, disclosure includes the nature of the control relationship even if there are no transactions between the entities. Disclosure may also include the aggregate amount of current and deferred tax expense for each statement of earnings presented where the entity is a member of a group that files a consolidated tax return, the amount of any tax related balances due to or from affiliates as of the date of each statement of financial position presented, the principal provisions of the method by which the consolidated amount of current and deferred tax expense is allocated to the members of the group and the nature and effect of any changes in that method. 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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 4
-Section 08
-Paragraph k

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 3A
-Section 04
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 57
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-Topic 850
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-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39678-107864

+ Details

Commitments and Contingencies

12 Months Ended

Dec. 31, 2011

Commitments and Contingencies

Commitments and Contingencies

NOTE 19. Commitments and Contingencies

White Mountains leases certain office space under non-cancellable operating leases that expired on various dates through 2011. Rental expense for all of White Mountains’ locations was $22.8 million, $28.1 million and $35.2 million for the years ended December 31, 2011, 2010 and 2009. White Mountains also has various other lease obligations that are immaterial in the aggregate. White Mountains’ future annual minimum rental payments required under non-cancellable leases, which are primarily for office space, are $17.5 million, $13.8 million, $10.3 million and $25.4 million for 2012, 2013, 2014 and 2015 and thereafter, respectively.

White Mountains also has future binding commitments to fund certain other-long term investments, these commitments which total $91.7 million do not have fixed funding dates.

Capital Lease

OBIC sold the majority of its fixed assets and capitalized software to OneBeacon Services LLC (“OB Services”) at a cost equal to book value with no gain or loss recorded on the sale. Subsequent to purchasing the fixed assets and capitalized software from OBIC, OB Services entered into lease financing arrangements with US Bancorp and Fifth Third whereby OB Services sold its furniture and equipment and its capitalized software, respectively, to US Bancorp and Fifth Third. The assets were sold at a cost equal to net book value. OB Services 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. OB Services received cash proceeds of $23.1 million as a result of entering into the sale-leaseback transactions. At the end of the lease terms, OB Services will be obligated to purchase the leased assets for a nominal fee, after which all rights, title and interest would transfer to OB Services. 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 of $23.1 million included within other liabilities and a capital lease asset of $22.9 million included within other assets as of December 31, 2011. The underlying assets will continue to be depreciated over their respective useful lives. OB Services’ future annual minimum rental payments are $5.3 million for each of the years ended December 31, 2012, 2013, 2014 and 2015 and $1.9 million for the year ended December 31, 2016.

Assigned Risks

As a condition of its license to do business in certain states, White Mountains’ 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’ 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. At December 31, 2011, the reserve for such assessments totaled $16.0 million.

Esurance

On October 7, 2011, the Company completed the sale of its Esurance and Answer Financial subsidiaries (the “Transferred Subsidiaries”) to Allstate pursuant 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 contingent liabilities under the Agreement as follows: (i) the final purchase price payable by Allstate under the Agreement, which is based upon the book value of the Transferred Subsidiaries at the closing date, is subject to a true-up process that has not yet been concluded, (ii) 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, (iii) the Company indemnifies Allstate for breaches of certain covenants in the Agreement, including certain agreements by the Company not to engage in certain competing business activities for two years after the closing and not to solicit certain employees of the Transferred Subsidiaries for three years after the closing, and (iv) 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), to be computed annually on the first three anniversaries of the closing date.

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’ 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 is not a party to any material non-claims litigation or arbitration. 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’ financial condition, results of operations or cash flows.

Tribune Company

In June 2011, Deutsche Bank Trust Company Americas, Law Debenture Company of New York and Wilmington Trust Company (collectively referred to as the “Plaintiff”), in their capacity as trustees for certain senior notes issued by the Tribune Company (the “Tribune”), filed lawsuits in various jurisdictions against numerous defendants including certain of White Mountains’ subsidiaries in their capacity as former shareholders of the Tribune seeking recovery of the proceeds from the sale of common stock of the Tribune in connection with the Tribune’s leveraged buyout in 2007 (the “LBO”). The Plaintiff seeks recovery of the proceeds received by the former Tribune shareholders on the basis that the 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. Certain subsidiaries of White Mountains, received a total of approximately $39 million for the Tribune common stock it tendered in connection with the leveraged buyout. The various cases are now pending before a Multi District Litigation panel (“MDL”) in the federal district court in New York.

In December 2011, the MDL granted a motion to consolidate all of the lawsuits brought by Plaintiffs for pretrial matters and transfer all such proceedings to the United States District Court for the Southern District of New York. The consolidated cases are currently stayed pending further order of the Bankruptcy Court.

In addition OneBeacon, OBIC-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, 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 adversary proceeding is currently pending in Bankruptcy Court. That case is also stayed pending further order of the Bankruptcy Court. In the event that White Mountains does not obtain a favorable outcome, management does not believe that the outcome of such litigation will have a material adverse effect on White Mountains’ financial condition, results of operations or cash flows.

- Definition

The entire disclosure for commitments and contingencies.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Interpretation (FIN)
-Number 14
-Paragraph 3
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 5
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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Paragraph 1
-Subparagraph (SX 210.5-02.25)
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-URI http://asc.fasb.org/extlink&oid=6449706&loc=d3e16207-108621

+ Details

Discontinued Operations

12 Months Ended

Dec. 31, 2011

Discontinued Operations

Discontinued Operations

NOTE 20. Discontinued Operations

Esurance

On October 7, 2011, White Mountains completed the sale of Esurance Insurance and AFI to Allstate (see Note 2). As a result of the transaction, Esurance Insurance, AFI and the business Esurance Insurance cedes to Sirius Group (collectively, “the Esurance Disposal Group”) are reported as discontinued operations. White Mountains recognized a gain of $677.5 million on the Esurance Sale which is recorded net of tax in discontinued operations. Effective as of December 31, 2011, the results of operations for the Esurance Disposal Group have been classified as discontinued operations and are presented, net of related income taxes, in the statement of comprehensive income. The assets and liabilities of the Esurance Disposal Group have been presented in the balance sheet as held for sale. Prior year amounts have been reclassified to conform to the current period’s presentation.

AutoOne

On August 30, 2011, OneBeacon entered into an agreement to sell the AutoOne business to Interboro. AutoOne operates as a division within OneBeacon, offering products and services to automobile assigned risk markets. The transaction includes the sale of two insurance entities, AOIC and AOSIC, through which substantially all of the AutoOne business is written on a direct basis. During the year ended December 31, 2011, OneBeacon recorded a net charge of $29.6 million pre-tax, $19.2 million after tax, reflecting the estimated loss on sale of the AutoOne business, which includes the $25.0 million of net assets held for sale as well as estimates for transaction costs. As of December 31, 2011, the results of operations for the AutoOne business have been classified as discontinued operations and are presented, net of related income taxes, in the statement of comprehensive income. Prior year results of operations have been reclassified to conform to the current period’s presentation.

The AutoOne disposal group excludes investing and financing activities from amounts classified as discontinued operations. OneBeacon’s investing and financing operations are conducted on an overall consolidated level and accordingly, there were no separately identifiable cash investing or financing cash flows associated with AutoOne. The assets and liabilities associated with the AutoOne business as of December 31, 2011 have been presented in the balance sheet as held for sale assuming the investing and financing steps required to affect the sale were completed as of the current balance sheet date. The prior year balance sheet has not been reclassified to conform to the current period’s presentation because the assets and liabilities associated with AutoOne in the prior year would not provide a meaningful comparison to the assets and liabilities presented as held for sale at December 31, 2011.

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

Millions	December 31, 2011		December 31, 2010
Assets held for sale
Fixed maturity investments, at fair value	$	111.8	$	593.8
Short-term investments, at amortized cost (which approximates fair value)	—		131.0
Common equity securities, at fair value	—		43.0
Convertible fixed maturity investments, at fair value	—		17.2
Other long-term investments	—		4.0
Total investments	111.8		789.0
Cash	5.5		39.8
Reinsurance recoverable on paid and unpaid losses	—		34.4
Insurance premiums receivable	8.8		102.9
Deferred acquisition costs	2.2		34.7
Deferred tax asset	1.9		67.8
Other assets	2.4		54.2
Total assets held for sale	$	132.6	$	1,122.8
Liabilities held for sale
Loss and loss adjustment expense reserves	$	64.7	$	450.4
Unearned insurance premiums	34.1		201.6
Accrued incentive compensation	—		19.1
Other liabilities	8.8		80.4
Total liabilities held for sale	107.6		751.5
Net assets held for sale	$	25.0	$	371.3

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

	Year Ended December 31,
Millions, except per share amounts	2011			2010			2009
Revenues
Earned insurance premiums	$	727.9		$	910.6		$	882.8
Net investment income	12.0			19.6			22.3
Net realized and unrealized investment gains	.7			13.3			22.9
Other revenue	53.5			60.9			55.2
Total revenues	794.1			1,004.4			983.2
Expenses
Loss and loss adjustment expenses	542.3			678.8			695.0
Insurance and reinsurance acquisition expenses	159.2			191.7			170.1
Other underwriting expenses	80.4			87.9			98.7
General and administrative expenses	38.3			48.6			52.6
Total expenses	820.2			1,007.0			1,016.4
Pre-tax loss	(26.1		)	(2.6		)	(33.2		)
Income tax benefit (expense)	13.1			(4.0		)	5.4
Loss from discontinued operations	(13.0		)	(6.6		)	(27.8		)
Gain on sale of Esurance and AFI, net of tax	677.5			—			—
Loss on sale of AutoOne, net of tax	(19.2		)	—			—
Net income (loss) from discontinued operations	$	645.3		$	(6.6	)	$	(27.8	)

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, 2011, 2010 and 2009:

	Year Ended December 31,
	2011			2010			2009
Basic and diluted earnings (loss) per share numerators (in millions):
Net income (loss) attributable to White Mountains’ common shareholders	$	645.3		$	(6.6	)	$	(27.8	)
Allocation of income for participating unvested restricted common shares	(5.7		)	.1			.3
Net income (loss) attributable to White Mountains’ common shareholders, net of restricted common share amounts(3)	$	639.6		$	(6.5	)	$	(27.5	)
Basic earnings (loss) per share denominators (in thousands):
Total average common shares outstanding during the period	7,881.0			8,548.4			8,849.4
Average unvested restricted common shares (1)	(69.4		)	(97.3		)	(85.3		)
Basic earnings (loss) per share denominator	7,811.6			8,451.1			8,764.1
Diluted earnings (loss) per share denominator (in thousands):
Total average common shares outstanding during the period	7,881.0			8,548.4			8,849.4
Average unvested restricted common shares (1)	(69.4		)	(97.3		)	(85.3		)
Average outstanding dilutive options to acquire common shares (2)	—			.5			1.5
Diluted earnings (loss) per share denominator	7,811.6			8,451.6			8,765.6
Basic and diluted earnings (loss) per share (in dollars):	$	81.88		$	(.77	)	$	(3.14	)

(1) Restricted common shares outstanding vest either in equal annual installments or upon a stated date (see Note 11).

(3) Net income (loss) attributable to White Mountains’ common shareholders, net of restricted share amounts, is equal to undistributed earnings (loss) for the years ended December 31, 2011, 2010, and 2009.

- 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 Statement of Financial Accounting Standard (FAS)
-Number 144
-Paragraph 43-48
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: 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

Reference 3: 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 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 5
-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e1020-107759

Reference 6: 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 7: 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 8: 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 9: 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=6390789&loc=d3e2443-110228

Reference 10: 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

+ Details

SELECTED QUARTERLY FINANCIAL DATA (Unaudited)

12 Months Ended

Dec. 31, 2011

SELECTED QUARTERLY FINANCIAL DATA (Unaudited)

SELECTED QUARTERLY FINANCIAL DATA (Unaudited)

Selected quarterly financial data for 2011 and 2010 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 and AutoOne Sale, the results of operations for Esurance and AutoOne 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 20).

	2011 Three Months Ended												2010 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	$	593.6		$	501.3		$	553.6		$	529.6		$	552.8		$	551.0		$	670.8		$	792.1
Expenses	535.6			500.1			517.5			563.3			457.2			475.8			664.9			815.7
Pre-tax income (loss)	58.0			1.2			36.1			(33.7		)	95.6			75.2			5.9			(23.6		)
Tax benefit (expense)	124.6			.6			(10.0		)	7.7			(6.6		)	(11.7		)	1.4			—
Income (loss) from continuing operations	182.6			1.8			26.1			(26.0		)	89.0			63.5			7.3			(23.6		)
Income (loss) from discontinued operations, net of tax	674.2			(30.1		)	(1.5		)	2.5			(7.8		)	3.6			.6			(3.0		)
Noncontrolling interest in consolidated subsidiaries	(20.3		)	11.0			(20.8		)	(11.4		)	(16.6		)	(24.3		)	(10.7		)	(1.4		)
Equity in (loss) earnings of unconsolidated affiliates	(36.3		)	1.5			7.9			6.7			8.3			7.9			5.3			(11.6		)
Income (loss) attributable to White Mountains’ common shareholders	$	800.2		$	(15.8	)	$	11.7		$	(28.2	)	$	72.9		$	50.7		$	2.5		$	(39.6	)
Income (loss) attributable to White Mountains’ common shareholders:
Basic
Continuing operations	$	16.54		$	1.81		$	1.66		$	(3.82	)	$	9.77		$	5.58		$	.21		$	(4.14	)
Discontinued operations	88.50			(3.81		)	(.18		)	.31			(.94		)	.43			.07			(.34		)
Total consolidated operations	105.04			(2.00		)	1.48			(3.51		)	8.83			6.01			.28			(4.48		)
Diluted
Continuing operations	$	16.54		$	1.81		$	1.66		$	(3.82	)	$	9.77		$	5.58		$	.21		$	(4.14	)
Discontinued operations	88.50			(3.81		)	(.18		)	.31			(.94		)	.43			.07			(.34		)
Total consolidated operations	105.04			(2.00		)	1.48			(3.51		)	8.83			6.01			.28			(4.48		)
Adjusted book value per share	$	542.11		$	436.18		$	447.69		$	446.70		$	440.59		$	428.79		$	405.94		$	410.59

- Definition

The entire disclosure for the quarterly financial data in the annual financial statements. The disclosure may include a tabular presentation of financial information for each fiscal quarter for the current and previous year, including revenues, gross profit, income or loss before extraordinary items and earnings per share data. It also includes an indication if the information in the note is unaudited, comments on the aggregate effect of year-end adjustments, and an explanation of matters or transactions that affect comparability or are pertinent to an understanding of the information furnished.

+ References + Details

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

12 Months Ended

Dec. 31, 2011

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

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

SCHEDULE I

WHITE MOUNTAINS INSURANCE GROUP, LTD.

SUMMARY OF INVESTMENTS—OTHER THAN

INVESTMENTS IN RELATED PARTIES

At December 31, 2011

Millions	Cost		Carrying Value(1)		Fair Value
Fixed maturities:
Bonds:
U.S. Government and government agencies and authorities	$	299.4	$	305.0	$	305.0
Debt securities issued by industrial corporations	2,072.1		2,135.1		2,135.1
Mortgage-backed and asset-backed securities	3,190.5		3,222.9		3,222.9
States, municipalities and political subdivisions	2.7		2.7		2.7
Foreign governments	581.2		589.2		589.2
Redeemable preferred stocks	82.3		78.8		78.8
Total fixed maturities(1)	6,228.2		6,333.7		6,333.7
Short-term investments	846.0		846.0		846.0
Common equity securities:
Banks, trust and insurance companies	205.3		219.2		219.2
Public utilities	39.4		42.0		42.0
Industrial, miscellaneous and other	447.0		493.8		493.8
Total common equity securities	691.7		755.0		755.0
Convertible fixed maturities	139.2		143.8		143.8
Other long-term investments	274.4		301.3		301.3
Total investments(1)	$	8,179.5	$	8,379.8	$	8,379.8

(1) Carrying value and fair value includes $111.8 that is classified as assets held for sale relating to AutoOne discontinued operations.

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT

12 Months Ended

Dec. 31, 2011

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT

SCHEDULE II

CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT

CONDENSED BALANCE SHEETS

	December 31,
Millions	2011			2010
Assets:
Cash	$	.7		$	.3
Fixed maturity investments, at fair value	1,334.5			5.8
Common equity securities, at fair value	1.9			1.8
Short-term investments, at amortized cost	72.3			54.9
Other assets	5.1			4.5
Investments in consolidated and unconsolidated affiliates (1)	2,687.3			3,821.2
Total assets	$	4,101.8		$	3,888.5
Liabilities:
Payable to subsidiary	$	(2.8	)	$	221.7
Accounts payable and other liabilities	16.9			13.8
Total liabilities	14.1			235.5
White Mountains’ common shareholders’ equity	4,087.7			3,653.0
Total liabilities and equity (1)	$	4,101.8		$	3,888.5

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS)

	Year Ended December 31,
Millions	2011			2010			2009
Revenues (including realized gains and losses)	$	6.4		$	1.1		$	—
Expenses	51.7			42.2			38.3
Pre-tax loss	(45.3		)	(41.1		)	(38.3		)
Income tax benefit (expense)	6.5			(.6		)	(3.6		)
Net loss	(38.8		)	(41.7		)	(41.9		)
Equity in earnings (losses) from consolidated and unconsolidated affiliates (1)	806.7			128.2			511.9
Net income (loss) attributable to White Mountains’ common shareholders	767.9			86.5			470.0
Other comprehensive (loss) income items, after-tax	(81.7		)	127.9			280.8
Comprehensive income attributable to White Mountains’ common shareholders	$	686.2		$	214.4		$	750.8
Computation of net income (loss) available to common shareholders:
Net income available to common shareholders	$	767.9		$	86.5		$	470.0

(1) In 2011, the Company revised the presentation of investments in consolidated and unconsolidated affiliates, total liabilities and equity and equity in earnings (losses) from consolidated and unconsolidated affiliates to be net of noncontrolling interests for all periods presented.

CONDENSED STATEMENTS OF CASH FLOWS

	Year Ended December 31,
Millions	2011			2010			2009
Net income attributable to White Mountains’ common shareholders (2)	$	767.9		$	86.5		$	470.0
Charges (credits) to reconcile net income to net cash from operations:
Net realized and unrealized losses (gains) on sales of investments	(3.1		)	.1			1.7
Undistributed current (earnings) losses from subsidiaries (2)	(806.7		)	(128.2		)	(511.9		)
Dividends received from subsidiaries	—			—			8.4
Net federal income tax (payments) receipts	—			—			—
Net change in other assets and other liabilities	13.7			27.9			18.6
Net cash used for operations	(28.2		)	(13.7		)	(13.2		)
Cash flows from investing activities:
Net decrease in short-term investments	267.3			166.5			20.8
Purchases of investment securities	(237.3		)	(5.8		)	(28.4		)
Sales and maturities of investment securities	59.0			—			—
Issuance of debt (to) from subsidiaries	—			86.8			—
Repayment of debt (to) from subsidiaries	192.5			—			200.0
Contributions to subsidiaries	—			—			—
Distributions from subsidiaries	7.2			—			29.0
Net change in unsettled investment purchases and sales	—			—			—
Net cash provided from investing activities	288.7			247.5			221.4
Cash flows from financing activities:
Issuance of debt	—			—			—
Repayment of debt	—			—			(200.0		)
Proceeds from issuances of common shares	.9			.7			.9
Repurchases and retirement of common shares	(253.0		)	(225.6		)	(.4		)
Dividends paid on common shares	(8.0		)	(8.8		)	(8.9		)
Net cash used for financing activities	(260.1		)	(233.7		)	(208.4		)
Net increase (decrease) in cash during the year	.4			.1			(.2		)
Cash balance at beginning of year	.3			.2			.4
Cash balance at end of year	$	.7		$	.3		$	.2

(2) In 2011, the Company revised the presentation of net income attributable to White Mountains’ common shareholders and undistributed current (earnings) losses from subsidiaries to be net of noncontrolling interests for all periods presented.

- Definition

The entire disclosure for condensed financial information, including the financial position, cash flows, and the results of operations of the registrant (parent company) as of the same dates or for the same periods for which audited consolidated financial statements are being presented. Alternatively, the details of this disclosure can be reported by the specific parent company taxonomy elements, indicating the appropriate date and period contexts in an instance document.

+ References + Details

SCHEDULE III SUPPLEMENTARY INSURANCE INFORMATION

12 Months Ended

Dec. 31, 2011

SCHEDULE III SUPPLEMENTARY INSURANCE INFORMATION

SCHEDULE III SUPPLEMENTARY INSURANCE INFORMATION

SCHEDULE III

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, 2011:
OneBeacon	$	123.5	$	3,358.6	$	528.0	$	—	$	1,015.5	$	66.8		$	580.9	$	219.0	$	173.3	$	1,062.9
Sirius Group	63.5		2,343.7		319.0		—		912.3		89.9			626.0		181.0		105.8		915.7
Other operations	—		—		—		—		—		8.0			—		—		—		—
December 31, 2010:
OneBeacon	$	114.5	$	3,295.5	$	627.5	$	—	$	1,487.7	$	96.3		$	930.2	$	320.7	$	246.5	$	1,236.3
Sirius Group	61.6		2,441.3		311.2		—		847.9		90.5			531.0		167.5		99.8		865.8
Other operations	—		—		—		—		—		1.3			—		—		—		—
December 31, 2009:
OneBeacon	$	215.0	$	3,934.8	$	1,018.3	$	—	$	1,959.5	$	127.4		$	1,121.9	$	398.3	$	330.0	$	1,906.7
Sirius Group	57.2		2,444.4		287.5		—		858.8		107.7			418.8		170.9		98.1		806.8
Other operations	—		—		—		—		—		(.1		)	—		—		—		—

(1) The amounts shown exclude net investment income (expense) relating to non-insurance operations in the other operations segment of $19.8, $14.8 and $12.5 for the twelve months ended December 31, 2011, 2010 and 2009, respectively.

SCHEDULE IV REINSURANCE

12 Months Ended

Dec. 31, 2011

SCHEDULE IV REINSURANCE

SCHEDULE IV REINSURANCE

SCHEDULE IV

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, 2011:
OneBeacon	$	1,138.5	$	(166.1	)	$	43.1	$	1,015.5	4.2	%
Sirius Group	128.5		(205.9		)	989.8		912.4		108.5	%
Other operations	—		—			—		—		—	%
December 31, 2010:
OneBeacon	$	1,732.5	$	(309.0	)	$	64.2	$	1,487.7	4.3	%
Sirius Group	117.9		(199.7		)	929.7		847.9		109.6	%
Other operations	—		—			—		—		—	%
December 31, 2009:
OneBeacon	$	2,122.4	$	(229.7	)	$	66.8	$	1,959.5	3.4	%
Sirius Group	107.2		(175.9		)	927.5		858.8		108.0	%
Other operations	—		—			—		—		—	%

SCHEDULE V VALUATION AND QUALIFYING ACCOUNTS

12 Months Ended

Dec. 31, 2011

SCHEDULE V VALUATION AND QUALIFYING ACCOUNTS

SCHEDULE V VALUATION AND QUALIFYING ACCOUNTS

SCHEDULE V

WHITE MOUNTAINS INSURANCE GROUP, LTD.

VALUATION AND QUALIFYING ACCOUNTS

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

December 31, 2011:
Reinsurance recoverable on paid losses:
Allowance for reinsurance balances	$	29.4	$	8.5		$	—		$	(3.9	)	$	34.0
Property and casualty insurance and reinsurance premiums receivable:
Allowance for uncollectible accounts	3.9		—			(.5		)	—			3.4

December 31, 2010:
Reinsurance recoverable on paid losses:
Allowance for reinsurance balances	$	30.0	$	(.4	)	$	—		$	(.2	)	$	29.4
Property and casualty insurance and reinsurance premiums receivable:
Allowance for uncollectible accounts	6.3		.2			(1.0		)	(1.6		)	3.9

December 31, 2009:
Reinsurance recoverable on paid losses:
Allowance for reinsurance balances	$	29.5	$	2.3		$	—		$	(1.8	)	$	30.0
Property and casualty insurance and reinsurance premiums receivable:
Allowance for uncollectible accounts	7.1		1.5			(1.8		)	(.5		)	6.3

(1) Represents net reinstatements (charge-offs) of balances receivables and foreign exchange.

SCHEDULE VI SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS

12 Months Ended

Dec. 31, 2011

SCHEDULE VI SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS

SCHEDULE VI SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS

SCHEDULE VI

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		Reserves for Unpaid Claims and Claims		Discount, if any,							Net		Claims and Claims Adjustment Expenses Incurred Related to					Amortization of deferred policy		Paid Claims and Claims
Affiliation with registrant	acquisition costs		Adjustment Expenses		deducted in Column C			Unearned Premiums		Earned Premiums		investment income		(1) Current Year		(2) Prior Year			acquisition costs		Adjustment Expenses		Premiums written
OneBeacon:
2011	$	123.5	$	3,358.6	$	271.6	(1)	$	528.0	$	1,015.5	$	71.4	$	583.8	$	(2.9	)	$	219.0	$	714.8	$	1,062.9
2010	114.5		3,295.5		295.9		(1)	627.5		1,487.7		96.6		981.4		(51.2		)	320.7		1,038.8		1,236.3
2009	215.0		3,934.8		317.5		(1)	1,018.3		1,959.5		125.5		1,205.3		(83.4		)	398.3		1,176.1		1,906.7
Sirius Group:
2011	$	63.5	$	2,343.7	$	12.8	(2)	$	319.0	$	912.3	$	89.9	$	672.9	$	(46.9	)	$	181.0	$	642.0	$	915.7
2010	61.6		2,441.3		21.1		(2)	311.2		847.9		90.5		588.1		(57.1		)	167.5		437.0		865.8
2009	57.2		2,444.4		29.5		(2)	287.5		858.8		107.7		449.1		(30.4		)	170.9		772.9		806.8
Other operations:
2011	$	—	$	—	$	—		$	—	$	—	$	—	$	—	$	—		$	—	$	—	$	—
2010	—		—		—			—		—		—		—		—			—		—		—
2009	—		—		—			—		—		—		—		—			—		—		—
50%-or-less owned property and casualty investees:(3)
Delos(4):
2011	$	—	$	—	$	—		$	—	$	—	$	—	$	—	$	—		$	—	$	—	$	—
2010	—		—		—			—		—		—		—		—			—		—		—
2009	3.9		73.3		—			26.1		33.3		1.7		24.3		—			—		18.2		31.7

(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 (4.5%, 5.0% and 5.3% at December 31, 2011, 2010 and 2009). Also the amounts shown include unamortized fair value adjustments to reserves for unpaid claims and claims adjustment expenses made in purchase accounting as a result of White Mountains’ purchase of OneBeacon for the years ended December 31, 2011, 2010 and 2009.

(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’ purchase of Sirius International during 2004.

(3) The amounts shown represent White Mountains’ share of its 50% owned unconsolidated property and casualty insurance affiliates.

(4) In August 2006, White Mountains acquired an equity interest of approximately 18% in Delos. During the fourth quarter of 2010, White Mountains sold its entire interest in Delos.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2011

Summary of Significant Accounting Policies

Transfers of Financial Assets and Amendments to FIN 46R

Other-Than-Temporary Impairments

Fair Value Measurements

Investment securities

Other long-term investments

Derivative financial instruments

Warrants

Derivatives Variable annuity reinsurance

Cash

Insurance and reinsurance operations

Mandatory Shared Market Mechanisms

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’ insurance subsidiaries record guaranty fund assessments when it is probable that an assessment will be made and the amount can be reasonably estimated.

Deferred Software Costs

Federal and foreign income taxes

Foreign currency exchange

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

Currency	Opening Rate 2011	Closing Rate 2011	Opening Rate 2010	Closing Rate 2010
Swedish kronor	6.7030	6.8645	7.1280	6.7030
British pound	.6420	.6434	.6191	.6420
Canadian dollar	.9981	1.0193	1.0485	.9981

Noncontrolling Interest

Policy Acquisition Costs

Offsetting Assets and Liabilities

Comprehensive Income

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2011

Summary of Significant Accounting Policies

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 2011	Closing Rate 2011	Opening Rate 2010	Closing Rate 2010
Swedish kronor	6.7030	6.8645	7.1280	6.7030
British pound	.6420	.6434	.6191	.6420
Canadian dollar	.9981	1.0193	1.0485	.9981

Reserves for Unpaid Losses and Loss Adjustment Expenses (Tables)

12 Months Ended

Dec. 31, 2011

Reserves for Unpaid Losses and Loss Adjustment Expenses

Loss and LAE reserve activities

The following table summarizes the loss and LAE reserve activities of White Mountains’ insurance and reinsurance subsidiaries for the years ended December 31, 2011, 2010 and 2009:

	Year Ended December 31,
Millions	2011			2010			2009
Gross beginning balance	$	5,736.8		$	6,379.2		$	7,029.4
Less beginning reinsurance recoverable on unpaid losses	(2,344.0		)	(2,771.5		)	(3,049.0		)
Net loss and LAE reserves	3,392.8			3,607.7			3,980.4

Less: Beginning net loss and LAE reserves for AutoOne (1)	(77.3		)	(95.8		)	(102.0		)

Loss and LAE reserves acquired—Old Lyme	21.0			—			—
Loss and LAE reserves acquired—Central National	—			17.6			—
Loss and LAE reserves sold—OneBeacon Personal Lines	—			(231.0		)	—

Losses and LAE incurred relating to:
Current year losses	1,256.7			1,503.4			1,571.2
Prior year losses	(49.8		)	(114.2		)	(147.1		)
Total incurred losses and LAE	1,206.9			1,389.2			1,424.1

Accretion of fair value adjustment to net loss and LAE reserves	8.3			8.5			12.2
Foreign currency translation adjustment to net loss and LAE reserves	.1			4.7			23.5

Loss and LAE paid relating to:
Current year losses	(404.0		)	(544.9		)	(591.6		)
Prior year losses	(952.8		)	(840.5		)	(1,234.7		)
Total loss and LAE payments	(1,356.8		)	(1,385.4		)	(1,826.3		)

Less: Beginning net loss and LAE reserves for AutoOne (1)	—			77.3			95.8

Net ending balance	3,195.0			3,392.8			3,607.7
Plus ending reinsurance recoverable on unpaid losses	2,507.3			2,344.0			2,771.5
Gross ending balance	$	5,702.3		$	5,736.8		$	6,379.2

(1)	Adjustment is to present loss and LAE reserve activities from continuing operations. At December 31, 2011, loss and LAE reserves for AutoOne have been reclassified as liabilities held for sale. Loss and LAE reserve balances for AutoOne prior to December 31, 2011 were not reclassified.

Schedule of asbestos and environmental loss and LAE reserve activities

OneBeacon

Net A&E Loss	Year Ended December 31,
Reserve Activity	2011									2010									2009
				Pre-NICO									Pre-NICO									Pre-NICO
Millions	Gross			Net(1)			Net			Gross			Net(1)			Net			Gross			Net(1)			Net
Asbestos:
Beginning balance	$	904.0		$	647.3		$	6.4		$	985.6		$	688.8		$	6.5		$	1,098.4		$	741.5		$	6.5
Incurred losses and LAE	256.8			32.2			(4.0		)	—			—			—			1.0			—			—
Paid losses and LAE	(86.5		)	1.7			(.2		)	(81.6		)	(41.5		)	(.1		)	(113.8		)	(52.7		)	—
Ending balance	1,074.3			681.2			2.2			904.0			647.3			6.4			985.6			688.8			6.5
Environmental:
Beginning balance	119.0			93.8			9.2			350.7			218.6			7.6			470.3			261.2			5.5
Incurred losses and LAE	231.8			62.2			10.0			6.2			6.0			6.0			4.9			5.0			5.0
Paid losses and LAE	(71.0		)	(4.4		)	(10.2		)	(237.9		)	(130.8		)	(4.4		)	(124.5		)	(47.6		)	(2.9		)
Ending balance	279.8			151.6			9.0			119.0			93.8			9.2			350.7			218.6			7.6
Total asbestos and environmental:
Beginning balance	1,023.0			741.1			15.6			1,336.3			907.4			14.1			1,568.7			1,002.7			12.0
Incurred losses and LAE	488.6			94.4			6.0			6.2			6.0			6.0			5.9			5.0			5.0
Paid losses and LAE	(157.5		)	(2.7		)	(10.4		)	(319.5		)	(172.3		)	(4.5		)	(238.3		)	(100.3		)	(2.9		)
Ending balance	$	1,354.1		$	832.8		$	11.2		$	1,023.0		$	741.1		$	15.6		$	1,336.3		$	907.4		$	14.1

(1)	Represents A&E reserve activity, net of third-party reinsurance, but prior to the NICO Cover.

