0000776867-21-000008 | 10-Q | XBRL Viewer | White Mountains Insurance Group LTD

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Cover Page - shares	3 Months Ended
Cover Page - shares	Mar. 31, 2021	May 07, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
Document Transition Report	false
Entity File Number	1-8993
Entity Registrant Name	WHITE MOUNTAINS INSURANCE GROUP, LTD
Entity Incorporation, State or Country Code	D0
Entity Tax Identification Number	94-2708455
Entity Address, Address Line One	23 South Main Street, Suite 3B
Entity Address, Postal Zip Code	03755-2053
Entity Address, City or Town	Hanover,
Entity Address, State or Province	NH
City Area Code	603
Local Phone Number	640-2200
Title of 12(b) Security	Common Shares, par value $1.00
Trading Symbol	WTM
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		3,107,267
Entity Central Index Key	0000776867
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Investments
Other long-term investments	$ 1,032.2	$ 786.8
Goodwill and other intangible assets	1,037.0	782.4
Total assets	6,900.7	4,831.4
Liabilities
Loss and loss adjustment expense reserves	447.5	433.4
Debt	429.7	376.4
Total liabilities	2,964.8	1,013.5
White Mountains’s common shareholders’ equity
White Mountains’s common shares at $1 par value per share—authorized 50,000,000 shares; issued and outstanding 3,107,267 and 3,102,011 shares and paid-in surplus	3.1	3.1
Paid-in surplus	594.8	592.1
Retained earnings	3,226.7	3,311.2
Accumulated other comprehensive gain (loss), after-tax:
Net unrealized foreign currency translation and interest rate swap gains (losses)	1.3	(0.4)
Total White Mountains’s common shareholders’ equity	3,825.9	3,906.0
Non-controlling interests	110.0	(88.1)
Total equity	3,935.9	3,817.9
Total liabilities and equity	6,900.7	4,831.4
Financial Guarantee (HG Global/BAM)
Investments
Fixed maturity investments, at fair value	857.0	859.5
Short-term investments, at fair value	45.3	60.4
Total investments	902.3	919.9
Cash	18.9	42.8
Insurance premiums receivable	6.9	6.9
Deferred acquisition costs	28.7	27.8
Accrued investment income	5.2	5.0
Other assets	14.8	15.4
Total assets	976.8	1,017.8
Liabilities
Unearned insurance premiums	243.7	237.5
Accrued incentive compensation	11.0	25.7
Other liabilities	28.6	28.3
Total liabilities	283.3	291.5
P&C Insurance and Reinsurance (Ark)
Investments
Fixed maturity investments, at fair value	305.8	0.0
Common equity securities, at fair value	118.6	0.0
Short-term investments, at fair value	328.6	0.0
Other long-term investments	234.7	0.0
Total investments	987.7	0.0
Cash	308.8	0.0
Reinsurance recoverables	449.0	0.0
Insurance premiums receivable	435.4	0.0
Ceded unearned premiums	145.5	0.0
Deferred acquisition costs	79.2	0.0
Value of in-force business acquired	42.9	0.0
Goodwill and other intangible assets	292.5	0.0
Other assets	99.2	0.0
Total assets	2,840.2	0.0
Liabilities
Loss and loss adjustment expense reserves	751.9	0.0
Unearned insurance premiums	565.4	0.0
Debt	44.1	0.0
Premiums payable	487.5	0.0
Contingent consideration related to the Ark Transaction	22.5	0.0
Accounts payable on unsettled investment purchases	61.6	0.0
Other liabilities	73.8	0.0
Total liabilities	2,006.8	0.0
Specialty Insurance Distribution (NSM)
Investments
Cash	121.0	126.5
Premiums and commissions receivable	77.0	76.7
Goodwill and other intangible assets	699.7	736.8
Other assets	65.0	59.6
Total assets	962.7	999.6
Liabilities
Debt	272.7	272.6
Premiums payable	116.0	113.4
Contingent consideration earnout liabilities	7.9	14.6
Other liabilities	83.5	91.2
Total liabilities	480.1	491.8
Asset Management (Kudu)
Investments
Short-term investments, at fair value	0.1	0.1
Other long-term investments	427.4	400.6
Total investments	427.5	400.7
Cash	10.9	7.8
Accrued investment income	7.5	9.8
Goodwill and other intangible assets	9.1	9.2
Other assets	2.7	2.7
Total assets	457.7	430.2
Liabilities
Debt	95.9	86.3
Other liabilities	15.4	10.0
Total liabilities	111.3	96.3
Other Operations
Investments
Fixed maturity investments, at fair value	318.8	347.7
Short-term investments, at fair value	251.8	82.4
Investment in MediaAlpha, at fair value	600.2	802.2
Other long-term investments	370.1	386.2
Total investments	1,540.9	1,618.5
Cash	28.9	34.1
Cash pre-funded/placed in escrow for Ark Transaction	0.0	646.3
Accrued investment income	3.9	2.4
Accounts receivable on unsettled investment sales	3.5	3.4
Goodwill and other intangible assets	35.7	36.4
Other assets	49.7	40.4
Assets held for sale	0.7	2.3
Total assets	1,663.3	2,383.8
Liabilities
Debt	17.0	17.5
Accrued incentive compensation	40.4	70.1
Other liabilities	25.9	46.3
Total liabilities	$ 83.3	$ 133.9

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Common shares, par value per share (in dollars per share)	$ 1.00	$ 1.00
Common shares, authorized shares (in shares)	50,000,000	50,000,000
Common shares, issued shares (in shares)	3,107,267	3,102,011
Common shares, outstanding shares (in shares)	3,107,267	3,102,011
Specialty Insurance Distribution (NSM)
Restricted cash	$ 79.3	$ 78.4
Kudu
Restricted cash	$ 3.9	$ 0.0

CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenues:
Earned insurance premiums	$ 111.0	$ 5.4
Net investment income	20.6	22.9
Net realized and unrealized investment (losses) gains	1.1	(186.7)
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	(40.6)	(156.7)
Commission revenues	61.9	55.1
Other revenues	25.3	14.1
Total revenues	178.2	(59.2)
Expenses:
Insurance acquisition expenses		1.7
Loss and loss adjustment expenses	66.0
Insurance and reinsurance acquisition expenses	38.6
Cost of sales	4.0	2.0
General and administrative expenses	138.4	74.3
Broker commission expenses	18.9	18.3
Change in fair value of contingent consideration earnout liabilities	0.0	(0.6)
Amortization of other intangible assets	9.2	5.1
Loss on assets held for sale	28.7
Interest expense	13.1	6.0
Total expenses	316.9	106.8
Pre-tax loss from continuing operations	(138.7)	(166.0)
Income tax benefit	9.5	25.5
Net loss from continuing operations	(129.2)	(140.5)
Net income from sale of discontinued operations, net of tax	18.7	0.9
Net loss	(110.5)	(139.6)
Net loss attributable to non-controlling interests	35.2	10.8
Net loss attributable to White Mountains’s common shareholders	(75.3)	(128.8)
Marketing Technology (MediaAlpha)
Revenues:
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	(41.7)	30.0
Financial Guarantee (HG Global/BAM)
Revenues:
Earned insurance premiums	6.4	5.4
Net investment income	4.5	5.5
Net realized and unrealized investment (losses) gains	(17.9)	6.1
Commission revenues	0.0	0.0
Other revenues	0.3	0.5
Total revenues	(6.7)	17.5
Expenses:
Insurance acquisition expenses		1.7
Loss and loss adjustment expenses	0.0
Insurance and reinsurance acquisition expenses	1.9
Cost of sales	0.0	0.0
General and administrative expenses	16.4	14.7
Broker commission expenses	0.0	0.0
Change in fair value of contingent consideration earnout liabilities	0.0	0.0
Amortization of other intangible assets	0.0	0.0
Loss on assets held for sale	0.0
Interest expense	0.0	0.0
Total expenses	18.3	16.4
Pre-tax loss from continuing operations	(25.0)	1.1
Financial Guarantee (HG Global/BAM) \| Marketing Technology (MediaAlpha)
Revenues:
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	0.0	0.0
P&C Insurance and Reinsurance (Ark)
Revenues:
Earned insurance premiums	104.6	0.0
Net investment income	0.8	0.0
Net realized and unrealized investment (losses) gains	1.1	0.0
Commission revenues	0.0
Other revenues	2.6	0.0
Total revenues	109.1	0.0
Expenses:
Loss and loss adjustment expenses	66.0	0.0
Insurance and reinsurance acquisition expenses	36.7	0.0
Other underwriting expenses	11.2	0.0
Cost of sales	0.0
General and administrative expenses	26.6	0.0
Broker commission expenses	0.0
Change in fair value of contingent consideration earnout liabilities	0.0
Amortization of other intangible assets	0.0
Loss on assets held for sale	0.0
Interest expense	1.1	0.0
Total expenses	141.6	0.0
Pre-tax loss from continuing operations	(32.5)
P&C Insurance and Reinsurance (Ark) \| Marketing Technology (MediaAlpha)
Revenues:
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	0.0
Specialty Insurance Distribution (NSM)
Revenues:
Earned insurance premiums	0.0	0.0
Net investment income	0.0	0.0
Net realized and unrealized investment (losses) gains	0.0	0.0
Commission revenues	59.6	53.0
Other revenues	15.2	12.0
Total revenues	74.8	65.0
Expenses:
Insurance acquisition expenses		0.0
Loss and loss adjustment expenses	0.0
Insurance and reinsurance acquisition expenses	0.0
Cost of sales	0.0	0.0
General and administrative expenses	46.0	39.6
Broker commission expenses	18.9	18.3
Change in fair value of contingent consideration earnout liabilities	0.0	(0.6)
Amortization of other intangible assets	8.6	4.8
Loss on assets held for sale	28.7	0.0
Interest expense	5.9	4.3
Total expenses	108.1	66.4
Pre-tax loss from continuing operations	(33.3)	(1.4)
Specialty Insurance Distribution (NSM) \| Marketing Technology (MediaAlpha)
Revenues:
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	0.0	0.0
Asset Management (Kudu)
Revenues:
Earned insurance premiums	0.0	0.0
Net investment income	8.2	7.3
Net realized and unrealized investment (losses) gains	15.8	(24.8)
Commission revenues	0.0	0.0
Other revenues	0.1	0.1
Total revenues	24.1	(17.4)
Expenses:
Insurance acquisition expenses		0.0
Loss and loss adjustment expenses	0.0
Insurance and reinsurance acquisition expenses	0.0
Cost of sales	0.0	0.0
General and administrative expenses	2.5	2.5
Broker commission expenses	0.0	0.0
Change in fair value of contingent consideration earnout liabilities	0.0	0.0
Amortization of other intangible assets	0.1	0.1
Loss on assets held for sale	0.0
Interest expense	5.8	1.4
Total expenses	8.4	4.0
Pre-tax loss from continuing operations	15.7	(21.4)
Asset Management (Kudu) \| Marketing Technology (MediaAlpha)
Revenues:
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	0.0	0.0
Other Operations
Revenues:
Earned insurance premiums	0.0	0.0
Net investment income	7.1	10.1
Net realized and unrealized investment (losses) gains	2.1	(168.0)
Commission revenues	2.3	2.1
Other revenues	7.1	1.5
Total revenues	(23.1)	(124.3)
Expenses:
Insurance acquisition expenses		0.0
Loss and loss adjustment expenses	0.0
Insurance and reinsurance acquisition expenses	0.0
Cost of sales	4.0	2.0
General and administrative expenses	35.7	17.5
Broker commission expenses	0.0	0.0
Change in fair value of contingent consideration earnout liabilities	0.0	0.0
Amortization of other intangible assets	0.5	0.2
Loss on assets held for sale	0.0
Interest expense	0.3	0.3
Total expenses	40.5	20.0
Pre-tax loss from continuing operations	(63.6)	(144.3)
Other Operations \| Marketing Technology (MediaAlpha)
Revenues:
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	$ (41.7)	$ 30.0

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net loss attributable to White Mountains’s common shareholders	$ (75.3)	$ (128.8)
Other comprehensive income (loss), net of tax	1.8	(3.4)
Comprehensive loss	(73.5)	(132.2)
Other comprehensive income attributable to non-controlling interests	(0.1)	0.0
Comprehensive loss attributable to White Mountains’s common shareholders	$ (73.6)	$ (132.2)
Basic (loss) earnings per share
Continuing operations (in usd per share)	$ (30.33)	$ (40.82)
Discontinued operations (in usd per share)	6.03	0.28
Total consolidated operations (in usd per share)	(24.30)	(40.54)
Diluted (loss) earnings per share
Continuing operations (in usd per share)	(30.33)	(40.82)
Discontinued operations (in usd per share)	6.03	0.28
Total consolidated operations (in usd per share)	(24.30)	(40.54)
Dividends declared per White Mountains’s common share (in USD per share)	$ 1.00	$ 1.00