Sirius Group

Net A&E Loss Reserve Activity	Year Ended December 31,
	2011						2010						2009
Millions	Gross			Net			Gross			Net			Gross			Net
Asbestos:
Beginning balance	$	191.9		$	151.5		$	187.0		$	146.6		$	173.7		$	138.5
Losses and LAE acquired — Central National	—			—			10.4			9.7			—			—
Incurred losses and LAE	13.6			10.3			9.0			7.3			24.7			18.4
Paid losses and LAE	(20.4		)	(15.6		)	(14.5		)	(12.1		)	(11.4		)	(10.3		)
Ending balance	185.1			146.2			191.9			151.5			187.0			146.6
Environmental:
Beginning balance	22.4			18.1			22.2			17.9			24.5			20.1
Losses and LAE acquired — Central National	—			—			3.5			2.4			—			—
Incurred losses and LAE	2.9			2.0			(2.5		)	(1.3		)	(.8		)	(.7		)
Paid losses and LAE	(3.2		)	(3.6		)	(.8		)	(.9		)	(1.5		)	(1.5		)
Ending balance	22.1			16.5			22.4			18.1			22.2			17.9
Total asbestos and environmental:
Beginning balance	214.3			169.6			209.2			164.5			198.2			158.6
Losses and LAE acquired — Central National	—			—			13.9			12.1			—			—
Incurred losses and LAE	16.5			12.3			6.5			6.0			23.9			17.7
Paid losses and LAE	(23.6		)	(19.2		)	(15.3		)	(13.0		)	(12.9		)	(11.8		)
Ending balance	$	207.2		$	162.7		$	214.3		$	169.6		$	209.2		$	164.5

Third-Party Reinsurance (Tables)

12 Months Ended

Dec. 31, 2011

Third-Party Reinsurance

Schedule of direct assumed and ceded amounts

The effects of reinsurance on White Mountains’ insurance and reinsurance subsidiaries’ written and earned premiums and on losses and LAE were as follows:

	Year ended December 31, 2011
Millions	OneBeacon			Sirius Group			Other Operations		Total
Written premiums:
Direct	$	1,077.6		$	139.5		$	—	$	1,217.1
Assumed	48.2			988.6			—		1,036.8
Gross written premiums	1,125.8			1,128.1			—		2,253.9
Ceded	(62.9		)	(212.4		)	—		(275.3		)
Net written premiums	$	1,062.9		$	915.7		$	—	$	1,978.6
Earned premiums:
Direct	$	1,138.5		$	128.5		$	—	$	1,267.0
Assumed	43.1			989.8			—		1,032.9
Gross earned premiums	1,181.6			1,118.3			—		2,299.9
Ceded	(166.1		)	(206.0		)	—		(372.1		)
Net earned premiums	$	1, 015.5		$	912.3		$	—	$	1,927.8
Losses and LAE:
Direct	$	1,151.1		$	80.0		$	—	$	1,231.1
Assumed	36.1			627.8			—		663.9
Gross losses and LAE	1,187.2			707.8			—		1,895.0
Ceded	(606.3		)	(81.8		)	—		(688.1		)
Net losses and LAE	$	580.9		$	626.0		$	—	$	1,206.9

	Year ended December 31, 2010
Millions	OneBeacon			Sirius Group			Other Operations		Total
Written premiums:
Direct	$	1,501.5		$	121.6		$	—	$	1,623.1
Assumed	57.7			957.5			—		1,015.2
Gross written premiums	1,559.2			1,079.1			—		2,638.3
Ceded (1)	(400.2		)	(213.3		)	—		(613.5		)
Net written premiums	$	1,159.0		$	865.8		$	—	$	2,024.8
Earned premiums:
Direct	$	1,648.7		$	117.9		$	—	$	1,766.6
Assumed	64.2			929.7			—		993.9
Gross earned premiums	1,712.9			1,047.6			—		2,760.5
Ceded (1)	(309.0		)	(199.7		)	—		(508.7		)
Net earned premiums	$	1,403.9		$	847.9		$	—	$	2,251.8
Losses and LAE:
Direct	$	877.1		$	59.4		$	—	$	936.5
Assumed	138.4			684.4			—		822.8
Gross losses and LAE	1,015.5			743.8			—		1,759.3
Ceded (1)	(157.3		)	(212.8		)	—		(370.1		)
Net losses and LAE	$	858.2		$	531.0		$	—	$	1,389.2

(1)	During 2010, OneBeacon ceded written premiums of $262.2, earned premiums of $165.0 and loss and LAE of $86.5 pursuant to the Commercial Lines Transaction.

Listing of OneBeacon's top reinsurers

Top Reinsurers ($ in millions)	Balance at December 31, 2011		% of Total		A.M. Best Rating(1)
National Indemnity Company and General Reinsurance Corporation (2)	$	1,540.6	66	%		A++
Hanover Insurance Group Ltd.	90.9		4	%		A
Tokio Marine and Nichido Fire (3)	57.1		2	%		A++
Tower Group Inc.	35.1		1	%		A-
Munich Reinsurance America	26.4		1	%		A+

(1)	A.M. Best ratings as detailed above are: “A++” (Superior, which is the highest of fifteen financial strength ratings), “A+” (Superior, which is the second highest of fifteen financial strength ratings), “A” (Excellent, which is the third highest of fifteen financial strength ratings), and “A-” (Excellent, which is the fourth highest of fifteen financial strength ratings). Ratings are as of December 31, 2011.
(2)	Includes $198.3 of Third-Party Recoverables, which NICO would pay under the terms of the NICO Cover if they are unable to collect from third-party reinsurers.
(3)	Includes $30.5 of reinsurance recoverables from various third-party reinsurers that are guaranteed by Tokio Marine and Nichido Fire under the terms of a 100% quota share reinsurance agreement between Houston General Insurance Company and Tokio Marine and Nichido Fire.

Listing of Sirius's top reinsurers

The following table provides a listing of Sirius Group’s top reinsurers based upon recoverable amounts, the percentage of total recoverables and the reinsurer’s A.M. Best Rating.

Top Reinsurers ($ in millions)	Balance at December 31, 2011		% of Total		A.M. Best Rating(1)		% Collateralized
General Reinsurance Corporation	$	42.7	12	%		A++	1	%
Swiss Re Group	40.2		11	%		A+	20	%
Olympus (2)	35.5		10	%		NR-5	100	%
Lloyds of London(3)	27.2		8	%		A	8	%
Michigan Catastrophic Claims Association	14.6		4	%		N/A(4)	—	%

(1)	A.M. Best ratings as detailed above are: “NR-5” (Not formally followed), “A++” (Superior, which is the highest of fifteen financial strength ratings), “A+” (Superior, which is the second highest of fifteen financial strength ratings), and “A” (Excellent, which is the third highest of fifteen financial strength ratings).
(2)	Non-U.S. insurance entities. Balances are fully collateralized through funds held, letters of credit or trust agreements.
(3)	Represents the total of reinsurance recoverables due to Sirius Group from all Lloyds Syndicates.
(4)	Michigan Catastrophic Claims Association (“MCCA”) is a non-profit unincorporated association of which every insurance company that sells automobile coverage in Michigan is required to be a member. A.M. Best does not rate MCCA. Sirius Group acquired its recoverable from MCCA as a result of its acquisition of Stockbridge Insurance Company.

Investment Securities (Tables)

12 Months Ended

Dec. 31, 2011

Investment Securities

Pre-tax net investment income

	Year Ended December 31,
Millions	2011			2010			2009
Investment income:
Fixed maturity investments	$	166.2		$	194.7		$	243.3
Short-term investments	4.5			3.0			5.5
Common equity securities	15.4			10.2			4.9
Convertible fixed maturity investments	5.5			5.6			8.0
Other long-term investments	4.2			6.0			4.2
Interest on funds held under reinsurance treaties	(.4		)	(1.7		)	(7.3		)
Total investment income	195.4			217.8			258.6
Third-party investment expenses	(10.9		)	(8.9		)	(8.5		)
Net investment income, pre-tax	$	184.5		$	208.9		$	250.1

Net Realized and Unrealized Investment Gains and Losses

	Year ended December 31,
Millions	2011			2010			2009
Net realized investment gains (losses), pre-tax	$	117.0		$	136.4		$	(69.9	)
Net unrealized investment gains (losses), pre-tax	5.8			(53.8		)	431.6
Net realized and unrealized investment gains (losses), pre-tax	122.8			82.6			361.7
Income taxes attributable to realized and unrealized investment gains (losses)	(30.9		)	(22.8		)	(124.4		)
Net realized and unrealized investment gains (losses), after-tax	$	91.9		$	59.8		$	237.3

Net realized investment gains (losses)

	Year Ended December 31,
Millions	2011			2010			2009
Fixed maturity investments	$	49.4		$	96.9		$	(7.4	)
Short-term investments	—			—			.2
Common equity securities	34.6			6.9			(46.4		)
Convertible fixed maturity investments	(2.2		)	16.7			15.6
Other long-term investments	35.2			15.9			(31.9		)
Net realized investment gains (losses), pre-tax	117.0			136.4			(69.9		)
Income taxes attributable to realized investment gains and (losses)	(37.0		)	(42.1		)	14.9
Net realized investment gains (losses), after-tax	$	80.0		$	94.3		$	(55.0	)

Net unrealized investment gains (losses)

The following table summarizes changes in the carrying value of investments measured at fair value:

	Year Ended December 31, 2011
Millions	Net unrealized gains (losses)			Net foreign currency gains (losses)			Total changes in fair value reflected in earnings
Fixed maturities	$	7.6		$	68.9		$	76.5
Short-term investments	—			(1.1		)	(1.1		)
Common equity securities	(40.6		)	(1.8		)	(42.4		)
Convertible fixed maturity investments	(11.5		)	—			(11.5		)
Other long-term investments	(19.1		)	3.4			(15.7		)
Net unrealized investment gains (losses), pre-tax	(63.6		)	69.4			5.8
Income taxes attributable to unrealized investment gains (losses)	24.0			(17.9		)	6.1
Net unrealized investment gains (losses), after-tax	$	(39.6	)	$	51.5		$	11.9

	Year Ended December 31, 2010
Millions	Net unrealized gains (losses)			Net foreign currency gains (losses)			Total changes in fair value reflected in earnings
Fixed maturities	$	(67.4	)	$	(53.8	)	$	(121.2	)
Short-term investments	—			.2			.2
Common equity securities	72.4			(9.6		)	62.8
Convertible fixed maturity investments	(5.4		)	—			(5.4		)
Other long-term investments	17.6			(7.8		)	9.8
Net unrealized investment gains (losses), pre-tax	17.2			(71.0		)	(53.8		)
Income taxes attributable to unrealized investment gains (losses)	.5			18.8			19.3
Net unrealized investment gains (losses), after-tax	$	17.7		$	(52.2	)	$	(34.5	)

	Year Ended December 31, 2009
Millions	Net unrealized gains (losses)			Net foreign currency gains (losses)			Total changes in fair value reflected in earnings
Fixed maturities	$	333.9		$	(53.6	)	$	280.3
Short-term investments	(.3		)	1.6			1.3
Common equity securities	57.9			(9.9		)	48.0
Convertible fixed maturity investments	39.8			—			39.8
Other long-term investments	67.2			(5.0		)	62.2
Net unrealized investment gains (losses), pre-tax	498.5			(66.9		)	431.6
Income taxes attributable to unrealized investment gains (losses)	(154.3		)	15.0			(139.3		)
Net unrealized investment gains (losses), after-tax	$	344.2		$	(51.9	)	$	292.3

Net unrealized investment gains (losses) for Level 3 investments

	Year Ended December 31,
Millions	2011			2010			2009
Fixed maturities	$	(12.2	)	$	10.2		$	47.3
Common equity securities	(16.6		)	(19.2		)	14.7
Convertible fixed maturities	—			—			.1
Other long-term investments	(16.8		)	39.0			65.0
Total unrealized investment gains (losses), pre-tax - Level 3 investments	$	(45.6	)	$	30.0		$	127.1

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

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

	Year Ended December 31,
Millions	2011			2010			2009
Net change in pre-tax unrealized gains (losses) on investments in unconsolidated affiliates	$	(63.6	)	$	72.7		$	192.7
Income taxes	5.1			.8			(.3		)
Net change in unrealized gains (losses) on investments in unconsolidated affiliates, after tax	(58.5		)	73.5			192.4
Net unrealized foreign currency gains (losses) on investments	(90.1		)	102.9			185.1
Total investments gains (losses) through accumulated other comprehensive income	(148.6		)	176.4			377.5
Change in net unrealized investment gains (losses), after-tax	11.9			(34.5		)	292.3
Net realized investment gains (losses), after-tax	80.0			94.3			(55.0		)
Total investment gains (losses) recorded during the period, after-tax	$	(56.7	)	$	236.2		$	614.8

Investment holdings, fixed maturity investments

	December 31, 2011
Millions	Cost or amortized cost		Gross unrealized gains		Gross unrealized losses			Net foreign currency gains(losses)			Carrying value
US Government and agency obligations	$	299.4	$	5.3	$	(.1	)	$	.4		$	305.0
Debt securities issued by industrial corporations	2,072.1		73.7		(7.8		)	(2.9		)	2,135.1
Municipal obligations	2.7		—		—			—			2.7
Mortgage-backed and asset-backed securities	3,190.5		25.9		(3.9		)	10.4			3,222.9
Foreign government, agency and provincial obligations	581.2		11.0		(.1		)	(2.9		)	589.2
Preferred stocks	82.3		3.2		(6.7		)	—			78.8
Total fixed maturity investments including assets held for sale	$	6,228.2	$	119.1	$	(18.6	)	$	5.0		$	6,333.7
Fixed maturity investments reclassified to assets held for sale related to AutoOne											(111.8		)
Total fixed maturity investments											$	6,221.9

	December 31, 2010
Millions	Cost or amortized cost		Gross unrealized gains		Gross unrealized losses			Net foreign currency gains (losses)			Carrying value
US Government and agency obligations	$	385.9	$	13.6	$	(.8	)	$	—		$	398.7
Debt securities issued by industrial corporations	2,149.2		87.9		(21.1		)	(37.9		)	2,178.1
Municipal obligations	3.3		.1		(.1		)	—			3.3
Mortgage-backed and asset-backed securities	2,082.0		18.2		(15.6		)	(12.9		)	2,071.7
Foreign government, agency and provincial obligations	1,053.6		7.7		(6.6		)	(8.3		)	1,046.4
Preferred stocks	81.9		6.1		—			(.1		)	87.9
Total fixed maturity investments	$	5,755.9	$	133.6	$	(44.2	)	$	(59.2	)	$	5,786.1

Schedule of contractual maturities of fixed maturities

	December 31, 2011
Millions	Cost or amortized cost		Carrying value
Due in one year or less	$	669.6	$	681.0
Due after one year through five years	1,809.1		1,857.5
Due after five years through ten years	563.1		582.8
Due after ten years	52.8		54.5
Mortgage-backed and asset-backed securities	3,190.5		3,222.9
Preferred stocks	82.3		78.8
Total	$	6,367.4	$	6,477.5

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

	December 31, 2011
Millions	Cost or amortized cost		Gross unrealized gains		Gross unrealized losses			Net foreign currency gains (losses)			Carrying value
Common equity securities	$	691.7	$	72.0	$	(8.7	)	$	—		$	755.0
Convertible fixed maturities	$	139.2	$	6.2	$	(1.6	)	$	—		$	143.8
Other long-term investments	$	274.4	$	55.5	$	(25.2	)	$	(3.4	)	$	301.3

	December 31, 2010
Millions	Cost or amortized cost		Gross unrealized gains		Gross unrealized losses			Net foreign currency gains (losses)			Carrying value
Common equity securities	$	561.2	$	105.5	$	(1.5	)	$	1.8		$	667.0
Convertible fixed maturities	$	126.9	$	16.2	$	(.1	)	$	—		$	143.0
Other long-term investments	$	329.5	$	62.4	$	(13.0	)	$	(6.8	)	$	372.1

Fair value measurements by level, investment securities

	December 31, 2011
Millions	Fair value		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs

Fixed maturities:
US Government and agency obligations	$	305.0	$	296.2	$	8.8	$	—

Debt securities issued by corporations:
Consumer	790.7		—		790.7		—
Industrial	359.4		—		359.4		—
Financials	239.6		3.8		235.8		—
Communications	225.8		—		225.8		—
Basic materials	195.7		—		195.7		—
Utilities	140.1		—		140.1		—
Energy	155.8		—		155.8		—
Technology	24.5		—		24.5		—
Diversified	3.5		—		3.5		—
Total debt securities issued by corporations:	2,135.1		3.8		2,131.3		—

Municipal obligations	2.7		—		2.7		—
Mortgage-backed and asset-backed securities	3,222.9		—		3,207.8		15.1
Foreign government, agency and provincial obligations	589.2		65.7		523.5		—
Preferred stocks	78.8		—		15.0		63.8
Total fixed maturities(1)	6,333.7		365.7		5,889.1		78.9

Short-term investments	846.0		846.0		—		—

Common equity securities:
Financials	219.2		185.8		1.5		31.9
Consumer	188.8		188.5		.3		—
Basic materials	121.0		119.9		1.1		—
Energy	72.6		72.6		—		—
Utilities	42.0		41.8		.2		—
Technology	25.8		25.8		—		—
Other	85.6		33.0		52.2		.4
Total common equity securities	755.0		667.4		55.3		32.3

Convertible fixed maturity investments	143.8		—		143.8		—
Other long-term investments(2)	268.3		—		—		268.3
Total investments	$	8,346.8	$	1,879.1	$	6,088.2	$	379.5

(1) Carrying value includes $111.8 that is classified as assets held for sale relating to AutoOne discontinued operations.

(2) Excludes carrying value of $33.0 associated with other long-term investments accounted for using the equity method.

	December 31, 2010
Millions	Fair value		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs

Fixed maturities:
US Government and agency obligations	$	398.7	$	388.9	$	9.8	$	—

Debt securities issued by corporations:
Consumer	769.0		—		769.0		—
Industrial	511.3		—		511.3		—
Financials	265.8		6.3		259.5		—
Communications	226.3		—		226.3		—
Basic materials	125.3		—		125.3		—
Utilities	106.7		—		106.7		—
Energy	151.5		—		151.5		—
Technology	22.1		—		22.1		—
Total debt securities issued by corporations:	2,178.0		6.3		2,171.7		—

Municipal obligations	3.3		—		3.3
Mortgage-backed and asset-backed securities	2,071.7		—		2,014.7		57.0
Foreign government, agency and provincial obligations	1,046.5		82.6		963.9		—
Preferred stocks	87.9		—		16.5		71.4
Total fixed maturities	5,786.1		477.8		5,179.9		128.4

Short-term investments	975.3		878.7		96.6		—

Common equity securities:
Financials	221.6		152.6		1.2		67.8
Consumer	123.3		122.5		.8		—
Basic materials	98.8		97.1		1.7		—
Energy	60.2		60.2		—		—
Utilities	47.6		44.6		—		3.0
Technology	31.8		30.4		1.4		—
Other	83.7		30.5		52.8		.4
Total common equity securities	667.0		537.9		57.9		71.2

Convertible fixed maturity investments	143.0		—		143.0		—
Other long-term investments(1)	330.2		—		—		330.2
Total investments	$	7,901.6	$	1,894.4	$	5,477.4	$	529.8

(1) Excludes carrying value of $41.9 associated with other long-term investments accounted for using the equity method.

Debt securities issued by corporations, credit ratings

The following table summarizes the ratings of the corporate debt securities held in White Mountains’ investment portfolio as of December 31, 2011 and 2010:

Millions	December 31, 2011		December 31, 2010
AAA	$	—	$	—
AA	206.8		210.0
A	802.8		833.7
BBB	1,110.8		1,109.1
BB	6.2		24.5
Other	8.5		.7
Debt securities issued by corporations	$	2,135.1	$	2,178.0

Mortgage-backed, asset-backed securities

	December 31, 2011						December 31, 2010
Millions	Fair Value		Level 2		Level 3		Fair Value		Level 2		Level 3
Mortgage-backed securities:
Agency:
GNMA	$	1,365.8	$	1,365.8	$	—	$	1,143.6	$	1,102.7	$	40.9
FNMA	712.6		712.6		—		234.9		234.9		—
FHLMC	35.9		35.9		—		39.1		39.1		—
Total Agency(1)	2,114.3		2,114.3		—		1,417.6		1,376.7		40.9
Non-agency:
Residential	83.1		68.0		15.1		90.6		74.5		16.1
Commercial	276.7		276.7		—		87.0		87.0		—
Total Non-agency	359.8		344.7		15.1		177.6		161.5		16.1

Total mortgage-backed securities	2,474.1		2,459.0		15.1		1,595.2		1,538.2		57.0
Other asset-backed securities:
Credit card receivables	380.6		380.6		—		248.3		248.3		—
Vehicle receivables	345.6		345.6		—		228.1		228.1		—
Other	22.6		22.6		—		.1		.1		—
Total other asset-backed securities	748.8		748.8		—		476.5		476.5		—
Total mortgage and asset-backed securities	$	3,222.9	$	3,207.8	$	15.1	$	2,071.7	$	2,014.7	$	57.0

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

The security issuance years of White Mountains’ investments in non-agency RMBS and non-agency CMBS securities as of December 31, 2011 are as follows:

			Security Issuance Year
Millions	Fair Value		2003		2006		2007		2009		2010		2011
Non-agency RMBS	$	83.1	$	3.3	$	23.0	$	26.4	$	—	$	10.5	$	19.9
Non-agency CMBS	276.7		—		—		17.4		11.2		2.3		245.8
Total	$	359.8	$	3.3	$	23.0	$	43.8	$	11.2	$	12.8	$	265.7

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

The classification of the underlying collateral quality and the tranche levels of White Mountains’ non-agency RMBS securities are as follows as of December 31, 2011:

Millions	Fair Value		Super Senior (1)		Senior (2)		Subordinate(3)
Prime	$	67.2	$	20.5	$	46.7	$	—
Non-prime	15.9		15.2		.7		—
Sub-prime	—		—		—		—
Total	$	83.1	$	35.7	$	47.4	$	—

(1) At issuance, Super Senior 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 were rated AAA by Standard & Poor’s or Aaa by Moody’s and were senior to non-AAA or non-Aaa bonds.

(3) At issuance, Subordinate were not rated AAA by Standard & Poor’s or Aaa by Moody’s 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’ non-agency CMBS securities are as follows as of December 31, 2011:

Millions	Fair Value		Super Senior (1)		Senior(2)		Subordinate(3)
Fixed rate CMBS	$	249.3	$	46.7	$	202.6	$	—
Floating rate CMBS	27.4		17.4		10.0		—
Total	$	276.7	$	64.1	$	212.6	$	—

(1) At issuance, Super Senior were rated AAA by Standard & Poor’s or Aaa by Moody’s and were senior to other AAA or Aaa bonds.

(2) At issuance, Senior were rated AAA by Standard & Poor’s or Aaa by Moody’s and were senior to non-AAA or non-Aaa bonds.

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

Other long-term investments

The following table summarizes investments in hedge funds and private equity interests by investment objective and sector at December 31, 2011 and December 31, 2010:

	December 31, 2011				December 31, 2010
Millions	Fair Value		Unfunded Commitments		Fair Value		Unfunded Commitments
Hedge funds
Long/short equity	$	48.8	$	—	$	50.4	$	—
Long/short credit & distressed	32.3		—		34.1		—
Long diversified strategies	16.9		—		25.2		—
Long/short equity REIT	14.5		—		24.0		—
Long/short equity activist	12.3		—		16.9		—
Long bank loan	.5		—		5.1		—
Total hedge funds	125.3		—		155.7		—

Private equity funds
Energy infrastructure & services	28.0		9.9		24.2		10.8
Distressed residential real estate	27.4		—		49.2		—
Multi-sector	26.9		8.2		26.0		10.6
Private equity secondaries	11.3		4.0		10.4		4.4
Real estate	9.5		3.3		9.1		4.6
International multi-sector, Europe	7.8		4.7		10.5		5.3
Manufacturing/Industrial	6.2		—		17.9		—
International multi-sector, Asia	3.6		2.6		4.9		2.7
Insurance	3.5		41.3		3.9		41.3
Venture capital	2.4		.5		2.2		1.0
Healthcare	2.3		7.0		1.5		8.0
Total private equity funds	128.9		81.5		159.8		88.7

Total hedge and private equity funds included in other long-term investments	$	254.2	$	81.5	$	315.5	$	88.7

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, 2011 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	$	—	$	—	$	—	$	6.5	$	6.5
Quarterly	27.5		27.0		20.1		—		74.6
Semi-annual	—		5.1		—		14.5		19.6
Annual	16.9		—		7.2		.5		24.6
Total	$	44.4	$	32.1	$	27.3	$	21.5	$	125.3

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

At December 31, 2011, 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		$	42.9		$	—		$	79.8		$	6.2		$	128.9

Rollforward of fair value investments by level

The following table summarizes the changes in White Mountains’ fair value measurements by level for the year ended December 31, 2011:

							Level 3 Investments
Millions	Level 1 Investments			Level 2 Investments			Fixed Maturities			Common equity securities			Convertible fixed maturities		Other long-term investments			Total
Balance at January 1, 2011	$	1,894.4		$	5,477.4		$	128.4		$	71.2		$	—	$	330.2	(1)	$	7,901.6	(1)
Total realized and unrealized gains (losses) (1) (2)	(1.4		)	113.2			(8.1		)	(4.7		)	—		19.5			118.5
Foreign currency gains (losses) through OCI and other revenue	4.6			(76.1		)	(4.4		)	1.6			—		(5.0		)	(79.3		)
Amortization/Accretion	2.3			(54.2		)	.3			—			—		—			(51.6		)
Purchases	10,653.6			8,905.6			213.7			19.7			—		58.4			19,851.0
Sales	(10,674.4		)	(8,528.7		)	—			(55.5		)	—		(134.8		)	(19,393.4		)
Transfers in	—			269.2			18.2			—			—		—			287.4
Transfers out	—			(18.2		)	(269.2		)	—			—		—			(287.4		)
Balance at December 31, 2011	$	1,879.1		$	6,088.2	(2)	$	78.9		$	32.3		$	—	$	268.3	(1)	$	8,346.8	(1)

(1) Excludes carrying value of $41.9 and $33.0 at January 1, 2011 and December 31, 2011 associated with other long-term investments accounted for using the equity method.

(2) Carrying value includes $111.8 that is classified as assets held for sale relating to AutoOne discontinued operations.

Debt (Tables)

12 Months Ended

Dec. 31, 2011

Debt

Schedule of debt outstanding

White Mountains’ debt outstanding as of December 31, 2011 and 2010 consisted of the following:

	December 31,
Millions	2011			2010
OBH Senior Notes, at face value	$	269.9		$	419.9
Unamortized original issue discount	(.1		)	(.3		)
OBH Senior Notes, carrying value	269.8			419.6

SIG Senior Notes, at face value	400.0			400.0
Unamortized original issue discount	(.7		)	(.8		)
SIG Senior Notes, carrying value	399.3			399.2
WTM Bank Facility	—			—
Old Lyme	2.1			—
Total debt	$	671.2		$	818.8

Schedule of contractual repayments of debt

A schedule of contractual repayments of White Mountains’ debt as of December 31, 2011 follows:

Millions	December 31, 2011
Due in one year or less	$	—
Due in two to three years	269.9
Due in four to five years	2.1
Due after five years	400.0
Total	$	672.0

- 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 SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 22
-Article 5

Reference 2: 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 3: 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 4: 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 5: 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 6: 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 7: 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 8: 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 9: 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 10: 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 11: 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=6881521&loc=d3e23780-122690

+ Details

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2011

Income Taxes

Schedule of total income tax benefit (expense)

The total income tax benefit (expense) for the years ended December 31, 2011, 2010 and 2009 consisted of the following:

	Year Ended December 31,
Millions	2011			2010			2009
Current tax benefit (expense):
U.S. federal	$	39.5		$	52.4		$	(40.0	)
State	(2.5		)	(2.2		)	(1.5		)
Non-U.S.	5.1			(9.1		)	(2.7		)
Total current tax benefit (expense)	42.1			41.1			(44.2		)
Deferred tax benefit (expense):
U.S. federal	(34.1		)	(61.6		)	(139.0		)
State	—			—			—
Non-U.S.	114.7			3.6			(31.0		)
Total deferred tax benefit (expense)	80.6			(58.0		)	(170.0		)
Total income tax benefit (expense)	$	122.7		$	(16.9	)	$	(214.2	)

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

	Year Ended December 31,
Millions	2011			2010			2009
Tax (expense) benefit at the U.S. statutory rate	$	(21.5	)	$	(53.6	)	$	(279.1	)
Differences in taxes resulting from:
Change in valuation allowance	128.2			2.6			53.7
Non-U.S. earnings, net of foreign taxes	6.2			22.8			(1.2		)
Tax reserve adjustments	4.3			(2.8		)	8.8
Tax exempt interest and dividends	2.9			2.3			1.7
Tax rate change enacted in Luxembourg	1.2			2.8			—
Withholding tax	.2			(.2		)	(.7		)
Purchase of subsidiaries	—			4.5			—
Sale of subsidiaries	—			4.3			—
Other, net	1.2			.4			2.6
Total income tax benefit (expense) on pre-tax income	$	122.7		$	(16.9	)	$	(214.2	)

Schedule of components of deferred income tax assets and liabilities

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

	December 31,
Millions	2011			2010
Deferred income tax assets related to:
Non-U.S. net operating loss carryforwards	$	504.0		$	545.4
Loss reserve discount	114.2			142.4
U.S. federal and state net operating loss carryforwards	102.7			103.6
Incentive compensation	43.4			36.9
Unearned premiums	41.2			37.3
U.S. tax credit carryforwards	13.5			12.0
Deferred compensation	11.4			13.1
Loss on sale of AutoOne	10.4			—
Pension and benefit accruals	8.0			4.3
Accrued interest	3.5			.5
Investment basis differences	1.6			7.3
Fixed assets	(.1		)	4.8
Other items	9.5			14.1
Total gross deferred income tax assets	863.3			921.7
Less: valuation allowances	(232.7		)	(385.8		)
Total net deferred income tax assets	630.6			535.9
Deferred income tax liabilities related to:
Safety reserve	369.6			378.5
Deferred acquisition costs	48.8			41.5
Net unrealized investment gains	34.8			55.8
Purchase accounting	.7			2.1
Intangible assets	(.1		)	.1
Other items	5.4			(.8		)
Total deferred income tax liabilities	459.2			477.2
Net deferred tax asset (liability)	$	171.4		$	58.7

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, 2011, the expiration dates and the deferred tax assets thereon are as follows:

	December 31, 2011
Millions	United States			Luxembourg			Sweden			Total
2012	$	—		$	—		$	—		$	—
2013-2017	2.4			—			—			2.4
2018-2022	18.7			—			—			18.7
2023-2032	305.7			—			—			305.7
No expiration date	—			1,740.3			10.7			1,751.0
Total	$	326.8		$	1,740.3		$	10.7		$	2,077.8

Gross deferred tax asset	$	102.7		$	501.2		$	2.8		$	606.7
Valuation allowance	(1.8		)	(225.5		)	(.3		)	(227.6		)
Net deferred tax asset	$	100.9		$	275.7		$	2.5		$	379.1

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, 2009	$	61.4		$	17.1		$	8.3		$	86.8
Changes in prior year tax positions	7.2			46.1			3.1			56.4
Tax positions taken during the current year	—			16.4			—			16.4
Lapse in statute of limitations	(1.0		)	—			(.2		)	(1.2		)
Settlements with tax authorities	(53.7		)	(.9		)	(6.9		)	(61.5		)
Balance at December 31, 2009	13.9			78.7			4.3			96.9
Changes in prior year tax positions	.5			(8.5		)	1.9			(6.1		)
Tax positions taken during the current year	.4			5.0			—			5.4
Lapse in statute of limitations	—			—			—			—
Settlements with tax authorities	(.3		)	(.1		)	—			(.4		)
Balance at December 31, 2010	14.5			75.1			6.2			95.8
Changes in prior year tax positions	(.9		)	.1			2.0			1.2
Tax positions taken during the current year	—			(20.4		)	—			(20.4		)
Lapse in statute of limitations	(3.4		)	(5.7		)	(1.4		)	(10.5		)
Settlements with tax authorities	(.6		)	—			—			(.6		)
Balance at December 31, 2011	$	9.6		$	49.1		$	6.8		$	65.5

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

(3) Net of tax benefit.

- Definition

Tabular disclosure of tax positions taken in the tax returns filed or to be filed for which it is more likely than not that the tax position will not be sustained upon examination by taxing authorities (i.e., uncertain tax positions) and other types of income tax contingencies, including: (1) the policy on classification of interest and penalties; (2) a tabular reconciliation of the total amounts of unrecognized tax benefits at the beginning and end of the period; the total amount(s) of: (3) unrecognized tax benefits that, if recognized, would affect the effective tax rate, and (4) interest and penalties recognized in each of the income statement and balance sheet; (5) for positions for which it is reasonably possible that the total amounts unrecognized will significantly change within 12 months of the reporting date the: (i) nature of the uncertainty, (ii) nature of the event that could occur that would cause the change, and (iii) an estimate of the range of the reasonably possible change or a statement that an estimate of the range cannot be made; and (6) a description of tax years that remain subject to examination by major tax jurisdictions.

+ References + Details

Variable Annuity Reinsurance and Weather Derivatives (Tables)

12 Months Ended

Dec. 31, 2011

Variable Annuity Reinsurance and Weather Derivatives

Pre-tax operating results of WM Life Re

The following table summarizes the pre-tax operating results of WM Life Re for the years ended December 31, 2011, 2010 and 2009:

	Year Ended December 31,
Millions	2011			2010			2009
Fees, included in other revenues	$	32.5		$	30.2		$	28.5
Change in fair value of variable annuity liability, included in other revenues	(156.5		)	(223.5		)	77.1
Change in fair value of derivatives, included in other revenues	92.9			127.0			(158.4		)
Foreign exchange, included in other revenues	15.1			21.4			(3.9		)
Other investment income and gains (losses)	(.9		)	(.9		)	(1.4		)
Total revenues	(16.9		)	(45.8		)	(58.1		)
Change in fair value of variable annuity death benefit liabilities, included in other expenses	(1.8		)	(6.0		)	9.3
Death benefit claims paid, included in other expenses	(3.8		)	(2.7		)	(2.2		)
General and administrative expenses	(4.7		)	(6.3		)	(5.6		)
Pre-tax loss	$	(27.2	)	$	(60.8	)	$	(56.6	)

Changes in White Mountains' variable annuity reinsurance liabilities and derivative instruments

The following table summarizes the changes in White Mountains’ variable annuity reinsurance liabilities and derivative instruments for the year ended December 31, 2011:

	Variable Annuity (Liabilities)			Derivative Instruments
Millions	Level 3			Level 3 (1)			Level 2 (1)(2)			Level 1 (3)			Total(4)
Balance at January 1, 2011	$	(610.2	)	$	275.3		$	72.2		$	—		$	347.5
Purchases	—			5.0			—			—			5.0
Realized and unrealized gains (losses)	(158.3		)	14.5			67.7			10.7			92.9
Transfers in (out)	—			—			—			—			—
Sales/settlements	—			(47.7		)	(100.7		)	(6.6		)	(155.0		)
Balance at December 31, 2011	$	(768.5	)	$	247.1		$	39.2		$	4.1		$	290.4

(1) Comprises over-the-counter instruments.

(3) Comprises 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 $485.3 at December 31, 2011 posted as collateral to its counterparties.

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	2011		2010			2009			2011		2010
Fixed income/interest rate	$	8.9	$	17.6		$	8.0		$	31.1	$	43.9
Foreign exchange	29.5		144.6			(69.5		)	161.3		225.3
Equity	54.5		(35.2		)	(96.9		)	98.0		78.3
Total	$	92.9	$	127.0		$	(158.4	)	$	290.4	$	347.5

Summary of collateral provided to WM Life Re from counterparties

The following summarizes collateral provided to WM Life Re from counterparties:

	Year Ended December 31,
Millions	2011		2010
Short term investments	$	73.2	$	52.4
Fixed maturity securities	—		48.6
Total	$	73.2	$	101.0

Summary of value, collateral provided (held) by WM Life Re and net exposure on OTC derivative instruments

The following summarizes the value of collateral provided (held) by WM Life Re and net exposure on OTC derivative instruments recorded within other assets:

Millions	December 31, 2011			December 31, 2010
OTC derivative instruments(1)	$	295.4		$	351.5
Collateral held	(73.2		)	(101.0		)
Collateral provided	83.0			25.3
Net exposure on fair value of OTC instruments	$	305.2		$	275.8

(1) Value of OTC derivative instruments as of December 31, 2011 and 2010 excludes adjustments for counterparty credit risk of $(9.1) and $(4.0) included in fair value under GAAP.

Summary of uncollateralized amounts due under WM Life Re's OTC derivative contracts

The following table summarizes uncollateralized amounts due under WM Life Re’s OTC derivative contracts as of December 31, 2011 by counterparty:

Millions	Uncollateralized balance as of December 31, 2011		Standard & Poor’s Rating(1)
Royal Bank of Scotland	$	82.5	A-
Citigroup (2)	67.7		A-
Bank of America	54.2		A-
JP Morgan Chase(2)	34.2		A
Nomura(2)	31.9		BBB+
Barclays	25.1		A
Goldman Sachs	9.6		A-
Total	$	305.2

(2) Collateral provided (held) calculated under master netting agreement.

Summary of additional collateral posted for variable reinsurance counterparties

The total collateral comprises the following:

	Year Ended December 31,
Millions	2011		2010
Cash	$	453.5	$	291.1
Short-term investments	.6		31.6
Fixed maturity investments	31.2		3.3
Total	$	485.3	$	326.0

Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2011

Earnings Per Share

Computation of earnings per share

The following table outlines the Company’s computation of earnings per share for the years ended December 31, 2011, 2010 and 2009:

	Year Ended December 31,
	2011			2010			2009
Basic and diluted earnings per share numerators (in millions):
Net income attributable to White Mountains’ common shareholders	$	122.6		$	93.1		$	497.8

Allocation of income for participating unvested restricted common shares	(1.1		)	(1.1		)	(4.8		)
Dividends paid on participating restricted common shares	(.1		)	(.1		)	(.6		)
Total allocation to restricted common shares	(1.2		)	(1.2		)	(5.4		)
Net income attributable to White Mountains’ common shareholders, net of restricted share amounts	$	121.4		$	91.9		$	492.4
Undistributed net earnings:
Net income attributable to White Mountains’ common shareholders, net of restricted common share amounts	$	121.4		$	91.9		$	492.4
Dividends paid net of restricted common share amounts	(7.9		)	(8.7		)	(8.3		)
Total undistributed net earnings, net of restricted common share amounts	$	113.5		$	83.2		$	484.1
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period	7,881.0			8,548.4			8,849.4
Average unvested restricted common shares (1)	(69.4		)	(97.3		)	(85.3		)
Basic earnings per share denominator	7,811.6			8,451.1			8,764.1
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period	7,881.0			8,548.4			8,849.4
Average unvested restricted common shares (1)	(69.4		)	(97.3		)	(85.3		)
Average outstanding dilutive options to acquire common shares (2)	—			.5			1.5
Diluted earnings per share denominator	7,811.6			8,451.6			8,765.6
Basic earnings per share (in dollars):
Net income attributable to White Mountains’ common shareholders	$	15.56		$	10.89		$	56.25
Dividends declared and paid	(1.00		)	(1.00		)	(1.00		)
Undistributed earnings	$	14.56		$	9.89		$	55.25
Diluted earnings per share (in dollars)
Net income attributable to White Mountains’ common shareholders	$	15.56		$	10.89		$	56.24
Dividends declared and paid	(1.00		)	(1.00		)	(1.00		)
Undistributed earnings	$	14.56		$	9.89		$	55.24

(1) Restricted common shares outstanding vest either in equal annual installments or upon a stated date (see Note 11).

Retirement and Postretirement Plans (Tables)

12 Months Ended

Dec. 31, 2011

Retirement and Postretirement Plans

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 various pension plans at December 31, 2011 and 2010:

	Pension Benefits
Millions	2011			2010
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$	110.2		$	117.1
Service cost	.8			.8
Interest cost	5.2			6.0
Settlement gain	(.6		)	(2.2		)
Special termination benefit cost	.8			1.9
Assumption changes	7.7			6.6
Actuarial (gain) loss	(.3		)	(1.5		)
Benefits and expenses paid with plan assets, net of participant contributions	(8.4		)	(15.9		)
Benefits paid directly by OneBeacon	(2.4		)	(2.6		)
Projected benefit obligation at end of year	$	113.0		$	110.2
Change in plan assets:
Fair value of plan assets at beginning of year	$	133.0		$	130.2
Actual return on plan assets	(3.8		)	18.7
Benefits and expenses paid, net of participant contributions	(8.4		)	(15.9		)
Fair value of plan assets at end of year	$	120.8		$	133.0
Funded status at end of year	$	7.8		$	22.8

Schedule of amounts recorded in the financial statements

Amounts recognized in the financial statements as of December 31, 2011 and 2010 consist of:

	Pension Benefits
Millions	2011			2010
Net balance recorded in other assets	$	34.3		$	50.3
Net balance recorded in other liabilities	(26.5		)	(27.5		)
Net amount accrued in the financial statements	$	7.8		$	22.8

Information for the Non-qualified Plan, which had 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	2011		2010
Projected benefit obligation	$	26.5	$	27.5
Accumulated benefit obligation	$	26.5	$	27.5
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	2011		2010
Projected benefit obligation	$	86.5	$	82.7
Accumulated benefit obligation	$	86.5	$	82.7
Fair value of plan net assets (1)	$	120.8	$	133.0

(1) Includes receivables related to securities sold, interest and dividends as well as payables related to securities purchased.

Schedule of amount 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 noncontrolling interest for the years ended December 31, 2011 and 2010 were as follows:

	December 31,
Millions	2011			2010
Accumulated other comprehensive income (loss) beginning balance	$	.5		$	(8.5	)
Increase (decrease) in accumulated other comprehensive income (loss):
Amortization of net actuarial losses recognized during the year	.5			.6
Net actuarial (losses) gains occurring during the year(1)	(18.2		)	8.4
Other adjustments	.5			—
Accumulated other comprehensive (loss) income ending balance	$	(16.7	)	$	.5

(1) Primarily relates to investment results relating to the overfunded status of the Plans.

Schedule of components of net periodic benefit cost (income)

The components of net periodic benefit cost (income) for the years ended December 31, 2011, 2010 and 2009 were as follows:

	Year Ended December 31,
Millions	2011			2010			2009
Service cost	$	.8		$	.8		$	.5
Interest cost	5.2			6.0			6.5
Expected return on plan assets	(7.6		)	(7.3		)	(6.3		)
Amortization of unrecognized loss	.5			.6			1.6
Net periodic pension cost (income) before settlements, curtailments and special termination benefits	(1.1		)	.1			2.3
Settlement gain	.5			(.1		)	—
Special termination benefits expense(1)	.8			1.9			1.2
Total net periodic benefit cost	$	.2		$	1.9		$	3.5

(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 at December 31, 2011 by asset category were as follows:

	December 31, 2011								December 31, 2010
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	$	2.4	$	—	$	2.4	$	—	$	.5	$	—	$	.5	$	—
Common equity securities	72.2		72.2		—		—		74.5		74.5		—		—
Convertible fixed maturities	42.8		—		42.8		—		55.7		—		55.7		—
Cash and short-term investments	3.1		3.1		—		—		2.0		2.0		—		—
Total	$	120.5	$	75.3	$	45.2	$	—	$	132.7	$	76.5	$	56.2	$	—

There were no transfers between Levels 1, 2 or 3 during the years ended December 31, 2011 or 2010.

The Qualified Plan’s asset allocations at December 31, 2011 and 2010, by asset category were as follows:

	Plan Assets at December 31,
Asset Category	2011		2010
Fixed maturity investments	2.0	%	.4	%
Common equity securities	59.9		56.1
Convertible fixed maturities	35.5		42.0
Cash and short-term investments	2.6		1.5
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
2012	$	4.6
2013	5.0
2014	5.3
2015	5.7
2016	6.0
2017—2021	34.0

Employee Share-Based Incentive Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2011

Employee Share-Based Incentive Compensation Plans

Summary of performance share activity

The following summarizes performance share activity for the years ended December 31, 2011, 2010 and 2009 for performance shares granted under the WTM Incentive Plan and the WTM Phantom Share Plan:

	Year Ended December 31,
	2011					2010					2009
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	163,184		$	29.4		172,454		$	12.2		156,373		$	4.2
Shares expired (1)	(51,131	)	—			(49,127	)	—			(48,573	)	—
New grants	37,675		—			47,880		—			69,092		—
Assumed forfeitures and cancellations (2)	336		(.9		)	(8,023	)	(.7		)	(4,438	)	(.3		)
Expense recognized	—		37.6			—		17.9			—		8.3
Ending December 31,	150,064		$	66.1		163,184		$	29.4		172,454		$	12.2

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

Summary of performance shares outstanding and accrued expense for performance shares awarded under the WTM Incentive Plan

The following table summarizes performance shares outstanding and accrued expense for performance shares awarded under the WTM Incentive Plan at December 31, 2011 for each performance cycle:

Millions, except share amounts	Target WTM Performance Shares Outstanding		Accrued Expense
Performance cycle:
2009-2011	60,410		$	42.6
2010-2012	42,890		10.9
2011-2013	37,675		6.8
Sub-total	140,975		60.3
Assumed forfeitures	(3,524	)	(1.6		)
Total at December 31, 2011	137,451		$	58.7

Summary of performance shares outstanding and accrued expense for performance shares awarded under the Phantom Plan

The following summarizes phantom performance shares outstanding and accrued expense for awards made under the WTM Phantom Share Plan at December 31, 2011 for each performance cycle:

Millions, except share amounts	Target WTM Phantom Performance Shares Outstanding		Accrued Expense
Performance cycle:
2009-2011	7,947		$	6.0
2010-2012	4,990		1.5
2011-2013(1)	—		—
Sub-total	12,937		7.5
Assumed forfeitures	(324	)	(.1		)
Total at December 31, 2011	12,613		$	7.4

(1) All performance shares for the 2011-2013 performance cycle were granted from the WTM Incentive Plan.

Summary of restricted share activity

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, 2011, 2010 and 2009:

	Year Ended December 31,
	2011					2010					2009
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 at beginning of year	46,250		$	14.1		91,900		$	23.7		53,200		$	24.2
Issued	27,250		9.9			19,750		6.7			47,100		9.6
Vested	(1,500	)	—			(65,150	)	—			(8,400	)	—
Forfeited	—		—			(250	)	(.1		)	—		—
Modified(1)	—		—			—		(3.3		)	—		—
Expense recognized	—		(10.7		)	—		(12.9		)	—		(10.1		)
Non-vested at end of year	72,000		$	13.3		46,250		$	14.1		91,900		$	23.7

Summary of performance share activity for OneBeacon performance shares granted under OneBeacon Incentive Plan

The following table summarizes the Company’s Incentive Options activity for the years ended December 31, 2010 and 2009. There were no Incentive Options issued and outstanding in 2011.

	Year ended December 31,
Millions, except share and per share amounts	2010			2009
Opening balance—outstanding Incentive Options	2,400			6,000
Forfeited	—			—
Exercised	(2,400		)	(3,600		)
Ending balance—outstanding Incentive Options	—			2,400
Opening balance—exercisable Incentive Options	2,400			3,000
Vested	—			3,000
Exercised	(2,400		)	(3,600		)
Ending balance—exercisable Incentive Options	—			2,400
Intrinsic value of Incentive Options exercised (1)	$	.3		$	.5
Exercise price—beginning of year	$	188.43		$	177.76
Exercise price—end of year	$	—		$	188.43
Compensation expense (income)	$	—		$	—

(1) Amount is equal to the number of options exercised multiplied by amount the ending market value exceeds the strike price on the date of exercise.

Summary of OneBeacon performance shares outstanding and accrued expense for OneBeacon performance shares awarded under the OneBeacon Incentive Plan

The following summarizes activity for the years ended December 31, 2011, 2010, and 2009 for OneBeacon performance shares granted under the OneBeacon Incentive Plan:

	Year Ended December 31,
	2011					2010					2009
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	1,464,295		$	18.5		2,224,215		$	15.1		2,212,313		$	4.6
Payments and deferrals (1)(2)	(936,150	)	(10.5		)	(889,594	)	(4.6		)	(137,400	)	—
New awards	194,900		—			270,691		—			379,085		—
Forfeitures and cancellations	(80,378	)	(.5		)	(141,017	)	(2.2		)	(229,783	)	(.5		)
Expense recognized	—		2.2			—		10.2			—		11.0
End of period	642,667		$	9.7		1,464,295		$	18.5		2,224,215		$	15.1

Summary of OneBeacon option activity

The following summarizes OneBeacon performance shares outstanding awarded under the OneBeacon Incentive Plan at December 31, 2011 for each performance cycle:

Millions, except share amounts	Target OneBeacon Performance Shares Outstanding		Accrued Expense
Performance cycle:
2009-2011	256,751		$	7.7
2010-2012	244,248		1.2
2011-2013	151,563		.9
Sub-total	652,562		9.8
Assumed forfeitures	(9,895	)	(.1		)
Total at December 31, 2011	642,667		$	9.7

Summary of Incentive Option activity

The following table summarizes option activity for the years ended December 31, 2011, 2010 and 2009:

	Year ended December 31,
	2011				2010				2009
Millions	Target Outstanding Options		Expense Amortized		Target Outstanding Options		Expense Amortized		Target Outstanding Options		Expense Amortized
Beginning of period	768,652		$	4.5	1,015,610		$	3.6	1,237,872		$	2.5
New awards	—		—		—		—		—		—
Forfeitures	(27,782	)	—		(37,044	)	—		(222,262	)	—
Vested and expired(1)	—		—		(209,914	)	—		—		—
Exercised	—		—		—		—		—		—
Expense recognized	—		.5		—		.9		—		1.1
End of period	740,870		$	5.0	768,652		$	4.5	1,015,610		$	3.6

(1) During the year ended December 31, 2010, as a result of the Commercial Lines Transaction and Personal Lines Transaction, 209,914 options vested that were unexercised and expired.

Segment Information (Tables)

12 Months Ended

Dec. 31, 2011

Segment Information

Financial information for White Mountains' segments

Financial information for White Mountains’ segments follows:

Millions	OneBeacon			Sirius Group			Other Operations			Total
Year ended December 31, 2011:
Earned insurance and reinsurance premiums	$	1,015.5		$	912.3		$	—		$	1,927.8
Net investment income	71.4			89.9			23.2			184.5
Net realized and unrealized investment gains (losses)	10.6			101.9			10.3			122.8
Other revenue	(10.7		)	(44.6		)	(1.7		)	(57.0		)
Total revenues	1,086.8			1,059.5			31.8			2,178.1
Losses and LAE	580.9			626.0			—			1,206.9
Insurance and reinsurance acquisition expenses	219.0			181.0			—			400.0
Other underwriting expenses	173.3			105.8			—			279.1
General and administrative expenses	9.8			34.1			131.4			175.3
Interest expense on debt	20.5			31.6			3.1			55.2
Total expenses	1,003.5			978.5			134.5			2,116.5
Pre-tax income (loss)	$	83.3		$	81.0		$	(102.7	)	$	61.6

Millions	OneBeacon		Sirius Group			Other Operations			Total
Year ended December 31, 2010:
Earned insurance and reinsurance premiums	$	1,403.9	$	847.9		$	—		$	2,251.8
Net investment income	96.6		96.5			15.8			208.9
Net realized and unrealized investment gains (losses)	74.6		(9.8		)	17.8			82.6
Other revenue	9.6		35.9			(22.1		)	23.4
Total revenues	1,584.7		970.5			11.5			2,566.7
Losses and LAE	858.2		531.0			—			1,389.2
Insurance and reinsurance acquisition expenses	311.6		167.5			—			479.1
Other underwriting expenses	233.1		99.8			—			332.9
General and administrative expenses	13.0		31.6			110.5			155.1
Interest expense on debt	29.6		26.6			1.1			57.3
Total expenses	1,445.5		856.5			111.6			2,413.6
Pre-tax income (loss)	$	139.2	$	114.0		$	(100.1	)	$	153.1

Millions	OneBeacon		Sirius Group		Other Operations			Total
Year ended December 31, 2009:
Earned insurance and reinsurance premiums	$	1,858.8	$	858.8	$	—		$	2,717.6
Net investment income	125.5		110.3		14.3			250.1
Net realized and unrealized investment gains	248.6		112.6		.5			361.7
Other revenue	23.1		106.5		(15.7		)	113.9
Total revenues	2,256.0		1,188.2		(.9		)	3,443.3
Losses and LAE	1,005.3		418.8		—			1,424.1
Insurance and reinsurance acquisition expenses	376.3		170.9		—			547.2
Other underwriting expenses	308.5		98.1		—			406.6
General and administrative expenses	18.5		74.4		104.5			197.4
Interest expense on debt	39.7		26.3		4.8			70.8
Total expenses	1,748.3		788.5		109.3			2,646.1
Pre-tax income (loss)	$	507.7	$	399.7	$	(110.2	)	$	797.2

Schedule of selected balance sheet data of the segments

Selected Balance Sheet Data Millions	OneBeacon		Sirius Group		Other Operations		Discontinued Operations		Total
December 31, 2011:
Total investments	$	2,707.6	$	3,640.5	$	1,919.9	$	—	$	8,268.0
Reinsurance recoverable on paid and unpaid losses	2,184.1		353.7		—		—		2,537.8
Assets held for sale	132.6		—		—		—		132.6
Total assets	5,792.4		5,337.9		2,933.7		—		14,064.0
Loss and LAE reserves	3,358.6		2,343.7		—		—		5,702.3
Liabilities held for sale	107.6		—		—		—		107.6
Total liabilities	4,678.5		3,784.1		933.5		—		9,396.1
Noncontrolling interest	287.2		289.5		3.5		—		580.2
Total White Mountains’ common shareholders’ equity	826.7		1,264.3		1,996.7		—		4,087.7
December 31, 2010:
Total investments	$	3,266.0	$	4,116.2	$	561.3	$	—	$	7,943.5
Reinsurance recoverable on paid and unpaid losses	1,937.7		469.4		—		—		2,407.1
Assets held for sale	—		—		—		1,122.8		1,122.8
Total assets	6,138.3		5,618.7		1,654.3		1,122.8		14,534.1
Loss and LAE reserves	3,295.5		2,441.3		—		—		5,736.8
Liabilities held for sale	—		—		—		751.5		751.5
Total liabilities	4,889.4		3,863.0		769.4		751.5		10,273.3
Noncontrolling interest	314.9		290.6		2.3		—		607.8
Total White Mountains’ common shareholders’ equity	934.0		1,465.1		882.6		371.3		3,653.0

- Definition

Tabular disclosure of the profit or loss and total assets for each reportable segment. An entity discloses certain information on each reportable segment if the amounts (a) are included in the measure of segment profit or loss reviewed by the chief operating decision maker or (b) are otherwise regularly provided to the chief operating decision maker, even if not included in that measure of segment profit or loss.

+ References + Details

Investments in Unconsolidated Affiliates (Tables)

12 Months Ended

Dec. 31, 2011

Investments in Unconsolidated Affiliates

Schedule of investments in unconsolidated affiliates

Millions	December 31, 2011		December 31, 2010
Symetra common shares	$	261.0	$	350.4
Symetra warrants	12.6		37.1
Total investment in Symetra	273.6		387.5

Pentelia Capital Management	1.7		2.2
Total investments in unconsolidated affiliates	$	275.3	$	389.7

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 January 1, 2009	$	54.0		$	27.3		$	81.3
Equity in earnings of Symetra(1)(8)	23.9			—			23.9
Net unrealized losses from Symetra’s fixed maturity portfolio(5)	191.3			—			191.3
Increase in value of warrants	—			11.2			11.2
Carrying value of investment in Symetra as of December 31, 2009(2)	269.2			38.5			307.7
Equity in earnings of Symetra(1)(3)(8)	11.1			—			11.1
Net unrealized gains from Symetra’s fixed maturity portfolio(6)(7)	72.7			—			72.7
Dividends received	(2.6		)	—			(2.6		)
Decrease in value of warrants	—			(1.4		)	(1.4		)
Carrying value of investment in Symetra as of December 31, 2010(2)	350.4			37.1			387.5
Equity in earnings of Symetra(1)(8)	28.2			—			28.2
Impairment of equity in earnings of Symetra(4)	(50.0		)	—			(50.0		)
Net unrealized gains from Symetra’s fixed maturity portfolio(7)	85.0			—			85.0
Impairment of net unrealized gains from Symetra’s fixed maturity portfolio (5)	(148.6		)	—			(148.6		)
Dividends received	(4.0		)	—			(4.0		)
Decrease in value of warrants	—			(24.5		)	(24.5		)
Carrying value of investment in Symetra as of December 31, 2011(2)	$	261.0		$	12.6		$	273.6

(1) Equity in earnings for the years end December 31, 2011, 2010, and 2009 excludes tax expense of $2.3, $1.4, and $0.

(3) Includes a $17.9 loss from the dilutive effect of Symetra’s public offering

(4) Impairment of equity in earnings of Symetra excludes tax benefit of $4.1

(5) Impairment of net unrealized gains from Symetra’s fixed maturity portfolio excludes tax benefit of $12.0

(6) Includes a $1.9 gain from the dilutive effect of Symetra’s public offering.

(7) Net unrealized gains (losses) from Symetra’s fixed maturity portfolio excludes tax (expense) benefit of $(6.9), $0.8, and $0 for the years ended December 31, 2011, 2010, and 2009.

Summarized statement of financial position of Symetra

The following table summarizes financial information for Symetra as of December 31, 2011 and 2010:

	December 31,
Millions	2011		2010
Symetra balance sheet data:
Total investments	$	26,171.7	$	23,500.2
Separate account assets	795.8		881.7
Total assets	28,212.7		25,636.9
Policyholder liabilities	23,140.6		21,591.5
Long-term debt	449.2		449.0
Separate account liabilities	795.8		881.7
Total liabilities	25,078.7		23,256.3
Common shareholders’ equity	3,134.0		2,380.6

Summarized statement of operations of Symetra

The following table summarizes financial information for Symetra for the years ended December 31, 2011, 2010 and 2009:

	Year Ended December 31,
Millions	2011		2010		2009
Symetra income statement data:
Net premiums earned	$	540.5	$	473.0	$	470.1
Net investment income	1,270.9		1,199.4		1,113.6
Total revenues	1,999.0		1,878.5		1,714.3
Policy benefits	1,307.3		1,234.6		1,197.3
Total expenses	1,720.0		1,589.4		1,533.2
Net income	199.6		200.9		128.3
Comprehensive net income	780.6		683.1		1,018.6

Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2011

Fair Value of Financial Instruments

Summary of the fair value and carrying value of financial instruments

The following summarizes the carrying value and fair value of financial instruments that are not accounted for at fair value.

	December 31, 2011				December 31, 2010
Millions	Fair Value		Carrying Value		Fair Value		Carrying Value
OBH Senior Notes	$	277.4	$	269.8	$	435.1	$	419.6
SIG Senior Notes	418.6		399.3		390.9		399.2
SIG Preference Shares	217.5		250.0		212.5		250.0

- Definition

Tabular disclosure of the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments, assets, and liabilities. Such certain disclosures about the financial instruments, assets, and liabilities include: (1) the fair value of the required items together with their carrying amounts (as appropriate) and (2) the methodology and assumptions used in developing such estimates of fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 10
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 14
-Subparagraph a
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 15
-Subparagraph b-d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 157
-Paragraph 32
-Subparagraph a, c(1), c(2), c(3), d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 159
-Paragraph 18
-Subparagraph c(2), d, e, f
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 159
-Paragraph 19
-Subparagraph a, b, c(1), d(1)
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13433-108611

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13467-108611

Reference 9: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13476-108611

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-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14172-108612

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6925170&loc=d3e19207-110258

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6447952&loc=d3e13220-108610

+ Details

Discontinued Operations (Tables)

12 Months Ended

Dec. 31, 2011

Discontinued Operations

Schedule of discontinued operations balance sheet

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

Millions	December 31, 2011		December 31, 2010
Assets held for sale
Fixed maturity investments, at fair value	$	111.8	$	593.8
Short-term investments, at amortized cost (which approximates fair value)	—		131.0
Common equity securities, at fair value	—		43.0
Convertible fixed maturity investments, at fair value	—		17.2
Other long-term investments	—		4.0
Total investments	111.8		789.0
Cash	5.5		39.8
Reinsurance recoverable on paid and unpaid losses	—		34.4
Insurance premiums receivable	8.8		102.9
Deferred acquisition costs	2.2		34.7
Deferred tax asset	1.9		67.8
Other assets	2.4		54.2
Total assets held for sale	$	132.6	$	1,122.8
Liabilities held for sale
Loss and loss adjustment expense reserves	$	64.7	$	450.4
Unearned insurance premiums	34.1		201.6
Accrued incentive compensation	—		19.1
Other liabilities	8.8		80.4
Total liabilities held for sale	107.6		751.5
Net assets held for sale	$	25.0	$	371.3

Schedule of discontinued operations income statement

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

	Year Ended December 31,
Millions, except per share amounts	2011			2010			2009
Revenues
Earned insurance premiums	$	727.9		$	910.6		$	882.8
Net investment income	12.0			19.6			22.3
Net realized and unrealized investment gains	.7			13.3			22.9
Other revenue	53.5			60.9			55.2
Total revenues	794.1			1,004.4			983.2
Expenses
Loss and loss adjustment expenses	542.3			678.8			695.0
Insurance and reinsurance acquisition expenses	159.2			191.7			170.1
Other underwriting expenses	80.4			87.9			98.7
General and administrative expenses	38.3			48.6			52.6
Total expenses	820.2			1,007.0			1,016.4
Pre-tax loss	(26.1		)	(2.6		)	(33.2		)
Income tax benefit (expense)	13.1			(4.0		)	5.4
Loss from discontinued operations	(13.0		)	(6.6		)	(27.8		)
Gain on sale of Esurance and AFI, net of tax	677.5			—			—
Loss on sale of AutoOne, net of tax	(19.2		)	—			—
Net income (loss) from discontinued operations	$	645.3		$	(6.6	)	$	(27.8	)

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, 2011, 2010 and 2009:

	Year Ended December 31,
	2011			2010			2009
Basic and diluted earnings (loss) per share numerators (in millions):
Net income (loss) attributable to White Mountains’ common shareholders	$	645.3		$	(6.6	)	$	(27.8	)
Allocation of income for participating unvested restricted common shares	(5.7		)	.1			.3
Net income (loss) attributable to White Mountains’ common shareholders, net of restricted common share amounts(3)	$	639.6		$	(6.5	)	$	(27.5	)
Basic earnings (loss) per share denominators (in thousands):
Total average common shares outstanding during the period	7,881.0			8,548.4			8,849.4
Average unvested restricted common shares (1)	(69.4		)	(97.3		)	(85.3		)
Basic earnings (loss) per share denominator	7,811.6			8,451.1			8,764.1
Diluted earnings (loss) per share denominator (in thousands):
Total average common shares outstanding during the period	7,881.0			8,548.4			8,849.4
Average unvested restricted common shares (1)	(69.4		)	(97.3		)	(85.3		)
Average outstanding dilutive options to acquire common shares (2)	—			.5			1.5
Diluted earnings (loss) per share denominator	7,811.6			8,451.6			8,765.6
Basic and diluted earnings (loss) per share (in dollars):	$	81.88		$	(.77	)	$	(3.14	)

(1) Restricted common shares outstanding vest either in equal annual installments or upon a stated date (see Note 11).

Summary of Significant Accounting Policies (Details) - OneBeacon Ltd. - shares shares in Millions	12 Months Ended
	Dec. 31, 2006	Dec. 31, 2011	Dec. 31, 2010
Basis of Presentation
Ownership percentage in outstanding common shares		75.50%	76.00%
Number of common shares sold in an initial public offerings	27.6
Percentage of common shares sold in an initial public offerings	27.60%

Summary of Significant Accounting Policies (Details 2) $ in Millions	12 Months Ended
	Dec. 31, 2011 USD ($) Y security	Dec. 31, 2010
Significant Accounting Policies
Percentage of the investment portfolio recorded at fair value based upon quoted market prices or other observable inputs	95.00%	93.00%
Maturity period to classify an investment as short-term (in years) \| Y	1
Minimum percentage of variation from the expected price required to consider prices provided by the pricing services as outliers	5.00%
Minimum amount of variation from expected prices required to consider prices provided by the pricing services as outliers \| $	$ 1
Number of securities that fell outside White Mountains' variance threshold \| security	4

Summary of Significant Accounting Policies (Details 3) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jun. 30, 2001	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2004	Jun. 02, 2001
Insurance and reinsurance operations
Average discount rate used to discount long-term workers compensation loss and LAE reserves (as a percent)		4.50%	5.00%
Amount of discount on workers compensation loss and LAE reserves		$ 108.3	$ 119.4
OneBeacon Ltd. \| Purchase price adjustments
Purchase accounting adjustments
Adjustment to fair value loss and LAE reserves					$ 646.9
Adjustment to fair value of reinsurance recoverables related to loss and LAE reserves					$ 346.9
Net purchase accounting adjustment to net loss reserves	$ 300.0
Sirius International \| Purchase price adjustments
Purchase accounting adjustments
Adjustment to fair value loss and LAE reserves				$ 58.1

Summary of Significant Accounting Policies (Details 4) - Deferred Software Costs $ in Millions	12 Months Ended
	Dec. 31, 2011 USD ($) Y	Dec. 31, 2010 USD ($)
Information related to deferred software costs
Estimated useful life over which cost will be amortized, minimum (in years)	3
Estimated useful life over which cost will be amortized, maximum (in years)	5
Unamortized deferred software costs \| $	$ 22.8	$ 18.1

Summary of Significant Accounting Policies (Details 5) $ in Millions	Dec. 31, 2011 USD ($) SEK (kr) GBP (£) CAD ($)	Dec. 31, 2010 USD ($) SEK (kr) GBP (£) CAD ($)
Summary of Significant Accounting Policies
Unrealized foreign currency translation gains \| $	$ 46.1	$ 61.4
Swedish kronor
Rates of exchange for the U.S. dollar
Exchange rate \| kr	6.86
Swedish kronor \| Beginning of period
Rates of exchange for the U.S. dollar
Exchange rate \| kr	6.7030	7.1280
Swedish kronor \| End of period
Rates of exchange for the U.S. dollar
Exchange rate \| kr	6.8645	6.7030
British pound \| Beginning of period
Rates of exchange for the U.S. dollar
Exchange rate \| £	.6420	.6191
British pound \| End of period
Rates of exchange for the U.S. dollar
Exchange rate \| £	.6434	.6420
Canadian dollar \| Beginning of period
Rates of exchange for the U.S. dollar
Exchange rate \| $	.9981	1.0485
Canadian dollar \| End of period
Rates of exchange for the U.S. dollar
Exchange rate \| $	1.0193	.9981

- Definition

Accumulated adjustment, net of tax, that results from the process of translating subsidiary financial statements and foreign equity investments into the reporting currency from the functional currency of the reporting entity, net of reclassification of realized foreign currency translation gains or losses.