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Unaudited) - USD ($) $ in Millions	Total	Common shares and paid-in surplus	Retained earnings	AOCI, after tax	Total	Non-controlling interest	Total Equity	BAM Non-controlling interest	BAM Total Equity
Beginning Balances at Dec. 31, 2019		$ 596.3	$ 2,672.4	$ (7.2)	$ 3,261.5	$ (116.8)	$ 3,144.7
Increase (Decrease) in Shareholders' Equity
Net loss	$ (139.6)		(128.8)		(128.8)	(10.8)	(139.6)
Net change in foreign currency translation and other				(3.4)	(3.4)		(3.4)
Comprehensive loss	(132.2)		(128.8)	(3.4)	(132.2)	(10.8)	(143.0)
Dividends declared on common shares			(3.2)		(3.2)		(3.2)
Dividends to non-controlling interests						(0.5)	(0.5)
Repurchases and retirements of common shares		(12.1)	(42.4)		(54.5)		(54.5)
Capital contributions from BAM members, net of tax								$ 10.0	$ 10.0
Net contributions and dilution from other non-controlling interests						0.5	0.5
Amortization of restricted share awards		5.1			5.1		5.1
Ending Balances at Mar. 31, 2020		589.3	2,498.0	(10.6)	3,076.7	(117.6)	2,959.1
Beginning Balances at Dec. 31, 2020	3,817.9	595.2	3,311.2	(0.4)	3,906.0	(88.1)	3,817.9
Increase (Decrease) in Shareholders' Equity
Net loss	(110.5)		(75.3)		(75.3)	(35.2)	(110.5)
Net change in foreign currency translation and other				1.7	1.7	0.1	1.8
Comprehensive loss	(73.5)		(75.3)	1.7	(73.6)	(35.1)	(108.7)
Dividends declared on common shares			(3.1)		(3.1)		(3.1)
Dividends to non-controlling interests						(0.6)	(0.6)
Repurchases and retirements of common shares		(1.4)	(6.1)		(7.5)		(7.5)
Capital contributions from BAM members, net of tax								$ 13.8	$ 13.8
Net contributions and dilution from other non-controlling interests		(0.4)			(0.4)	(0.2)	(0.6)
Recognition of equity-based units of subsidiary		0.5			0.5		0.5
Acquisition of non-controlling interests						220.2	220.2
Amortization of restricted share awards		4.0			4.0		4.0
Ending Balances at Mar. 31, 2021	$ 3,935.9	$ 597.9	$ 3,226.7	$ 1.3	$ 3,825.9	$ 110.0	$ 3,935.9

CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Cash flows from operations:
Net loss	$ (110.5)	$ (139.6)
Adjustments to reconcile net income to net cash used for operations:
Net realized and unrealized investment (gains) losses	(1.1)	186.7
Net realized and unrealized investment losses (gains) from investment in MediaAlpha	40.6	156.7
Deferred income tax expense	(1.4)	(27.9)
Net gain from sale of discontinued operations, net of tax	(18.7)	(0.9)
Amortization of Restricted Shares	4.0	5.1
Amortization and depreciation	12.8	7.1
Other operating items:
Net change in reinsurance recoverables	(15.7)	0.0
Increase (Decrease) in Premiums Receivable	(199.7)	0.0
Net change in commissions receivable	(0.2)	(0.7)
Net change in ceded unearned premiums	24.8	0.0
Net change in loss and loss adjustment expense reserves	56.0	0.0
Net change in premiums payable	2.6	8.5
Net change in unearned insurance premiums	245.5	4.3
Net change in deferred acquisition costs	(51.3)	(1.2)
Net change in reinsurance payable	(40.7)	0.0
Net change in restricted cash	4.8	8.6
Investments in Kudu Participation Contracts	(11.0)	(21.0)
Net change in other assets and liabilities, net	(34.7)	(58.8)
Net cash used for operations	(92.8)	(59.8)
Cash flows from investing activities:
Net change in short-term investments	(103.1)	63.9
Sales of fixed maturity and convertible investments	97.8	116.1
Maturities, calls and paydowns of fixed maturity and convertible investments	31.4	58.9
Sales of common equity securities	160.3	40.3
Distributions and redemptions of other long-term investments and settlements of forward contracts	40.1	64.1
Payment For Escrow In Acquisition Transaction	646.3	0.0
Payments for (Proceeds from) Businesses and Interest in Affiliates	11.1	0.0
Purchases of other long-term investments	(101.0)	(10.9)
Purchases of common equity securities	(68.8)	(20.9)
Purchases of fixed maturity and convertible investments	(411.1)	(180.1)
Other investing activities, net	60.9	(50.9)
Net cash (used for) provided from investing activities	363.9	80.5
Cash flows from financing activities:
Draw down of debt and revolving line of credit	105.3	12.0
Repayment of debt and revolving line of credit	(93.7)	(1.0)
Cash dividends paid to the Company’s common shareholders	(3.1)	(3.2)
Common shares repurchased	0.0	(47.8)
Distribution to non-controlling interest shareholders	(0.9)	(0.7)
Contingent consideration payments related to acquisitions of subsidiaries	(6.7)	(6.4)
Capital contributions to non-controlling interest shareholders	(0.4)	0.4
Capital contributions from BAM members	13.8	10.0
Fidus Re premium payment	(3.2)	(0.8)
Other financing activities, net	(4.6)	(6.7)
Net cash provided from (used for) financing activities	6.5	(44.2)
Effect of exchange rate changes on cash	(0.3)	(1.1)
Net change in cash during the period - continuing operations, including the effect of exchange rate changes	277.3	(24.6)
Cash balances at beginning of period (includes restricted cash balances of $78.4 and $56.3)	211.2	161.0	$ 161.0
Cash balances at end of period (includes restricted cash balances of $83.2 and $64.9)	488.5	136.4	$ 211.2
Supplemental cash flows information:
Interest paid	(7.5)	(5.2)
Net income tax payments	(1.4)	0.0
Marketing Technology (MediaAlpha)
Adjustments to reconcile net income to net cash used for operations:
Net realized and unrealized investment losses (gains) from investment in MediaAlpha	$ 41.7	$ (30.0)

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Restricted cash balance	$ 83,200,000	$ 64,900,000	$ 78,400,000	$ 56,300,000
Cash acquired from acquisition	52,000,000.0	0
Cash Equivalents
Cash acquired from acquisition	$ 0	$ 0