+ References

+ Details

Summary of Significant Accounting Policies (Details 6) $ / shares in Units, $ in Millions	1 Months Ended
	May 31, 2007 USD ($) quarter director shares	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	May 24, 2007 USD ($) $ / shares
Noncontrolling Interest
Noncontrolling equity interest		$ 57.1	$ 62.8
OneBeacon Ltd.
Noncontrolling Interest
Noncontrolling ownership percentage in OneBeacon Ltd.		24.50%	24.00%
Sirius Group \| Non-cumulative perpetual preference shares
Noncontrolling Interest
Non-cumulative perpetual preference shares issued (in shares) \| shares	250,000,000
Non-cumulative perpetual preference shares per share liquidation preference (in dollars per share) \| $ / shares				$ 1,000
Proceeds from non-cumulative perpetual preference shares	$ 245.7
Non-cumulative perpetual preference shares issuance cost and commission				$ 4.3
Number of directors that can be elected to Sirius board \| director	2
Period for non-payment of dividend which give right to shareholders to elect directors on board (in quarters) \| quarter	6
Number of quarterly dividend payments which results in cessation of the right to elect directors \| quarter	4
Basis points on comparable treasury issue rate (as a percent)	0.45%
Sirius Group \| Non-cumulative perpetual preference shares \| Until June 30, 2017
Noncontrolling Interest
Annual rate of dividend on preferred stock (as a percent)	7.506%
Sirius Group \| Non-cumulative perpetual preference shares \| After June 30,2017
Noncontrolling Interest
Reference rate (LIBOR) used to determine floating annual rate of the dividend on the Sirius Group preference shares	3 month LIBOR
Amount in excess of LIBOR reference rate used to determine floating dividend rate	3.20%
Floating annual dividend rate (if in excess of LIBOR plus 3.20%)	7.506%
White Mountains consolidated limited partnerships
Noncontrolling Interest
Noncontrolling equity interest		$ 54.8	$ 59.7
A.W.G. Dewar Inc
Noncontrolling Interest
Noncontrolling equity interest		$ 2.3	$ 3.1

Summary of Significant Accounting Policies (Details 7) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2010	Dec. 31, 2009
Cumulative-Effect Adjustment, Deconsolidation of Variable Interest Entity \| Tuckerman Fund II
New Accounting Pronouncements or Change in Accounting Principle
Increase (decrease) in retained earnings	$ (0.4)
Symetra FAS115-2 \| Symetra
New Accounting Pronouncements or Change in Accounting Principle
Increase (decrease) in retained earnings		$ 2.9

- Definition

Amount of the cumulative effect of the change in accounting principle or new accounting pronouncement on retained earnings or other components of equity or net assets in the statement of financial position as of the beginning of the earliest period presented.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 154
-Paragraph 2, 17, 18
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=6801783&loc=d3e22499-107794

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6801783&loc=d3e22580-107794

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Indirect Effects of a Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6515603

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Accounting Change
-URI http://asc.fasb.org/extlink&oid=6503790

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6507316

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Direct Effects of a Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6510796

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6801783&loc=d3e22583-107794

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Retrospective Application
-URI http://asc.fasb.org/extlink&oid=6523989

+ Details

Significant Transactions (Details) $ / shares in Units, $ in Millions	12 Months Ended		62 Months Ended
	Dec. 31, 2011 USD ($) auction $ / shares shares	Dec. 31, 2010 USD ($) shares	Dec. 31, 2011 USD ($) shares
Significant Transactions
Common shares repurchased and retired during the period (in shares) \| shares	313,967	677,125	1,411,703
Value of common shares repurchased and retired during the period \| $	$ 114.2	$ 222.0	$ 537.5
Tender Offer
Significant Transactions
Common shares repurchased and retired during the period (in shares) \| shares	332,346
Value of common shares repurchased and retired during the period \| $	$ 138.8
Number of modified Dutch auction \| auction	2
Average price per share \| $ / shares	$ 417.55

Significant Transactions (Details 2) $ in Millions	1 Months Ended			3 Months Ended	12 Months Ended
Significant Transactions (Details 2) $ in Millions	Oct. 31, 2011 USD ($)	Jul. 31, 2010 USD ($) Y entity	Dec. 31, 2009 USD ($)	Jun. 30, 2011 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)
Significant Transactions
Consideration from sale of business					$ 1,010.6	$ 188.3
Gain on sale of business in discontinued operations					677.5
Loss on sale of business in discontinued operations					19.2
Written premiums for business sold, net					$ 1,978.6	$ 2,024.8	$ 2,624.6
Discount rate utilized for the revaluation of the plan obligations (as a percent)					4.38%	4.94%
Esurance
Significant Transactions
Consideration in excess of tangible book value	$ 700.0
Gain on sale of business in discontinued operations	$ 677.5
AutoOne
Significant Transactions
Loss on sale of business in discontinued operations					$ 19.2
Tax benefit from disposal of business					10.4
One Beacon Personal Lines
Significant Transactions
Consideration from sale of business		$ 166.6
Number of insurance companies sold \| entity		2
Ceded share of traditional personal lines business (as a percent)		100.00%
Assumed risk, certain specialty lines business written by York (as a percent)		100.00%
Number of attorneys-in-fact sold \| entity		2
Transition Service Agreement period (in years) \| Y		3
Gain (loss) from sale of business, net of tax						$ 24.6
Gain (loss) on disposal of business before tax						8.5
Tax benefit from disposal of business				$ 5.6		16.1
Written premiums for business sold, net							$ 420.0
OneBeacon Commercial Lines
Significant Transactions
Consideration from sale of business			$ 23.2		$ 0.8	10.2
Value of renewal rights sold in premiums			$ 490.0			$ 200.0

Significant Transactions (Details 3) - USD ($) $ in Millions	1 Months Ended		12 Months Ended		62 Months Ended
	Dec. 31, 2011	Feb. 28, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 30, 2011	Aug. 26, 2010	Feb. 26, 2010	Nov. 17, 2006
Share Repurchase
Authorized repurchase of common shares (in shares)									1,000,000
Additional authorized repurchase of common shares (in shares)							600,000
Common shares repurchased and retired during the period (in shares)			313,967	677,125	1,411,703
Value of common shares repurchased and retired during the period			$ 114.2	$ 222.0	$ 537.5
Central National
Business acquisition
Cash to be paid on acquisition								$ 5.0
Gain on acquisition		$ 12.8
Old Lyme
Business acquisition
Cash to be paid on acquisition						$ 6.0
Purchase note acquired						$ 2.1
Gain on acquisition	$ 7.2

Reserves for Unpaid Losses and Loss Adjustment Expenses (Details) - USD ($)	1 Months Ended			12 Months Ended
	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 22, 2006	Apr. 16, 2004	Jun. 02, 2001
Loss and Loss Adjustment Expense Reserve
Gross beginning balance				$ 5,736,800,000	$ 6,379,200,000	$ 7,029,400,000
Less beginning reinsurance recoverable on unpaid losses				(2,344,000,000)	(2,771,500,000)	(3,049,000,000)
Net loss and LAE reserves				3,392,800,000	3,607,700,000	3,980,400,000
Loss and LAE reserves sold - OneBeacon Personal Lines					(231,000,000)
Loss and LAE incurred relating to current year losses				1,256,700,000	1,503,400,000	1,571,200,000
Net favorable loss reserve development				(49,800,000)	(114,200,000)	(147,100,000)
Total incurred losses and LAE				1,206,900,000	1,389,200,000	1,424,100,000
Accretion of fair value adjustment to net loss and LAE reserves				8,300,000	8,500,000	12,200,000
Foreign currency translation adjustment to net loss and LAE reserves				100,000	4,700,000	23,500,000
Loss and LAE paid relating to current year losses				(404,000,000)	(544,900,000)	(591,600,000)
Loss and LAE paid relating to prior year losses				(952,800,000)	(840,500,000)	(1,234,700,000)
Total loss and LAE payments				(1,356,800,000)	(1,385,400,000)	(1,826,300,000)
Net ending balance	$ 3,392,800,000	$ 3,607,700,000	$ 3,980,400,000	3,195,000,000	3,392,800,000	3,607,700,000
Plus ending reinsurance recoverable on unpaid losses	(2,344,000,000)	(2,771,500,000)	(3,049,000,000)	(2,507,300,000)	(2,344,000,000)	(2,771,500,000)
Gross ending balance	5,736,800,000	6,379,200,000	7,029,400,000	5,702,300,000	5,736,800,000	6,379,200,000
Case incurred loss and ALAE during the period				1,206,900,000	1,389,200,000	1,424,100,000
Pre-tax un-accreted adjustment				12,700,000
One Beacon
Loss and Loss Adjustment Expense Reserve
Purchase accounting valuation of loss and LAE reserves, cash flow discount rate									11.00%
Scandinavian Re
Loss and Loss Adjustment Expense Reserve
Purchase accounting valuation of loss and LAE reserves, cash flow discount rate								12.00%
Stockbridge
Loss and Loss Adjustment Expense Reserve
Purchase accounting valuation of loss and LAE reserves, cash flow discount rate							2.00%
AutoOne
Loss and Loss Adjustment Expense Reserve
Net loss and LAE reserves				77,300,000	95,800,000	102,000,000
Net ending balance	77,300,000	95,800,000	102,000,000	0	77,300,000	95,800,000
Old Lyme
Loss and Loss Adjustment Expense Reserve
Loss and LAE reserves acquired					21,000,000
Central National
Loss and Loss Adjustment Expense Reserve
Loss and LAE reserves acquired					17,600,000
Other lines of business
Loss and Loss Adjustment Expense Reserve
Increase (decrease) in reserves	6,400,000
Multiple peril liability
Loss and Loss Adjustment Expense Reserve
Total incurred losses and LAE					65,800,000	36,800,000
Estimated IBNR	$ 86,200,000	$ 170,500,000			86,200,000	170,500,000
IBNR as a percentage of case reserves	57.00%	93.00%
Case reserves		$ 184,100,000	204,900,000			184,100,000
Case incurred loss and ALAE during the period					65,800,000	36,800,000
Increase (decrease) in reserves					(18,400,000)	(42,600,000)
General liability
Loss and Loss Adjustment Expense Reserve
Total incurred losses and LAE					33,100,000	15,600,000
Estimated IBNR	$ 61,700,000	$ 107,100,000			61,700,000	107,100,000
IBNR as a percentage of case reserves	164.00%	265.00%
Case reserves		$ 40,400,000	34,200,000			40,400,000
Case incurred loss and ALAE during the period					33,100,000	15,600,000
Increase (decrease) in reserves					(12,300,000)	(14,100,000)
Professional liability business
Loss and Loss Adjustment Expense Reserve
Increase (decrease) in reserves				(11,500,000)	(19,300,000)	(60,000,000)
Commercial lines underwriting unit
Loss and Loss Adjustment Expense Reserve
Increase (decrease) in reserves				(14,000,000)	(7,500,000)	7,500,000
OneBeacon
Loss and Loss Adjustment Expense Reserve
Net favorable loss reserve development				2,900,000	57,100,000	116,700,000
Increase (decrease) in reserves				(4,100,000)
OneBeacon \| Specialty insurance operations
Loss and Loss Adjustment Expense Reserve
Net favorable loss reserve development				29,600,000
OneBeacon \| Other lines of business
Loss and Loss Adjustment Expense Reserve
Net favorable loss reserve development				(26,700,000)
OneBeacon \| Multiple peril liability
Loss and Loss Adjustment Expense Reserve
Estimated IBNR		$ 95,400,000	$ 173,900,000			95,400,000
IBNR as a percentage of case reserves		73.00%	85.00%
OneBeacon \| General liability
Loss and Loss Adjustment Expense Reserve
Estimated IBNR		$ 61,600,000	$ 93,900,000			61,600,000
IBNR as a percentage of case reserves		214.00%	275.00%
Sirius group
Loss and Loss Adjustment Expense Reserve
Gross beginning balance				2,441,300,000
Net favorable loss reserve development				46,900,000	57,100,000	30,400,000
Total incurred losses and LAE				626,000,000	531,000,000	418,800,000
Plus ending reinsurance recoverable on unpaid losses				(339,700,000)
Gross ending balance	$ 2,441,300,000			2,343,700,000	2,441,300,000
Case incurred loss and ALAE during the period				626,000,000	531,000,000	418,800,000
Net favorable loss reserve development due to property lines				41,200,000
Net favorable loss reserve development due to 2010 Chilean earthquake				13,100,000
Net unfavorable loss reserve development due to asbestos and environmental reserves additions				$ 12,300,000
Deferred gains from a retrocessional reinsurance contract					$ 16,300,000
Losses incurred related to A&E exposures						17,700,000
Losses ceded under a retrocessional reinsurance contract						20,000,000
Retroceded premiums						10,000,000
Interest charges on funds held						$ 7,200,000

Reserves for Unpaid Losses and Loss Adjustment Expenses (Details 2) $ in Millions	12 Months Ended			127 Months Ended
	Dec. 31, 2011 USD ($) Y	Dec. 31, 2010 USD ($) Y	Dec. 31, 2009 USD ($)	Dec. 31, 2011 USD ($)
OneBeacon
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Net losses paid by NICO during the period				$ 1,400.0
Gross
Beginning balance	$ 1,023.0	$ 1,336.3	$ 1,568.7
Incurred losses and LAE	488.6	6.2	5.9
Paid losses and LAE	(157.5)	(319.5)	(238.3)
Ending balance	1,354.1	1,023.0	1,336.3	1,354.1
Pre-NICO Net
Beginning balance	741.1	907.4	1,002.7
Incurred losses and LAE	94.4	6.0	5.0
Paid losses and LAE	(2.7)	(172.3)	(100.3)
Ending balance	832.8	741.1	907.4	832.8
Net
Beginning balance	15.6	14.1	12.0
Incurred losses and LAE	6.0	6.0	5.0
Paid losses and LAE	(10.4)	(4.5)	(2.9)
Ending balance	$ 11.2	15.6	14.1	$ 11.2
OneBeacon \| NICO Cover
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Period during which asbestos and environmental losses have been recovered under the historical third-party reinsurance (in years) \| Y	11
Asbestos and environmental losses recovered under the historical third-party reinsurance (as a percent)	47.00%			47.00%
Utilized asbestos and environmental coverage				$ 2,300.0
Percentage of utilized coverage from NICO that relates to uncollectible Third-Party Recoverables				8.00%
Net
Beginning balance	$ 2,200.0
Increase in A&E reserves ceded to NICO	122.0
Ending balance	2,300.0	2,200.0		$ 2,300.0
OneBeacon \| Asbestos
Gross
Beginning balance	904.0	985.6	1,098.4
Incurred losses and LAE	256.8		1.0
Paid losses and LAE	(86.5)	(81.6)	(113.8)
Ending balance	1,074.3	904.0	985.6	1,074.3
Pre-NICO Net
Beginning balance	647.3	688.8	741.5
Incurred losses and LAE	32.2
Paid losses and LAE	1.7	(41.5)	(52.7)
Ending balance	681.2	647.3	688.8	681.2
Net
Beginning balance	6.4	6.5	6.5
Incurred losses and LAE	(4.0)
Paid losses and LAE	(0.2)	(0.1)
Ending balance	2.2	6.4	6.5	2.2
OneBeacon \| Environmental
Gross
Beginning balance	119.0	350.7	470.3
Incurred losses and LAE	231.8	6.2	4.9
Paid losses and LAE	(71.0)	(237.9)	(124.5)
Ending balance	279.8	119.0	350.7	279.8
Pre-NICO Net
Beginning balance	93.8	218.6	261.2
Incurred losses and LAE	62.2	6.0	5.0
Paid losses and LAE	(4.4)	(130.8)	(47.6)
Ending balance	151.6	93.8	218.6	151.6
Net
Beginning balance	9.2	7.6	5.5
Incurred losses and LAE	10.0	6.0	5.0
Paid losses and LAE	(10.2)	(4.4)	(2.9)
Ending balance	$ 9.0	$ 9.2	7.6	9.0
Sirius
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
A&E three year survival ratio (in years) \| Y	11.1	12.5
Gross
Beginning balance	$ 214.3	$ 209.2	198.2
Losses and LAE acquired Central National		13.9
Incurred losses and LAE	16.5	6.5	23.9
Paid losses and LAE	(23.6)	(15.3)	(12.9)
Ending balance	207.2	214.3	209.2	207.2
Net
Beginning balance	169.6	164.5	158.6
Losses and LAE acquired Central National		12.1
Incurred losses and LAE	12.3	6.0	17.7
Paid losses and LAE	(19.2)	(13.0)	(11.8)
Ending balance	162.8	169.6	164.5	162.8
Sirius \| Asbestos
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Increase (decrease) in reserves	10.3
Gross
Beginning balance	191.9	187.0	173.7
Losses and LAE acquired Central National		10.4
Incurred losses and LAE	13.6	9.0	24.7
Paid losses and LAE	(20.4)	(14.5)	(11.4)
Ending balance	185.1	191.9	187.0	185.1
Net
Beginning balance	151.5	146.6	138.5
Losses and LAE acquired Central National		9.7
Incurred losses and LAE	10.3	7.3	18.4
Paid losses and LAE	(15.6)	(12.1)	(10.3)
Ending balance	146.2	151.5	146.6	146.2
Sirius \| Environmental
Asbestos and Environmental Loss and Loss Adjustment Expense Reserve Activity
Increase (decrease) in reserves	2.0
Gross
Beginning balance	22.4	22.2	24.5
Losses and LAE acquired Central National		3.5
Incurred losses and LAE	2.9	(2.5)	(0.8)
Paid losses and LAE	(3.2)	(0.8)	(1.5)
Ending balance	22.1	22.4	22.2	22.1
Net
Beginning balance	18.1	17.9	20.1
Losses and LAE acquired Central National		2.4
Incurred losses and LAE	2.0	(1.3)	(0.7)
Paid losses and LAE	(3.6)	(0.9)	(1.5)
Ending balance	$ 16.5	$ 18.1	$ 17.9	$ 16.5

Third-Party Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
Third-Party Reinsurance (Details) - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Written premiums:
Direct	$ 1,217.1	$ 1,623.1	$ 2,079.7
Assumed	1,036.8	1,015.2	947.8
Gross written premiums	2,253.9	2,638.3	3,027.5
Ceded	(275.3)	(613.5)	(402.9)
Net written premiums	1,978.6	2,024.8	2,624.6
Earned premiums:
Direct	1,267.0	1,766.6	2,128.9
Assumed	1,032.9	993.9	994.3
Gross earned premiums	2,299.9	2,760.5	3,123.2
Ceded	(372.1)	(508.7)	(405.6)
Net earned premiums	1,927.8	2,251.8	2,717.6
Losses and LAE:
Direct	1,231.1	936.5	1,089.5
Assumed	663.9	822.8	533.0
Gross losses and LAE	1,895.0	1,759.3	1,622.5
Ceded	(688.1)	(370.1)	(198.4)
Total incurred losses and LAE	1,206.9	1,389.2	1,424.1
OneBeacon
Written premiums:
Direct	1,077.6	1,501.5	1,972.4
Assumed	48.2	57.7	58.6
Gross written premiums	1,125.8	1,559.2	2,031.0
Ceded	(62.9)	(400.2)	(213.2)
Net written premiums	1,062.9	1,159.0	1,817.8
Earned premiums:
Direct	1,138.5	1,648.7	2,021.7
Assumed	43.1	64.2	66.8
Gross earned premiums	1,181.6	1,712.9	2,088.5
Ceded	(166.1)	(309.0)	(229.7)
Net earned premiums	1,015.5	1,403.9	1,858.8
Losses and LAE:
Direct	1,151.1	877.1	1,020.7
Assumed	36.1	138.4	40.8
Gross losses and LAE	1,187.2	1,015.5	1,061.5
Ceded	(606.3)	(157.3)	(56.2)
Total incurred losses and LAE	580.9	858.2	1,005.3
OneBeacon \| OneBeacon Commercial Lines
Written premiums:
Ceded		(262.2)
Earned premiums:
Net earned premiums		165.0
Losses and LAE:
Total incurred losses and LAE		86.5
Sirius
Written premiums:
Direct	139.5	121.6	107.3
Assumed	988.6	957.5	889.2
Gross written premiums	1,128.1	1,079.1	996.5
Ceded	(212.4)	(213.3)	(189.7)
Net written premiums	915.7	865.8	806.8
Earned premiums:
Direct	128.5	117.9	107.2
Assumed	989.8	929.7	927.5
Gross earned premiums	1,118.3	1,047.6	1,034.7
Ceded	(206.0)	(199.7)	(175.9)
Net earned premiums	912.3	847.9	858.8
Losses and LAE:
Direct	80.0	59.4	68.8
Assumed	627.8	684.4	492.2
Gross losses and LAE	707.8	743.8	561.0
Ceded	(81.8)	(212.8)	(142.2)
Total incurred losses and LAE	$ 626.0	$ 531.0	$ 418.8

Third-Party Reinsurance (Details 2) € in Millions, $ in Millions	1 Months Ended					12 Months Ended						127 Months Ended
	Apr. 30, 2011 USD ($) Y	Jun. 30, 2010 USD ($)	Apr. 30, 2010 USD ($)	Apr. 30, 2009 USD ($)	Jun. 30, 2001 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($) contract	Dec. 31, 2011 EUR (€)	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2007 Y	Dec. 31, 2011 USD ($) contract	Dec. 31, 2008 USD ($)	Dec. 31, 2001 contract rating
Third-Party Reinsurance
Period for which the U.S. government extended the Terrorism Act (in years) \| Y											7
Reinsurance recoverable on paid losses							$ 30.5		$ 63.1			$ 30.5
Reinsurance recoverable on unpaid losses							2,507.3		2,344.0	$ 2,771.5		2,507.3	$ 3,049.0
Reinsurance recoverables							2,537.8		2,407.1			$ 2,537.8
Case incurred loss and ALAE during the period							1,206.9		1,389.2	1,424.1
Healthcare professional liability
Third-Party Reinsurance
Cover under reinsurance contract							$ 20.0
NICO Cover
Third-Party Reinsurance
Number of reinsurance contracts the seller caused OneBeacon to purchase immediately prior to the entity's acquisition of OneBeacon \| contract							1					1
Imagine Re \| Sirius America
Third-Party Reinsurance
Amount of unamortized deferred gains										16.3
Amount of deferred gains recognized									16.3	4.6
OneBeacon
Third-Party Reinsurance
Percentage of certified losses required to be shared by federal government under Terrorism Risk Insurance Act							85.00%	85.00%
Estimated individual retention level for commercial policies subject to the Terrorism Act							$ 100.0					$ 100.0
Number of reinsurance contracts the seller caused OneBeacon to purchase immediately prior to the entity's acquisition of OneBeacon \| contract														2
Number of ratings in Standard & Poors best ratings \| rating														21
Number of ratings in A.M. Best ratings \| rating														15
Reinsurance receivables paid by the reinsurer												1,400.0
Reinsurance recoverable on paid losses							16.5					16.5
Reinsurance recoverable on unpaid losses							2,330.8					2,330.8
Purchase accounting adjustments							163.3					163.3
Reinsurance recoverables							2,184.1		1,937.7			2,184.1
Case incurred loss and ALAE during the period							580.9		858.2	$ 1,005.3
OneBeacon \| Maximum
Third-Party Reinsurance
Aggregate liability to be paid by the government and industry without further action by Congress							100,000.0					$ 100,000.0
OneBeacon \| Property catastrophe reinsurance program
Third-Party Reinsurance
Amount of loss on a single catastrophe retained, first layer							50.0
Amount of loss on a single catastrophe reinsured, second layer							$ 175.0
First retention percentage of loss on a single catastrophe reinsured, second layer							26.00%					26.00%
Second retention percentage of loss on a single catastrophe reinsured, second layer							10.00%					10.00%
Amount of loss on a single catastrophe retained, third layer							$ 225.0
OneBeacon \| Property catastrophe reinsurance program \| Minimum
Third-Party Reinsurance
Amount of loss on a single catastrophe reinsured, first retention slab for second layer							50.0
Amount of loss on a single catastrophe reinsured, second retention slab for second layer							100.0
OneBeacon \| Property catastrophe reinsurance program \| Maximum
Third-Party Reinsurance
Amount of loss on a single catastrophe reinsured, first retention slab for second layer							100.0
Amount of loss on a single catastrophe reinsured, second retention slab for second layer							175.0
Cover under reinsurance contract							40.0
Amount of retention of losses by the entity							10.0
OneBeacon \| Northeast homeowners business
Third-Party Reinsurance
The percentage ceded under quota share reinsurance agreement										30.00%
Premiums ceded under quota share agreement		$ 25.6								$ 59.9
OneBeacon \| Property-per-risk reinsurance program
Third-Party Reinsurance
Amount above which individual risk facultative reinsurance may be purchased							100.0
OneBeacon \| Property-per-risk reinsurance program \| Minimum
Third-Party Reinsurance
Reinsurance protection on an individual risk basis for terrorism losses							10.0
OneBeacon \| Property-per-risk reinsurance program \| Maximum
Third-Party Reinsurance
Reinsurance protection on an individual risk basis for terrorism losses							100.0
OneBeacon \| Casualty reinsurance program \| Minimum
Third-Party Reinsurance
Reinsurance program, reinsured losses							5.0
OneBeacon \| Casualty reinsurance program \| Maximum
Third-Party Reinsurance
Reinsurance program, reinsured losses							21.0
OneBeacon \| NICO Cover
Third-Party Reinsurance
Cover under reinsurance contract					$ 2,500.0
Ceded estimated incurred losses							2,300.0					$ 2,300.0
Percentage of utilized coverage that relates to uncollectible Third Party Recoverables												8.00%
Utilized coverage from that relates to uncollectible Third-Party Recoverables							184.0
Utilized asbestos and environmental coverage												$ 2,300.0
Third-Party Recoverables in which reinsurer would pay if they are unable to collect from third-party reinsurers							198.3					198.3
OneBeacon \| NICO Cover \| Maximum
Third-Party Reinsurance
Cover under reinsurance contract							2,500.0
OneBeacon \| GRC Cover
Third-Party Reinsurance
Ceded estimated incurred losses							562.0					562.0
OneBeacon \| GRC Cover \| Maximum
Third-Party Reinsurance
Cover under reinsurance contract							570.0
OneBeacon \| National Indemnity Company and General Reinsurance Corporation
Third-Party Reinsurance
Reinsurance recoverables							$ 1,540.6					$ 1,540.6
Percentage of total paid and unpaid reinsurance recoverables							66.00%					66.00%
OneBeacon \| Hanover Insurance Group Ltd.
Third-Party Reinsurance
Reinsurance recoverables							$ 90.9					$ 90.9
Percentage of total paid and unpaid reinsurance recoverables							4.00%					4.00%
OneBeacon \| Tokio Marine and Nichido Fire
Third-Party Reinsurance
The percentage ceded under quota share reinsurance agreement							100.00%	100.00%
Reinsurance recoverables							$ 57.1					$ 57.1
Percentage of total paid and unpaid reinsurance recoverables							2.00%					2.00%
Reinsurance recoverable from various third-party reinsurers, guaranteed by the third-party reinsurer under reinsurance agreement							$ 30.5					$ 30.5
OneBeacon \| Tower Group Inc.
Third-Party Reinsurance
Reinsurance recoverables							$ 35.1					$ 35.1
Percentage of total paid and unpaid reinsurance recoverables							1.00%					1.00%
OneBeacon \| Munich Reinsurance America
Third-Party Reinsurance
Reinsurance recoverables							$ 26.4					$ 26.4
Percentage of total paid and unpaid reinsurance recoverables							1.00%					1.00%
OneBeacon \| General Reinsurance Corporation \| GRC Cover
Third-Party Reinsurance
Reinsurance receivables paid by the reinsurer							$ 73.5		61.3
Sirius group
Third-Party Reinsurance
Reinsurance recoverable on paid losses							13.9					$ 13.9
Reinsurance recoverable on unpaid losses							339.7					339.7
Reinsurance recoverables							$ 353.7		469.4			353.7
Percentage of trade credit business under a quota share retrocession							19.00%	19.00%
Percentage of trade credit business under a renewed quota share retrocession							20.00%	20.00%
Percentage of bond business under a renewed quota share retrocession							50.00%	50.00%
Amount of deferred gains recognized									(16.3)
Case incurred loss and ALAE during the period							$ 626.0		531.0	$ 418.8
Sirius group \| Catastrophe excess of loss cover
Third-Party Reinsurance
Period for which reinsurance cover was renewed (in years) \| Y	1
Cover under reinsurance contract	$ 61.0
Amount of retention of losses by the entity	35.0
Amount of earthquake losses at which reinsurance will be fully recovered	$ 110.0
Sirius group \| New Zealand earthquake losses cover
Third-Party Reinsurance
Cover under reinsurance contract			$ 65.0
Amount of retention of losses by the entity			$ 45.0				45.0
Case incurred loss and ALAE during the period							$ 44.4
Sirius group \| Chile earthquake losses cover
Third-Party Reinsurance
Cover under reinsurance contract				$ 65.0
Amount of retention of losses by the entity				$ 35.0
Utilized coverage									$ 65.0
Sirius group \| Facultative and proportional aviation portfolio reinsurance \| Minimum
Third-Party Reinsurance
Reinsurance program, reinsured losses						$ 150.0
Sirius group \| Facultative and proportional aviation portfolio reinsurance \| Maximum
Third-Party Reinsurance
Reinsurance program, reinsured losses						$ 2,250.0
Sirius group \| Non-proportional aviation portfolio reinsurance
Third-Party Reinsurance
The percentage ceded under quota share reinsurance agreement							15.00%	15.00%
Industry event level for first event industry loss warranties (ILW)							$ 30.0
Protection in second event industry loss warranties (ILW)							6.0
Sirius group \| Non-proportional aviation portfolio reinsurance \| Minimum
Third-Party Reinsurance
Protection in first event industry loss warranties (ILW)							400.0
Industry event level for second event industry loss warranties (ILW)							300.0
Sirius group \| Non-proportional aviation portfolio reinsurance \| Maximum
Third-Party Reinsurance
Protection in first event industry loss warranties (ILW)							900.0
Industry event level for second event industry loss warranties (ILW)							600.0
Sirius group \| Personal accident and life
Third-Party Reinsurance
Cover under reinsurance contract							13.0	€ 10.0
Amount of retention of losses by the entity							7.0	€ 5.0
Sirius group \| Olympus
Third-Party Reinsurance
Reinsurance recoverables							$ 35.5					$ 35.5
Percentage of total paid and unpaid reinsurance recoverables							10.00%					10.00%
Percentage of reinsurance recoverable that is collateralized							100.00%					100.00%
Sirius group \| Lloyds of London
Third-Party Reinsurance
Reinsurance recoverables							$ 27.2					$ 27.2
Percentage of total paid and unpaid reinsurance recoverables							8.00%					8.00%
Percentage of reinsurance recoverable that is collateralized							8.00%					8.00%
Sirius group \| General Reinsurance Corporation
Third-Party Reinsurance
Reinsurance recoverables							$ 42.7					$ 42.7
Percentage of total paid and unpaid reinsurance recoverables							12.00%					12.00%
Percentage of reinsurance recoverable that is collateralized							1.00%					1.00%
Sirius group \| Swiss Re Group
Third-Party Reinsurance
Reinsurance recoverables							$ 40.2					$ 40.2
Percentage of total paid and unpaid reinsurance recoverables							11.00%					11.00%
Percentage of reinsurance recoverable that is collateralized							20.00%					20.00%
Sirius group \| Michigan Catastrophic Claims Association
Third-Party Reinsurance
Reinsurance recoverables							$ 14.6					$ 14.6
Percentage of total paid and unpaid reinsurance recoverables							4.00%					4.00%

Investment Securities (Details) - USD ($) $ in Millions	12 Months Ended
Investment Securities (Details) - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Investment income
Total investment income	$ 195.4	$ 217.8	$ 258.6
Third-party investment expenses	(10.9)	(8.9)	(8.5)
Net investment income	184.5	208.9	250.1
Fixed maturity investments.
Investment income
Total investment income	166.2	194.7	243.3
Short-term investments
Investment income
Total investment income	4.5	3.0	5.5
Common shareholders' equity.
Investment income
Total investment income	15.4	10.2	4.9
Convertible fixed maturities
Investment income
Total investment income	5.5	5.6	8.0
Other long-term investments
Investment income
Total investment income	4.2	6.0	4.2
Interest on funds held under reinsurance treaties
Investment income
Total investment income	$ (0.4)	$ (1.7)	$ (7.3)

Investment Securities (Details 2) - USD ($) $ in Millions	12 Months Ended
Investment Securities (Details 2) - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net Realized and Unrealized Investment Gains and Losses
Net realized investment gains (losses), pre-tax	$ 117.0	$ 136.4	$ (69.9)
Net unrealized gains (losses), pre-tax	(63.6)	17.2	498.5
Net realized and unrealized investment gains (losses), pre-tax	122.8	82.6	361.7
Income taxes attributable to realized and unrealized investment gains (losses)	(30.9)	(22.8)	(124.4)
Net realized and unrealized investment gains (losses), after-tax	91.9	59.8	237.3
Net realized investment gains (losses)
Net realized investment gains (losses), pre-tax	117.0	136.4	(69.9)
Income taxes attributable to realized investment gains (losses)	(37.0)	(42.1)	14.9
Net realized investment gains (losses), after-tax	80.0	94.3	(55.0)
Gross realized investment gains recognized during the period	191.6	205.0	157.3
Gross realized investment losses recognized during the period	74.6	68.6	227.2
Accounts payable on unsettled investment purchases	34.6	22.3
Accounts receivable on unsettled investment sales	4.7	39.5
Net unrealized investment gains (losses)
Net unrealized gains (losses), pre-tax	(63.6)	17.2	498.5
Income taxes attributable to unrealized investment gains (losses)	24.0	0.5	(154.3)
Net unrealized investment gains (losses), after-tax	(39.6)	17.7	344.2
Net unrealized investment gains (losses), net foreign exchange gains (losses), pre-tax	69.4	(71.0)	(66.9)
Income taxes attributable to unrealized investment gains, net foreign exchange gains (losses)	(17.9)	18.8	15.0
Net unrealized investment gains (losses), net foreign currency gains (losses), after-tax	51.5	(52.2)	(51.9)
Net unrealized investment gains (losses) pre-tax, total changes in fair value reflected in earnings	5.8	(53.8)	431.6
Income taxes attributable to unrealized investment gains (losses), total changes in fair value reflected in earnings	6.1	19.3	(139.3)
Net unrealized investment gains (losses) after-tax, total changes in fair value reflected in earnings	11.9	(34.5)	292.3
Fixed maturity investments.
Net Realized and Unrealized Investment Gains and Losses
Net realized investment gains (losses), pre-tax	49.4	96.9	(7.4)
Net unrealized gains (losses), pre-tax	7.6	(67.4)	333.9
Net realized investment gains (losses)
Net realized investment gains (losses), pre-tax	49.4	96.9	(7.4)
Net unrealized investment gains (losses)
Net unrealized gains (losses), pre-tax	7.6	(67.4)	333.9
Net unrealized investment gains (losses), net foreign exchange gains (losses), pre-tax	68.9	(53.8)	(53.6)
Net unrealized investment gains (losses) pre-tax, total changes in fair value reflected in earnings	76.5	(121.2)	280.3
Short-term investments
Net Realized and Unrealized Investment Gains and Losses
Net realized investment gains (losses), pre-tax			0.2
Net unrealized gains (losses), pre-tax			(0.3)
Net realized investment gains (losses)
Net realized investment gains (losses), pre-tax			0.2
Net unrealized investment gains (losses)
Net unrealized gains (losses), pre-tax			(0.3)
Net unrealized investment gains (losses), net foreign exchange gains (losses), pre-tax	(1.1)	0.2	1.6
Net unrealized investment gains (losses) pre-tax, total changes in fair value reflected in earnings	(1.1)	0.2	1.3
Common equity securities
Net Realized and Unrealized Investment Gains and Losses
Net realized investment gains (losses), pre-tax	34.6	6.9	(46.4)
Net unrealized gains (losses), pre-tax	(40.6)	72.4	57.9
Net realized investment gains (losses)
Net realized investment gains (losses), pre-tax	34.6	6.9	(46.4)
Net unrealized investment gains (losses)
Net unrealized gains (losses), pre-tax	(40.6)	72.4	57.9
Net unrealized investment gains (losses), net foreign exchange gains (losses), pre-tax	(1.8)	(9.6)	(9.9)
Net unrealized investment gains (losses) pre-tax, total changes in fair value reflected in earnings	(42.4)	62.8	48.0
Convertible fixed maturities
Net Realized and Unrealized Investment Gains and Losses
Net realized investment gains (losses), pre-tax	(2.2)	16.7	15.6
Net unrealized gains (losses), pre-tax	(11.5)	(5.4)	39.8
Net realized investment gains (losses)
Net realized investment gains (losses), pre-tax	(2.2)	16.7	15.6
Net unrealized investment gains (losses)
Net unrealized gains (losses), pre-tax	(11.5)	(5.4)	39.8
Net unrealized investment gains (losses) pre-tax, total changes in fair value reflected in earnings	(11.5)	(5.4)	39.8
Other long-term investments
Net Realized and Unrealized Investment Gains and Losses
Net realized investment gains (losses), pre-tax	35.2	15.9	(31.9)
Net unrealized gains (losses), pre-tax	(19.1)	17.6	67.2
Net realized investment gains (losses)
Net realized investment gains (losses), pre-tax	35.2	15.9	(31.9)
Net unrealized investment gains (losses)
Net unrealized gains (losses), pre-tax	(19.1)	17.6	67.2
Net unrealized investment gains (losses), net foreign exchange gains (losses), pre-tax	3.4	(7.8)	(5.0)
Net unrealized investment gains (losses) pre-tax, total changes in fair value reflected in earnings	$ (15.7)	$ 9.8	$ 62.2

Investment Securities (Details 3) - USD ($) $ in Millions	12 Months Ended
Investment Securities (Details 3) - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Components of the entity's net realized and unrealized investment gains,(losses), after-tax
Net change in pre-tax unrealized gains (losses) on investments in unconsolidated affiliates	$ (63.6)	$ 72.7	$ 192.7
Income taxes	5.1	0.8	(0.3)
Net change in unrealized gains (losses) from investments in unconsolidated affiliates	(58.5)	73.5	192.4
Net unrealized foreign currency gains (losses) on investments	(90.1)	102.9	185.1
Total investment gains (losses) recognized through other comprehensive income	(148.6)	176.4	377.5
Change in net unrealized investment gains (losses), after-tax	11.9	(34.5)	292.3
Net realized investment gains (losses), after-tax	80.0	94.3	(55.0)
Total investment gains (losses) recorded during the period, after-tax	(56.7)	236.2	614.8
Level 3 Inputs
Investment securities
Total pre-tax gains (losses) included in earnings attributable to unrealized investment gains (losses) for Level 3 investments	(45.6)	30.0	127.1
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	(12.2)	10.2	47.3
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	(16.6)	(19.2)	14.7
Convertible fixed maturities \| Level 3 Inputs
Investment securities
Total pre-tax gains (losses) included in earnings attributable to unrealized investment gains (losses) for Level 3 investments			0.1
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	$ (16.8)	$ 39.0	$ 65.0

Investment Securities (Details 4) - USD ($) $ in Millions	12 Months Ended
Investment Securities (Details 4) - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Investment securities
Cost or amortized cost	$ 6,228.2	$ 5,755.9
Gross unrealized gains	119.1	133.6
Gross unrealized losses	(18.6)	(44.2)
Net foreign currency gains (losses)	5.0	(59.2)
Total fixed maturity investments including assets held for sale	6,333.7
Fixed maturity investments, at fair value	6,221.9	5,786.1
Cost or amortized cost
Total	6,228.2	5,755.9
Carrying value
Carrying value, common equity securities	755.0	667.0
Carrying value, convertible fixed securities	143.8	143.0
Carrying value, other long-term investments	301.3	372.1
Sales and maturities of investments, excluding short-term investments	5,044.5	4,492.6	$ 3,748.5
AutoOne
Investment securities
Fixed maturity investments reclassified to assets held for sale	(111.8)
U.S. Government and agency obligations
Investment securities
Cost or amortized cost	299.4	385.9
Gross unrealized gains	5.3	13.6
Gross unrealized losses	(0.1)	(0.8)
Net foreign currency gains (losses)	0.4
Fixed maturity investments, at fair value	305.0	398.7
Cost or amortized cost
Total	299.4	385.9
Debt securities issued by corporations
Investment securities
Cost or amortized cost	2,072.1	2,149.2
Gross unrealized gains	73.7	87.9
Gross unrealized losses	(7.8)	(21.1)
Net foreign currency gains (losses)	(2.9)	(37.9)
Fixed maturity investments, at fair value	2,135.1	2,178.1
Cost or amortized cost
Total	2,072.1	2,149.2
Municipal obligations
Investment securities
Cost or amortized cost	2.7	3.3
Gross unrealized gains		0.1
Gross unrealized losses		(0.1)
Fixed maturity investments, at fair value	2.7	3.3
Cost or amortized cost
Total	2.7	3.3
Mortgage-backed and asset-backed securities
Investment securities
Cost or amortized cost	3,190.5	2,082.0
Gross unrealized gains	25.9	18.2
Gross unrealized losses	(3.9)	(15.6)
Net foreign currency gains (losses)	10.4	(12.9)
Fixed maturity investments, at fair value	3,222.9	2,071.7
Cost or amortized cost
Securities not having single maturity date	3,190.5
Total	3,190.5	2,082.0
Carrying value
Securities not having single maturity date	3,222.9
Foreign government, agency and provincial obligations
Investment securities
Cost or amortized cost	581.2	1,053.6
Gross unrealized gains	11.0	7.7
Gross unrealized losses	(0.1)	(6.6)
Net foreign currency gains (losses)	(2.9)	(8.3)
Fixed maturity investments, at fair value	589.2	1,046.4
Cost or amortized cost
Total	581.2	1,053.6
Non-cumulative perpetual preference shares
Investment securities
Cost or amortized cost	82.3	81.9
Gross unrealized gains	3.2	6.1
Gross unrealized losses	(6.7)
Net foreign currency gains (losses)		(0.1)
Fixed maturity investments, at fair value	78.8	87.9
Cost or amortized cost
Securities not having single maturity date	82.3
Total	82.3	81.9
Carrying value
Securities not having single maturity date	78.8
Fixed maturity investments and convertible fixed maturity investments, excluding mortgage-backed securities, asset-backed securities and preferred stock
Cost or amortized cost
Due in one year or less	669.6
Due after one year through five years	1,809.1
Due after five years through ten years	563.1
Due after ten years	52.8
Carrying value
Due in one year or less	681.0
Due after one year through five years	1,857.5
Due after five years through ten years	582.8
Due after ten years	54.5
Fixed maturity investments and convertible fixed maturity investments
Investment securities
Cost or amortized cost	6,367.4
Cost or amortized cost
Total	6,367.4
Carrying value
Total	6,477.5
Common shareholders' equity.
Investment securities
Cost or amortized cost	691.7	561.2
Gross unrealized gains	72.0	105.5
Gross unrealized losses	(8.7)	(1.5)
Net foreign currency gains (losses)		1.8
Cost or amortized cost
Total	691.7	561.2
Convertible fixed maturities
Investment securities
Cost or amortized cost	139.2	126.9
Gross unrealized gains	6.2	16.2
Gross unrealized losses	(1.6)	(0.1)
Cost or amortized cost
Total	139.2	126.9
Other long-term investments.
Investment securities
Cost or amortized cost	274.4	329.5
Gross unrealized gains	55.5	62.4
Gross unrealized losses	(25.2)	(13.0)
Net foreign currency gains (losses)	(3.4)	(6.8)
Cost or amortized cost
Total	$ 274.4	$ 329.5

Investment Securities (Details 5) - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010
Investment securities
Carrying value	$ 6,221.9	$ 5,786.1
Total fixed maturity investments including assets held for sale	6,333.7
Fair Value
Investment securities
Fair value investments	8,346.8	7,901.6
Level 1 Inputs
Investment securities
Fair value investments	1,879.1	1,894.4
Level 2 Inputs
Investment securities
Fair value investments	6,088.2	5,477.4
Fixed maturity investments. \| Level 3 Inputs
Investment securities
Fair value investments	78.9	128.4
U.S. Government and agency obligations
Investment securities
Carrying value	305.0	398.7
Debt securities issued by corporations
Investment securities
Fair value investments	2,135.1	2,178.0
Carrying value	2,135.1	2,178.1
Municipal obligations
Investment securities
Carrying value	2.7	3.3
Mortgage-backed and asset-backed securities
Investment securities
Carrying value	3,222.9	2,071.7
Mortgage-backed and asset-backed securities \| Fair Value
Investment securities
Fair value investments	3,222.9	2,071.7
Mortgage-backed and asset-backed securities \| Level 2 Inputs
Investment securities
Fair value investments	3,207.8	2,014.7
Mortgage-backed and asset-backed securities \| Level 3 Inputs
Investment securities
Fair value investments	15.1	57.0
Non-cumulative perpetual preference shares
Investment securities
Carrying value	78.8	87.9
Common equity securities \| Level 3 Inputs
Investment securities
Fair value investments	32.3	71.2
Other long-term investments \| Level 3 Inputs
Investment securities
Fair value investments	268.3	330.2
Carrying value of investment accounted for using the equity method	33.0	41.9
Fair value measured on a recurring basis \| Fair Value
Investment securities
Fair value investments	8,346.8	7,901.6
Fair value measured on a recurring basis \| Level 1 Inputs
Investment securities
Fair value investments	1,879.1	1,894.4
Fair value measured on a recurring basis \| Level 2 Inputs
Investment securities
Fair value investments	6,088.2	5,477.4
Fair value measured on a recurring basis \| Level 3 Inputs
Investment securities
Fair value investments	379.5	529.8
Fair value measured on a recurring basis \| Fixed maturity investments. \| Fair Value
Investment securities
Fair value investments	6,333.7	5,786.1
Fair value measured on a recurring basis \| Fixed maturity investments. \| Fair Value \| AutoOne
Investment securities
Fair value investments	111.8
Fair value measured on a recurring basis \| Fixed maturity investments. \| Level 1 Inputs
Investment securities
Fair value investments	365.7	477.8
Fair value measured on a recurring basis \| Fixed maturity investments. \| Level 2 Inputs
Investment securities
Fair value investments	5,889.1	5,179.9
Fair value measured on a recurring basis \| Fixed maturity investments. \| Level 3 Inputs
Investment securities
Fair value investments	78.9	128.4
Fair value measured on a recurring basis \| U.S. Government and agency obligations \| Fair Value
Investment securities
Fair value investments	305.0	398.7
Fair value measured on a recurring basis \| U.S. Government and agency obligations \| Level 1 Inputs
Investment securities
Fair value investments	296.2	388.9
Fair value measured on a recurring basis \| U.S. Government and agency obligations \| Level 2 Inputs
Investment securities
Fair value investments	8.8	9.8
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Fair Value
Investment securities
Fair value investments	2,135.1	2,178.0
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Level 1 Inputs
Investment securities
Fair value investments	3.8	6.3
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Level 2 Inputs
Investment securities
Fair value investments	2,131.3	2,171.7
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Consumer \| Fair Value
Investment securities
Fair value investments	790.7	769.0
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Consumer \| Level 2 Inputs
Investment securities
Fair value investments	790.7	769.0
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Industrial \| Fair Value
Investment securities
Fair value investments	359.4	511.3
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Industrial \| Level 2 Inputs
Investment securities
Fair value investments	359.4	511.3
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Financials \| Fair Value
Investment securities
Fair value investments	239.6	265.8
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Financials \| Level 1 Inputs
Investment securities
Fair value investments	3.8	6.3
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Financials \| Level 2 Inputs
Investment securities
Fair value investments	235.8	259.5
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Communications \| Fair Value
Investment securities
Fair value investments	225.8	226.3
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Communications \| Level 2 Inputs
Investment securities
Fair value investments	225.8	226.3
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Basic materials \| Fair Value
Investment securities
Fair value investments	195.7	125.3
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Basic materials \| Level 2 Inputs
Investment securities
Fair value investments	195.7	125.3
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Utilities \| Fair Value
Investment securities
Fair value investments	140.1	106.7
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Utilities \| Level 2 Inputs
Investment securities
Fair value investments	140.1	106.7
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Energy \| Fair Value
Investment securities
Fair value investments	155.8	151.5
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Energy \| Level 2 Inputs
Investment securities
Fair value investments	155.8	151.5
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Technology \| Fair Value
Investment securities
Fair value investments	24.5	22.1
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Technology \| Level 2 Inputs
Investment securities
Fair value investments	24.5	22.1
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Diversified \| Fair Value
Investment securities
Fair value investments	3.5
Fair value measured on a recurring basis \| Debt securities issued by corporations \| Diversified \| Level 2 Inputs
Investment securities
Fair value investments	3.5
Fair value measured on a recurring basis \| Municipal obligations \| Fair Value
Investment securities
Fair value investments	2.7	3.3
Fair value measured on a recurring basis \| Municipal obligations \| Level 2 Inputs
Investment securities
Fair value investments	2.7	3.3
Fair value measured on a recurring basis \| Mortgage-backed and asset-backed securities \| Fair Value
Investment securities
Fair value investments	3,222.9	2,071.7
Fair value measured on a recurring basis \| Mortgage-backed and asset-backed securities \| Level 2 Inputs
Investment securities
Fair value investments	3,207.8	2,014.7
Fair value measured on a recurring basis \| Mortgage-backed and asset-backed securities \| Level 3 Inputs
Investment securities
Fair value investments	15.1	57.0
Fair value measured on a recurring basis \| Foreign government, agency and provincial obligations \| Fair Value
Investment securities
Fair value investments	589.2	1,046.5
Fair value measured on a recurring basis \| Foreign government, agency and provincial obligations \| Level 1 Inputs
Investment securities
Fair value investments	65.7	82.6
Fair value measured on a recurring basis \| Foreign government, agency and provincial obligations \| Level 2 Inputs
Investment securities
Fair value investments	523.5	963.9
Fair value measured on a recurring basis \| Non-cumulative perpetual preference shares \| Fair Value
Investment securities
Fair value investments	78.8	87.9
Fair value measured on a recurring basis \| Non-cumulative perpetual preference shares \| Level 2 Inputs
Investment securities
Fair value investments	15.0	16.5
Fair value measured on a recurring basis \| Non-cumulative perpetual preference shares \| Level 3 Inputs
Investment securities
Fair value investments	63.8	71.4
Fair value measured on a recurring basis \| Common equity securities \| Fair Value
Investment securities
Fair value investments	755.0	667.0
Fair value measured on a recurring basis \| Common equity securities \| Level 1 Inputs
Investment securities
Fair value investments	667.4	537.9
Fair value measured on a recurring basis \| Common equity securities \| Level 2 Inputs
Investment securities
Fair value investments	55.3	57.9
Fair value measured on a recurring basis \| Common equity securities \| Level 3 Inputs
Investment securities
Fair value investments	32.3	71.2
Fair value measured on a recurring basis \| Common equity securities \| Consumer \| Fair Value
Investment securities
Fair value investments	188.8	123.3
Fair value measured on a recurring basis \| Common equity securities \| Consumer \| Level 1 Inputs
Investment securities
Fair value investments	188.5	122.5
Fair value measured on a recurring basis \| Common equity securities \| Consumer \| Level 2 Inputs
Investment securities
Fair value investments	0.3	0.8
Fair value measured on a recurring basis \| Common equity securities \| Financials \| Fair Value
Investment securities
Fair value investments	219.2	221.6
Fair value measured on a recurring basis \| Common equity securities \| Financials \| Level 1 Inputs
Investment securities
Fair value investments	185.8	152.6
Fair value measured on a recurring basis \| Common equity securities \| Financials \| Level 2 Inputs
Investment securities
Fair value investments	1.5	1.2
Fair value measured on a recurring basis \| Common equity securities \| Financials \| Level 3 Inputs
Investment securities
Fair value investments	31.9	67.8
Fair value measured on a recurring basis \| Common equity securities \| Basic materials \| Fair Value
Investment securities
Fair value investments	121.0	98.8
Fair value measured on a recurring basis \| Common equity securities \| Basic materials \| Level 1 Inputs
Investment securities
Fair value investments	119.9	97.1
Fair value measured on a recurring basis \| Common equity securities \| Basic materials \| Level 2 Inputs
Investment securities
Fair value investments	1.1	1.7
Fair value measured on a recurring basis \| Common equity securities \| Utilities \| Fair Value
Investment securities
Fair value investments	42.0	47.6
Fair value measured on a recurring basis \| Common equity securities \| Utilities \| Level 1 Inputs
Investment securities
Fair value investments	41.8	44.6
Fair value measured on a recurring basis \| Common equity securities \| Utilities \| Level 2 Inputs
Investment securities
Fair value investments	0.2
Fair value measured on a recurring basis \| Common equity securities \| Utilities \| Level 3 Inputs
Investment securities
Fair value investments		3.0
Fair value measured on a recurring basis \| Common equity securities \| Energy \| Fair Value
Investment securities
Fair value investments	72.6	60.2
Fair value measured on a recurring basis \| Common equity securities \| Energy \| Level 1 Inputs
Investment securities
Fair value investments	72.6	60.2
Fair value measured on a recurring basis \| Common equity securities \| Technology \| Fair Value
Investment securities
Fair value investments	25.8	31.8
Fair value measured on a recurring basis \| Common equity securities \| Technology \| Level 1 Inputs
Investment securities
Fair value investments	25.8	30.4
Fair value measured on a recurring basis \| Common equity securities \| Technology \| Level 2 Inputs
Investment securities
Fair value investments		1.4
Fair value measured on a recurring basis \| Common equity securities \| Other: \| Fair Value
Investment securities
Fair value investments	85.6	83.7
Fair value measured on a recurring basis \| Common equity securities \| Other: \| Level 1 Inputs
Investment securities
Fair value investments	33.0	30.5
Fair value measured on a recurring basis \| Common equity securities \| Other: \| Level 2 Inputs
Investment securities
Fair value investments	52.2	52.8
Fair value measured on a recurring basis \| Common equity securities \| Other: \| Level 3 Inputs
Investment securities
Fair value investments	0.4	0.4
Fair value measured on a recurring basis \| Short-term investments \| Fair Value
Investment securities
Fair value investments	846.0	975.3
Fair value measured on a recurring basis \| Short-term investments \| Level 1 Inputs
Investment securities
Fair value investments	846.0	878.7
Fair value measured on a recurring basis \| Short-term investments \| Level 2 Inputs
Investment securities
Fair value investments		96.6
Fair value measured on a recurring basis \| Convertible fixed maturities \| Fair Value
Investment securities
Fair value investments	143.8	143.0
Fair value measured on a recurring basis \| Convertible fixed maturities \| Level 2 Inputs
Investment securities
Fair value investments	143.8	143.0
Fair value measured on a recurring basis \| Other long-term investments \| Fair Value
Investment securities
Fair value investments	268.3	330.2
Fair value measured on a recurring basis \| Other long-term investments \| Level 3 Inputs
Investment securities
Fair value investments	268.3	330.2
Carrying value of investment accounted for using the equity method	$ 33.0	$ 41.9

Investment Securities (Details 6) - Debt securities issued by corporations - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010
Investment securities
Fair value investments	$ 2,135.1	$ 2,178.0
AA
Investment securities
Fair value investments	206.8	210.0
A
Investment securities
Fair value investments	802.8	833.7
BBB
Investment securities
Fair value investments	1,110.8	1,109.1
BB
Investment securities
Fair value investments	6.2	24.5
Other rating
Investment securities
Fair value investments	$ 8.5	$ 0.7

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents investment securities as of the balance sheet date which may include marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References + Details

Investment Securities (Details 7) $ in Millions	12 Months Ended
Investment Securities (Details 7) $ in Millions	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)
Fair Value
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	$ 8,346.8	$ 7,901.6
Level 2 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	6,088.2	5,477.4
Mortgage-backed and asset-backed securities \| Fair Value
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	3,222.9	2,071.7
Mortgage-backed and asset-backed securities \| Level 2 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	3,207.8	2,014.7
Mortgage-backed and asset-backed securities \| Level 3 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	15.1	57.0
Mortgage-backed securities \| Fair Value
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	2,474.1	1,595.2
Mortgage-backed securities \| Level 2 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	2,459.0	1,538.2
Mortgage-backed securities \| Level 3 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	15.1	57.0
Agency mortgage-backed securities \| Fair Value
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	2,114.3	1,417.6
Agency mortgage-backed securities \| Level 2 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	2,114.3	1,376.7
Agency mortgage-backed securities \| Level 3 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments		40.9
GNMA \| Fair Value
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	1,365.8	1,143.6
GNMA \| Level 2 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	1,365.8	1,102.7
GNMA \| Level 3 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments		40.9
FNMA \| Fair Value
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	712.6	234.9
FNMA \| Level 2 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	712.6	234.9
FHLMC \| Fair Value
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	35.9	39.1
FHLMC \| Level 2 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	35.9	39.1
Non-agency mortgage-backed securities \| 2003
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	3.3
Non-agency mortgage-backed securities \| 2006
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	23.0
Non-agency mortgage-backed securities \| 2007
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	43.8
Non-agency mortgage-backed securities \| 2009
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	11.2
Non-agency mortgage-backed securities \| 2010
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	12.8
Non-agency mortgage-backed securities \| 2011
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	265.7
Non-agency mortgage-backed securities \| Fair Value
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	359.8	177.6
Non-agency mortgage-backed securities \| Level 2 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	344.7	161.5
Non-agency mortgage-backed securities \| Level 3 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	15.1	16.1
Non-agency residential mortgage-backed securities (RMBS) \| Super Senior
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	35.7
Non-agency residential mortgage-backed securities (RMBS) \| Super Senior \| Prime
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	20.5
Non-agency residential mortgage-backed securities (RMBS) \| Super Senior \| Non-prime
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	15.2
Non-agency residential mortgage-backed securities (RMBS) \| Senior
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	47.4
Non-agency residential mortgage-backed securities (RMBS) \| Senior \| Prime
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	46.7
Non-agency residential mortgage-backed securities (RMBS) \| Senior \| Non-prime
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	0.7
Non-agency residential mortgage-backed securities (RMBS) \| 2003
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	3.3
Non-agency residential mortgage-backed securities (RMBS) \| 2006
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	23.0
Non-agency residential mortgage-backed securities (RMBS) \| 2007
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	26.4
Non-agency residential mortgage-backed securities (RMBS) \| 2010
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	10.5
Non-agency residential mortgage-backed securities (RMBS) \| 2011
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	19.9
Non-agency residential mortgage-backed securities (RMBS) \| Fair Value
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	83.1	90.6
Non-agency residential mortgage-backed securities (RMBS) \| Fair Value \| Prime
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	67.2
Non-agency residential mortgage-backed securities (RMBS) \| Fair Value \| Non-prime
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	15.9
Non-agency residential mortgage-backed securities (RMBS) \| Level 2 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	68.0	74.5
Non-agency residential mortgage-backed securities (RMBS) \| Level 3 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	15.1	16.1
Non-agency commercial mortgage-backed securities (CMBS) \| Super Senior
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	64.1
Non-agency commercial mortgage-backed securities (CMBS) \| Senior
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	212.6
Non-agency commercial mortgage-backed securities (CMBS) \| 2007
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	17.4
Non-agency commercial mortgage-backed securities (CMBS) \| 2009
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	11.2
Non-agency commercial mortgage-backed securities (CMBS) \| 2010
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	2.3
Non-agency commercial mortgage-backed securities (CMBS) \| 2011
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	245.8
Non-agency commercial mortgage-backed securities (CMBS) \| Fair Value
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	276.7	87.0
Non-agency commercial mortgage-backed securities (CMBS) \| Level 2 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	$ 276.7	87.0
Non-agency commercial mortgage-backed securities (CMBS) \| Maximum
Mortgage-backed, Asset-backed Securities Abstract
Percentage of underlying loans reported as non-performing	2.00%
Fixed Rate CMBS
Mortgage-backed, Asset-backed Securities Abstract
Average basis points of subordination (as a percent)	20
Fixed Rate CMBS \| Super Senior
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	$ 46.7
Fixed Rate CMBS \| Senior
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	202.6
Fixed Rate CMBS \| Fair Value
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	$ 249.3
Floating Rate CMBS
Mortgage-backed, Asset-backed Securities Abstract
Average basis points of subordination (as a percent)	45
Floating Rate CMBS \| Super Senior
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	$ 17.4
Floating Rate CMBS \| Senior
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	10.0
Floating Rate CMBS \| Fair Value
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	27.4
Other asset-backed securities \| Fair Value
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	748.8	476.5
Other asset-backed securities \| Level 2 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	748.8	476.5
Credit card receivables \| Fair Value
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	380.6	248.3
Credit card receivables \| Level 2 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	380.6	248.3
Vehicle receivables \| Fair Value
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	345.6	228.1
Vehicle receivables \| Level 2 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	345.6	228.1
Other \| Fair Value
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	22.6	0.1
Other \| Level 2 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Fair value investments	$ 22.6	$ 0.1

Investment Securities (Details 8) $ in Millions	Dec. 31, 2011 USD ($) entity	Dec. 31, 2010 USD ($)
Hedge and private equity funds included in other long-term investments
Other long-term investments
Largest single fund investment	$ 27.4	$ 49.2
Other long-term investments	254.2	315.5
Unfunded Commitments	$ 81.5	88.7
Hedge funds
Other long-term investments
Number of investments \| entity	16
Other long-term investments	$ 125.3	155.7
Distributions outstanding	3.3
Redemption requests	2.2
Hedge funds \| 30-59 days notice
Other long-term investments
Other long-term investments	44.4
Hedge funds \| 60-89 days notice
Other long-term investments
Other long-term investments	32.1
Hedge funds \| 90-119 days notice
Other long-term investments
Other long-term investments	27.3
Hedge funds \| 120+ days notice
Other long-term investments
Other long-term investments	21.5
Hedge funds \| Monthly
Other long-term investments
Other long-term investments	6.5
Hedge funds \| Monthly \| 120+ days notice
Other long-term investments
Other long-term investments	6.5
Hedge funds \| Quarterly
Other long-term investments
Other long-term investments	74.6
Hedge funds \| Quarterly \| 30-59 days notice
Other long-term investments
Other long-term investments	27.5
Hedge funds \| Quarterly \| 60-89 days notice
Other long-term investments
Other long-term investments	27.0
Hedge funds \| Quarterly \| 90-119 days notice
Other long-term investments
Other long-term investments	20.1
Hedge funds \| Semi-annual
Other long-term investments
Other long-term investments	19.6
Hedge funds \| Semi-annual \| 60-89 days notice
Other long-term investments
Other long-term investments	5.1
Hedge funds \| Semi-annual \| 120+ days notice
Other long-term investments
Other long-term investments	14.5
Hedge funds \| Annual
Other long-term investments
Other long-term investments	24.6
Hedge funds \| Annual \| 30-59 days notice
Other long-term investments
Other long-term investments	16.9
Hedge funds \| Annual \| 90-119 days notice
Other long-term investments
Other long-term investments	7.2
Hedge funds \| Annual \| 120+ days notice
Other long-term investments
Other long-term investments	0.5
Long/short equity
Other long-term investments
Other long-term investments	48.8	50.4
Long/short credit & distressed
Other long-term investments
Other long-term investments	32.3	34.1
Long diversified strategies
Other long-term investments
Other long-term investments	16.9	25.2
Long/short equity REIT
Other long-term investments
Other long-term investments	14.5	24.0
Long/short equity activist
Other long-term investments
Other long-term investments	12.3	16.9
Long bank loan
Other long-term investments
Other long-term investments	$ 0.5	5.1
Private equity funds
Other long-term investments
Number of investments \| entity	32
Other long-term investments	$ 128.9	159.8
Unfunded Commitments	81.5	88.7
Private equity funds \| 1-3 years
Other long-term investments
Other long-term investments	42.9
Private equity funds \| 5-10 years
Other long-term investments
Other long-term investments	79.8
Private equity funds \| >10 years
Other long-term investments
Other long-term investments	6.2
Energy infrastructure and services
Other long-term investments
Other long-term investments	28.0	24.2
Unfunded Commitments	9.9	10.8
Distressed residential real estate
Other long-term investments
Other long-term investments	27.4	49.2
Multi-sector
Other long-term investments
Other long-term investments	26.9	26.0
Unfunded Commitments	8.2	10.6
Private equity secondaries
Other long-term investments
Other long-term investments	11.3	10.4
Unfunded Commitments	4.0	4.4
Real estate
Other long-term investments
Other long-term investments	9.5	9.1
Unfunded Commitments	3.3	4.6
International multi-sector, Europe
Other long-term investments
Other long-term investments	7.8	10.5
Unfunded Commitments	4.7	5.3
Manufacturing/Industrial
Other long-term investments
Other long-term investments	6.2	17.9
International multi-sector, Asia
Other long-term investments
Other long-term investments	3.6	4.9
Unfunded Commitments	2.6	2.7
Insurance
Other long-term investments
Other long-term investments	3.5	3.9
Unfunded Commitments	41.3	41.3
Venture capital fund
Other long-term investments
Other long-term investments	2.4	2.2
Unfunded Commitments	0.5	1.0
Healthcare
Other long-term investments
Other long-term investments	2.3	1.5
Unfunded Commitments	7.0	$ 8.0
Federal affordable housing development fund
Other long-term investments
Unfunded Commitments	10.1
Investment in a tax advantaged federal affordable housing development fund included in other long-term investments	$ 21.8

Investment Securities (Details 9) $ in Millions	12 Months Ended
Investment Securities (Details 9) $ in Millions	Dec. 31, 2011 USD ($) security	Dec. 31, 2010 USD ($)
AutoOne
Investment securities
Investments reclassified to assets held for sale	$ 111.8
Level 1 Inputs
Investment securities
Fair value investments	1,879.1	$ 1,894.4
Total realized and unrealized gains (losses)	(1.4)
Foreign currency gains (losses) through OCI and other revenue	4.6
Amortization/Accretion	2.3
Purchases	10,653.6
Sales	(10,674.4)
Level 2 Inputs
Investment securities
Fair value investments	6,088.2	5,477.4
Total realized and unrealized gains (losses)	113.2
Foreign currency gains (losses) through OCI and other revenue	(76.1)
Amortization/Accretion	(54.2)
Purchases	8,905.6
Sales	(8,528.7)
Transfers in	269.2
Transfers out	(18.2)
Securities of level 3 measurements recategorized as level 2 measurements	$ 269.2
Number of securities with unobservable inputs (in securities) \| security	2
Level 3 Inputs
Investment securities
Number of securities with unobservable inputs (in securities) \| security	10
Difference in value between securities determined using the industry standard pricing models and securities based upon quoted prices provided by a third party	$ 1.6
Fair Value
Investment securities
Fair value investments	8,346.8	7,901.6
Total realized and unrealized gains (losses)	118.5
Foreign currency gains (losses) through OCI and other revenue	(79.3)
Amortization/Accretion	(51.6)
Purchases	19,851.0
Sales	(19,393.4)
Transfers in	287.4
Transfers out	(287.4)
Fixed maturity investments. \| Level 3 Inputs
Investment securities
Fair value investments	78.9	128.4
Total realized and unrealized gains (losses)	(8.1)
Foreign currency gains (losses) through OCI and other revenue	(4.4)
Amortization/Accretion	0.3
Purchases	213.7
Transfers in	18.2
Transfers out	(269.2)
Common equity securities \| Level 3 Inputs
Investment securities
Fair value investments	32.3	71.2
Total realized and unrealized gains (losses)	(4.7)
Foreign currency gains (losses) through OCI and other revenue	1.6
Purchases	19.7
Sales	(55.5)
Other long-term investments \| Level 3 Inputs
Investment securities
Fair value investments	268.3	330.2
Total realized and unrealized gains (losses)	19.5
Foreign currency gains (losses) through OCI and other revenue	(5.0)
Purchases	58.4
Sales	(134.8)
Carrying value of investment accounted for using the equity method	$ 33.0	$ 41.9

Investment Securities (Details 10) - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010
Investments held on deposit or as collateral
Investments held in trusts	$ 100.2	$ 314.1
Fair value of deposits with certain insurance regulatory agencies	313.4	352.6
Fair value, investment-related liabilities	$ 68.1	$ 77.8

- Definition

Carrying value as of the balance sheet date of obligations incurred from short sales.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Audit and Accounting Guide (AAG)
-Number AAG-BRD
-Chapter 4
-Paragraph 38
-IssueDate 2006-05-01
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Audit and Accounting Guide (AAG)
-Number AAG-BRD
-Chapter 7
-Paragraph 19
-IssueDate 2006-05-01
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Audit and Accounting Guide (AAG)
-Number AAG-BRD
-Chapter 7
-Paragraph 2
-IssueDate 2006-05-01
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Audit and Accounting Guide (AAG)
-Number AAG-BRD
-Chapter 7
-Paragraph 40
-IssueDate 2006-05-01
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 320
-Section 35
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6475908&loc=d3e42429-110968