Basis of Presentation and Significant Accounting Policies	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	Basis of Presentation and Significant Accounting Policies Basis of Presentation The Company is an exempted Bermuda limited liability company whose principal businesses are conducted through its subsidiaries and other affiliates. The Company’s headquarters is located at 26 Reid Street, Hamilton, Bermuda HM 11, its principal executive office is located at 23 South Main Street, Suite 3B, Hanover, New Hampshire 03755-2053 and its registered office is located at Clarendon House, 2 Church Street, Hamilton, Bermuda HM 11. The Company’s website is located at www.whitemountains.com. The information contained on White Mountains’s website is not incorporated by reference into, and is not a part of, this report. The accompanying consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) and include the accounts of White Mountains Insurance Group, Ltd. (the “Company” or the “Registrant”), its subsidiaries (collectively with the Company, “White Mountains”) and other entities required to be consolidated under GAAP. Consolidation Principles Under GAAP, the Company is required to consolidate any entity in which it holds a controlling financial interest. A controlling financial interest is usually in the form of an investment representing the majority of the subsidiary’s voting interests. However, a controlling financial interest may also arise from a financial interest in a variable interest entity (“VIE”) through arrangements that do not involve ownership of voting interests. The Company consolidates a VIE if it determines that it is the primary beneficiary. The primary beneficiary is defined as the entity who holds a variable interest that gives it both the power to direct the VIE’s activities that most significantly impact its economic performance and the obligation to absorb losses of, or the right to receive returns from, the VIE that could potentially be significant to the VIE. Intercompany transactions have been eliminated in consolidation. These interim financial statements include all adjustments considered necessary by management to fairly state the financial position, results of operations and cash flows of White Mountains. These interim financial statements may not be indicative of financial results for the full year and should be read in conjunction with the Company’s 2020 Annual Report on Form 10-K. Business Combinations White Mountains accounts for purchases of businesses using the acquisition method, which requires the measurement of assets acquired, including goodwill and other intangible assets, and liabilities assumed, including contingent liabilities, at their estimated fair values as of the acquisition date. The acquisition date fair values represent management’s best estimates and are based upon established valuation techniques, reasonable assumptions and, where appropriate, valuations performed by independent third parties. In circumstances where additional information is required in order to determine the acquisition date fair value of balance sheet amounts, provisional amounts may be recorded as of the acquisition date and may be subject to subsequent adjustment throughout the measurement period, which is up to one year from the acquisition date. Measurement period adjustments are recognized in the period in which they are determined. The results of operations and cash flows of businesses acquired are included in the consolidated financial statements from the date of acquisition. White Mountains accounts for purchases of other intangible assets that do not meet the definition of a business as asset acquisitions. Asset acquisitions are recognized at the amount of consideration paid, which is deemed to equal fair value. Use of Estimates 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. Fair Value Measurements Fair value measurements are categorized into a hierarchy that distinguishes between inputs based on market data from independent sources (“observable inputs”) and a reporting entity’s internal assumptions based upon the best information available when external market data is limited or unavailable (“unobservable inputs”). Quoted prices in active markets for identical assets or liabilities have the highest priority (“Level 1”), followed by observable inputs other than quoted prices, including prices for similar but not identical assets or liabilities (“Level 2”) and unobservable inputs, including the reporting entity’s estimates of the assumptions that market participants would use, having the lowest priority (“Level 3”). Reportable Segments White Mountains has determined its reportable segments based on the nature of the underlying businesses, the manner in which the Company’s subsidiaries and affiliates are organized and managed and the organization of the financial information provided to the chief operating decision maker to assess performance and make decisions regarding allocation of resources. As of March 31, 2021, White Mountains’s reportable segments were HG Global/BAM, Ark, NSM, Kudu and Other Operations. The HG Global/BAM segment consists of HG Global Ltd. and its wholly-owned subsidiaries (“HG Global”) and the consolidated results of Build America Mutual Assurance Company (“BAM”) (collectively, “HG Global/BAM”). BAM is the first and only mutual municipal bond insurance company in the United States. By insuring the timely payment of principal and interest, BAM provides market access to, and lowers interest expense for, issuers of municipal bonds used to finance essential public purposes such as schools, utilities and transportation facilities. BAM is owned by and operated for the benefit of its members, the municipalities that purchase BAM’s insurance for their debt issuances. HG Global was established to fund the startup of BAM and, through its wholly-owned subsidiary, HG Re Ltd. (“HG Re”), to provide up to 15%-of-par, first loss reinsurance protection for policies underwritten by BAM. For capital appreciation bonds, par is adjusted to the estimated equivalent par value for current interest paying bonds. HG Global, together with its subsidiaries, funded the initial capitalization of BAM through the purchase of $503.0 million of surplus notes issued by BAM, consisting of $203.0 million of Series A Notes and $300.0 million of Series B Notes (the “BAM Surplus Notes”). As of March 31, 2021 and December 31, 2020, White Mountains owned 96.9% of HG Global’s preferred equity and 88.4% of its common equity. White Mountains does not have an ownership interest in BAM. However, White Mountains is required to consolidate BAM’s results in its financial statements because BAM is a VIE for which White Mountains is the primary beneficiary. BAM’s results are attributed to non-controlling interests. The Ark segment consists of Ark Insurance Holdings Limited and its subsidiaries (collectively, “Ark”). Ark writes a diversified and balanced portfolio of reinsurance and insurance, including property, accident & health, energy, marine and political risks, through Lloyd’s Syndicates 4020 and 3902 (the “Syndicates”). Beginning in January 2021, Ark began writing certain classes of its business through Group Ark Insurance Limited (“GAIL”), Ark’s wholly-owned Bermuda-based insurance and reinsurance company. As of March 31, 2021, White Mountains owned 72.0% of Ark on a basic shares outstanding basis (63.0% on a fully-diluted, fully-converted basis, taking account of management’s equity incentives). If the additional $200.0 million of equity capital that White Mountains has agreed to contribute to Ark is contributed in full, White Mountains will own 77.1% of Ark on a basic shares outstanding basis (67.5% on a fully-diluted, fully-converted basis). The remaining shares are owned by employees. In the future, management rollover shareholders could earn additional shares in the company if and to the extent that White Mountains achieves certain multiple of invested capital return thresholds. If fully earned, these additional shares would represent 12.5% of the shares outstanding at closing. See Note 2 — “Significant Transactions”. The NSM segment consists of NSM Insurance HoldCo, LLC and its subsidiaries (collectively, “NSM”). NSM is a full-service managing general underwriting agency (“MGU”) and program administrator for specialty property and casualty insurance. The company places insurance in niche sectors such as specialty transportation, real estate, social services and pet. On behalf of its insurance carrier partners, NSM typically manages all aspects of the placement process, including product development, marketing, underwriting, policy issuance and claims. NSM earns commissions based on the volume and profitability of the insurance that it places. NSM does not take insurance risk. As of March 31, 2021 and December 31, 2020, White Mountains owned 96.6% of the basic units outstanding of NSM (89.6% on a fully diluted, fully converted basis). See Note 2 — “Significant Transactions”. The Kudu segment consists of Kudu Investment Management, LLC and its subsidiaries (collectively “Kudu”), a capital solutions provider for asset management firms. Kudu provides capital solutions for boutique asset managers for a variety of purposes including generational ownership transfers, management buyouts, acquisition and growth finance and legacy partner liquidity. Kudu also provides strategic assistance to investees from time to time. Kudu’s capital solutions typically are structured as minority preferred equity stakes with distribution rights, typically tied to gross revenues and designed to generate immediate strong, stable cash yields. As of March 31, 2021 and December 31, 2020, White Mountains owned 99.3% of the basic units outstanding (84.8% on a fully diluted, fully converted basis). See Note 2 — “Significant Transactions”. The Other Operations segment consists of the Company and its wholly-owned subsidiary, White Mountains Capital, LLC, (“WM Capital”) its other intermediate holding companies, its wholly-owned investment management subsidiary, White Mountains Advisors LLC (“WM Advisors”), investment assets managed by WM Advisors, its interests in MediaAlpha, Inc. (“MediaAlpha”), PassportCard Limited (“PassportCard”) and DavidShield Life Insurance Agency (2000) Ltd. (“DavidShield”) (collectively, “PassportCard/ DavidShield”), Elementum Holdings LP (“Elementum”), and certain other consolidated and unconsolidated entities and certain other assets. Discontinued Operations and Assets Held for Sale In the first quarter of 2021, White Mountains recorded a gain on sale of discontinued operations as a result of reversing a liability arising from the tax indemnification provided in connection with the sale of Sirius International Insurance Group, Ltd. (“Sirius Group”) in 2016. As of December 31, 2020, assets held for sale included a corporate aircraft, which was sold on February 12, 2021. On April 12, 2021, NSM sold the Fresh Insurance Services Group Limited (“Fresh Insurance”) motor business. As of March 31, 2021, assets held for sale included the net realizable value of Fresh Insurance’s motor business, which was recorded in other assets in the NSM segment. Note 19 — “Held for Sale and Discontinued Operations”. Significant Accounting Policies In addition to the following, refer to the Notes to Consolidated Financial Statements in the Company’s 2020 Annual Report on Form 10-K for a complete discussion regarding White Mountains’s significant accounting policies. Ark Insurance Operations Ark writes a diversified and balanced portfolio of reinsurance and insurance, including property, accident & health, energy, marine and political risks, through the Syndicates. Beginning in January 2021, Ark began writing certain classes of its business through GAIL. For the years of account prior to White Mountains’s transaction with Ark, a significant proportion of the Syndicates’ underwriting capital was provided by other third-party insurance and reinsurance groups (“TPC Providers”) using whole account reinsurance contracts through Ark’s corporate member. The TPC Providers’ economic participation in the Syndicates for the remaining open years of account prior to White Mountains’s transaction with Ark is approximately 51% of the total net result of the Syndicates. Captions within results of operations and other comprehensive income are shown net of amounts relating to the TPC Providers share of the Syndicates’ results, including investment results. Ark’s premiums written comprise premiums on insurance contracts incepted during the year as well as premium adjustments related to prior accounting years. Insurance premiums are recognized in earnings over the loss exposure or coverage period in proportion to the level of protection provided. In most cases, such premiums are earned ratably over the term of the contract with unearned premiums calculated on a monthly pro-rata basis. Premiums earned are presented net of amounts ceded to reinsurers. Premiums receivable, representing amounts due from insureds, are presented net of an allowance for uncollectible premiums, including expected credit losses, both dispute and credit related. The allowance is based upon Ark’s ongoing review of amounts outstanding, historical loss data, including delinquencies and write-offs, current and forecasted economic conditions and other relevant factors. Credit risk is partially mitigated by Ark’s ability to cancel the policy if the policyholder does not pay the premium. Deferred acquisition costs comprise brokerage and taxes which are directly attributable to and vary with the production of business. These costs are deferred and amortized to the extent they related to successful contract acquisitions over the applicable premium recognition period. Losses and loss adjustment expenses (“LAE”) are charged against income as incurred. Unpaid losses and LAE, including estimates for amounts incurred and not reported (“IBNR”) are based on estimates of the ultimate costs of settling claims, including the effects of inflation and other societal and economic factors. 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 results of 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. Reinsurance recoverables represent amounts of paid losses and loss adjustment expenses, case reserves and IBNR amounts ceded to reinsurers under reinsurance treaties. Amounts recoverable from reinsurers are estimated in a manner consistent with the associated claim liability. Ark reports its reinsurance recoverables net of an allowance for estimated uncollectible reinsurance, including expected credit losses. The allowance is based upon its ongoing review of amounts outstanding, length of collection periods, changes in reinsurer credit standing, disputes, applicable coverage defenses and other relevant factors. Derivatives From time to time, White Mountains holds derivative financial instruments for risk management purposes. White Mountains recognizes all derivatives as either assets or liabilities, measured at fair value, on the consolidated balance sheet. Changes in the fair value of derivative instruments that meet the criteria for hedge accounting are recognized in other comprehensive income and reclassified into current period pre-tax income when the hedged items are recognized therein. Changes in the fair value of derivative instruments that do not meet the criteria for hedge accounting are recognized in current period pre-tax income. As of March 31, 2021 and December 31, 2020, NSM holds an interest rate swap derivative instrument that meets the criteria for hedge accounting. See Note 9 — “Derivatives”. Goodwill and Other Intangible Assets Goodwill represents the excess of the amount paid to acquire subsidiaries over the fair value of identifiable net assets at the date of acquisition. Other intangible assets consist primarily of the Lloyds underwriting capacity, trade names, URL and online names, customer relationships and contracts, information technology platforms and insurance licenses. Reinsurance Contracts Accounted for as Deposits Reinsurance contracts that do not meet the risk transfer requirements necessary to be accounted for as reinsurance are accounted for using the deposit method. Under the deposit method, ceded premiums paid are not recognized through income but rather treated as a deposit. BAM entered into ceded reinsurance agreements with Fidus Re Ltd. (“Fidus Re”) during the second quarter of 2018 and the first quarter of 2021, which are both accounted for using the deposit method. See Note 10 — “Municipal Bond Guarantee Insurance”. The nonrefundable consideration paid by BAM to Fidus Re is charged to financing expense within general and administrative expenses. Ark has an aggregate excess of loss contract with Third Point Reinsurance Ltd. (“Third Point Re”) in the amount of $50.0 million, which is accounted for using the deposit method. Ark earns an annual crediting rate of 3% which is recorded within other revenue. As of March 31, 2021, the carrying value of Ark’s deposit in Third Point Re, including accrued interest, was $51.7 million and is recorded in other assets. Cash and Restricted 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. Cash balances that are not immediately available for general corporate purposes, including fiduciary accounts held by NSM on behalf of insurance carriers, are classified as restricted. Recently Adopted Changes in Accounting Principles Income Taxes On January 1, 2020, White Mountains adopted ASU 2019-12, Simplifying the Accounting for Income Taxes (ASC 740), which removes exceptions to standard guidance. Under the new guidance non-income-based taxes, such as franchise taxes, are reported within pre-tax income rather than being included in income taxes. In addition, the new guidance eliminated the exception to the incremental approach for inter-period tax allocation, which previously allowed consideration of the tax effect of items such as discontinued operations and items recognized through other comprehensive income. For periods subsequent to the adoption of ASU 2019-12, White Mountains has recorded both the tax expense related to BAM’s member surplus contributions (“MSC”) and the related valuation allowance on such taxes through the non-controlling interest equity. Prior to the adoption of ASU 2019-12, White Mountains recorded the tax expense related to BAM’s MSC directly to non-controlling interest equity, while the valuation allowance on such taxes was recorded through the income statement. Goodwill On January 1, 2020, White Mountains adopted ASU 2017-04, Simplifying the Test for Goodwill Impairment (ASC 350), which changed the guidance on goodwill impairment testing. Under the new guidance, the qualitative assessment of the recoverability of goodwill remains the same, but the second step of the two-step qualitative test, which required calculation of the implied fair value of goodwill, has been eliminated. Instead, an impairment charge is recognized when the carrying value of a reporting unit exceeds its fair value. Any excess of carrying value over fair value is written down as an impairment. White Mountains did not identify any impairment indicators associated with its reporting units and therefore did not recognize an impairment of goodwill during the quarter ended March 31, 2021. White Mountains’s adoption of ASU 2017-04 did not have any impact on White Mountains’s financial statements. Credit LossesOn January 1, 2020, White Mountains adopted ASU 2016-13, Measurement of Credit Losses on Financial Instruments (ASC 326), which establishes new guidance for the recognition of credit losses for financial assets measured at amortized cost. The new ASU requires reporting entities to estimate the credit losses expected over the life of a credit exposure using historical information, current information and reasonable and supportable forecasts that affect the collectability of the financial asset. White Mountains measures its portfolio of investment securities at fair value with changes therein recognized through current period earnings and, accordingly, adoption of ASU 2016-13 did not have any impact on White Mountains’s financial statements.

Significant Transactions

3 Months Ended

Mar. 31, 2021

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Significant Transactions

MediaAlpha

On October 30, 2020, MediaAlpha completed an initial public offering (the “MediaAlpha IPO”). In the offering, White Mountains sold 3.6 million shares at $19.00 per share ($17.67 per share net of underwriting fees) and received total proceeds of $63.8 million. White Mountains also received $55.0 million of net proceeds related to a dividend recapitalization at MediaAlpha. Following the MediaAlpha IPO, White Mountains owned 20.5 million MediaAlpha shares, representing a 35.0% ownership interest (32.3% on a fully-diluted, fully converted basis).

On March 23, 2021, MediaAlpha completed a secondary offering of 8.05 million shares. In the secondary offering, White Mountains sold 3.6 million shares at $46.00 per share ($44.62 per share net of underwriting fees) for net proceeds of $160.3 million. Following the completion of the offering, White Mountains owns 16.9 million shares, representing a 28.5% basic ownership interest (26.3% fully-diluted/fully-converted basis). At the March 31, 2021, closing price of $35.43 per share, the fair value of White Mountains’s remaining investment in MediaAlpha was $600.2 million. See Note 16 — “Equity-Method Eligible Investments”.

Ark

On October 1, 2020, White Mountains entered into a subscription and purchase agreement (the “Ark SPA”) with Ark and certain selling shareholders (collectively with Ark, the “Ark Sellers”). Certain Ark Sellers also entered into a related management warranty deed (together with the Ark SPA, the “Ark Acquisition Agreement”) pursuant to which they made certain warranties about the Ark business (collectively the “Ark Transaction”). Under the terms of the Ark SPA, White Mountains agreed to contribute $605.4 million of equity capital to Ark, at a pre-money valuation of $300.0 million, and purchase $40.9 million of shares from the Ark Sellers. White Mountains also agreed to contribute up to an additional $200.0 million of equity capital to Ark in 2021. In accordance with the Ark SPA, in the fourth quarter of 2020 White Mountains pre-funded/placed in escrow a total of $646.3 million in preparation for closing the Ark Transaction, including $280.0 million funded directly to Lloyd’s on behalf of Ark under the terms of a Deposit Trust Deed and $366.3 million placed in escrow, which is reflected on the balance sheet within the Other Operations segment as of December 31, 2020.

On January 1, 2021, White Mountains completed the Ark Transaction in accordance with the terms of the Ark SPA. As of March 31, 2021, White Mountains owned 72.0% of Ark on a basic shares outstanding basis (63.0% on a fully-diluted, fully-converted basis, taking account of management’s equity incentives). If the additional $200 million of equity capital that White Mountains has agreed to contribute to Ark is contributed in full, White Mountains will own 77.1% of Ark on a basic shares outstanding basis (67.5% on a fully-diluted, fully-converted basis). The remaining shares are owned by employees. In the future, management rollover shareholders could earn additional shares in the company if and to the extent that White Mountains achieves certain multiple of invested capital return thresholds. If fully earned, these additional shares would represent 12.5% of the shares outstanding at closing.

White Mountains recognized total assets acquired related to the Ark Transaction of $2.5 billion, including goodwill and other intangible assets of $292.5 million, and total liabilities of $1.7 billion, including contingent consideration of $22.5 million and non-controlling interest of $220.2 million. Ark incurred transaction costs of $25.3 million in the first quarter of 2021.

The following presents additional details of the assets acquired and liabilities assumed as of the January 1, 2021 acquisition date:


Millions	As of January 1, 2021
Investments	$	594.3
Cash	52.0		(1)
Reinsurance recoverables	433.4
Insurance premiums receivable	236.7
Ceded unearned premiums	170.2
Value of in-force business acquired	71.7
Other assets	88.9
Loss and loss adjustment expense reserves	(696.0)
Unearned insurance premiums	(326.1)
Debt	(46.4)

Ceded reinsurance payable	(528.3)
Other liabilities	(25.9)
Net tangible assets acquired	24.5
Goodwill	116.8
Other intangible assets - syndicate underwriting capacity	175.7
Deferred tax liability on other intangible assets	(33.4)
Net assets acquired	$	283.6

(1) Cash excludes the White Mountains cash contribution of $605.4 as part of the Ark transaction.

The acquisition date fair values of assets and liabilities, including insurance reserves and intangible assets, are provisional and are subject to revision within one year of the acquisition date.

The values of net tangible assets acquired and the resulting goodwill, other intangible assets and contingent consideration were recorded at fair value using Level 3 inputs. The majority of the tangible assets acquired and liabilities assumed were recorded at their carrying values, as their carrying values approximated their fair values due to their short-term nature. The fair values of goodwill, other intangible assets and the contingent consideration liability were internally estimated primarily based on the income approach. The income approach estimates fair value based on the present value of the cash flows that the assets are expected to generate in the future. White Mountains developed internal estimates for the expected future cash flows and discount rates used in the present value calculations.

The value of in-force business acquired represents the estimated profits relating to the unexpired contracts, net of related prepaid reinsurance at the acquisition date through the expiration date of the contracts. The value of the syndicate underwriting capacity intangible asset was estimated using net cash flows attributable to Ark’s rights to write business in the Lloyd’s market. The value of the in-force business acquired and the syndicate underwriting capacity were estimated using a discounted cash flow method. Significant inputs to the valuation models include estimates of growth in premium revenues, investment returns, claim costs, expenses and discount rates based on a weighted average cost of capital.

In evaluating the fair value of Ark’s loss and loss adjustment expense reserves, White Mountains determined that the risk-free rate of interest was approximately equal to the risk factor reflecting the uncertainty within the reserves and that no adjustment was necessary.

Ark’s segment income and expenses for the three months ended March 31, 2021 are presented in Note 15 - “Segment Information.” Pro forma financial information for Ark for the three months ended March 31, 2020 has not been presented because as a private U.K. domiciled company Ark does not have quarterly financial reporting requirements and therefore quarterly financial information is not available for periods prior to the January 1, 2021 acquisition date.

NSM

On May 18, 2018, NSM acquired 100% of Fresh Insurance, which is an insurance broker that offers non-standard personal lines products in the United Kingdom. NSM paid $49.6 million of upfront cash consideration for Fresh Insurance. NSM borrowed $51.0 million to fund the transaction. During the nine months ended September 30, 2019, NSM paid a purchase price adjustment of an additional $0.7 million of consideration. The purchase price is subject to additional adjustments based upon growth in EBITDA during two earnout periods, one which ended in February 2020 and one ending in February 2022. NSM did not make any payments related to the first Fresh Insurance earnout period.

On April 12, 2021, NSM sold Fresh Insurance’s motor business. The assets and liabilities included in the transaction, principally goodwill, have been classified as held for sale as of March 31, 2021 and have been measured at their estimated fair values, net of disposal costs. As a result, White Mountains recognized a loss of $28.7 million. White Mountains determined that the transaction qualified as a held for sale business in the first quarter 2021, however, it did not meet the criteria to be classified as discontinued operations.

On December 3, 2018, NSM acquired all the net assets of KBK Insurance Group, Inc. (“KBK”), a specialized MGU focused on the towing and transportation space. NSM paid $60.0 million of upfront cash consideration for KBK. White Mountains contributed $29.0 million to NSM and NSM borrowed $30.1 million to fund the transaction. As of March 31, 2019, White Mountains determined that the relative values of goodwill and other intangible assets from the KBK transaction were $32.6 million and $32.7 million, reflecting acquisition date fair values, and recorded a liability of $5.9 million relating to the fair value of contingent consideration earnouts made in connection with the acquisition. The purchase price is subject to adjustments based upon growth in EBITDA during three earnout periods, one which ended in December 2019, one ending in December 2020 and one ending in December 2021. In the first quarter of 2021 and 2020, NSM paid $6.7 million and $6.4 million related to the first and second KBK earnout period. As of March 31, 2021, the KBK contingent consideration earnout liability was $6.4 million.

On April 7, 2020, NSM acquired 100% of Kingsbridge Group Limited (“Kingsbridge”), a leading provider of commercial lines insurance and consulting services for the professional contractor and freelancer markets in the United Kingdom. NSM paid £107.2 million (approximately $132.2 million based upon the foreign exchange spot rate at the date of acquisition) of upfront cash consideration for Kingsbridge. White Mountains contributed $80.3 million to NSM and NSM borrowed £42.5 million (approximately $52.4 million based upon the foreign exchange spot rate at the date of acquisition) to fund the transaction. During 2020, NSM determined that the relative values of goodwill and other intangible assets recorded in connection with the Kingsbridge transaction were $111.5 million and $20.2 million, reflecting acquisition date fair values. The purchase price is subject to adjustment based upon growth in EBITDA during an earnout period ending in January 2022. During 2020, NSM initially recorded a liability relating to the fair value of the Kingsbridge contingent consideration earnout of $4.1 million. During 2020, NSM recognized pre-tax income of $4.1 million for the change in fair value of the Kingsbridge contingent consideration earnout liability and a foreign currency translation unrealized gain of $0.3 million. As of March 31, 2021, the Kingsbridge contingent consideration earnout liability was $0.2 million.

The contingent consideration earnout liabilities related to NSM’s acquisitions are subject to adjustments based upon EBITDA, EBITDA projections, and present value factors for acquired entities. For the three months ended March 31, 2021 and 2020, NSM recognized no pre-tax (revenue) expense and $(0.6) million pre-tax revenue for the change in the fair value of its contingent consideration earnout liabilities. Any future adjustments to contingent consideration earnout liabilities under the agreements will be recognized through pre-tax income. As of March 31, 2021 and December 31, 2020, NSM recorded total contingent consideration earnout liabilities of $7.9 million and $14.6 million.

PassportCard/DavidShield

On January 24, 2018, White Mountains acquired a 50% ownership interest in DavidShield, its joint venture partner in PassportCard. DavidShield is a managing general agency that is the leading provider of expatriate medical insurance in Israel and uses the same card-based delivery system as PassportCard. As part of the transaction, White Mountains reorganized its equity stake in PassportCard so that White Mountains and its partner in DavidShield would each own 50% of both businesses. To facilitate the transaction, White Mountains provided financing to its partner in the form of a non-interest bearing loan that is secured by the partner’s equity in PassportCard and DavidShield. The gross purchase price for the 50% interest in DavidShield was $41.8 million, or $28.3 million net of the financing provided for the restructuring.

On May 7, 2020, White Mountains made an additional $15.0 million investment in PassportCard/DavidShield to support operations through the ongoing COVID-19 pandemic. The transaction increased White Mountains’s ownership interest from 50.0% to 53.8%, but had no impact on the governance structure of the companies, including White Mountains’s board representation or other investor rights. The governance structures for both PassportCard and DavidShield were designed to give White Mountains and its co-investor equal power to make the decisions that most significantly impact the operations of PassportCard and DavidShield.

As a result of the transaction, White Mountains’s re-evaluated its accounting treatment for PassportCard and DavidShield. Because White Mountains does not have the unilateral power to direct the operations of PassportCard or DavidShield, White Mountains does not hold a controlling financial interest in either PassportCard or DavidShield and does not consolidate either entity. White Mountains’s ownership interest gives White Mountains the opportunity to exert significant influence over the significant financial and operating activities of PassportCard and DavidShield. Accordingly, PassportCard and DavidShield meet the criteria to be accounted for under the equity method. White Mountains has taken the fair value option for its investment in PassportCard and DavidShield. Changes in the fair value of PassportCard and DavidShield are recorded in realized and unrealized investment gains. White Mountains’s maximum exposure to loss on its equity investment in PassportCard/DavidShield and the non-interest bearing loan to its partner is limited to the total carrying value of $104.2 million.

Loss and Loss Adjustment Expense Reserves

3 Months Ended

Mar. 31, 2021

Insurance Loss Reserves [Abstract]

Loss and Loss Adjustment Expense Reserves

Ark establishes loss and loss adjustment expense (“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 typically comprise case reserves for claims reported and reserves for losses that have occurred but for which claims have not yet been reported, referred to as incurred but not reported (“IBNR”) reserves. IBNR reserves include a provision for expected future development on case reserves. Case reserves are estimated based on the experience and knowledge of claims staff regarding the nature and potential cost of each claim and are adjusted as additional information becomes known or payments are made. IBNR reserves are typically derived by subtracting paid loss and LAE and case reserves from estimates of ultimate losses 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. Ark’s own experience, particularly claims development experience, such as trends in case reserves, payments on and closings of claims, as well as changes in business mix and coverage limits, is the most important information for estimating its reserves. Ultimate loss and LAE for major losses and catastrophes are estimated based on the known and expected exposures to the loss event, rather than simply relying on the extrapolation of reported and settled claims.

Uncertainties in estimating ultimate loss and LAE are magnified by the time lag between when a claim actually occurs and when it is reported and eventually settled. This time lag is sometimes referred to as the “claim-tail”. The claim-tail for most property coverages is typically short (usually a few days up to a few months). The claim-tail for liability/casualty coverages can be quite long as claims are often reported and ultimately paid or settled years 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, Ark 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. 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.

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 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. Because of the factors previously discussed, the process requires the use of informed judgment and is inherently uncertain.

Ark performs an actuarial review of its recorded reserves each quarter, using 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.

The following table summarizes the loss and LAE reserve activities of Ark’s insurance and reinsurance subsidiaries for the three months ended March 31, 2021:


Millions	Three Months Ended March 31, 2021
Gross beginning balance as of January 1, 2021	$	696.0
Less: beginning reinsurance recoverable on unpaid losses	(433.4)
Net loss and LAE reserves	262.6

Loss and LAE incurred relating to:
Current year losses	65.5
Prior year losses	.5
Total incurred losses and LAE	66.0

Foreign currency translation adjustment to loss and LAE reserves	.7

Loss and LAE paid relating to:
Current year losses	(5.2)
Prior year losses	(19.7)
Total loss and LAE payments	(24.9)

Net ending balance	304.4
Plus: ending reinsurance recoverable on unpaid losses	447.5
Gross ending balance as of March 31, 2021	$	751.9

See Note 10 — “Municipal Bond Guarantee Insurance” for loss and LAE reserve balances related to White Mountains financial guarantee business.

Third Party Reinsurance

3 Months Ended

Mar. 31, 2021

Reinsurance Disclosures [Abstract]

Third Party Reinsurance

In the normal course of business, Ark may seek to limit losses that may arise from catastrophes or other events by reinsuring with third party reinsurers. Ark remains liable for risks reinsured in the event that the reinsurer does not honor its obligations under reinsurance contracts. The following table summarizes the effects of reinsurance on written and earned premiums and on losses and LAE for Ark.


	Three Months Ended March 31, 2021
Millions
Written premiums:
Gross	$	404.5


Ceded	(62.1)
Net written premiums	$	342.4
Earned premiums:
Gross	$	162.6


Ceded	(58.0)
Net earned premiums	$	104.6
Losses and LAE:
Gross	$	115.6


Ceded	(49.6)
Net Losses and LAE	$	66.0

As of March 31, 2021, Ark had $447.5 million and $1.5 million of reinsurance recoverables on unpaid and paid losses. As reinsurance contracts do not relieve Ark of its obligation to its policyholders, Ark seeks to reduce the credit risk associated with reinsurance balances by avoiding over-reliance on specific reinsurers through the application of concentration limits and thresholds. Ark is selective with its reinsurers, placing reinsurance with only those reinsurers having a strong financial condition. Ark monitors the financial strength of its reinsurers on an ongoing basis.

As of March 31, 2021, Ark’s reinsurance recoverables on unpaid losses of $447.5 million included $331.0 million related to TPC Providers, which are collateralized. Of the remaining $116.5 million of reinsurance recoverables on unpaid losses, 90% are from reinsurers with an A.M. Best rating of “A” (Excellent, which is the third highest of 16 financial strength ratings).

See Note 10 — “Municipal Bond Guarantee Insurance” for third-party reinsurance balances related to White Mountains financial guarantee business.

Investment Securities

3 Months Ended

Mar. 31, 2021

Investments, Debt and Equity Securities [Abstract]

Investment Securities

White Mountains’s portfolio of investment securities held for general investment purposes consists of fixed maturity investments, short-term investments, common equity securities, its investment in MediaAlpha and other long-term investments, which are classified as trading securities. Trading securities are reported at fair value as of the balance sheet date. Net realized and unrealized investment gains (losses) on trading securities are reported in pre-tax revenues.

White Mountains’s fixed maturity investments are generally valued using industry standard pricing methodologies. Key inputs include benchmark yields, benchmark securities, reported trades, issuer spreads, bids, offers, credit ratings and prepayment speeds. Income on mortgage 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.