+ Details

Debt (Details) $ in Millions	1 Months Ended							3 Months Ended	12 Months Ended
Debt (Details) $ in Millions	Apr. 30, 2011 USD ($)	Sep. 30, 2010 USD ($)	Jun. 30, 2010 USD ($)	Mar. 31, 2007 USD ($)	Dec. 31, 2005 USD ($) Y	Mar. 31, 2004 USD ($) Y	May 31, 2003 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2008 USD ($)	Dec. 31, 2007 USD ($)	Dec. 31, 2005 USD ($) Y	Dec. 30, 2011 USD ($) Y	Aug. 12, 2011 USD ($)	Sep. 15, 2010 USD ($)	May 30, 2003 USD ($)
Debt Instrument
Total debt								$ 671.2	$ 671.2	$ 818.8
Interest expense, inclusive of amortization of issuance costs									55.2	57.3	$ 70.8
Aggregate purchase price of senior notes purchased and retired									161.6	197.3	63.1
After-tax change in the fair value of the interest rate swap									92.9	127.0	(158.4)
Interest paid									59.0	64.1	69.8
Repayment of debt, principal										14.0	242.8
Contractual repayments of debt
Due in two to three years								269.9	269.9
Due in four to five years								2.1	2.1
Due after five years								400.0	400.0
Total								$ 672.0	$ 672.0
OneBeacon Ltd.
Debt Instrument
Minimum voting interest in subsidiary (as a percent)								50.00%	50.00%
OBH Senior Notes
Debt Instrument
Debt instrument at face value							$ 700.0	$ 269.9	$ 269.9	419.9
Unamortized original issue discount								(0.1)	(0.1)	(0.3)
Total debt								$ 269.8	$ 269.8	419.6
Percentage of par value at which debt was issued							99.70%
Cash received from debt issuance							$ 693.4
Debt issue costs																		$ 7.3
Underwriting discount							$ 4.5
Interest rate ( as a percent)								5.875%	5.875%
Effective yield (as a percent)								6.00%	6.00%
Expenses related to issuance, including underwriting fees																		$ 7.3
Interest expense, inclusive of amortization of issuance costs									$ 20.5	29.5	38.1
OBH Senior Notes \| Tender offer
Debt Instrument
Aggregate principal amount of senior notes purchased and retired	$ 150.0		$ 156.4							29.7
Aggregate purchase price of senior notes purchased and retired	161.6		165.4							30.8
Loss on retirement of debt	$ 12.0		$ 9.6							1.2
OBH Senior Notes \| Repurchase and retirement of debt
Debt Instrument
Aggregate principal amount of senior notes purchased and retired										1.1
Aggregate purchase price of senior notes purchased and retired										1.1
OBH Senior Notes \| OneBeacon Ltd.
Debt Instrument
Guarantee fee basis points per annum on outstanding principal amount of debt (as a percent)								0.25%	0.25%
Maximum guarantee fee (as a percent)								4.25%	4.25%
SIG Senior Notes
Debt Instrument
Debt instrument at face value				$ 400.0				$ 400.0	$ 400.0	400.0
Unamortized original issue discount								(0.7)	(0.7)	(0.8)
Total debt								$ 399.3	$ 399.3	399.2
Percentage of par value at which debt was issued				99.715%
Cash received from debt issuance				$ 392.0
Debt issue costs				3.6
Underwriting discount				2.6
Interest rate ( as a percent)								6.375%	6.375%
Effective yield (as a percent)								6.49%	6.49%
Expenses related to issuance, including underwriting fees				3.6
Interest expense, inclusive of amortization of issuance costs									$ 26.1	26.1	26.1
Loss from interest rate hedge recorded in other comprehensive income				$ 2.4
Unamortized loss remaining in accumulated other comprehensive income								$ 1.2	$ 1.2
Prior WTM Bank Facility
Debt Instrument
Total commitment under revolving credit facility																$ 475.0
Mortgage Note \| OneBeacon Ltd.
Debt Instrument
Mortgage note outstanding					$ 40.8									$ 40.8
Debt Instrument Term (in years) \| Y					18									18
Variable interest rate basis					30-day LIBOR
Amount paid to settle interest rate swap											7.4
Mortgage Note \| OneBeacon Ltd. \| Interest rate swap
Debt Instrument
Gain (loss) recorded on settlement of derivative, pre tax											7.4
Gain (loss) recorded on settlement of derivative, after tax											4.8
After-tax change in the fair value of the interest rate swap											$ 2.0
Sierra Note
Debt Instrument
Interest expense, inclusive of amortization of issuance costs								$ 5.5
Sierra Note \| Sirius Group
Debt Instrument
Debt instrument at face value						$ 62.0
Interest rate ( as a percent)						4.00%
Debt Instrument Term (in years) \| Y						6
Amount of debt available for adjustment						$ 58.0
Increase decrease in the principal of the note issued						$ (29.0)				1.9		$ (5.2)	$ 9.1	$ (22.8)
Undisputed amounts, principal and interest																	$ 42.8
Repayment of debt, principal		$ 33.0
Repayment of debt, accrued interest		9.8
Reimbursement of debt repayment by Berkshire		36.7
Reimbursement of debt repayment by Berkshire, principal portion		33.0
Reimbursement of debt prepayment by Berkshire, accrued interest portion		$ 3.7
Atlantic Specialty Note \| OneBeacon Ltd.
Debt Instrument
Interest rate ( as a percent)						5.20%
Total commitment under revolving credit facility						$ 20.0
Debt Instrument Term (in years) \| Y						10
Repayment of debt, principal										$ 14.0
Interest rate if outstanding principal amount of debt exceeds specified limit (as a percent)						3.60%
Specified limit of outstanding principal amount of debt						$ 15.0
Old Lyme
Debt Instrument
Total debt															$ 2.1
Percentage of principal amount of debt subject to upward or downward adjustments															50.00%
Principal amount of purchase note															$ 6.0
Debt Instrument Term (in years) \| Y															5
WTM Bank Facility
Debt Instrument
Total commitment under revolving credit facility																$ 375.0

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended							12 Months Ended
Income Taxes (Details) - USD ($) $ in Millions	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Current tax benefit (expense):
U.S. federal								$ 39.5	$ 52.4	$ (40.0)
State								(2.5)	(2.2)	(1.5)
Non-U.S.								5.1	(9.1)	(2.7)
Total current tax benefit (expense)								42.1	41.1	(44.2)
Deferred tax benefit (expense):
U.S. federal								(34.1)	(61.6)	(139.0)
Non-U.S.								114.7	3.6	(31.0)
Total deferred tax benefit (expense)								80.6	(58.0)	(170.0)
Total income tax benefit (expense)	$ 124.6	$ 0.6	$ (10.0)	$ 7.7	$ (6.6)	$ (11.7)	$ 1.4	$ 122.7	$ (16.9)	$ (214.2)

Income Taxes (Details 2) - USD ($) $ in Millions	3 Months Ended							12 Months Ended
Income Taxes (Details 2) - USD ($) $ in Millions	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Taxes
U.S. statutory rate (as a percent)								35.00%
Tax (expense) benefit at the U.S. statutory rate								$ (21.5)	$ (53.6)	$ (279.1)
Differences in taxes resulting from:
Change in valuation allowance								128.2	2.6	53.7
Non-U.S. earnings, net of foreign taxes								6.2	22.8	(1.2)
Tax reserve adjustments								4.3	(2.8)	8.8
Tax exempt interest and dividends								2.9	2.3	1.7
Tax rate change enacted in Luxembourg								1.2	2.8
Withholding tax								0.2	(0.2)	(0.7)
Purchase of subsidiaries									4.5
Sale of subsidiaries									4.3
Other, net								1.2	0.4	2.6
Total income tax benefit (expense)	$ 124.6	$ 0.6	$ (10.0)	$ 7.7	$ (6.6)	$ (11.7)	$ 1.4	122.7	(16.9)	(214.2)
Non-U.S. component of pre-tax income								65.4	74.4	221.0
Tax Payments and Receipts
Net income tax payments to (receipts from) national governments, total								$ 12.5	$ (47.0)	$ (17.5)

Income Taxes (Details 3) - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010
Deferred income tax assets related to:
Non-U.S. net operating loss carryforwards	$ 504.0	$ 545.4
Loss reserve discount	114.2	142.4
U.S. federal and state net operating loss carryforwards	102.7	103.6
Incentive compensation	43.4	36.9
Unearned premiums	41.2	37.3
U.S. tax credit carryforwards	13.5	12.0
Deferred compensation	11.4	13.1
Loss on sale of AutoOne	10.4
Pension and benefit accruals	8.0	4.3
Accrued interest	3.5	0.5
Investment basis differences	1.6	7.3
Fixed assets	(0.1)	4.8
Other items	9.5	14.1
Total gross deferred income tax assets	863.3	921.7
Less: valuation allowances	(232.7)	(385.8)
Total net deferred income tax assets	630.6	535.9
Deferred income tax liabilities related to:
Safety reserve	369.6	378.5
Deferred acquisition costs	48.8	41.5
Net unrealized investment gains	34.8	55.8
Purchase accounting	0.7	2.1
Intangible assets	(0.1)	0.1
Other items	5.4	(0.8)
Total deferred income tax liabilities	459.2	477.2
Net deferred tax asset (liability)	$ 171.4	$ 58.7

Income Taxes (Details 4) $ in Millions	3 Months Ended
Income Taxes (Details 4) $ in Millions	Dec. 31, 2011 USD ($) Y subsidary	Dec. 31, 2010 USD ($)
Valuation Allowance
Valuation allowance	$ 232.7	$ 385.8
Tax benefit from the release of a valuation allowance against a deferred tax asset in a Luxembourg	129.5
Net operating losses in Luxembourg subsidiaries
Valuation Allowance
Valuation allowance	$ 225.5	379.6
Number of Luxembourg domiciled subsidiaries related to which tax benefit is recorded from release of valuation allowances against deferred tax assets \| subsidary	2
Term of longest dated note of notes having staggered maturity dates (in years) \| Y	30
U.S. losses and other federal deferred tax benefits
Valuation Allowance
Valuation allowance	$ 6.9	$ 6.2

Income Taxes (Details 5) - USD ($) $ in Millions	12 Months Ended
Income Taxes (Details 5) - USD ($) $ in Millions	Dec. 31, 2010	Dec. 31, 2011
Summary of net operating loss and capital loss carryforwards, the expiration dates and the deferred tax assets thereon
2013-2017		$ 2.4
2018-2022		18.7
2023-2032		305.7
No expiration date		1,751.0
Total		2,077.8
Net deferred tax assets
Gross deferred tax asset		606.7
Valuation allowance		(227.6)
Net deferred tax asset		379.1
Foreign tax credit carryforwards, subject to expiration		8.8
Low-income housing tax credit		2.0
Alternative minimum tax credit carryforwards, not subject to expiration		2.7
United States
Summary of net operating loss and capital loss carryforwards, the expiration dates and the deferred tax assets thereon
2013-2017		2.4
2018-2022		18.7
2023-2032		305.7
Total		326.8
Net deferred tax assets
Gross deferred tax asset		102.7
Valuation allowance		(1.8)
Net deferred tax asset		100.9
Net operating loss carryforwards, subject to an annual limitation		29.1
Luxembourg
Summary of net operating loss and capital loss carryforwards, the expiration dates and the deferred tax assets thereon
No expiration date		1,740.3
Total		1,740.3
Net deferred tax assets
Gross deferred tax asset		501.2
Valuation allowance		(225.5)
Net deferred tax asset		275.7
Net operating loss carryforwards expected to be utilized		999.7
Deferred tax benefit due to increase in its NOLs	$ 11.9
Sweden
Summary of net operating loss and capital loss carryforwards, the expiration dates and the deferred tax assets thereon
No expiration date		10.7
Total		10.7
Net deferred tax assets
Gross deferred tax asset		2.8
Valuation allowance		(0.3)
Net deferred tax asset		$ 2.5

Income Taxes (Details 6) - USD ($) $ in Millions	12 Months Ended
Income Taxes (Details 6) - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Taxes
Percentage of Likelihood for Realization of Benefit Upon Ultimate Settlement	50.00%
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance at year beginning	$ 95.8	$ 96.9	$ 86.8
Increase in prior year tax positions	1.2		56.4
Decrease in prior year tax positions		(6.1)
Tax positions taken during the current year	(20.4)	5.4	16.4
Lapse in statute of limitations	(10.5)		(1.2)
Settlements with tax authorities	(0.6)	(0.4)	(61.5)
Balance at year end	65.5	95.8	96.9
Unrecognized tax benefit recognition including interest and penalties, if recognized, would effect income tax expense	16.4
Tax positions for which ultimate deductibility is highly certain but the timing of deductibility is uncertain	49.1
Interest (benefit) expense, net of any tax benefit	0.6	1.9	(4.0)
Accrued interest, net of any tax benefit	6.8	6.2
Permanent Differences
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance at year beginning	14.5	13.9	61.4
Increase in prior year tax positions		0.5	7.2
Decrease in prior year tax positions	(0.9)
Tax positions taken during the current year		0.4
Lapse in statute of limitations	(3.4)		(1.0)
Settlements with tax authorities	(0.6)	(0.3)	(53.7)
Balance at year end	9.6	14.5	13.9
Temporary Differences
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance at year beginning	75.1	78.7	17.1
Increase in prior year tax positions	0.1		46.1
Decrease in prior year tax positions		(8.5)
Tax positions taken during the current year	(20.4)	5.0	16.4
Lapse in statute of limitations	(5.7)
Settlements with tax authorities		(0.1)	(0.9)
Balance at year end	49.1	75.1	78.7
Interest and Penalties
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance at year beginning	6.2	4.3	8.3
Increase in prior year tax positions	2.0	1.9	3.1
Lapse in statute of limitations	(1.4)		(0.2)
Settlements with tax authorities			(6.9)
Balance at year end	$ 6.8	$ 6.2	$ 4.3

Income Taxes (Details 7) - IRS $ in Millions	1 Months Ended
Income Taxes (Details 7) - IRS $ in Millions	Jan. 31, 2011 M	Jan. 05, 2011 USD ($)	Oct. 14, 2009 USD ($)
Tax Examinations
Additional income tax from assessment of tax years 2003 and 2004			$ 24.9
Total assessment from assessment of tax years 2003 and 2004 including interest, withholding tax and utilization of credits			51.9
Income tax benefit from the settlement of the 2003 through 2004 tax examination			$ 17.8
Total assessment from assessment of tax years 2005 and 2006 including interest, withholding tax and utilization of credits		$ 19.6
Reasonably possible period during which resolution could occur (in months) \| M	12

Variable Annuity Reinsurance and Weather Derivatives (Details) $ in Millions, ¥ in Billions	3 Months Ended								12 Months Ended
	Dec. 31, 2011 USD ($)	Sep. 30, 2011 USD ($)	Jun. 30, 2011 USD ($)	Mar. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Sep. 30, 2010 USD ($)	Jun. 30, 2010 USD ($)	Mar. 31, 2010 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2011 JPY (¥)	Dec. 31, 2010 USD ($)
Variable annuity reinsurance
Total guarantee value												$ 3,000.0	¥ 233.7
Collective account values of underlying variable annuities as a percentage of the guarantee value												78.00%	78.00%
Pre-tax operating results of WM Life Re
Change in fair value of derivatives, included in other revenues									$ 92.9	$ 127.0	$ (158.4)
Total revenues	$ 593.6	$ 501.3	$ 553.6	$ 529.6	$ 552.8	$ 551.0	$ 670.8	$ 792.1	2,178.1	2,566.7	3,443.3
General and administrative expenses									(175.3)	(155.1)	(197.4)
Pre-tax loss	58.0	$ 1.2	$ 36.1	(33.7)	95.6	$ 75.2	$ 5.9	$ (23.6)	61.6	153.1	797.2
Changes in derivative instruments
Balance of assets at the beginning of the period				347.5					347.5
Realized and unrealized gains (losses)									92.9	127.0	(158.4)
Balance of assets at the end of the period	290.4				347.5				290.4	347.5
Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values of instruments
Realized and unrealized derivative gains (losses) recognized in other revenues									92.9	127.0	(158.4)
Carrying value	290.4			347.5	347.5				290.4	347.5		$ 290.4		$ 347.5
Fixed income/Interest rate
Pre-tax operating results of WM Life Re
Change in fair value of derivatives, included in other revenues									8.9	17.6	8.0
Changes in derivative instruments
Balance of assets at the beginning of the period				43.9					43.9
Realized and unrealized gains (losses)									8.9	17.6	8.0
Balance of assets at the end of the period	31.1				43.9				31.1	43.9
Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values of instruments
Realized and unrealized derivative gains (losses) recognized in other revenues									8.9	17.6	8.0
Carrying value	31.1			43.9	43.9				31.1	43.9		31.1		43.9
Foreign exchange
Changes in derivative instruments
Balance of assets at the beginning of the period				225.3					225.3
Balance of assets at the end of the period					225.3					225.3
Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values of instruments
Carrying value				225.3	225.3				225.3	225.3				225.3
Equity
Changes in derivative instruments
Balance of assets at the beginning of the period				78.3					78.3
Balance of assets at the end of the period					78.3					78.3
Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values of instruments
Carrying value				78.3	78.3				78.3	78.3				78.3
Weather Derivatives
Weather Derivatives
Net losses recognized on weather derivatives and weather contingent derivatives portfolio											2.6
Level 1 Inputs
Pre-tax operating results of WM Life Re
Change in fair value of derivatives, included in other revenues									10.7
Changes in derivative instruments
Realized and unrealized gains (losses)									10.7
Sales/settlements									(6.6)
Balance of assets at the end of the period	4.1								4.1
Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values of instruments
Realized and unrealized derivative gains (losses) recognized in other revenues									10.7
Carrying value	4.1								4.1			4.1
Level 2 Inputs
Pre-tax operating results of WM Life Re
Change in fair value of derivatives, included in other revenues									67.7
Changes in derivative instruments
Balance of assets at the beginning of the period				72.2					72.2
Realized and unrealized gains (losses)									67.7
Sales/settlements									(100.7)
Balance of assets at the end of the period	39.2				72.2				39.2	72.2
Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values of instruments
Realized and unrealized derivative gains (losses) recognized in other revenues									67.7
Carrying value	39.2			72.2	72.2				72.2	72.2		39.2		72.2
Level 3 Inputs
Pre-tax operating results of WM Life Re
Change in fair value of derivatives, included in other revenues									14.5
Changes in variable annuity liabilities
Balance of liabilities at the beginning of the period				(610.2)					(610.2)
Realized and unrealized gains (losses)									(158.3)
Balance of liabilities at the end of the period	(768.5)				(610.2)				(768.5)	(610.2)
Changes in derivative instruments
Balance of assets at the beginning of the period				275.3					275.3
Purchases									5.0
Realized and unrealized gains (losses)									14.5
Sales/settlements									(47.7)
Balance of assets at the end of the period	247.1				275.3				247.1	275.3
Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values of instruments
Realized and unrealized derivative gains (losses) recognized in other revenues									14.5
Carrying value	247.1			275.3	275.3				275.3	275.3		247.1		275.3
Fair Value
Pre-tax operating results of WM Life Re
Change in fair value of derivatives, included in other revenues									92.9
Changes in derivative instruments
Balance of assets at the beginning of the period				347.5					347.5
Purchases									5.0
Realized and unrealized gains (losses)									92.9
Sales/settlements									(155.0)
Balance of assets at the end of the period	290.4				347.5				290.4	347.5
Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values of instruments
Realized and unrealized derivative gains (losses) recognized in other revenues									92.9
Carrying value	290.4			$ 347.5	$ 347.5				347.5	347.5		290.4		347.5
Variable annuity reinsurance
Pre-tax operating results of WM Life Re
Change in fair value of variable annuity liability, included in other revenues									7.2	47.7	22.4
Variable annuity reinsurance \| Level 1 Inputs \| Foreign exchange \| Cash \| Citigroup
Pre-tax operating results of WM Life Re
Change in fair value of derivatives, included in other revenues									29.5	144.6	(69.5)
Changes in derivative instruments
Realized and unrealized gains (losses)									29.5	144.6	(69.5)
Balance of assets at the end of the period	161.3								161.3
Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values of instruments
Realized and unrealized derivative gains (losses) recognized in other revenues									29.5	144.6	(69.5)
Carrying value	161.3								161.3			161.3
Variable annuity reinsurance \| Level 1 Inputs \| Equity \| Cash \| Citigroup
Pre-tax operating results of WM Life Re
Change in fair value of derivatives, included in other revenues									54.5	(35.2)	(96.9)
Changes in derivative instruments
Realized and unrealized gains (losses)									54.5	(35.2)	(96.9)
Balance of assets at the end of the period	98.0								98.0
Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values of instruments
Realized and unrealized derivative gains (losses) recognized in other revenues									54.5	(35.2)	(96.9)
Carrying value	$ 98.0								98.0			98.0
WM Life Re
Pre-tax operating results of WM Life Re
Fees, included in other revenues									32.5	30.2	28.5
Change in fair value of variable annuity liability, included in other revenues									(156.5)	(223.5)	77.1
Change in fair value of derivatives, included in other revenues									92.9	127.0	(158.4)
Foreign exchange, included in other revenues									15.1	21.4	(3.9)
Other investment income and gain (loss)									(0.9)	(0.9)	(1.4)
Total revenues									(16.9)	(45.8)	(58.1)
Change in fair value of variable annuity death benefit liabilities, included in other expenses									(1.8)	(6.0)	9.3
Death benefit claims paid, included in other expenses									(3.8)	(2.7)	(2.2)
General and administrative expenses									(4.7)	(6.3)	(5.6)
Pre-tax loss									(27.2)	(60.8)	(56.6)
Changes in derivative instruments
Realized and unrealized gains (losses)									92.9	127.0	(158.4)
Realized and unrealized derivative gains (losses) recognized in other revenues and carrying values of instruments
Realized and unrealized derivative gains (losses) recognized in other revenues									$ 92.9	$ 127.0	$ (158.4)
Credit risk on derivative instruments
OTC derivative instruments												295.4		351.5
Collateral held												73.2		101.0
Collateral provided												83.0		25.3
Cash and short-term investments held and posted as collateral to its reinsurance counterparties												485.3		326.0
Net exposure to credit losses on fair value of OTC instruments												$ 305.2		275.8
Number of creditworthiness ratings												21	21
Adjustments for counterparty credit risk												$ (9.1)		(4.0)
WM Life Re \| Citigroup
Credit risk on derivative instruments
Net exposure to credit losses on fair value of OTC instruments												67.7
WM Life Re \| Royal Bank of Scotland
Credit risk on derivative instruments
Net exposure to credit losses on fair value of OTC instruments												82.5
WM Life Re \| Bank of America
Credit risk on derivative instruments
Net exposure to credit losses on fair value of OTC instruments												54.2
WM Life Re \| JP Morgan Chase
Credit risk on derivative instruments
Net exposure to credit losses on fair value of OTC instruments												34.2
WM Life Re \| Nomura
Credit risk on derivative instruments
Net exposure to credit losses on fair value of OTC instruments												31.9
WM Life Re \| Barclays
Credit risk on derivative instruments
Net exposure to credit losses on fair value of OTC instruments												25.1
WM Life Re \| Goldman Sachs
Credit risk on derivative instruments
Net exposure to credit losses on fair value of OTC instruments												9.6
WM Life Re \| Cash
Credit risk on derivative instruments
Collateral held												(453.5)		(291.1)
WM Life Re \| Fixed maturity investments.
Credit risk on derivative instruments
Collateral held												(31.2)		(3.3)
Collateral provided														(48.6)
WM Life Re \| Short-term investments
Credit risk on derivative instruments
Collateral held												(0.6)		(31.6)
Collateral provided												$ (73.2)		$ (52.4)

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Basic and diluted earnings per share numerators (in millions):
Net income from continuing operations attributable to White Mountains' common shareholders									$ 122.6	$ 93.1	$ 497.8
Allocation of income for participating unvested restricted common shares									(1.1)	(1.1)	(4.8)
Dividends paid on participating restricted common shares									(0.1)	(0.1)	(0.6)
Total allocation to restricted common shares									(1.2)	(1.2)	(5.4)
Net income attributable to White Mountains' common shareholders, net of restricted share amounts									121.4	91.9	492.4
Undistributed net earnings:
Net income attributable to White Mountains' common shareholders, net of restricted common share amounts									121.4	91.9	492.4
Dividends paid net of restricted common share amounts									(7.9)	(8.7)	(8.3)
Total undistributed net earnings, net of restricted common share amounts									113.5	83.2	484.1
Net income attributable to White Mountains' common shareholders, net of restricted share amounts									$ 122.6	$ 93.1	$ 497.8
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period (in shares)									7,881,000	8,548,400	8,849,400
Average unvested restricted common shares (in shares)									(69,400)	(97,300)	(85,300)
Basic earnings per share denominator (in shares)									7,811,600	8,451,100	8,764,100
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period (in shares)									7,881,000	8,548,400	8,849,400
Average unvested restricted common shares (in shares)									(69,400)	(97,300)	(85,300)
Average outstanding dilutive options to acquire common shares (in shares)										500	1,500
Diluted earnings per share denominator (in shares)									7,811,600	8,451,600	8,765,600
Basic earnings per share (in dollars):
Net income attributable to White Mountains' common shareholders	$ 16.54	$ 1.81	$ 1.66	$ (3.82)	$ 9.77	$ 5.58	$ 0.21	$ (4.14)	$ 15.56	$ 10.89	$ 56.25
Dividends declared and paid (in dollars per share)									(1.00)	(1.00)	(1.00)
Undistributed earnings (in dollars per share)									14.56	9.89	55.25
Diluted earnings per share (in dollars)
Net income (loss) attributable to White Mountains' common shareholders (in dollars per share)	$ 16.54	$ 1.81	$ 1.66	$ (3.82)	9.77	$ 5.58	$ 0.21	$ (4.14)	15.56	10.89	56.24
Dividends declared and paid (in dollars per share)									(1.00)	(1.00)	(1.00)
Undistributed earnings (in dollars per share)									$ 14.56	$ 9.89	$ 55.25
Common shares issuable upon exercise of incentive options (in shares)										1,200	5,280
Average strike price of options (in dollars per share)					$ 189.31					$ 189.31	$ 183.03

Retirement and Postretirement Plans (Details)	12 Months Ended
Retirement and Postretirement Plans (Details)	Dec. 31, 2011 Y
Retirement and Postretirement Plans
Period of service after which plan gets vested (in years)	5

Retirement and Postretirement Plans (Details 2) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 110.2	$ 117.1
Service cost	0.8	0.8	$ 0.5
Interest cost	5.2	6.0	6.5
Settlement gain	(0.6)	(2.2)
Special termination benefits expense	0.8	1.9	1.2
Assumption changes	7.7	6.6
Actuarial (gain) loss	(0.3)	(1.5)
Benefits and expenses paid with plan assets, net of participant contributions	(8.4)	(15.9)
Benefits paid directly by OneBeacon	(2.4)	(2.6)
Projected benefit obligation at end of year	113.0	110.2	117.1
Change in plan assets:
Fair value of plan assets at beginning of year	133.0	130.2
Actual return on plan assets	(3.8)	18.7
Benefits and expenses paid with plan assets, net of participant contributions	(8.4)	(15.9)
Fair value of plan assets at end of year	120.8	133.0	$ 130.2
Funded status at end of year	7.8	22.8
Amounts recognized in the financial statements
Net balance recorded in other assets	34.3	50.3
Net balance recorded in other liabilities	(26.5)	(27.5)
Net amount accrued in the financial statements	7.8	22.8
Qualified Plan
Change in plan assets:
Fair value of plan assets at beginning of year	132.7
Fair value of plan assets at end of year	120.5	$ 132.7
Funded status at end of year	34.3
OneBeacon segment
Change in plan assets:
Funded status at end of year	26.5
Amount set aside under irrevocable rabbi trust for the benefit of Plan participants	$ 12.2

Retirement and Postretirement Plans (Details 3) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Information for the Non-qualified Plan, which had accumulated benefit obligations in excess of plan assets
Projected benefit obligation		$ 26.5	$ 27.5
Accumulated benefit obligation		26.5	27.5
Information for the Qualified Plan, which had accumulated benefit obligations less than plan assets
Projected benefit obligation		86.5	82.7
Accumulated benefit obligation		86.5	82.7
Fair value of plan net assets		120.8	133.0
Amounts recognized in accumulated other comprehensive income (loss) on a pre-tax basis noncontrolling interest
Accumulated other comprehensive income (loss) beginning balance	$ (16.7)	0.5	(8.5)
Increase (decrease) in accumulated other comprehensive income (loss):
Amortization of net actuarial losses recognized during the year		0.5	0.6
Net actuarial (losses) gains occurring during the year		(18.2)	8.4
Other adjustments		0.5
Accumulated other comprehensive (loss) income ending balance		$ (16.7)	$ 0.5
Amount expected to be amortized from accumulated other comprehensive income (loss) into net periodic benefit cost during 2012	$ 0.7

Retirement and Postretirement Plans (Details 4) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Components of net periodic benefit cost (income)
Service cost	$ 0.8	$ 0.8	$ 0.5
Interest cost	5.2	6.0	6.5
Expected return on plan assets	(7.6)	(7.3)	(6.3)
Amortization of unrecognized loss	0.5	0.6	1.6
Net periodic pension cost (income) before settlements, curtailments and special termination benefits	(1.1)	0.1	2.3
Settlement loss (gain)	0.5	(0.1)
Special termination benefits expense	0.8	1.9	1.2
Total net periodic benefit cost	$ 0.2	$ 1.9	$ 3.5
Weighted average discount rate assumptions used to determine benefit obligations
Discount rate (as a percent)	4.38%	4.94%
Weighted average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)	4.94%	5.16%
Expected long-term rate of return on plan assets (as a percent)	5.75%	5.75%

Retirement and Postretirement Plans (Details 5) - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Plan Assets
Fair value	$ 120.8	$ 133.0	$ 130.2
Qualified Plan
Plan Assets
Asset allocations (as a percent)	100.00%	100.00%
Fair value	$ 120.5	$ 132.7
Qualified Plan \| Level 1 Inputs
Plan Assets
Fair value	75.3	76.5
Qualified Plan \| Level 2 Inputs
Plan Assets
Fair value	$ 45.2	$ 56.2
Qualified Plan \| Fixed maturity investments
Plan Assets
Asset allocations (as a percent)	2.00%	0.40%
Fair value	$ 2.4	$ 0.5
Qualified Plan \| Fixed maturity investments \| Level 2 Inputs
Plan Assets
Fair value	$ 2.4	$ 0.5
Qualified Plan \| Common equity securities
Plan Assets
Asset allocations (as a percent)	59.90%	56.10%
Fair value	$ 72.2	$ 74.5
Qualified Plan \| Common equity securities \| Level 1 Inputs
Plan Assets
Fair value	$ 72.2	$ 74.5
Qualified Plan \| Convertible fixed maturities
Plan Assets
Asset allocations (as a percent)	35.50%	42.00%
Fair value	$ 42.8	$ 55.7
Qualified Plan \| Convertible fixed maturities \| Level 2 Inputs
Plan Assets
Fair value	$ 42.8	$ 55.7
Qualified Plan \| Cash
Plan Assets
Asset allocations (as a percent)	2.60%	1.50%
Fair value	$ 3.1	$ 2.0
Qualified Plan \| Cash \| Level 1 Inputs
Plan Assets
Fair value	$ 3.1	$ 2.0

Retirement and Postretirement Plans (Details 6) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Retirement and Postretirement Plans
Anticipated contribution to the non-Qualified Plan in 2012	$ 2.4
Expected Benefit Payments
2012	4.6
2013	5.0
2014	5.3
2015	5.7
2016	6.0
2017-2021	$ 34.0
Employee savings plan
Percentage of employer's matching contribution for first six percent of salary	50.00%
Maximum percentage of salary eligible for employer's fifty percent matching contribution	6.00%
Total expense for the plan during the period	$ 3.0	$ 3.8	$ 4.6
Post-employment benefit liability	$ 6.7	$ 7.9

Employee Share-Based Incentive Compensation Plans (Details)	1 Months Ended		12 Months Ended
	May 31, 2011 shares	May 31, 2010 USD ($)	Dec. 31, 2011 USD ($) multiplier Y shares	Dec. 31, 2010 USD ($) shares	Dec. 31, 2009 USD ($) shares
Expense Amortized
Accrued expense at the beginning of period			$ 157,400,000
Accrued expense at the end of the period			$ 187,900,000	$ 157,400,000
OneBeacons employee stock ownership plan
Share-based compensation arrangement by share-based payment award
Annual base contribution in common shares provided to participants expressed as a percentage of salary (as a percent)			3.00%
Social Security wage base amount, maximum			$ 106,800
Percentage of variable contribution for participants not otherwise eligible to receive certain other OneBeacon benefits			6.00%
Sirius Group's profit sharing plan
Share-based compensation arrangement by share-based payment award
Percentage of variable contribution for participants under Sirius Group's profit sharing plan			7.00%
Performance shares
Share-based compensation arrangement by share-based payment award
Multiplier of number of shares initially granted to determine payout, low end of range \| multiplier			0
Multiplier of number of shares initially granted to determine payout, high end of range \| multiplier			2
Performance cycle (in years) \| Y			3
Non-Qualified Options
Expense Amortized
Expense (income) recognized		$ 8,700,000	$ 100,000	$ 11,900,000	$ 5,400,000
WTM Incentive Plan and WTM Phantom Share Plans \| Performance shares
Share-based compensation arrangement by share-based payment award
Vesting period (in years)			3 years
Target Performance Share activity
Beginning of period (in shares) \| shares			163,184	172,454	156,373
Shares expired (in shares) \| shares			(51,131)	(49,127)	(48,573)
New grants (in shares) \| shares			37,675	47,880	69,092
Cancellations and change in assumed forfeitures (in shares) \| shares			336	(8,023)	(4,438)
Ending of period (in shares) \| shares			150,064	163,184	172,454
Expense Amortized
Accrued expense at the beginning of period			$ 29,400,000	$ 12,200,000	$ 4,200,000
Assumed forfeitures and cancellations			(900,000)	(700,000)	(300,000)
Expense (income) recognized			37,600,000	17,900,000	8,300,000
Accrued expense at the end of the period			$ 66,100,000	$ 29,400,000	$ 12,200,000
Target vesting percentage of performance shares			100.00%
Additional compensation cost that would be recognized if all outstanding performance shares vested			$ 19,300,000
OneBeacon Long-Term Incentive Plan \| Performance shares
Target Performance Share activity
Beginning of period (in shares) \| shares			1,464,295	2,224,215	2,212,313
Shares expired (in shares) \| shares			(936,150)	(889,594)	(137,400)
New grants (in shares) \| shares			194,900	270,691	379,085
Cancellations and change in assumed forfeitures (in shares) \| shares	(35,000)		(80,378)	(141,017)	(229,783)
Ending of period (in shares) \| shares			642,667	1,464,295	2,224,215
Expense Amortized
Accrued expense at the beginning of period			$ 18,500,000	$ 15,100,000	$ 4,600,000
Payments and deferrals			(10,500,000)	(4,600,000)
Assumed forfeitures and cancellations			(500,000)	(2,200,000)	(500,000)
Expense (income) recognized			2,200,000	10,200,000	11,000,000
Accrued expense at the end of the period			$ 9,700,000	$ 18,500,000	$ 15,100,000
Target vesting percentage of performance shares			100.00%
Additional compensation cost that would be recognized if all outstanding performance shares vested			$ 2,300,000
OneBeacon Long-Term Incentive Plan \| Performance shares \| Performance cycle 2007-2009
Expense Amortized
Percentage of target achieved by former employees as a result of the Commercial Lines and Personal Lines Transactions				14.20%
OneBeacon Long-Term Incentive Plan \| Performance shares \| Performance cycle 2007-2008
Expense Amortized
Percentage of target achieved by former employees as a result of the Commercial Lines and Personal Lines Transactions					1.40%
OneBeacon Long-Term Incentive Plan \| Performance shares \| Performance cycle 2008-2010
Expense Amortized
Percentage of target achieved by former employees as a result of the Commercial Lines and Personal Lines Transactions			68.50%
OneBeacon Long-Term Incentive Plan \| Non-Qualified Options
Share-based compensation arrangement by share-based payment award
Vesting period (in years)			Third, fourth and fifth anniversaries
Expense Amortized
Accrued expense at the beginning of period			$ 4,500,000	$ 3,600,000	$ 2,500,000
Expense (income) recognized			500,000	900,000	1,100,000
Accrued expense at the end of the period			$ 5,000,000	$ 4,500,000	$ 3,600,000