Realized investment gains (losses) resulting from sales of investment securities are accounted for using the specific identification method. Premiums and discounts on all fixed maturity investments are amortized or accreted to income over the anticipated life of the investment. Short-term investments consist of interest-bearing 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 fair value as of March 31, 2021 and December 31, 2020.

Other long-term investments consist primarily of unconsolidated entities, including Kudu’s Participation Contracts, private equity funds, a hedge fund, Lloyd’s trust deposits, a bank loan fund, ILS funds and private debt instruments.

Net Investment Income

White Mountains’s net investment income is comprised primarily of interest income associated with White Mountains’s fixed maturity investments and short-term investments, dividend income from common equity securities, distributions from its investment in MediaAlpha and distributions from other long-term investments.

The following table presents pre-tax net investment income for the three months ended March 31, 2021 and 2020:


	Three Months Ended
	March 31,
Millions		2021		2020
Fixed maturity investments		$	6.5	$	8.1
Short-term investments		1.6		.8
Common equity securities		—		3.8

Investment in MediaAlpha		—		2.4
Other long-term investments		13.8		8.1
Amount attributable to TPC Providers		(.9)		—
Total investment income		21.0		23.2
Third-party investment expenses		(.4)		(.3)
Net investment income, pre-tax		$	20.6	$	22.9

Net Realized and Unrealized Investment Gains (Losses)

The following table presents net realized and unrealized investment gains (losses) for the three months ended March 31, 2021 and 2020:


	Three Months Ended
	March 31,
Millions	2021		2020
Fixed maturity investments	$	(25.4)	$	2.2
Short-term investments	(1.3)		.4
Common equity securities	1.0		(140.8)
Investment in MediaAlpha	(41.7)		30.0
Other long-term investments	28.1		(48.5)
Amount attributable to TPC Providers	(1.3)		—
Net realized and unrealized investment losses (1)	(40.6)		(156.7)
Less: net losses on investment securities sold during the period	(.2)		(8.7)
Net realized and unrealized investment losses on investment securities held at the end of the period	$	(40.4)	$	(148.0)

(1) For the three months ended March 31, 2021 and 2020, includes $(0.2) and $(0.4) of realized and unrealized investment losses related to foreign currency exchange.

The following table presents total gains (losses) included in earnings attributable to net unrealized investment gains (losses) for Level 3 investments for the three months ended March 31, 2021 and 2020 for investments still held at the end of the period:


	Three Months Ended
	March 31,
Millions	2021		2020



Other long-term investments	$	16.7	$	(9.4)
Total net unrealized investment gains (losses), pre-tax - Level 3 investments	$	16.7	$	(9.4)

Investment Holdings

The following tables present the cost or amortized cost, gross unrealized investment gains (losses) and carrying values of White Mountains’s fixed maturity investments as of March 31, 2021 and December 31, 2020:


	March 31, 2021
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains		Carrying Value
U.S. Government and agency obligations	$	220.1	$	2.1	$	(.6)	$	—	$	221.6
Debt securities issued by corporations	678.6		13.9		(5.7)		.1		686.9
Municipal obligations	269.4		15.4		(1.0)		—		283.8
Mortgage and asset-backed securities	225.8		5.4		(1.3)		—		229.9

Collateralized loan obligations	59.5		—		(.1)		—		59.4
Total fixed maturity investments	$	1,453.4	$	36.8	$	(8.7)	$	.1	$	1,481.6


	December 31, 2020
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Carrying Value
U.S. Government and agency obligations	$	173.2	$	3.1	$	—	$	176.3
Debt securities issued by corporations	522.8		24.7		(.1)		547.4
Municipal obligations	244.0		21.0		—		265.0
Mortgage and asset-backed securities	211.7		6.8		—		218.5


Total fixed maturity investments	$	1,151.7	$	55.6	$	(.1)	$	1,207.2

The following tables present the cost or amortized cost, gross unrealized investment gains (losses), net foreign currency gains (losses), and carrying values of common equity securities, White Mountains’s investment in MediaAlpha and other long-term investments as of March 31, 2021 and December 31, 2020:


	March 31, 2021
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains (Losses)		Carrying Value
Common equity securities	$	117.6	$	1.1	$	(.2)	$	.1	$	118.6
Investment in MediaAlpha	$	—	$	600.2	$	—	$	—	$	600.2

Other long-term investments	$	965.5	$	125.8	$	(56.5)	$	(2.6)	$	1,032.2


	December 31, 2020
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains		Carrying Value
Common equity securities	$	—	$	—	$	—	$	—	$	—
Investment in MediaAlpha	$	—	$	802.2	$	—	$	—	$	802.2

Other long-term investments	$	767.4	$	95.8	$	(78.1)	$	1.7	$	786.8

Fair Value Measurements as of March 31, 2021

As of March 31, 2021 and December 31, 2020, White Mountains used quoted market prices or other observable inputs to determine fair value for approximately 73% of the investment portfolio.

Fair Value Measurements by Level

The following tables present White Mountains’s fair value measurements for investments as of March 31, 2021 and December 31, 2020 by level. The major security types were based on the legal form of the securities. White Mountains has disaggregated its fixed maturity investments based on the issuing entity type, which impacts credit quality, with debt securities issued by U.S. government entities carrying minimal credit risk, while the credit and other risks associated with other issuers, such as corporations, municipalities or entities issuing mortgage and asset-backed securities vary depending on the nature of the issuing entity type. White Mountains further disaggregates debt securities issued by corporations by industry sector because investors often reference commonly used benchmarks and their subsectors to monitor risk and performance. Accordingly, White Mountains has further disaggregated this asset class into subclasses based on the similar sectors and industry classifications it uses to evaluate investment risk and performance against commonly used benchmarks, such as the Bloomberg Barclays U.S. Intermediate Aggregate.


	March 31, 2021
Millions	Fair Value		Level 1		Level 2		Level 3
Fixed maturity investments:
U.S. Government and agency obligations	$	221.6	$	221.6	$	—	$	—

Debt securities issued by corporations:
Financials	183.1		—		183.1		—
Consumer	96.3		—		96.3		—
Technology	81.9		—		81.9		—
Healthcare	76.6		—		76.6		—
Industrial	74.2		—		74.2		—
Communications	53.4		—		53.4		—
Utilities	51.4		—		51.4		—
Energy	39.3		—		39.3		—
Materials	30.7		—		30.7		—

Total debt securities issued by corporations	686.9		—		686.9		—

Municipal obligations	283.8		—		283.8		—
Mortgage and asset-backed securities	229.9		—		229.9		—

Collateralized loan obligations	59.4		—		59.4		—
Total fixed maturity investments	1,481.6		221.6		1,260.0		—

Short-term investments	625.8		481.2		144.6		—

Common equity securities (1)	118.6		—		118.6		—
Investment in MediaAlpha	600.2		600.2		—		—














Other long-term investments	656.4		—		—		656.4
Other long-term investments — NAV (2)	375.8		—		—		—
Total other long-term investments	1,032.2		—		—		656.4
Total investments	$	3,858.4	$	1,303.0	$	1,523.2	$	656.4

(1) Consist of investments in listed funds that predominantly invest in international equities.

(2) Consists of private equity funds, a hedge funds, Lloyd’s trust deposits, a bank loan fund and ILS funds for which fair value is measured at NAV using the practical expedient. Investments for which fair value is measured at NAV are not classified within the fair value hierarchy.


	December 31, 2020
Millions	Fair Value		Level 1		Level 2		Level 3
Fixed maturity investments:
U.S. Government and agency obligations	$	176.3	$	176.3	$	—	$	—

Debt securities issued by corporations:
Financials	133.9		—		133.9
Consumer	81.9		—		81.9		—
Industrial	66.9		—		66.9		—
Technology	66.7		—		66.7		—
Healthcare	51.5		—		51.5		—
Communications	44.5		—		44.5		—
Energy	35.8		—		35.8		—
Materials	33.9		—		33.9		—
Utilities	32.3		—		32.3		—

Total debt securities issued by corporations	547.4		—		547.4		—

Municipal obligations	265.0		—		265.0		—
Mortgage and asset-backed securities	218.5		—		218.5		—


Total fixed maturity investments	1,207.2		176.3		1,030.9		—

Short-term investments	142.9		142.9		—		—

Investment in MediaAlpha	802.2		802.2		—		—















Other long-term investments	614.2		—		—		614.2
Other long-term investments — NAV (1)	172.6		—		—		—
Total other long-term investments	786.8		—		—		614.2
Total investments	$	2,939.1	$	1,121.4	$	1,030.9	$	614.2

(1) Consists of private equity funds and ILS funds for which fair value is measured at NAV using the practical expedient. Investments for which fair value is measured at NAV are not classified within the fair value hierarchy.

Debt Securities Issued by Corporations

The following table presents the credit ratings of debt securities issued by corporations held in White Mountains’s investment portfolio as of March 31, 2021 and December 31, 2020:


	Fair Value at
Millions	March 31, 2021		December 31, 2020
AAA	$	12.7	$	10.6
AA	60.2		57.9
A	353.2		318.3
BBB	250.9		159.6
BB	1.0		1.0

Other	8.9		—
Debt securities issued by corporations (1)	$	686.9	$	547.4

(1) Credit ratings are based upon issuer credit ratings provided by Standard & Poor’s Financial Services LLC (“Standard & Poor’s”), or if unrated by Standard & Poor’s, long-term obligation ratings provided by Moody’s Investor Service, Inc.

Mortgage and Asset-backed Securities and Collateralized Loan Obligations

The following table presents the fair value of White Mountains’s mortgage and asset-backed securities and collateralized loan obligations as of March 31, 2021 and December 31, 2020:


	March 31, 2021						December 31, 2020
Millions	Fair Value		Level 2		Level 3		Fair Value		Level 2		Level 3
Mortgage-backed securities:
Agency:
FNMA	$	98.4	$	98.4	$	—	$	88.7	$	88.7	$	—
FHLMC	76.9		76.9		—		70.1		70.1		—
GNMA	36.7		36.7		—		40.6		40.6		—
Total agency (1)	212.0		212.0		—		199.4		199.4		—

Non-agency: Residential	.6		.6		—		—		—		—

Total non-agency	.6		.6		—		—		—		—
Total mortgage-backed securities	212.6		212.6		—		199.4		199.4		—
Other asset-backed securities:
Credit card receivables	11.3		11.3		—		11.3		11.3		—
Vehicle receivables	6.0		6.0		—		7.8		7.8		—

Total other asset-backed securities	17.3		17.3		—		19.1		19.1		—
Total mortgage and asset-backed securities	229.9		229.9		—		218.5		218.5		—
Collateralized loan obligations	59.4		59.4		—		—		—		—
Total mortgage and asset-backed securities and collateralized loan obligations	$	289.3	$	289.3	$	—	$	218.5	$	218.5	$	—

(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).

As of March 31, 2021, White Mountains’s investment portfolio included $59.4 million of collateralized loan obligations that are within the senior tranches of their respective fund securitization structures. All of White Mountains’s collateral loan obligations were rated AAA or AA as of March 31, 2021.

Investment in MediaAlpha

On October 30, 2020, MediaAlpha completed the MediaAlpha IPO. In the offering, White Mountains sold 3.6 million shares at $19.00 per share ($17.67 per share net of underwriting discount) and received total proceeds of $63.8 million. White Mountains also received $55.0 million of net proceeds related to a dividend recapitalization at MediaAlpha. Following the MediaAlpha IPO, White Mountains owned 20.5 million MediaAlpha shares, representing a 35.0% ownership interest (32.3% on a fully-diluted, fully converted basis). At the December 31, 2020 closing price of $39.07 per share, the fair value of White Mountains’s remaining investment in MediaAlpha was $802.2 million. Subsequent to the MediaAlpha IPO, White Mountains’s investment in MediaAlpha is accounted for at fair value based on the publicly traded share price of MediaAlpha’s common stock and White Mountains presents its investment in MediaAlpha as a separate line item on the balance sheet.

On March 23, 2021, MediaAlpha completed a secondary offering of 8.05 million shares. In the secondary offering, White Mountains sold 3.6 million shares at $46.00 per share ($44.62 per share net of underwriting fees) for net proceeds of $160.3 million. Following the completion of the offering, White Mountains owns 16.9 million shares, representing a 28.5% basic ownership interest (26.3% fully-diluted/fully-converted basis). At the March 31, 2021 closing price of $35.43 per share, the fair value of White Mountains’s remaining investment in MediaAlpha was $600.2 million. See Note 16 — “Equity-Method Eligible Investments”.

Other Long-Term Investments

The following table presents the carrying values of White Mountains’s other long-term investments as of March 31, 2021 and December 31, 2020:


	Carrying Value at
Millions	March 31, 2021		December 31, 2020
Kudu’s Participation Contracts	$	427.4	$	400.6
PassportCard/DavidShield	95.0		95.0
Elementum Holdings L.P.	56.7		55.1
Other unconsolidated entities (1)	43.3		42.4





Total unconsolidated entities (2)	622.4		593.1
Private equity funds and hedge funds	133.5		121.2

Lloyd’s trust deposits	99.2		—
Bank loan fund	89.2		—
ILS funds	53.8		51.4
Private debt investments (2)	21.0		21.1
Other	13.1		—
Total other long-term investments	$	1,032.2	$	786.8

(1) Includes White Mountains’s non-controlling equity interests in certain private common equity securities, limited liability companies and convertible preferred securities and Simple Agreement for Future Equity (“SAFE”) investments.

(2) See Fair Value Measurements by Level table.

Private Equity Funds and Hedge Funds

White Mountains invests in private equity funds and hedge funds, which are included in other long-term investments. The fair value of these investments is generally estimated using the net asset value (“NAV”) of the funds. As of March 31, 2021, White Mountains held investments in thirteen private equity funds and one hedge fund. The largest investment in a single private equity fund or hedge fund was $23.5 million as of March 31, 2021 and $29.1 million as of December 31, 2020.

The following table presents investments and unfunded commitments in private equity funds and hedge funds by investment objective and sector as of March 31, 2021 and December 31, 2020:


	March 31, 2021				December 31, 2020
Millions	Fair Value		Unfunded Commitments		Fair Value		Unfunded Commitments
Private equity funds
Aerospace/Defense/Government	$	73.0	$	14.0	$	69.1	$	15.3
Financial services	43.2		35.3		23.5		30.4
Real estate	4.0		3.0		—		—
Manufacturing/Industrial	1.3		—		28.6		—

Total private equity funds	121.5		52.3		121.2		45.7
Hedge funds

European small/mid cap	12.0		—		—		—


Total hedge funds	12.0		—		—		—
Total private equity funds and hedge funds included in other long-term investments	$	133.5	$	52.3	$	121.2	$	45.7

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 have the option to extend the lock-up period.

The following table presents investments in private equity funds that were subject to lock-up periods as of March 31, 2021:


Millions	1 – 3 years	3 – 5 years	5 – 10 years	>10 years	Total
Private equity funds — expected lock-up period remaining	$6.8	$27.0	$74.5	$13.2	$121.5

Investors in private equity funds are generally subject to indemnification obligations outside of the capital commitment period and prior to the winding up of the fund. As of March 31, 2021 and December 31, 2020, White Mountains is not aware of any indemnification claims relating to its investments in private equity funds.

Redemption of investments in most 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. White Mountains’s hedge fund investment is subject to a perpetual two-year restriction on redemption frequency from the initial investment in the fund and a 90-days advanced notice period requirement.

Lloyd’s Trust Deposits

White Mountains’s other long-term investments include Lloyd’s Trust Deposits, which consists of overseas deposits and Canadian comingled pooled funds. The Lloyd’s Trust Deposits invest primarily in short-term government securities, agency securities and corporate bonds held in trusts that are managed by Lloyd's of London. These investments are required of Lloyd's syndicates to protect policyholders in overseas markets and are pledged into Lloyd’s trust accounts to provide a portion of the capital needed to support obligations at Lloyd’s. The fair value of the Lloyd’s Trust Deposits is generally estimated using the NAV of the funds. As of March 31, 2021, White Mountains held Lloyd’s Trust Deposits with a fair value of $99.2 million.

Bank Loan Fund

White Mountains’s other long-term investments include a bank loan fund with a fair value of $89.2 million as of March 31, 2021. The fair value of this investment is estimated using the NAV of the fund. The bank loan fund’s investment objective is to provide, on an unleveraged basis, high current income consistent with preservation of capital and low duration. The bank loan fund primarily invests in a broad portfolio of U.S. dollar-denominated, non-investment grade, floating-rate senior secured loans and may invest in other financial instruments, such as secured and unsecured corporate debt, credit default swaps, reverse repurchase agreements and synthetic indices and cash and cash equivalents.

The investment in the bank loan fund is subject to 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. White Mountains may redeem all or a portion of its bank loan fund investment as of any calendar month-end upon 15 calendar days advanced written notice.

Insurance-Linked Securities Funds

White Mountains’s other long-term investments include ILS fund investments. The fair value of these investments is generally estimated using the NAV of the funds. As of March 31, 2021, White Mountains held investments in ILS funds with a fair value of $53.8 million.

Investments in ILS funds are generally subject to restrictions, including lock-up periods where no redemptions or withdrawals are allowed, non-renewal clauses, restrictions on redemption frequency and advance notice periods for redemptions. From time to time, natural catastrophe, liquidity, market or other events will occur that make the determination of fair value for underlying investments in ILS funds less certain due to the potential for loss development. In such circumstances, the impacted investments may be subject to additional lock-up provisions.

ILS funds are typically subject to monthly and annual restrictions on redemptions and advance redemption notice period requirements that range between 30 and 90 days. Amounts requested for redemption remain subject to market fluctuations until the redemption effective date, which generally falls at the end of the defined redemption period.

One of the ILS funds in White Mountains’s portfolio requires shareholders to provide advance redemption notice on or before September 15 of each calendar year. Amounts requested for redemption in this fund remain subject to market fluctuation until the underlying investment has fully matured or been commuted, which may be up to a period of three years from the start of each calendar year.

Rollforward of Fair Value Measurements by Level

White Mountains uses quoted market prices where available as the inputs to estimate fair value for its investments in active markets. Such measurements are considered to be either Level 1 or Level 2 measurements, depending on whether the quoted market price inputs are for identical securities (Level 1) or similar securities (Level 2). Level 3 measurements for fixed maturity investments, common equity securities and other long-term investments as of March 31, 2021 and 2020 consist of securities for which the estimated fair value has not been determined based upon quoted market price inputs for identical or similar securities.

The following tables present the changes in White Mountains’s fair value measurements by level for the three months ended March 31, 2021 and 2020:


					Level 3 Investments		Other Long-term Investments Measured at NAV (1)
Millions	Level 1 Investments		Level 2 Investments		Other Long-term Investments				Total
Balance at December 31, 2020	$	978.5	$	1,030.9	$	614.2	$	172.6	$	2,796.2	(2)
Net realized and unrealized (losses) gains	(43.2)		(22.9)		16.7		11.4		(38.0)		(3)

Amortization/Accretion	—		(1.4)		—		—		(1.4)
Purchases	53.4		426.4		17.5		94.5		591.8
Sales	(166.9)		(122.6)		(1.6)		(38.5)		(329.6)


Effect of Ark Transaction	—		68.2		9.6		135.8		213.6
Transfers in	—		—		—		—		—
Transfers out	—		—		—		—		—
Balance at March 31, 2021	$	821.8	$	1,378.6	$	656.4	$	375.8	$	3,232.6	(1)

(1) Consists of private equity funds, a hedge fund, Lloyd’s trust deposits, bank loans, and ILS funds for which fair value is measured at NAV using the practical expedient. Investments for which fair value is measured at NAV are not classified within the fair value hierarchy. See Note 1 — “Basis of Presentation and Significant Accounting Policies”.

(2) Excludes carrying value of $625.8 and $142.9 as of March 31, 2021 and December 31, 2020 classified as short-term investments.

(3) Excludes realized and unrealized losses associated with short-term investments of $(1.3) and includes amounts attributable to TPC Providers of $1.3 for the three months ended March 31, 2021.


							Level 3 Investments		Other Long-term Investments Measured at NAV (1)
Millions	Level 1 Investments		Level 2 Investments		Common equity securities		Other Long- term Investments and Investment in MediaAlpha Pre-IPO				Total
Balance at December 31, 2019	$	780.0	$	1,109.6	$	.1	$	654.0	$	202.3	$	2,746.0	(2)
Net realized and unrealized losses	(98.7)		(39.9)		—		(9.7)		(8.8)		(157.1)		(3)

Amortization/Accretion	—		(.8)		—		—		—		(.8)
Purchases	74.2		126.8		—		24.7		7.2		232.9
Sales	(109.9)		(105.4)		—		(8.1)		(56.0)		(279.4)


Transfers in	—		—		—		—		—		—
Transfers out	—		—		—		—		—		—
Balance at March 31, 2020	$	645.6	$	1,090.3	$	.1	$	660.9	$	144.7	$	2,541.6	(2)

(1) Includes private equity funds, a hedge fund and ILS funds for which fair value is measured at NAV using the practical expedient are no longer classified within the fair value hierarchy. See Note 1 — “Basis of Presentation and Significant Accounting Policies”.

(2) Excludes carrying value of $137.6 and $201.2 as of March 31, 2020 and December 31, 2019 classified as short-term investments.

(3) Excludes realized and unrealized losses associated with short-term investments of $0.4 for the three months ended March 31, 2020.

Fair Value Measurements — Transfers Between Levels - Three-months ended March 31, 2021 and 2020

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 the first three months of 2021 and 2020, there were no fixed maturity investments or other long-term investments classified as Level 3 measurements in the prior period that were transferred to Level 2 measurements.

During the first three months of 2021 and 2020, there were no fixed maturity investments or other long-term investments classified as Level 2 measurements in the prior period that were transferred to Level 3 measurements.

Significant Unobservable Inputs

The following tables present significant unobservable inputs used in estimating the fair value of White Mountains’s other long-term investments, other than private equity funds, hedge funds, Lloyd’s trust deposits, bank loans funds and ILS funds, classified within Level 3 as of March 31, 2021 and December 31, 2020. The fair value of investments in private equity funds, hedge funds, Lloyd’s trust deposits, bank loans funds and ILS funds are generally estimated using the NAV of the funds.

$ in Millions

March 31, 2021

Description

Valuation Technique(s) (1)

Fair Value (2)

Unobservable Inputs

Discount Rate (3)(4)

Terminal Cash Flow Exit Multiple (x) or Terminal Revenue Growth Rate (%) (4)

Kudu’s Participation Contracts (5)

Discounted cash flow

$427.4

18% - 23%

7x - 12x

PassportCard/DavidShield

Discounted cash flow

$95.0

23%

Elementum Holdings, L.P.

Discounted cash flow

$56.7

17%

Private debt instruments

Discounted cash flow

$17.0

4% - 8%

N/A

All other

Discounted cash flow

$19.8

20% - 24%

New Market Solutions, LLC

Recent transaction

$9.9

Transaction price:

$9.9

Noblr, Inc.

Recent transaction

$8.7

Transaction price:

$8.7

Zillion Insurance Services, Inc.

Recent transaction

$5.0

Transaction price:

$5.0

(1) Key inputs to the discounted cash flow analysis generally include projections of future revenue and earnings, discount rates and terminal exit multiples or growth rates.

(2) Includes the net unrealized investment gains (losses) associated with foreign currency; foreign currency effects based on observable inputs.

(3) Since Kudu’s Participation Contracts are not subject to corporate taxes within Kudu Investment Management, LLC, pre-tax discount rates are applied to pre-tax cash flows in determining fair values.

(4) Increases (decreases) to the discount rates in isolation would result in lower (higher) fair value measurements, while increases (decreases) to the terminal cash flow exit multiples or terminal revenue growth rates in isolation would result in higher (lower) fair value measurements.

(5) In the first quarter of 2021, Kudu deployed a total of $10.9 in TIG Advisors LLC, an existing Kudu Participation Contract.

$ in Millions

December 31, 2020

Description

Valuation Technique(s) (1)

Fair Value (2)

Unobservable Inputs

Discount Rate (3)(4)

Terminal Cash Flow Exit Multiple (x) or Terminal Revenue Growth Rate (%) (4)

Kudu’s Participation Contracts (5)

Discounted cash flow

$400.6

18% - 23%

7x - 12x

PassportCard/DavidShield (6)

Discounted cash flow

$95.0

23%

Elementum Holdings, L.P.

Discounted cash flow

$55.1

17%

Private debt instruments

Discounted cash flow

$17.1

4% - 8%

N/A

All other

Discounted cash flow

$18.8

20% - 24%

New Market Solutions, LLC

Recent transaction

$9.9

Transaction price:

$9.9

Noblr, Inc.

Recent transaction

$8.7

Transaction price:

$8.7

Zillion Insurance Services, Inc.(7)

Recent transaction

$5.0

Transaction price:

$5.0

(1) Key inputs to the discounted cash flow analysis generally include projections of future revenue and earnings, discount rates and terminal exit multiples or growth rates.

(2) Includes the net unrealized investment gains (losses) associated with foreign currency; foreign currency effects based on observable inputs.

(5) In 2020, Kudu deployed a total of $118.2 in new Kudu Participation Contracts, including Creation Investments Capital, Sequoia Financial Group, Channel Capital and Ranger Investment Management.

(6) In 2020, White Mountains made an additional $15.0 investment in PassportCard/DavidShield. See Note 2 — “Significant Transactions”.

(7) In 2020, White Mountains made an additional $2.5 investment in Zillion Insurance Services, Inc.