Employee Share-Based Incentive Compensation Plans (Details 2) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Share-based compensation arrangement by share-based payment award
Accrued incentive compensation	$ 187.9	$ 157.4
WTM Incentive Plan \| Performance shares
Share-based compensation arrangement by share-based payment award
Target Performance Shares Outstanding (in shares)	140,975
Accrued Expense	$ 60.3
Assumed forfeitures (in shares)	(3,524)
Assumed forfeitures	$ (1.6)
Target Performance Shares Outstanding	137,451
Accrued incentive compensation	$ 58.7
WTM Incentive Plan \| Performance cycle 2009-2011 \| Performance shares
Share-based compensation arrangement by share-based payment award
Target Performance Shares Outstanding (in shares)	60,410
Accrued Expense	$ 42.6
Growth in intrinsic business value per share, target (as a percent)	10.00%
Growth in intrinsic business value per share, maximum (as a percent)	17.00%
Percentage of payout for maximum growth target percentage	200.00%
Growth in intrinsic business value per share, minimum (as a percent)	3.00%
WTM Incentive Plan \| Performance cycle 2010-2012 \| Performance shares
Share-based compensation arrangement by share-based payment award
Target Performance Shares Outstanding (in shares)	42,890
Accrued Expense	$ 10.9
Growth in intrinsic business value per share, target (as a percent)	11.00%
Growth in intrinsic business value per share, maximum (as a percent)	18.00%
Percentage of payout for maximum growth target percentage	200.00%
Growth in intrinsic business value per share, minimum (as a percent)	4.00%
WTM Incentive Plan \| Performance cycle 2011-2013 \| Performance shares
Share-based compensation arrangement by share-based payment award
Target Performance Shares Outstanding (in shares)	37,675
Accrued Expense	$ 6.8
Growth in intrinsic business value per share, target (as a percent)	10.00%
Growth in intrinsic business value per share, maximum (as a percent)	17.00%
Percentage of payout for maximum growth target percentage	200.00%
Growth in intrinsic business value per share, minimum (as a percent)	3.00%
WTM Phantom Share Plans \| Performance shares
Share-based compensation arrangement by share-based payment award
Target Performance Shares Outstanding (in shares)	12,937
Accrued Expense	$ 7.5
Assumed forfeitures (in shares)	(324)
Assumed forfeitures	$ (0.1)
Target Performance Shares Outstanding	12,613
Accrued incentive compensation	$ 7.4
WTM Phantom Share Plans \| Performance cycle 2009-2011 \| Performance shares
Share-based compensation arrangement by share-based payment award
Target Performance Shares Outstanding (in shares)	7,947
Accrued Expense	$ 6.0
WTM Phantom Share Plans \| Performance cycle 2010-2012 \| Performance shares
Share-based compensation arrangement by share-based payment award
Target Performance Shares Outstanding (in shares)	4,990
Accrued Expense	$ 1.5
WTM Phantom Share Plans \| Performance cycle 2011-2013 \| Performance shares
Share-based compensation arrangement by share-based payment award
Assumed forfeitures (in shares)	0
Assumed forfeitures	$ 0.0
OneBeacon Long-Term Incentive Plan \| Performance shares
Share-based compensation arrangement by share-based payment award
Target Performance Shares Outstanding (in shares)	652,562
Accrued Expense	$ 9.8
Assumed forfeitures (in shares)	(9,895)
Assumed forfeitures	$ (0.1)
Target Performance Shares Outstanding	642,667	1,464,295	2,224,215	2,212,313
Accrued incentive compensation	$ 9.7	$ 18.5	$ 15.1	$ 4.6
Growth in intrinsic business value per share, target (as a percent)	11.00%	12.00%
Growth in intrinsic business value per share, maximum (as a percent)	18.00%	19.00%
Percentage of payout for maximum growth target percentage	200.00%	200.00%
Growth in intrinsic business value per share, minimum (as a percent)	4.00%	5.00%
OneBeacon Long-Term Incentive Plan \| Performance cycle 2011-2013 \| Performance shares
Share-based compensation arrangement by share-based payment award
Target Performance Shares Outstanding (in shares)	151,563
Accrued Expense	$ 0.9
OneBeacon Long-Term Incentive Plan \| Performance cycle 2009-2011 \| Performance shares
Share-based compensation arrangement by share-based payment award
Target Performance Shares Outstanding (in shares)	256,751
Accrued Expense	$ 7.7
OneBeacon Long-Term Incentive Plan \| Performance cycle 2010-2012 \| Performance shares
Share-based compensation arrangement by share-based payment award
Target Performance Shares Outstanding (in shares)	244,248
Accrued Expense	$ 1.2

Employee Share-Based Incentive Compensation Plans (Details 3) $ in Millions	3 Months Ended				12 Months Ended
	Jun. 30, 2011 shares	Mar. 31, 2011 USD ($) shares	Mar. 31, 2010 USD ($) shares	Mar. 31, 2007 shares	Dec. 31, 2011 USD ($) shares	Dec. 31, 2010 USD ($) installments shares	Dec. 31, 2009 USD ($) shares
Activity in plan
Issued (in shares)					27,250	19,750	47,820
WTM Restricted Stock
Activity in plan
Beginning of period (in shares)		46,250	91,900		46,250	91,900	53,200
Issued (in shares)	250	27,000			27,250	19,750	47,100
Vested (in shares)					(1,500)	(65,150)	(8,400)
Cancellations and change in assumed forfeitures (in shares)						(250)
Ending of period (in shares)					72,000	46,250	91,900
Unamortized grant date fair value
Unamortized grant date fair value, beginning balance \| $		$ 14.1	$ 23.7		$ 14.1	$ 23.7	$ 24.2
Issued \| $					9.9	6.7	9.6
Forfeited \| $						(0.1)
Modified \| $						(3.3)
Expense recognized \| $					(10.7)	(12.9)	(10.1)
Unamortized grant date fair value, ending balance \| $					$ 13.3	$ 14.1	$ 23.7
WTM Restricted Stock \| Chairman and CEO
Activity in plan
Issued (in shares)				15,000
Unamortized grant date fair value
Number of installments in which the shares vest (in installments) \| installments						3
Restricted shares that will vest in December, 2012
Activity in plan
Issued (in shares)			19,750
Restricted shares cliff that will vest in November, 2010
Activity in plan
Issued (in shares)							2,500
Restricted shares cliff that will vest in December, 2010
Activity in plan
Issued (in shares)							40,100
Restricted shares that vest in three equal annual installments beginning in December 2011
Activity in plan
Issued (in shares)							4,500

Employee Share-Based Incentive Compensation Plans (Details 4) $ / shares in Units, $ in Millions	1 Months Ended			12 Months Ended
	May 31, 2010 USD ($) Y	Jan. 31, 2007 USD ($) Y $ / shares shares	Feb. 29, 2000 shares	Dec. 31, 2011 USD ($) Y shares	Dec. 31, 2010 USD ($) $ / shares shares	Dec. 31, 2009 USD ($) $ / shares shares	May 26, 2010 USD ($) $ / shares shares
Incentive option activity
Exercised (in shares)				0	(2,400)	(3,600)
Non-Qualified Options
Assumptions of stock-based compensation awards
Expense recognized \| $	$ 8.7			$ 0.1	$ 11.9	$ 5.4
Non-Qualified Options \| Before amendments
Share-based compensation arrangement by share-based payment award
Stock-based awards, contractual term (in years)		P7Y
Vesting period (in years)		5 years
Initial exercise price (in dollars per share) \| $ / shares		$ 650
Fair value \| $		$ 27.2					$ 3.5
Annual percentage increase in exercise price		5.00%
Assumptions of stock-based compensation awards
Expected volatility (as a percent)	41.00%	29.70%
Risk-free rate (as a percent)	1.57%	1.10%
Risk-free rate less the Escalator (as a percent)		4.70%
Forfeiture (as a percent)	0.00%	0.00%
Expected dividend yield (as a percent)	0.32%	1.40%
Expected life (in years) \| Y	3.67	7
Unamortized amount at modification date \| $							9.0
Granted (in shares)		200,000
Non-Qualified Options \| Amended Grant
Share-based compensation arrangement by share-based payment award
Fair value \| $							$ 4.4
Assumptions of stock-based compensation awards
Expected volatility (as a percent)	34.00%
Risk-free rate (as a percent)	2.43%
Forfeiture (as a percent)	0.00%
Expected dividend yield (as a percent)	0.32%
Expected life (in years) \| Y	6.67
Extension of contractual term (in years) \| Y	3
Exercise price (in dollar per share) \| $ / shares							$ 742
Number of shares extinguished (in shares)							75,000
Threshold for in-the-money potential \| $	$ 100.0
Limit on value of in-the-money options over $100 million (as a percent)	50.00%
Amount amortized into income prior to the modification \| $							$ 18.2
Incentive Options
Share-based compensation arrangement by share-based payment award
Vesting period (in years)				10 years
Assumptions of stock-based compensation awards
Expected volatility (as a percent)				18.50%
Risk-free rate (as a percent)				6.40%
Expected life (in years) \| Y				10
Granted (in shares)			81,000
Percentage increase to exercise price				6.00%
Incentive option activity
Opening balance - outstanding Options (in shares)					2,400	6,000
Exercised (in shares)					(2,400)	(3,600)
Ending balance - outstanding Options (in shares)						2,400
Opening balance exercisable Incentive Options (in shares)					2,400	3,000
Vested (in shares)						3,000
Ending balance exercisable Incentive Options (in shares)						2,400
Intrinsic value of Incentive options exercised \| $					$ 0.3	$ 0.5
Exercise price - Outstanding options at the beginning of the period (in dollars per share) \| $ / shares					$ 188.43	$ 177.76
Exercise price - outstanding Options at the end of the period (in dollars per share) \| $ / shares						$ 188.43

Employee Share-Based Incentive Compensation Plans (Details 5) $ / shares in Units, $ in Millions	1 Months Ended		12 Months Ended
	May 31, 2010 USD ($)	Nov. 30, 2006 Y $ / shares shares	Dec. 31, 2011 USD ($) shares	Dec. 31, 2010 USD ($) shares	Dec. 31, 2009 USD ($) shares	Nov. 16, 2010 $ / shares	May 27, 2008 $ / shares	Mar. 31, 2008 $ / shares
Expense Amortized
Accrued expense at the beginning of period			$ 157.4
Accrued expense at the end of the period			187.9	$ 157.4
Non-Qualified Options
Expense Amortized
Expense recognized	$ 8.7		$ 0.1	$ 11.9	$ 5.4
OneBeacon Long-Term Incentive Plan \| Non-Qualified Options
Share-based compensation arrangement by share-based payment award
Granted (in shares) \| shares		1,420,000
Options vesting period (in years)			Third, fourth and fifth anniversaries
Expiration period of award (in years)		P5.5Y
Expected volatility (as a percent)		30.00%
Risk-free rate (as a percent)		4.60%
Forfeiture (as a percent)		5.00%
Expected dividend yield (as a percent)		3.40%
Expected life (in years) \| Y		5.5
Initial exercise price (in dollars per share) \| $ / shares		$ 30.00
Amended exercise price of option (in dollars per share) \| $ / shares						$ 25.47	$ 27.97
OneBeacon special dividend (in dollars per share) \| $ / shares						$ 2.50		$ 2.03
Target options outstanding
Opening balance - outstanding Options (in shares) \| shares			768,652	1,015,610	1,237,872
Forfeitures and cancellations (in shares) \| shares			(27,782)	(37,044)	(222,262)
Vested and expired (in shares) \| shares				(209,914)
Ending balance - outstanding Options (in shares) \| shares			740,870	768,652	1,015,610
Expense Amortized
Accrued expense at the beginning of period			$ 4.5	$ 3.6	$ 2.5
Expense recognized			0.5	0.9	1.1
Accrued expense at the end of the period			$ 5.0	$ 4.5	$ 3.6

Employee Share-Based Incentive Compensation Plans (Details 6) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	May 31, 2011 Y shares	Mar. 31, 2008 shares	Dec. 31, 2011 USD ($) shares	Dec. 31, 2010 USD ($) shares	Dec. 31, 2009 USD ($) shares	May 25, 2011 shares	Dec. 31, 2008 shares
Qualified Plan
Share-based compensation arrangement by share-based payment award
Variable contribution amounts earned by eligible participants of the KSOP as a percentage of salary			2.00%	0.00%	4.00%
Compensation expense to pay benefits and allocate common shares \| $			$ 6.3	$ 3.0	$ 11.0
Total common shares outstanding owned by the plans (as a percent)			3.00%	3.00%
OneBeacon Long-Term Incentive Plan \| Restricted Stock Units, RSU
Share-based compensation arrangement by share-based payment award
New grants (in shares)		116,270
Proportion of award vests on each of Nov 9, 2009, 2010 and 2011		0.33
Minimum percentage of growth in book value per share for vesting each tranche of units		4.00%
Expense recognized \| $			$ 0.1	$ 0.5	$ 0.6
OneBeacon Long-Term Incentive Plan \| OneBeacon Restricted Stock
Share-based compensation arrangement by share-based payment award
Noncontrolling interest expense recognized for the dilution of ownership \| $			$ 7.7
OneBeacon Long-Term Incentive Plan \| OneBeacon Restricted Stock \| Chairman and CEO
Share-based compensation arrangement by share-based payment award
One Beacon Restricted shares issued (in shares)						630,000
Numerator value of the ratio in which restricted shares vest	1
Denominator value of the ratio in which restricted shares vest	4
Period in which performance share awards will be reduced by a similar number of shares (in years) \| Y	5
OneBeacon Long-Term Incentive Plan \| Performance shares
Share-based compensation arrangement by share-based payment award
New grants (in shares)			194,900	270,691	379,085
Expense recognized \| $			$ 2.2	$ 10.2	$ 11.0
Outstanding (in shares)			642,667	1,464,295	2,224,215		2,212,313
Forfeiture of performance shares granted for the 2011 - 2013 performance cycle (in shares)	35,000		80,378	141,017	229,783

Common Shareholders' Equity (Details) $ / shares in Units, $ in Millions	12 Months Ended			62 Months Ended
	Dec. 31, 2011 USD ($) auction $ / shares shares	Dec. 31, 2010 USD ($) $ / shares shares	Dec. 31, 2009 USD ($) $ / shares shares	Dec. 31, 2011 USD ($) shares	Aug. 26, 2010 shares	Nov. 17, 2006 shares
Common Shares Repurchased and Retired
Authorized repurchase of common shares (in shares)						1,000,000
Additional authorized repurchase of common shares (in shares)					600,000
Shares remaining under share repurchase authorization	188,297			188,297
Common shares repurchased and retired during the period (in shares)	313,967	677,125		1,411,703
Value of common shares repurchased and retired during the period \| $	$ 114.2	$ 222.0		$ 537.5
Shares repurchased by the entity that were not subject to the Share Repurchase Plan (in shares)	189	10,186	1,113
Common Shares Issued
Common shares issued, total (in shares)	29,432	23,050	52,420
Shares issued in satisfaction of options exercised (in shares)	0	2,400	3,600
Restricted shares issued to key management personnel (in shares)	27,250	19,750	47,820
Shares issued to directors (in shares)	2,182	900	1,000
Dividends on Common Shares
Cash dividends declared and paid \| $	$ 8.0	$ 8.8	$ 8.9
Dividends declared and paid (in dollars per share) \| $ / shares	$ 1.00	$ 1.00	$ 1.00
Tender Offer
Common Shares Repurchased and Retired
Number of modified Dutch auction \| auction	2
Common shares repurchased and retired during the period (in shares)	332,346
Value of each common share repurchased and retired during the period (in dollars per share) \| $ / shares	$ 417.55
Value of common shares repurchased and retired during the period \| $	$ 138.8

Statutory Capital and Surplus (Details)	1 Months Ended	12 Months Ended
Statutory Capital and Surplus (Details)	Nov. 30, 2011 USD ($)	Dec. 31, 2011 USD ($) rating	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2011 SEK (kr) rating	Dec. 31, 2001 rating
Disclosure of statutory capital and surplus
Other long-term investments		$ 301,300,000	$ 372,100,000
Other long-term investments outside of Sirius America and Sirius International		301,300,000	372,100,000
Safety Reserve
Amount of Deferred Tax Liabilities on Safety Reserve		$ 369,600,000	378,500,000
Swedish tax rate (as a percent)		26.30%
Swedish kronor
Disclosure of statutory capital and surplus
Exchange rate \| kr					6.86
OneBeacon
Disclosure of statutory capital and surplus
Statutory net income (loss)		$ 119,600,000	257,200,000	$ 210,500,000
Statutory capital and surplus		1,000,000,000	1,100,000,000
Number of ratings in A.M. Best ratings \| rating						15
Sirius group \| Dividends resulting from reorganization
Disclosure of statutory capital and surplus
Distributions made		425,000,000
Other Operations
Disclosure of statutory capital and surplus
Net unrestricted cash, short-term investments and fixed maturity investments		1,554,300,000
Equity securities		316,600,000
Other long-term investments		33,400,000
Other long-term investments outside of Sirius America and Sirius International		$ 33,400,000
Regulated insurance operations \| OneBeacon
Disclosure of statutory capital and surplus
Percentage of prior year statutory surplus that may be paid as dividends without prior approval of regulatory authorities		10.00%
Amount available for dividend distributions without prior approval of regulatory authorities		$ 103,000,000
Unassigned funds		700,000,000
Unregulated insurance operations \| OneBeacon
Disclosure of statutory capital and surplus
Distributions made		4,300,000
Net unrestricted cash, short-term investments and fixed maturity investments		183,000,000
Common equity securities and other long-term investments		30,000,000
OneBeacon Ltd.
Disclosure of statutory capital and surplus
Common equity securities and other long-term investments		30,000,000
OneBeacon Ltd. \| OneBeacon
Disclosure of statutory capital and surplus
Represents dividends paid by OneBeacon's unregulated insurance operating subsidiaries to their immediate parent		150,000,000
Net unrestricted cash, short-term investments and fixed maturity investments		16,900,000
OneBeacon Ltd. \| OneBeacon \| Ordinary dividends
Disclosure of statutory capital and surplus
Distributions made		79,700,000
OneBeacon Ltd. \| OneBeacon \| Special dividends
Disclosure of statutory capital and surplus
Distributions made		95,100,000
OneBeacon Ltd. \| OneBeacon \| Dividend received by White Mountains
Disclosure of statutory capital and surplus
Distributions made		$ 132,000,000
Sirius International
Disclosure of statutory capital and surplus
Number of ratings in A.M. Best ratings \| rating		15			15
Sirius International \| Sirius group
Disclosure of statutory capital and surplus
Statutory capital and surplus		$ 2,100,000,000
Distributions made		594,000,000
Increase in unrestricted statutory surplus due to reorganization	$ 436,300,000
2010 pre-tax income transferred to parent company		74,000,000
2011 pre-tax income intended to be transferred to parent company		80,000,000
Unrestricted statutory surplus available for distribution		514,900,000
Dividends intended to pay to the immediate parent		177,000,000
Safety Reserve
Amount of safety reserve		1,400,000,000			kr 9,600,000,000
Amount of Deferred Tax Liabilities on Safety Reserve		369,600,000
Sirius International \| Sirius group \| Sweden
Disclosure of statutory capital and surplus
Restricted equity		1,600,000,000
Sirius America \| Sirius group
Disclosure of statutory capital and surplus
Statutory net income (loss)		101,400,000	70,200,000	$ 46,900,000
Statutory capital and surplus		$ 533,700,000	742,600,000
Percentage of statutory surplus most recently reported to regulatory authorities that may be paid as dividends without prior approval of regulatory authorities		10.00%
Amount available for dividend distributions without prior approval of regulatory authorities		$ 53,400,000
Earned surplus		75,500,000
Central National
Disclosure of statutory capital and surplus
Statutory net income (loss)		100,000	1,600,000
Statutory capital and surplus		13,400,000	$ 15,000,000
Scandinavian Re \| Sirius group
Disclosure of statutory capital and surplus
Statutory capital and surplus		27,600,000
White Shoals Re \| Sirius group
Disclosure of statutory capital and surplus
Statutory capital and surplus		15,400,000
Sirius Group
Disclosure of statutory capital and surplus
Distributions made		169,000,000
Sirius Group \| Sirius group
Disclosure of statutory capital and surplus
Net unrestricted cash, short-term investments and fixed maturity investments		75,100,000
Other long-term investments		16,300,000
Other long-term investments outside of Sirius America and Sirius International		16,300,000
Sirius Group \| Sirius group \| Ordinary dividends
Disclosure of statutory capital and surplus
Distributions made		177,000,000
WM Life Re \| Other Operations
Disclosure of statutory capital and surplus
Statutory capital and surplus		26,400,000
WM Advisors
Disclosure of statutory capital and surplus
Distributions made		5,000,000
WM Advisors \| Other Operations
Disclosure of statutory capital and surplus
Net unrestricted cash, short-term investments and fixed maturity investments		$ 25,800,000

Segment Information (Details) $ in Millions	3 Months Ended								12 Months Ended
Segment Information (Details) $ in Millions	Dec. 31, 2011 USD ($)	Sep. 30, 2011 USD ($)	Jun. 30, 2011 USD ($)	Mar. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Sep. 30, 2010 USD ($)	Jun. 30, 2010 USD ($)	Mar. 31, 2010 USD ($)	Dec. 31, 2011 USD ($) transaction	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2008 USD ($)
Segment reporting information
Earned insurance and reinsurance premiums									$ 1,927.8	$ 2,251.8	$ 2,717.6
Net investment income									184.5	208.9	250.1
Net realized and unrealized investment gains									122.8	82.6	361.7
Other revenue									(57.0)	23.4	113.9
Total revenues	$ 593.6	$ 501.3	$ 553.6	$ 529.6	$ 552.8	$ 551.0	$ 670.8	$ 792.1	2,178.1	2,566.7	3,443.3
Losses and LAE									1,206.9	1,389.2	1,424.1
Insurance and reinsurance acquisition expenses									400.0	479.1	547.2
Other underwriting expenses									279.1	332.9	406.6
General and administrative expenses									175.3	155.1	197.4
Interest expense on debt									55.2	57.3	70.8
Total expenses	535.6	500.1	517.5	563.3	457.2	475.8	664.9	815.7	2,116.5	2,413.6	2,646.1
Pre-tax income	58.0	$ 1.2	$ 36.1	$ (33.7)	95.6	$ 75.2	$ 5.9	$ (23.6)	61.6	153.1	797.2
Selected Balance Sheet Data
Total investments	8,268.0				7,943.5				8,268.0	7,943.5
Reinsurance recoverable on paid and unpaid losses	2,537.8				2,407.1				2,537.8	2,407.1
Assets held for sale	132.6				1,122.8				132.6	1,122.8
Total assets	14,064.0				14,534.1				14,064.0	14,534.1
Loss and LAE reserves	5,702.3				5,736.8				5,702.3	5,736.8	6,379.2	$ 7,029.4
Liabilities held for sale	107.6				751.5				107.6	751.5
Total liabilities	9,396.1				10,273.3				9,396.1	10,273.3
Noncontrolling interest	580.2				607.8				580.2	607.8
Total White Mountains' common shareholders' equity	4,087.7				3,653.0				$ 4,087.7	3,653.0
OneBeacon
Segment reporting information
Number of transactions completed, which transformed the reportable segment into a specialty insurance company \| transaction									2
Earned insurance and reinsurance premiums									$ 1,015.5	1,403.9	1,858.8
Net investment income									71.4	96.6	125.5
Net realized and unrealized investment gains									10.6	74.6	248.6
Other revenue									(10.7)	9.6	23.1
Total revenues									1,086.8	1,584.7	2,256.0
Losses and LAE									580.9	858.2	1,005.3
Insurance and reinsurance acquisition expenses									219.0	311.6	376.3
Other underwriting expenses									173.3	233.1	308.5
General and administrative expenses									9.8	13.0	18.5
Interest expense on debt									20.5	29.6	39.7
Total expenses									1,003.5	1,445.5	1,748.3
Pre-tax income									83.3	139.2	507.7
Selected Balance Sheet Data
Total investments	2,707.6				3,266.0				2,707.6	3,266.0
Reinsurance recoverable on paid and unpaid losses	2,184.1				1,937.7				2,184.1	1,937.7
Assets held for sale	132.6								132.6
Total assets	5,792.4				6,138.3				5,792.4	6,138.3
Loss and LAE reserves	3,358.6				3,295.5				3,358.6	3,295.5
Liabilities held for sale	107.6								107.6
Total liabilities	4,678.5				4,889.4				4,678.5	4,889.4
Noncontrolling interest	287.2				314.9				287.2	314.9
Total White Mountains' common shareholders' equity	826.7				934.0				826.7	934.0
Sirius
Segment reporting information
Earned insurance and reinsurance premiums									912.3	847.9	858.8
Net investment income									89.9	96.5	110.3
Net realized and unrealized investment gains									101.9	(9.8)	112.6
Other revenue									(44.6)	35.9	106.5
Total revenues									1,059.5	970.5	1,188.2
Losses and LAE									626.0	531.0	418.8
Insurance and reinsurance acquisition expenses									181.0	167.5	170.9
Other underwriting expenses									105.8	99.8	98.1
General and administrative expenses									34.1	31.6	74.4
Interest expense on debt									31.6	26.6	26.3
Total expenses									978.5	856.5	788.5
Pre-tax income									81.0	114.0	399.7
Selected Balance Sheet Data
Total investments	3,640.5				4,116.2				3,640.5	4,116.2
Reinsurance recoverable on paid and unpaid losses	353.7				469.4				353.7	469.4
Total assets	5,337.9				5,618.7				5,337.9	5,618.7
Loss and LAE reserves	2,343.7				2,441.3				2,343.7	2,441.3
Total liabilities	3,784.1				3,863.0				3,784.1	3,863.0
Noncontrolling interest	289.5				290.6				289.5	290.6
Total White Mountains' common shareholders' equity	1,264.3				1,465.1				1,264.3	1,465.1
Other Operations
Segment reporting information
Net investment income									23.2	15.8	14.3
Net realized and unrealized investment gains									10.3	17.8	0.5
Other revenue									(1.7)	(22.1)	(15.7)
Total revenues									31.8	11.5	(0.9)
General and administrative expenses									131.4	110.5	104.5
Interest expense on debt									3.1	1.1	4.8
Total expenses									134.5	111.6	109.3
Pre-tax income									(102.7)	(100.1)	$ (110.2)
Selected Balance Sheet Data
Total investments	1,919.9				561.3				1,919.9	561.3
Total assets	2,933.7				1,654.3				2,933.7	1,654.3
Total liabilities	933.5				769.4				933.5	769.4
Noncontrolling interest	3.5				2.3				3.5	2.3
Total White Mountains' common shareholders' equity	$ 1,996.7				882.6				$ 1,996.7	882.6
Discontinued Operations.
Selected Balance Sheet Data
Assets held for sale					1,122.8					1,122.8
Total assets					1,122.8					1,122.8
Liabilities held for sale					751.5					751.5
Total liabilities					751.5					751.5
Total White Mountains' common shareholders' equity					$ 371.3					$ 371.3

Investments in Unconsolidated Affiliates (Details) - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Investments in unconsolidated affiliates
Total investments in unconsolidated affiliates	$ 275.3	$ 389.7
Symetra
Investments in unconsolidated affiliates
Total investments in unconsolidated affiliates	273.6	387.5	$ 307.7	$ 81.3
Symetra \| Common shareholders' equity.
Investments in unconsolidated affiliates
Total investments in unconsolidated affiliates	261.0	350.4	269.2	54.0
Symetra \| Warrants
Investments in unconsolidated affiliates
Total investments in unconsolidated affiliates	12.6	37.1	$ 38.5	$ 27.3
Pentelia Capital Management
Investments in unconsolidated affiliates
Total investments in unconsolidated affiliates	$ 1.7	$ 2.2

Investments in Unconsolidated Affiliates (Details 2) - Symetra $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2010 USD ($) $ / shares shares	Mar. 31, 2010	Dec. 31, 2011 USD ($) Y technic representative $ / shares shares
Investments in unconsolidated affiliates
Investments in unconsolidated affiliates (in shares) \| shares			17.4
Additional common shares (in shares) \| shares			9.5
Ownership interest (as a percent)			15.00%
Fair value of investment \| $			$ 261.0
Estimated fair value of investment per share			$ 15
Number of valuation techniques \| technic			3
Number of representatives \| representative			2
After-tax equity in losses of unconsolidated affiliates \| $			$ 45.9
Equity in net unrealized gains (losses) \| $			$ 136.6
Risk free interest rate (as a percent)			0.31%
Volatility rate (as a percent)			36.00%
Expected life (in years) \| Y			2.58
Strike price (in dollars per share)			$ 11.49
Share price (in dollars per share)			9.07
Minimum
Investments in unconsolidated affiliates
Estimated fair value of investment per share			16
Maximum
Investments in unconsolidated affiliates
Estimated fair value of investment per share			$ 30
Initial public offering
Investments in unconsolidated affiliates
Initial public offering issue price (in dollars per share)	$ 12.00
Sale of Symetra common shares by Symetra (in shares) \| shares	25.3
Sale of Symetra common shares by existing shareholders (in shares) \| shares	9.7
Ownership interest before initial public offering (as a percent)		24.00%
Ownership interest after initial public offering (as a percent)		20.00%
Decrease in carrying value of Symetra from dilution \| $	$ 16.0

Investments in Unconsolidated Affiliates (Details 3) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Changes in carrying value of investment in Symetra
Carrying value at the beginning of the period				$ 389.7					$ 389.7
Equity in earnings of Symetra	$ (36.3)	$ 1.5	$ 7.9	6.7	$ 8.3	$ 7.9	$ 5.3	$ (11.6)	(20.2)	$ 9.9	$ 24.3
Carrying value at the end of the period	275.3				389.7				275.3	389.7
Symetra
Changes in carrying value of investment in Symetra
Carrying value at the beginning of the period				387.5				307.7	387.5	307.7	81.3
Equity in earnings of Symetra									28.2	11.1	23.9
Impairment of equity in earnings of investee									(50.0)
Net unrealized gains from investee's fixed maturity portfolio									85.0	72.7	191.3
Impairment of net unrealized gains from investee's fixed maturity portfolio									(148.6)
Dividends received									(4.0)	(2.6)
Decrease (increase) in value of warrants									(24.5)	(1.4)	11.2
Carrying value at the end of the period	273.6				387.5				273.6	387.5	307.7
Tax on equity in earnings									2.3	1.4	0.0
Equity in net unrealized gains (losses)										63.7	(9.0)
Tax on equity in net unrealized gains (losses)									0.0	5.2	0.0
Loss from dilutive effect resulting from public offering										17.9
Gain from dilutive effect resulting from public offering										1.9
Tax on net unrealized gains from investee's fixed maturity portfolio									(6.9)	0.8	0.0
Loss from dilutive effect resulting from dividend and issuance of restricted shares									1.0	0.8	0.0
Cash dividends received on warrants									2.2
Symetra \| Common shareholders' equity.
Changes in carrying value of investment in Symetra
Carrying value at the beginning of the period				350.4				269.2	350.4	269.2	54.0
Equity in earnings of Symetra									28.2	11.1	23.9
Impairment of equity in earnings of investee									(50.0)
Net unrealized gains from investee's fixed maturity portfolio									85.0	72.7	191.3
Impairment of net unrealized gains from investee's fixed maturity portfolio									(148.6)
Dividends received									(4.0)	(2.6)
Carrying value at the end of the period	261.0				350.4				261.0	350.4	269.2
Tax benefit on impairment of equity in earnings									4.1
Impairment of net unrealized gains from investee's fixed maturity portfolio									12.0
Symetra \| Warrants
Changes in carrying value of investment in Symetra
Carrying value at the beginning of the period				$ 37.1				$ 38.5	37.1	38.5	27.3
Decrease (increase) in value of warrants									(24.5)	(1.4)	11.2
Carrying value at the end of the period	$ 12.6				$ 37.1				$ 12.6	$ 37.1	$ 38.5