Goodwill and Other Intangible Assets

3 Months Ended

Mar. 31, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Other Intangible Assets

White Mountains accounts for purchases of businesses using the acquisition method. Under the acquisition method, White Mountains recognizes and measures the assets acquired, liabilities assumed and any non-controlling interest in the acquired entities at their acquisition date fair values. The acquisition date fair values of certain assets and liabilities, generally consisting of intangible assets and liabilities for contingent consideration, may be recorded at provisional amounts in circumstances where the information necessary to complete the acquisition accounting is not available at the reporting date. Any such provisional amounts are finalized as measurement period adjustments within one year of the acquisition date.

The following table presents the acquisition date fair values, accumulated amortization and net carrying values for other intangible assets and goodwill, by segment as of March 31, 2021 and December 31, 2020:


$ in Millions	Weighted Average Economic Life (in years)	March 31, 2021								December 31, 2020
		Acquisition Date Fair Value		Accumulated Amortization		Impairments and Amounts Allocated to Held for Sale		Net Carrying Value		Acquisition Date Fair Value		Accumulated Amortization		Impairments		Net Carrying Value
Goodwill:
Ark	N/A	$	116.8	$	—	$	—	$	116.8	$	—	$	—	$	—	$	—
NSM (1)	N/A	507.9		—		30.2		477.7		506.4		—		—		506.4
Kudu	N/A	7.6		—		—		7.6		7.6		—		—		7.6
Other Operations	N/A	11.3		—		—		11.3		11.5		—		—		11.5
Total goodwill		643.6		—		30.2		613.4		525.5		—		—		525.5

Other intangible assets:
Ark
Underwriting Capacity	N/A	175.7		—		—		175.7		—		—		—		—

NSM (1)
Customer relationships	8.9	136.4		41.7		3.5		91.2		136.2		36.7		3.5		96.0
Trade names	16	65.4		9.1		1.0		55.3		65.4		8.3		1.0		56.1
Information technology platform	0	3.1		1.4		1.7		—		3.1		1.4		1.7		—
Renewal rights	12	82.5		7.6		—		74.9		82.5		4.9				77.6
Other	3.4	1.7		1.1		—		.6		1.7		1.0				.7
Subtotal		289.1		60.9		6.2		222.0		288.9		52.3		6.2		230.4

Kudu
Trade names	7	2.2		.7		—		1.5		2.2		.6		—		1.6

Other Operations
Trade names	9.6	3.6		.4		—		3.2		3.6		.3		—		3.3
Customer relationships	10.7	14.2		1.8		—		12.4		14.2		1.4		—		12.8

Insurance Licenses	N/A	8.6		—		—		8.6		8.6		—		—		8.6
Other	5.4	.3		.1		—		.2		.3		.1		—		.2
Subtotal		26.7		2.3		—		24.4		26.7		1.8		—		24.9
Total other intangible assets		493.7		63.9		6.2		423.6		317.8		54.7		6.2		256.9
Total goodwill and other intangible assets		$	1,137.3	$	63.9	$	36.4	1,037.0		$	843.3	$	54.7	6.2		782.4
Goodwill and other intangible assets attributed to non-controlling interests								(108.4)								(28.1)
Goodwill and other intangible assets included in White Mountains’s common shareholders’ equity								$	928.6							$	754.3

(1) As of March 31, 2021, NSM’s goodwill and intangible assets included $1.5 and $0.2 of the effect of foreign currency translation. As of December 31, 2020, NSM’s goodwill and intangible assets included $13.4 and $1.6 of the effect of foreign currency translation.

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

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

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

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

The following table presents a summary of the acquisition date fair values of goodwill and other intangible assets for

acquisitions completed from January 1, 2020 through March 31, 2021:

$ in Millions

Acquisition of subsidiary/ asset

Goodwill and

Other intangible asset (1)

Acquisition Date

Kingsbridge

131.7

April 7, 2020

Ark

292.5

January 1, 2021

Other Operations

15.2

July 2, 2020

(1) Acquisition date fair values include the effect of adjustments during the measurement period and excludes the effect of foreign currency translation subsequent to the acquisition date.

On at least an annual basis beginning no later than the interim period included in the one-year anniversary of an acquisition, White Mountains evaluates goodwill and other intangible assets for potential impairment. Between annual evaluations, White Mountains considers changes in circumstances or events subsequent to the most recent evaluation that may indicate that an impairment may exist and, if necessary will perform an interim review for potential impairment.

In April 2021, NSM sold Fresh Insurance’s motor business. The assets and liabilities included in the transaction, principally goodwill, have been classified as held for sale as of March 31, 2021 and have been measured at their estimated fair values, net of disposal costs. In connection with the classification of the Fresh Insurance’s motor business as held for sale, White Mountains recognized a loss of $28.7 million. See Note 2 — “Significant Transactions”.

During the three months ended March 31, 2021, White Mountains concluded that there was no impairment of the intangible assets associated with NSM.

The following tables present the change in goodwill and other intangible assets for the three months ended March 31, 2021 and 2020:


	Three Months Ended March 31,
	2021						2020
Millions	Goodwill		Other Intangible Assets		Total Goodwill and Other Intangible Assets		Goodwill		Other Intangible Assets		Total Goodwill and Other Intangible Assets
Beginning balance	$	525.5	$	256.9	$	782.4	$	394.7	$	260.0	$	654.7

Ark Transaction	116.8		175.7		292.5		—		—		—

Foreign currency translation	1.5		.2		1.7		(2.5)		(.5)		(3.0)

Loss on assets held for sale (1)	(30.2)		—		(30.2)		—		—		—
Measurement period adjustments (2)	(.2)		—		(.2)		.2		—		.2
Amortization	—		(9.2)		(9.2)		—		(5.1)		(5.1)
Ending balance	$	613.4	$	423.6	$	1,037.0	$	392.4	$	254.4	$	646.8

(1) Relates to the sale of NSM’s Fresh motor business recorded in the first quarter of 2021.This amounts excludes $1.5 of net proceeds related to the sale.

(2) Measurement period adjustments relate to updated information about acquisition date fair values of assets acquired and liabilities assumed. During the three months ended March 31, 2021, adjustments primarily relate to the acquisition in the Other Operations segment.

Debt

3 Months Ended

Mar. 31, 2021

Debt Disclosure [Abstract]

Debt

The following table presents White Mountains’s debt outstanding as of March 31, 2021 and December 31, 2020:


Millions	March 31, 2021		Effective Rate	(1)	December 31, 2020		Effective Rate	(1)

Ark Alesco Notes, carrying value	$	30.0			$	—
Ark Dekania Note, carrying value	14.1				—
Ark Subordinated Notes, carrying value	44.1		4.6%		—
NSM Bank Facility	277.3		7.6%	(2)	277.4		7.5%	(2)
Unamortized issuance cost	(5.8)				(6.1)
NSM Bank Facility, carrying value	271.5				271.3
Other NSM debt, carrying value	1.2		2.3%		1.3		2.5%
Kudu Credit Facility	102.0		5.2%		—
Unamortized issuance cost	(6.1)				—
Kudu Credit Facility, carrying value	95.9				—
Kudu Bank Facility	—				89.2		8.3%
Unamortized issuance cost	—				(2.9)
Kudu Bank Facility, carrying value	—				86.3



Other Operations debt	17.5		7.6%		18.0		7.4%
Unamortized issuance cost	(.5)				(.5)
Other Operations, carrying value	17.0				17.5
Total debt	$	429.7			$	376.4

(1) Effective rate includes the effect of the amortization of debt issuance costs.

(2) NSM’s effective rate excludes the effect of the interest rate swap on the hedged portion of the debt. The weighted average interest rate for the quarter ended March 31, 2021 and December 31, 2020, excluding the effect of amortization of debt issuance costs, was 7.1% and 7.0%. The weighted average interest rate for the quarter ended March 31, 2021 and December 31, 2020 on the total NSM Bank Facility including both the effect of the amortization of debt issuance costs and the effect of the interest rate swap was 8.5% and 8.4%.

Ark Subordinated Notes

In March 2007, Ark issued $30.0 million face value of floating rate unsecured junior subordinated deferrable interest notes to Alesco Preferred Funding XII Ltd., Alesco Preferred Funding XIII Ltd. and Alesco Preferred Funding XIV Ltd (the “Ark Alesco Notes”) and a €12.0 million floating rate subordinated note to Dekania Europe CDO II plc (the “Ark Dekania Note”) (together, the “Ark Subordinated Notes”). The Alesco Notes, which mature in June 2037, accrue interest at a floating rate equal to the three-month U.S. LIBOR plus 4.6%. The Ark Dekania Note, which matures in June 2027, accrues interest at a floating rate equal to the three-month EURIBOR plus 4.6%. As of March 31, 2021, the Ark Alesco Notes had an outstanding balance of $30.0 million and the Ark Dekania Note had an outstanding balance of €12.0 million (approximately $14.1 million based upon the foreign exchange spot rate as of March 31, 2021).

Ark Stand By Letter of Credit Facility

Ark has a secured stand by letter of credit facility (the “Ark LOC Facility”) with three lenders, Lloyds Bank plc, National Westminster Bank plc and ING Bank N.V, London Branch to provide capital support for the Syndicates. As of March 31, 2021, the utilized level of the facility was $45.0 million, with the ability to increase to $150.0 million. The Ark LOC Facility has a termination date of December 31, 2025. During the three months ended March 31, 2021, Ark did not borrow or make any repayments under the Ark LOC Facility.

The Ark LOC Facility, which provides funds at Lloyd’s, is secured by all property of the loan parties and contains various affirmative, negative and financial covenants that White Mountains considers to be customary for such borrowings, including a minimum tangible net worth covenant.

NSM Bank Facility

On April 7, 2020, NSM amended its secured credit facility (the “NSM Bank Facility”) with Ares Capital Corporation in connection with the acquisition of Kingsbridge. Under the amendment, the total commitment increased from $234.0 million, comprised of term loans of $224.0 million and a revolving credit loan of $10.0 million, to $291.4 million, comprised of term loans of $276.4 million, including £42.5 million (approximately $52.4 million based upon the foreign exchange spot rate as of the date of the transaction) in a GBP term loan, and a revolving credit loan commitment of $15.0 million. The term loans under the NSM Bank Facility mature on May 11, 2026, and the revolving loan matures on November 11, 2025.

Under GAAP, if the terms of a debt instrument are amended, unless there is greater than 10% change in the expected discounted future cash flows of such instrument, the instrument’s carrying value does not change. White Mountains has determined that the impact of the changes to the terms of the NSM Bank Facility on the expected discounted future cash flows was less than 10%.

Interest on the NSM Bank Facility accrues at a floating interest rate equal to the three-month LIBOR plus an applicable margin. In connection with the amendment, the reference rates for USD denominated borrowings increased. The USD-LIBOR rate floor increased to 1.25% and the margin over USD-LIBOR increased from a range of 4.25% to 4.75% to a range of 5.50% to 6.00%. For GBP denominated borrowings, the GBP-LIBOR rate floor is 1.25% and the margin over GBP-LIBOR ranges from 6.00% to 6.50%. The margins over the reference interest rates vary within the range depending on the consolidated total leverage ratio of NSM.

The following table presents the change in debt under the NSM Bank Facility for the three months ended March 31, 2021 and 2020:


NSM Bank Facility	Three Months Ended
	March 31,
Millions		2021		2020
Beginning balance		$	277.4	$	221.3
Term loans
Borrowings		—		—
Repayments		(.7)		(.6)
Foreign currency translation		.6		—
Revolving credit loan
Borrowings		—		—
Repayments		—		—
Ending balance		$	277.3	$	220.7

As of March 31, 2021, the term loans had an outstanding balance of $277.3 million, including £42.5 million (approximately $58.2 million based upon the foreign exchange spot rate as of March 31, 2021) in a GBP term loan, and the revolving credit loan was undrawn.

On June 15, 2018, NSM entered into an interest rate swap agreement to hedge its exposure to interest rate risk on $151.0 million of its USD denominated variable rate term loans.

As of March 31, 2021, $147.2 million of the outstanding term loans were hedged by the swap and $130.1 million of the outstanding term loans were unhedged. The following table presents the NSM weighted average interest rate for the three months ended March 31, 2021 and 2020:


NSM Weighted Average Interest Rate	Three Months ended March 31,
	2021						2020
Millions	Weighted Average		Interest Expense (1)		Weighted Average Interest rate		Weighted Average		Interest Expense (1)		Weighted Average Interest rate
Term loan - hedged	$	147.6	$	3.4	9.2	%	$	148.4	$	3.0	8.1	%
Term loan - unhedged	129.8		2.5		7.7	%	72.6		1.2		6.6	%
Total NSM Facility	$	277.4	$	5.9	8.5	%	$	221.0	$	4.2	7.6	%

(1) Interest expense includes the amortization of debt issuance costs and the effect of the interest rate swap and excludes interest expense related to the Other NSM Debt.

The NSM Bank Facility is secured by all property of the loan parties and contains various affirmative, negative and financial covenants that White Mountains considers to be customary for such borrowings, including a maximum consolidated total leverage ratio covenant.