Investments in Unconsolidated Affiliates (Details 4) - USD ($) $ in Millions	1 Months Ended		3 Months Ended								12 Months Ended
	Apr. 30, 2007	Aug. 31, 2006	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Symetra income statement data
Equity in earnings			$ (36.3)	$ 1.5	$ 7.9	$ 6.7	$ 8.3	$ 7.9	$ 5.3	$ (11.6)	$ (20.2)	$ 9.9	$ 24.3
Equity method investments			275.3				389.7				275.3	389.7
Symetra
Summarized financial information
Total investments			26,171.7				23,500.2				26,171.7	23,500.2
Separate account assets			795.8				881.7				795.8	881.7
Total assets			28,212.7				25,636.9				28,212.7	25,636.9
Policyholder liabilities			23,140.6				21,591.5				23,140.6	21,591.5
Long-term debt			449.2				449.0				449.2	449.0
Separate account liabilities			795.8				881.7				795.8	881.7
Total liabilities			25,078.7				23,256.3				25,078.7	23,256.3
Common shareholders equity			$ 3,134.0				2,380.6				3,134.0	2,380.6
Symetra income statement data
Net premiums earned											540.5	473.0	470.1
Net investment income											1,270.9	1,199.4	1,113.6
Total revenues											1,999.0	1,878.5	1,714.3
Policy benefits											1,307.3	1,234.6	1,197.3
Total expenses											1,720.0	1,589.4	1,533.2
Net income											199.6	200.9	128.3
Comprehensive net income											$ 780.6	683.1	1,018.6
Ownership interest (as a percent)			15.00%								15.00%
Equity in earnings											$ 28.2	11.1	23.9
Equity method investments			$ 273.6				387.5				273.6	387.5	307.7	$ 81.3
Pre-tax unrealized gains (losses)												63.7	(9.0)
Delos
Symetra income statement data
Ownership interest (as a percent)								18.00%
Amount of investment								$ 32.0
Sale of investments		$ 138.8										21.7
Pre-tax gain (loss) in other revenue		$ (14.0)										10.9
Pentelia Capital Management
Symetra income statement data
Ownership interest (as a percent)	33.00%
Amount of investment	$ 1.6
Equity in earnings											(0.2)	0.5	$ 0.1
Equity method investments			$ 1.7				$ 2.2				$ 1.7	$ 2.2

Variable Interest Entities (Details) $ in Millions	3 Months Ended								12 Months Ended
Variable Interest Entities (Details) $ in Millions	Dec. 31, 2011 USD ($)	Sep. 30, 2011 USD ($)	Jun. 30, 2011 USD ($)	Mar. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Sep. 30, 2010 USD ($)	Jun. 30, 2010 USD ($)	Mar. 31, 2010 USD ($)	Dec. 31, 2011 USD ($) entity	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)
Variable Interest Entities
Accumulated losses	$ 2,789.7				$ 2,175.6				$ 2,789.7	$ 2,175.6
Noncontrolling interest in VIE	580.2				607.8				580.2	607.8
Noncontrolling interest income (expense) related to VIE	20.3	$ (11.0)	$ 20.8	$ 11.4	16.6	$ 24.3	$ 10.7	$ 1.4	41.5	53.0	$ 109.5
OneBeacon
Variable Interest Entities
Noncontrolling interest in VIE	287.2				314.9				$ 287.2	314.9
Reciprocals \| OneBeacon
Variable Interest Entities
Number of reciprocals capitalized									3
Houston General Insurance
Variable Interest Entities
Total assets related to consolidated VIE's	105.9				118.0				$ 105.9	118.0
Total liabilities related to consolidated VIE's	126.2				136.2				126.2	136.2
Houston General Insurance \| OneBeacon
Variable Interest Entities
Surplus notes	23.7								23.7
Accumulated losses	20.3								20.3
Accrued interest on surplus notes	17.0								17.0
Prospector Offshore Fund
Variable Interest Entities
Capital at risk, investment in the fund	65.3								65.3
Total assets related to consolidated VIE's	135.8				145.3				135.8	145.3
Total liabilities related to consolidated VIE's	31.6				39.1				31.6	39.1
Noncontrolling interest in VIE	38.9				40.6				38.9	40.6
Noncontrolling interest income (expense) related to VIE									$ 0.2	(3.2)	(5.0)
Ownership interest in VIE (as a percent)									62.65%
Tuckerman Fund I
Variable Interest Entities
Total assets related to consolidated VIE's	17.6				19.4				$ 17.6	19.4
Total liabilities related to consolidated VIE's	9.9				12.3				9.9	12.3
Noncontrolling interest in VIE	$ 3.5				$ 2.4				3.5	2.4
Noncontrolling interest income (expense) related to VIE									$ 2.2	$ 1.0	$ 0.7
Ownership interest in VIE (as a percent)									94.00%
Companies owned by the Tuckerman Fund I
Variable Interest Entities
Number of small manufacturing companies owned by the Tuckerman Fund I from whom the entity received shares \| entity									2

Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Senior notes	$ 671.2	$ 818.8
SIG Preference Shares	250.0	250.0
OBH Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Senior notes	269.8	419.6
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
SIG Preference Shares	250.0	250.0
Carrying Value \| OBH Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Senior notes	269.8	419.6
Carrying Value \| SIG Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Senior notes	399.3	399.2
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
SIG Preference Shares	217.5	212.5
Fair Value \| OBH Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Senior notes	277.4	435.1
Fair Value \| SIG Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Senior notes	$ 418.6	$ 390.9

Transactions with Related Persons (Details)	1 Months Ended	12 Months Ended
Transactions with Related Persons (Details)	Feb. 29, 2012 USD ($)	Dec. 31, 2011 USD ($) entity shares	Dec. 31, 2010 USD ($) shares	Dec. 31, 2009 USD ($) shares	Dec. 31, 2006 USD ($)	Jan. 07, 2011 $ / shares shares
Prospector
Transactions with Related Persons
Asset management total fees earned		$ 6,000,000	$ 6,600,000	$ 6,500,000
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
Revenue sharing agreement fee earned		200,000	$ 700,000	$ 200,000
Invested in limited partnership investment interests		$ 109,100,000
Prospector \| Minimum
Transactions with Related Persons
Target number of performance shares granted (as a percent)		0.00%
Prospector \| Maximum
Transactions with Related Persons
Target number of performance shares granted (as a percent)		200.00%
Prospector \| Performance cycle 2012-2014
Transactions with Related Persons
Number of performance shares granted \| shares		7,750
Prospector \| Performance cycle 2011-2013
Transactions with Related Persons
Number of performance shares granted \| shares			8,500
Prospector \| Performance cycle 2010-2012
Transactions with Related Persons
Number of performance shares granted \| shares				9,200
Prospector \| Performance cycle 2009-2011
Transactions with Related Persons
Percentage of target number granted actually received by prospector	151.00%
Number of performance shares granted \| shares				10,800
Payment made with respect to the performance shares granted to the related party	$ 7,700,000
Prospector \| OneBeacon
Transactions with Related Persons
Assets under management		$ 558,200,000
ERISA Assets		216,600,000
Invested in limited partnership investment interests		42,900,000
Management fees incurred		1,100,000
Incentive fees incurred		0
Symetra
Transactions with Related Persons
Assets under management		26,300,000,000	$ 23,600,000,000
Asset management total fees earned		$ 15,200,000	$ 13,800,000	$ 13,700,000
Franklin Mutual Advisers
Transactions with Related Persons
Number of shares repurchased \| shares						140,000
Purchase price per share of shares repurchased (in dollars per share) \| $ / shares						$ 342.50
Excess of market price over purchase price per share of shares repurchased (in dollars per share) \| $ / shares						$ 2.50
Dowling & Partners Connecticut Fund III, LP (Fund III) \| Mr. John Gillespie
Transactions with Related Persons
Interest in Dowling & Partners Connecticut Fund III, LP (as a percent)		33.00%
Number of indirect subsidiaries borrowing from Fund III \| entity		2
Tax credits generated by related party				$ 500,000
WM Advisors \| Prospector
Transactions with Related Persons
Advisors fees charged on first $200 million of assets under management (as a percent)		1.00%
First threshold limit of assets under management		$ 200,000,000
Advisors fees charged on second $200 million of assets under management (as a percent)		0.50%
Second threshold limit of assets under management		$ 200,000,000
Advisors fees charged on over $400 million of assets under management (as a percent)		0.25%
Third threshold limit of assets under management		$ 400,000,000
Assets under management		$ 408,200,000
OneBeacon Professional Insurance
Transactions with Related Persons
Borrowings from Fund III					$ 8,000,000
White Mountains Specialty Underwriting, Inc.
Transactions with Related Persons
Borrowings from Fund III					$ 7,000,000

Commitments and Contingencies (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jun. 30, 2007	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Commitments and Contingencies
Rent expense		$ 22.8	$ 28.1	$ 35.2
Future annual minimum rental payments required under non-cancellable leases
2012		17.5
2013		13.8
2014		10.3
2015 and thereafter		25.4
Commitments to fund other-long term investments		91.7
Assigned Risks
Reserve for probable liability from mandatory shared market mechanisms		$ 16.0
Tribune Company
Legal Contingencies
Proceeds in connection with Tribune leveraged buyout	$ 39.0

Commitments and Contingencies (Details 2) $ in Millions	1 Months Ended	12 Months Ended
Commitments and Contingencies (Details 2) $ in Millions	Oct. 31, 2011 Y M anniversary	Dec. 31, 2011 USD ($) Y	Oct. 07, 2011
Esurance
Period for which company has indemnified Allstate for breaches of representations and warranties (in months) \| M	18
Period for which the entity has agreed not to engage in certain competing business activities (in years) \| Y	2
Period for which the entity has agreed not to solicit certain employees of the Transferred Subsidiaries (in years) \| Y	3
Percentage of positive or negative development in the loss reserves of the Transferred Subsidiaries retained			90.00%
Number of anniversaries from the closing date for which positive or negative development in the loss reserves of the Transferred Subsidiaries are to be computed \| anniversary	3
OB Services
Capital Lease
Cash proceeds received a result of entering into the sale-leaseback transactions		$ 23.1
Capital lease obligation		23.1
Capital lease asset		22.9
Future annual minimum rental payments
2012		5.3
2013		5.3
2014		5.3
2015		5.3
2016		$ 1.9
Furniture and equipment \| OB Services
Capital Lease
Capital lease term (in years) \| Y		5
Capitalized software \| OB Services
Capital Lease
Capital lease term (in years) \| Y		4

Discontinued Operations (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
Discontinued Operations (Details) - USD ($) $ in Millions	Oct. 31, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Assets held for sale
Fixed maturity investments, at fair value		$ 6,221.9	$ 5,786.1
Short-term investments, at amortized cost (which approximates fair value)		846.0	975.3
Common equity securities, at fair value		755.0	667.0
Convertible fixed maturity investments, at fair value		143.8	143.0
Other long-term investments		301.3	372.1
Total investments		8,268.0	7,943.5
Cash		705.4	395.0
Reinsurance recoverable on paid and unpaid losses		2,537.8	2,407.1
Insurance premiums receivable		489.2	532.5
Deferred acquisition costs		187.0	176.1
Deferred tax asset		630.6	535.9
Other assets		681.9	730.0
Total assets		14,064.0	14,534.1
Liabilities held for sale
Loss and loss adjustment expense reserves		5,702.3	5,736.8	$ 6,379.2	$ 7,029.4
Unearned insurance premiums		846.9	938.7
Accrued incentive compensation		187.9	157.4
Other liabilities		534.1	557.5
Total liabilities		9,396.1	10,273.3
Esurance
Discontinued Operations
Gain (loss) on sale of discontinued operation, net of tax	$ 677.5
AutoOne
Discontinued Operations
Gain (loss) on sale of discontinued operation, pre-tax		29.6
Gain (loss) on sale of discontinued operation, net of tax		19.2
Liabilities held for sale
Net assets held for sale		25.0
Discontinued Operations.
Assets held for sale
Fixed maturity investments, at fair value		111.8	593.8
Short-term investments, at amortized cost (which approximates fair value)			131.0
Common equity securities, at fair value			43.0
Convertible fixed maturity investments, at fair value			17.2
Other long-term investments			4.0
Total investments		111.8	789.0
Cash		5.5	39.8
Reinsurance recoverable on paid and unpaid losses			34.4
Insurance premiums receivable		8.8	102.9
Deferred acquisition costs		2.2	34.7
Deferred tax asset		1.9	67.8
Other assets		2.4	54.2
Total assets		132.6	1,122.8
Liabilities held for sale
Loss and loss adjustment expense reserves		64.7	450.4
Unearned insurance premiums		34.1	201.6
Accrued incentive compensation			19.1
Other liabilities		8.8	80.4
Total liabilities		107.6	751.5
Net assets held for sale		25.0	371.3
Sirius group
Assets held for sale
Total investments		3,640.5	4,116.2
Reinsurance recoverable on paid and unpaid losses		353.7	469.4
Total assets		5,337.9	5,618.7
Liabilities held for sale
Loss and loss adjustment expense reserves		2,343.7	2,441.3
Total liabilities		$ 3,784.1	$ 3,863.0

Discontinued Operations (Details 2) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
Discontinued Operations (Details 2) - USD ($) $ in Millions	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues
Earned insurance premiums									$ 1,927.8	$ 2,251.8	$ 2,717.6
Net investment income									184.5	208.9	250.1
Net realized and unrealized investment gains									122.8	82.6	361.7
Other revenue									(57.0)	23.4	113.9
Total revenues	$ 593.6	$ 501.3	$ 553.6	$ 529.6	$ 552.8	$ 551.0	$ 670.8	$ 792.1	2,178.1	2,566.7	3,443.3
Expenses
Loss and loss adjustment expenses									1,206.9	1,389.2	1,424.1
Insurance and reinsurance acquisition expenses									400.0	479.1	547.2
Other underwriting expenses									279.1	332.9	406.6
General and administrative expenses									175.3	155.1	197.4
Total expenses	535.6	500.1	517.5	563.3	457.2	475.8	664.9	815.7	2,116.5	2,413.6	2,646.1
Loss from discontinued operations	$ 674.2	$ (30.1)	$ (1.5)	$ 2.5	$ (7.8)	$ 3.6	$ 0.6	$ (3.0)	(13.0)	(6.6)	(27.8)
Discontinued Operations.
Revenues
Earned insurance premiums									727.9	910.6	882.8
Net investment income									12.0	19.6	22.3
Net realized and unrealized investment gains									0.7	13.3	22.9
Other revenue									53.5	60.9	55.2
Total revenues									794.1	1,004.4	983.2
Expenses
Loss and loss adjustment expenses									542.3	678.8	695.0
Insurance and reinsurance acquisition expenses									159.2	191.7	170.1
Other underwriting expenses									80.4	87.9	98.7
General and administrative expenses									38.3	48.6	52.6
Total expenses									820.2	1,007.0	1,016.4
Pre-tax (loss)									(26.1)	(2.6)	(33.2)
Income tax benefit (expense)									13.1	(4.0)	5.4
Loss from discontinued operations									645.3	$ (6.6)	$ (27.8)
Discontinued Operations. \| Esurance
Expenses
Loss from discontinued operations									677.5
Discontinued Operations. \| AutoOne
Expenses
Loss from discontinued operations									$ (19.2)

Discontinued Operations (Details 3) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Basic and diluted earnings per share numerators (in millions):
Net income (loss) attributable to White Mountains' common shareholders	$ 674.2	$ (30.1)	$ (1.5)	$ 2.5	$ (7.8)	$ 3.6	$ 0.6	$ (3.0)	$ (13.0)	$ (6.6)	$ (27.8)
Allocation of income for participating unvested restricted common shares									1.1	1.1	4.8
Net income (loss) attributable to White Mountains' common shareholders, net of restricted common share amounts	$ 800.2	$ (15.8)	$ 11.7	$ (28.2)	$ 72.9	$ 50.7	$ 2.5	$ (39.6)	$ 767.9	$ 86.5	$ 470.0
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period									7,881,000	8,548,400	8,849,400
Average unvested restricted common shares									(69,400)	(97,300)	(85,300)
Basic earnings per share denominator (in shares)									7,811,600	8,451,100	8,764,100
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period									7,881,000	8,548,400	8,849,400
Average unvested restricted common shares									(69,400)	(97,300)	(85,300)
Average outstanding dilutive options to acquire common shares (in shares)										500	1,500
Diluted earnings per share denominator (in shares)									7,811,600	8,451,600	8,765,600
Common shares issuable upon exercise of incentive options (in shares)										1,200	5,280
Average strike price of options (in dollars per share)					$ 189.31					$ 189.31	$ 183.03
Discontinued Operations.
Basic and diluted earnings per share numerators (in millions):
Net income (loss) attributable to White Mountains' common shareholders									$ 645.3	$ (6.6)	$ (27.8)
Allocation of income for participating unvested restricted common shares									(5.7)	0.1	0.3
Net income (loss) attributable to White Mountains' common shareholders, net of restricted common share amounts									$ 639.5	$ (6.5)	$ (27.5)
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period									7,881,000	8,548,400	8,849,400
Average unvested restricted common shares									(69,400)	(97,300)	(85,300)
Basic earnings per share denominator (in shares)									7,811,600	8,451,100	8,764,100
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period									7,881,000	8,548,400	8,849,400
Average unvested restricted common shares									(69,400)	(97,300)	(85,300)
Average outstanding dilutive options to acquire common shares (in shares)										500	1,500
Diluted earnings per share denominator (in shares)									7,811,600	8,451,600	8,765,600
Basic and diluted earnings (loss) per share (in dollars):									$ 81.88	$ (0.77)	$ (3.14)

SELECTED QUARTERLY FINANCIAL DATA (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
SELECTED QUARTERLY FINANCIAL DATA (Unaudited)
Revenues	$ 593.6	$ 501.3	$ 553.6	$ 529.6	$ 552.8	$ 551.0	$ 670.8	$ 792.1	$ 2,178.1	$ 2,566.7	$ 3,443.3
Expenses	535.6	500.1	517.5	563.3	457.2	475.8	664.9	815.7	2,116.5	2,413.6	2,646.1
Pre-tax income	58.0	1.2	36.1	(33.7)	95.6	75.2	5.9	(23.6)	61.6	153.1	797.2
Tax benefit (expense)	124.6	0.6	(10.0)	7.7	(6.6)	(11.7)	1.4		122.7	(16.9)	(214.2)
Net income from continuing operations	182.6	1.8	26.1	(26.0)	89.0	63.5	7.3	(23.6)	184.3	136.2	583.0
Net loss from discontinued operations, net of tax	674.2	(30.1)	(1.5)	2.5	(7.8)	3.6	0.6	(3.0)	(13.0)	(6.6)	(27.8)
Noncontrolling interest in consolidated subsidiaries	(20.3)	11.0	(20.8)	(11.4)	(16.6)	(24.3)	(10.7)	(1.4)	(41.5)	(53.0)	(109.5)
Equity in (losses) earnings of unconsolidated affiliates	(36.3)	1.5	7.9	6.7	8.3	7.9	5.3	(11.6)	(20.2)	9.9	24.3
Net income attributable to White Mountains' common shareholders	$ 800.2	$ (15.8)	$ 11.7	$ (28.2)	$ 72.9	$ 50.7	$ 2.5	$ (39.6)	$ 767.9	$ 86.5	$ 470.0
Basic
Continuing operations (in dollars per share)	$ 16.54	$ 1.81	$ 1.66	$ (3.82)	$ 9.77	$ 5.58	$ 0.21	$ (4.14)	$ 15.56	$ 10.89	$ 56.25
Discontinued operations (in dollars per share)	88.50	(3.81)	(0.18)	0.31	(0.94)	0.43	0.07	(0.34)	81.88	(0.77)	(3.14)
Total consolidated operations (in dollars per share)	105.04	(2.00)	1.48	(3.51)	8.83	6.01	0.28	(4.48)	97.44	10.12	53.11
Diluted
Continuing operations (in dollars per share)	16.54	1.81	1.66	(3.82)	9.77	5.58	0.21	(4.14)	15.56	10.89	56.24
Discontinued operations (in dollars per share)	88.50	(3.81)	(0.18)	0.31	(0.94)	0.43	0.07	(0.34)	81.88	(0.77)	(3.14)
Total consolidated operations (in dollars per share)	105.04	(2.00)	1.48	(3.51)	8.83	6.01	0.28	(4.48)	$ 97.44	$ 10.12	$ 53.10
Adjusted book value per share (in dollars per share)	$ 542.11	$ 436.18	$ 447.69	$ 446.70	$ 440.59	$ 428.79	$ 405.94	$ 410.59

SCHEDULE I SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES (Details) $ in Millions	Dec. 31, 2011 USD ($)
Summary of investments other than investments in related parties
Cost	$ 8,179.5
Carrying Value	8,379.8
Fair Value	8,379.8
AutoOne
Summary of investments other than investments in related parties
Investments reclassified to assets held for sale	111.8
Fixed maturity investments.
Summary of investments other than investments in related parties
Cost	6,228.2
Carrying Value	6,333.7
Fair Value	6,333.7
U.S. Government and agency obligations
Summary of investments other than investments in related parties
Cost	299.4
Carrying Value	305.0
Fair Value	305.0
Debt securities issued by corporations
Summary of investments other than investments in related parties
Cost	2,072.1
Carrying Value	2,135.1
Fair Value	2,135.1
Mortgage-backed and asset-backed securities
Summary of investments other than investments in related parties
Cost	3,190.5
Carrying Value	3,222.9
Fair Value	3,222.9
Municipal obligations
Summary of investments other than investments in related parties
Cost	2.7
Carrying Value	2.7
Fair Value	2.7
Foreign government, agency and provincial obligations
Summary of investments other than investments in related parties
Cost	581.2
Carrying Value	589.2
Fair Value	589.2
Non-cumulative perpetual preference shares
Summary of investments other than investments in related parties
Cost	82.3
Carrying Value	78.8
Fair Value	78.8
Short-term investments
Summary of investments other than investments in related parties
Cost	846.0
Carrying Value	846.0
Fair Value	846.0
Common equity securities
Summary of investments other than investments in related parties
Cost	691.7
Carrying Value	755.0
Fair Value	755.0
Banks, trust and insurance companies
Summary of investments other than investments in related parties
Cost	205.3
Carrying Value	219.2
Fair Value	219.2
Public utilities
Summary of investments other than investments in related parties
Cost	39.4
Carrying Value	42.0
Fair Value	42.0
Industrial, miscellaneous and other
Summary of investments other than investments in related parties
Cost	447.0
Carrying Value	493.8
Fair Value	493.8
Convertible fixed maturities
Summary of investments other than investments in related parties
Cost	139.2
Carrying Value	143.8
Fair Value	143.8
Other long-term investments
Summary of investments other than investments in related parties
Cost	274.4
Carrying Value	301.3
Fair Value	$ 301.3

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT (Details) - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010
Assets:
Cash	$ 705.4	$ 395.0
Fixed maturity investments, at fair value	6,221.9	5,786.1
Common equity securities, at fair value	755.0	667.0
Short-term investments, at amortized cost	846.0	975.3
Other assets	681.9	730.0
Total assets	14,064.0	14,534.1
Liabilities
Accounts payable and other liabilities	534.1	557.5
Total liabilities	9,396.1	10,273.3
White Mountains common shareholders equity	4,087.7	3,653.0
Total liabilities and equity	14,064.0	14,534.1
White Mountains Insurance Group Ltd.
Assets:
Cash	0.7	0.3
Fixed maturity investments, at fair value	1,334.5	5.8
Common equity securities, at fair value	1.9	1.8
Short-term investments, at amortized cost	72.3	54.9
Other assets	5.1	4.5
Investments in consolidated and unconsolidated affiliates	2,687.3	3,821.2
Total assets	4,101.8	3,888.5
Liabilities
Payable to subsidiaries	(2.8)	221.7
Accounts payable and other liabilities	16.9	13.8
Total liabilities	14.1	235.5
White Mountains common shareholders equity	4,087.7	3,653.0
Total liabilities and equity	$ 4,101.8	$ 3,888.5

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT (Details 2) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Revenues (including realized gains and losses)	$ 593.6	$ 501.3	$ 553.6	$ 529.6	$ 552.8	$ 551.0	$ 670.8	$ 792.1	$ 2,178.1	$ 2,566.7	$ 3,443.3
Expenses	535.6	500.1	517.5	563.3	457.2	475.8	664.9	815.7	2,116.5	2,413.6	2,646.1
Pre-tax loss	58.0	1.2	36.1	(33.7)	95.6	75.2	5.9	(23.6)	61.6	153.1	797.2
Income tax benefit (expense)	124.6	0.6	(10.0)	7.7	(6.6)	(11.7)	1.4		122.7	(16.9)	(214.2)
Net loss	182.6	1.8	26.1	(26.0)	89.0	63.5	7.3	(23.6)	184.3	136.2	583.0
Net income attributable to White Mountains' common shareholders	800.2	(15.8)	11.7	(28.2)	72.9	50.7	2.5	(39.6)	767.9	86.5	470.0
Comprehensive income attributable to White Mountains' common shareholders									686.2	214.4	750.8
Computation of net income (loss) available to common shareholders:
Net income available to common shareholders	$ 800.2	$ (15.8)	$ 11.7	$ (28.2)	$ 72.9	$ 50.7	$ 2.5	$ (39.6)	767.9	86.5	470.0
White Mountains Insurance Group Ltd.
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Revenues (including realized gains and losses)									6.4	1.1
Expenses									51.7	42.2	38.3
Pre-tax loss									(45.3)	(41.1)	(38.3)
Income tax benefit (expense)									6.5	(0.6)	(3.6)
Net loss									(38.8)	(41.7)	(41.9)
Equity in earnings (losses) from consolidated and unconsolidated affiliates									806.7	128.2	511.9
Net income attributable to White Mountains' common shareholders									767.9	86.5	470.0
Other comprehensive (loss) income items, after-tax									(81.7)	127.9	280.8
Comprehensive income attributable to White Mountains' common shareholders									686.2	214.4	750.8
Computation of net income (loss) available to common shareholders:
Net income available to common shareholders									$ 767.9	$ 86.5	$ 470.0

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT (Details 3) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Net income attributable to White Mountains' common shareholders	$ 800.2	$ (15.8)	$ 11.7	$ (28.2)	$ 72.9	$ 50.7	$ 2.5	$ (39.6)	$ 767.9	$ 86.5	$ 470.0
Charges (credits) to reconcile net income to net cash (used for) provided from operations:
Net realized and unrealized investment (gains) losses									(122.8)	(82.6)	(361.7)
Net federal income tax (payments) receipts									12.5	(47.0)	(17.5)
Net change in other assets and liabilities, net									(96.5)	(238.6)	27.5
Net cash (used for) provided from operations									(114.5)	56.0	(46.7)
Cash flows from investing activities:
Net decrease in short-term investments									174.5	475.6	218.4
Net change in unsettled investment purchases and sales									47.0	1.6	52.1
Net cash provided from investing activities									799.6	485.3	365.1
Cash flows from financing activities:
Repayment of debt										(14.0)	(242.8)
Proceeds from issuances of common shares									0.9	0.7	0.9
Repurchases and retirement of common shares									(253.0)	(225.6)	(0.4)
Dividends paid on common shares									(8.0)	(8.8)	(8.9)
Net cash (used for) provided from financing activities									(460.2)	(550.2)	(360.2)
Net increase (decrease) in cash during year									223.4	(0.8)	(35.0)
Cash balance at beginning of year	251.9				103.6				251.9	103.6	119.9	$ 158.7
Cash balance at end of year	251.9				103.6				251.9	103.6	119.9	158.7
White Mountains Insurance Group Ltd.
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Net income attributable to White Mountains' common shareholders									767.9	86.5	470.0
Charges (credits) to reconcile net income to net cash (used for) provided from operations:
Net realized and unrealized investment (gains) losses									(3.1)	0.1	1.7
Undistributed current (earnings) losses from subsidiaries									(806.7)	(128.2)	(511.9)
Dividends received from subsidiaries											8.4
Net change in other assets and liabilities, net									13.7	27.9	18.6
Net cash (used for) provided from operations									(28.2)	(13.7)	(13.2)
Cash flows from investing activities:
Net decrease in short-term investments									267.3	166.5	20.8
Purchases of investment securities									(237.3)	(5.8)	(28.4)
Sales and maturities of investment securities									59.0
Issuance of debt (to) from subsidiaries										86.8
Repayment of debt (to) from subsidiaries									192.5		200.0
Distributions from subsidiaries									7.2		29.0
Net cash provided from investing activities									288.7	247.5	221.4
Cash flows from financing activities:
Repayment of debt											(200.0)
Proceeds from issuances of common shares									0.9	0.7	0.9
Repurchases and retirement of common shares									(253.0)	(225.6)	(0.4)
Dividends paid on common shares									(8.0)	(8.8)	(8.9)
Net cash (used for) provided from financing activities									(260.1)	(233.7)	(208.4)
Net increase (decrease) in cash during year									0.4	0.1	(0.2)
Cash balance at beginning of year	0.7				0.3				0.7	0.3	0.2	0.4
Cash balance at end of year	$ 0.7				$ 0.3				$ 0.7	$ 0.3	$ 0.2	$ 0.4

SCHEDULE III SUPPLEMENTARY INSURANCE INFORMATION (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
SUPPLEMENTARY INSURANCE INFORMATION
Net investment income of non-insurance operations	$ 19.8	$ 14.8	$ 12.5
OneBeacon
SUPPLEMENTARY INSURANCE INFORMATION
Deferred acquisition costs	123.5	114.5	215.0
Future policy benefits, losses, claims and loss expenses	3,358.6	3,295.5	3,934.8
Unearned premiums	528.0	627.5	1,018.3
Premiums earned	1,015.5	1,487.7	1,959.5
Net investment income	66.8	96.3	127.4
Benefits, claims, losses, and settlement expenses	580.9	930.2	1,121.9
Amortization of deferred policy acquisition costs	219.0	320.7	398.3
Other operating expenses	173.3	246.5	330.0
Premiums written	1,062.9	1,236.3	1,906.7
Sirius group
SUPPLEMENTARY INSURANCE INFORMATION
Deferred acquisition costs	63.5	61.6	57.2
Future policy benefits, losses, claims and loss expenses	2,343.7	2,441.3	2,444.4
Unearned premiums	319.0	311.2	287.5
Premiums earned	912.3	847.9	858.8
Net investment income	89.9	90.5	107.7
Benefits, claims, losses, and settlement expenses	626.0	531.0	418.8
Amortization of deferred policy acquisition costs	181.0	167.5	170.9
Other operating expenses	105.8	99.8	98.1
Premiums written	915.7	865.8	806.8
Other Operations
SUPPLEMENTARY INSURANCE INFORMATION
Net investment income	$ 8.0	$ 1.3	$ (0.1)

SCHEDULE IV REINSURANCE (Details) - USD ($) $ in Millions	12 Months Ended
SCHEDULE IV REINSURANCE (Details) - USD ($) $ in Millions	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
OneBeacon
Premiums earned
Gross amount	$ 1,138.5	$ 1,732.5	$ 2,122.4
Ceded to other companies	(166.1)	(309.0)	(229.7)
Assumed from other companies	43.1	64.2	66.8
Net amount	$ 1,015.5	$ 1,487.7	$ 1,959.5
Percent of amount assumed to net	4.20%	4.30%	3.40%
Sirius group
Premiums earned
Gross amount	$ 128.5	$ 117.9	$ 107.2
Ceded to other companies	(205.9)	(199.7)	(175.9)
Assumed from other companies	989.8	929.7	927.5
Net amount	$ 912.4	$ 847.9	$ 858.8
Percent of amount assumed to net	108.50%	109.60%	108.00%

SCHEDULE V VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reinsurance recoverable on paid losses: Allowance for reinsurance balances
VALUATION AND QUALIFYING ACCOUNTS
Balance at beginning of period	$ 29.4	$ 30.0	$ 29.5
Charged to costs and expenses	8.5	(0.4)	2.3
Deductions described	(3.9)	(0.2)	(1.8)
Balance at end of period	34.0	29.4	30.0
Property and casualty insurance and reinsurance premiums receivable: Allowance for uncollectible accounts
VALUATION AND QUALIFYING ACCOUNTS
Balance at beginning of period	3.9	6.3	7.1
Charged to costs and expenses		0.2	1.5
Charged to other accounts	(0.5)	(1.0)	(1.8)
Deductions described		(1.6)	(0.5)
Balance at end of period	$ 3.4	$ 3.9	$ 6.3

SCHEDULE VI SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Aug. 03, 2006
OneBeacon
SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS
Deferred acquisition costs	$ 123.5	$ 114.5	$ 215.0
Reserves for Unpaid Claims and Claims Adjustment Expenses	3,358.6	3,295.5	3,934.8
Discount, if any, deducted in Column C	271.6	295.9	317.5
Unearned Premiums	528.0	627.5	1,018.3
Earned Premiums	1,015.5	1,487.7	1,959.5
Net investment income	71.4	96.6	125.5
Current Year	583.8	981.4	1,205.3
Prior Year	(2.9)	(51.2)	(83.4)
Amortization of deferred policy acquisition costs	219.0	320.7	398.3
Paid Claims and Claims Adjustment Expenses	714.8	1,038.8	1,176.1
Premiums written	$ 1,062.9	$ 1,236.3	$ 1,906.7
Rate at which reserves are discounted (as a percent)	4.50%	5.00%	5.30%
Sirius
SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS
Deferred acquisition costs	$ 63.5	$ 61.6	$ 57.2
Reserves for Unpaid Claims and Claims Adjustment Expenses	2,343.7	2,441.3	2,444.4
Discount, if any, deducted in Column C	12.8	21.1	29.5
Unearned Premiums	319.0	311.2	287.5
Earned Premiums	912.3	847.9	858.8
Net investment income	89.9	90.5	107.7
Current Year	672.9	588.1	449.1
Prior Year	(46.9)	(57.1)	(30.4)
Amortization of deferred policy acquisition costs	181.0	167.5	170.9
Paid Claims and Claims Adjustment Expenses	642.0	437.0	772.9
Premiums written	$ 915.7	$ 865.8	806.8
50%-or-less owned property and casualty investees - Delos
SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS
Deferred acquisition costs			3.9
Reserves for Unpaid Claims and Claims Adjustment Expenses			73.3
Unearned Premiums			26.1
Earned Premiums			33.3
Net investment income			1.7
Current Year			24.3
Paid Claims and Claims Adjustment Expenses			18.2
Premiums written			$ 31.7
Ownership interest in property and casualty insurance affiliates (as a percent)	50.00%			18.00%

Summary of Significant Accounting Policies (Details 9) - Symetra	12 Months Ended
	Dec. 31, 2011 Y $ / shares
Investments in unconsolidated affiliates
Risk free interest rate (as a percent)	0.31%
Volatility rate (as a percent)	36.00%
Expected life (in years) \| Y	2.58
Strike price (in dollars per share)	$ 11.49
Share price (in dollars per share)	$ 9.07