Other NSM Debt

NSM also has a secured term loan related to its U.K. vertical. As of March 31, 2021, the secured term loan had an outstanding balance of $1.4 million and a maturity date of December 31, 2022.

Kudu Credit Facility and Kudu Bank Facility

On December 23, 2019, Kudu entered into a secured credit facility with Monroe Capital Management Advisors, LLC (the “Kudu Bank Facility”). On March 23, 2021, Kudu replaced the Kudu Bank Facility and entered into a secured revolving credit facility (the “Kudu Credit Facility”) with Massachusetts Mutual Life Insurance Company to fund new investments and related transaction expenses. The maximum borrowing capacity of the Kudu Credit Facility is $300.0 million, which includes the initial advanced amount of $102.0 million. The Kudu Credit Facility matures on March 23, 2036. During the three months ended March 31, 2021, Kudu borrowed $3.0 million and repaid the outstanding Kudu Bank Facility balance of $92.2 million. As of March 31, 2021, the Kudu Credit Facility had an undrawn balance of $198.0 million. Kudu may borrow undrawn balances within the initial three year availability period, subject to customary terms and conditions, to the extent the amount borrowed under the Kudu Credit Facility does not exceed 35% of the borrowing base, which is comprised of Kudu’s qualifying participation contracts (the “LTV percentage”). When considering White Mountains’s remaining equity commitment to Kudu, the available undrawn balance was $60.8 million as of March 31, 2021.

Interest on the Kudu Credit Facility accrues at a floating interest rate equal to the greater of the three-month USD-LIBOR and 0.25%, plus in each case, the applicable spread of 4.30%. The Kudu Credit Facility requires Kudu to maintain an interest reserve account, which is included in restricted cash. As of March 31, 2021, the interest reserve account is $3.9 million. The Kudu Credit Facility requires Kudu to maintain an LTV percentage of less than 50% in years 0-3, 40% in years 4-6, 25% in years 7-8, 15% in years 9-10, and 0% thereafter. As of March 31, 2021, Kudu has a 29.5% LTV.

The Kudu Credit Facility is secured by all property of the loan parties and contains various affirmative and negative covenants that White Mountains considers to be customary for such borrowings.

Other Operations Debt

As of March 31, 2021, debt in White Mountains’s Other Operations segment consisted of two secured credit facilities. The first credit facility has a maximum borrowing capacity of $16.3 million, which is comprised of a term loan of $11.3 million, a delayed-draw term loan of $3.0 million and a revolving credit loan commitment of $2.0 million, all with a maturity date of March 12, 2024. During the three months ended March 31, 2021, White Mountains’s Other Operations segment borrowed $0.3 million on the revolving credit loan and made repayments of $0.6 million on the term loans, under the first credit facility. As of March 31, 2021, the first credit facility had an outstanding balance of $8.8 million. The second credit facility has a maximum borrowing capacity of $15.0 million, which is comprised of a term loan of $9.0 million, a delayed-draw term loan of $4.0 million and a revolving credit loan commitment of $2.0 million, all with a maturity date of July 2, 2025. During the three months ended March 31, 2021, White Mountains’s Other Operations segment had no borrowings and made repayments of $0.2 million on the term loans under the second credit facility. As of March 31, 2021, the second credit facility had an outstanding balance of $8.7 million.

Compliance

At March 31, 2021, White Mountains was in compliance in all material respects with the covenants under all of its debt instruments.

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	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 and 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 Ireland, Israel, Luxembourg, the United Kingdom and the United States. In the first quarter of 2020, White Mountains adopted ASU 2019-12, Simplifying the Accounting for Income Taxes (ASC 740) (“ASU 2019-12”). For periods subsequent to the adoption of ASU 2019-12, White Mountains records both the tax expense related to BAM’s MSC and the related valuation allowance on such taxes through the non-controlling interest equity. Prior to the adoption of ASU 2019-12, White Mountains recorded the tax expense related to BAM’s MSC directly to non-controlling interest equity, while the valuation allowance on such taxes was recorded through the income statement. White Mountains’s income tax benefit related to pre-tax loss from continuing operations for the three months ended March 31, 2021 represented an effective tax rate of 6.9%. The effective tax rate was different from the U.S. statutory rate of 21.0% due to income generated in jurisdictions with lower tax rates than the United States. White Mountains’s income tax benefit related to pre-tax loss from continuing operations for the three months ended March 31, 2020 represented an effective tax rate of 15.4%. The effective tax rate was different from the U.S. statutory rate of 21.0% due to income generated in jurisdictions with lower tax rates than the United States and state income taxes. In arriving at the effective tax rate for the three months ended March 31, 2021 and 2020, White Mountains forecasted all income and expense items including the change in unrealized investment gains (losses) and realized investment gains (losses) for the years ending December 31, 2021 and 2020. 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. 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 2015.

- 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 + Details

Derivatives	3 Months Ended
Derivatives	Mar. 31, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives	Derivatives NSM Interest Rate Swap On June 15, 2018, NSM entered into an interest rate swap agreement to hedge its exposure to interest rate risk on $151.0 million of its USD denominated variable rate term loans under the NSM Bank Facility. Under the terms of the swap agreement, NSM pays a fixed-rate of 2.97% and receives a variable rate, which is reset monthly, based on the then-current USD-LIBOR. As of December 31, 2020, the variable rate received by NSM under the swap agreement was 1.00%. Over the term of the swap, the notional amount decreases in accordance with the principal repayments NSM expects to make on its term loans. As of March 31, 2021, $147.2 million of the outstanding term loans were hedged by the swap. For the three months ended March 31, 2021, the weighted average effective interest rate on the outstanding term loans that were hedged, including the effect of the amortization of debt issuance costs and the effect of the interest rate swap, was 9.2%. NSM’s obligations under the swap are secured by the same collateral securing the NSM Bank Facility on a pari passu basis. NSM does not currently hold any collateral deposits from or provide any collateral deposits to the swap counterparty. NSM evaluated the effectiveness of the swap to hedge its interest rate risk associated with its variable rate debt and concluded at the swap inception date that the swap was highly effective in hedging that risk. NSM evaluates the effectiveness of the hedging relationship on an ongoing basis. For the three months ended March 31, 2021 and 2020, White Mountains recognized net interest expense of $0.6 million and $0.5 million for the periodic net settlement payments on the swap. As of March 31, 2021 and December 31, 2020, the estimated fair value of the swap and the accrual of the periodic net settlement payments recorded in other liabilities was $7.2 million and $8.2 million. There was no ineffectiveness in the hedge for the three months ended March 31, 2021 and 2020. For the three months ended March 31, 2021 and 2020, the $1.0 million and $(3.2) million change in the fair value of the swap is included within White Mountains’s accumulated other comprehensive income (loss). NSM Interest Rate Cap On June 4, 2020, NSM entered into an interest rate cap agreement to limit its exposure to the risk of interest rate increases on the GBP denominated term loan under the NSM Bank Facility. The notional amount of the interest rate cap is £42.5 million (approximately $52.4 million based upon the foreign exchange spot rate as of the date of the transaction) and the termination date is June 4, 2022. On August 18, 2020, NSM entered into a separate interest rate cap agreement to extend the term of the original interest rate cap agreement by one year. The second interest rate cap agreement has an effective date of June 15, 2022 and a termination date of June 15, 2023. NSM paid total initial premiums of approximately $0.1 million for the interest rate caps. Under the terms of the interest rate cap agreements, if the current GBP-LIBOR at the measurement date exceeds 1.25%, NSM will receive payments from the counterparty equal to the then-current GBP-LIBOR rate, less the 1.25% cap rate. As of March 31, 2021, the GBP-LIBOR rate was 0.09%. NSM accounts for the interest rate caps as derivatives at fair value, with changes in fair value recognized in current period earnings within interest expense. For the three months ended March 31, 2021, White Mountains recognized a change in fair value of less than $0.1 million on the interest rate caps within interest expense. As of March 31, 2021 and December 31, 2020, the estimated fair value of the caps recorded in other assets was less than $0.1 million.

Municipal Bond Guarantee Insurance

3 Months Ended

Mar. 31, 2021

Guarantees [Abstract]

Municipal Bond Guarantee Insurance

HG Global was established to fund the startup of BAM, a newly formed mutual municipal bond insurer, and, through HG Re, to provide up to 15%-of-par, first loss reinsurance protection for policies underwritten by BAM. At inception in 2012, HG Global was capitalized with $594.5 million from White Mountains and $14.5 million from non-controlling interests. HG Global, together with its subsidiaries, provided the initial capitalization of BAM through the purchase of $503.0 million of BAM Surplus Notes. As of March 31, 2021, White Mountains owned 96.9% of HG Global’s preferred equity and 88.4% of its common equity.

Reinsurance Treaties

FLRT

BAM is a party to a first loss reinsurance treaty (“FLRT”) with HG Re under which HG Re provides first loss protection up to 15%-of-par outstanding on each municipal bond insured by BAM. For capital appreciation bonds, par is adjusted to the estimated equivalent par value for current interest paying bonds. In return, BAM cedes up to 60% of the risk premium charged for insuring the municipal bond, which is net of a ceding commission. The FLRT is a perpetual agreement, with an initial term through the end of 2022.

Fidus Re

BAM is party to two collateralized financial guarantee excess of loss reinsurance agreements thats serve to increase BAM’s claims paying resources and are provided by Fidus Re, a Bermuda based special purpose insurer created in 2018 solely to provide reinsurance protection to BAM.

In the second quarter of 2018, Fidus Re was initially capitalized by the issuance of $100.0 million of insurance linked securities (the “Fidus Re 2018 Agreement”. The proceeds from issuance were placed in a collateral trust supporting Fidus Re’s obligations to BAM. The insurance linked securities were issued by Fidus Re with an initial term of 12 years and are callable five years after the date of issuance. Under the Fidus Re 2018 Agreement, Fidus Re reinsures 90% of aggregate losses exceeding $165.0 million on a portion of BAM’s financial guarantee portfolio (the “2018 Covered Portfolio”) up to a total reimbursement of $100.0 million. The Fidus Re 2018 Agreement does not provide coverage for losses in excess of $276.1 million. The 2018 Covered Portfolio consists of approximately 41% of BAM’s portfolio of financial guaranty policies issued through March 31, 2021.

In the first quarter of 2021, Fidus Re issued an additional $150.0 million of insurance linked securities (the “Fidus Re 2021 Agreement”) with an initial term of 12 years and are callable five years after the date of issuance. Under the Fidus Re 2021 Agreement, Fidus Re reinsures 90% of aggregate losses exceeding $135.0 million on a portion of BAM’s financial guarantee portfolio (the “2021 Covered Portfolio”) up to a total reimbursement of $150.0 million. The Fidus Re 2021 Agreement does not provide coverage for losses in excess of $301.7 million. The 2021 Covered Portfolio consists of approximately 41% of BAM’s portfolio of financial guaranty policies issued through March 31, 2021.

The Fidus Re Agreements are accounted for using deposit accounting and any related financing expenses are recorded in general and administrative expenses as they do not meet the risk transfer requirements necessary to be accounted for as reinsurance.

XOLT

In January 2020, BAM entered into an excess of loss reinsurance agreement (the “XOLT”) with HG Re. Under the XOLT, HG Re provides last dollar protection for exposures on municipal bonds insured by BAM in excess of NYDFS single issuer limits. The XOLT is subject to an aggregate limit equal to the lesser of $75.0 million or the assets held in the Supplemental Trust at any point in time. The agreement is accounted for using deposit accounting and any related financing expenses are recorded in general and administrative expenses as the agreement does not meet the risk transfer requirements necessary to be accounted for as reinsurance.

Collateral Trusts

HG Re’s obligations under the FLRT are limited to the assets in two collateral trusts: a Regulation 114 Trust and a supplemental collateral trust (the “Supplemental Trust” and together with the Regulation 114 Trust, the “Collateral Trusts”). Losses required to be reimbursed under the FLRT are subject to an aggregate limit equal to the assets held in the Collateral Trusts at any point in time.

At inception, the Supplemental Trust contained the original $300.0 million of Series B Notes and $100.0 million of cash and fixed income securities. During 2017, in order to further support BAM’s long-term capital position and business prospects, HG Global agreed to contribute the original $203.0 million of Series A Notes into the Supplemental Trust. In connection with the contribution, the Series A Notes were merged into the Series B Notes.

On a monthly basis, BAM deposits cash equal to ceded premiums, net of ceding commissions, due to HG Re under the FLRT directly into the Regulation 114 Trust. The Regulation 114 Trust target balance is equal to gross ceded unearned premiums and unpaid ceded loss and LAE expenses, if any. If, at the end of any quarter, the Regulation 114 Trust balance is below the target balance, funds will be withdrawn from the Supplemental Trust and deposited into the Regulation 114 Trust in an amount equal to the shortfall. If, at the end of any quarter, the Regulation 114 Trust balance is above 102% of the target balance, funds will be withdrawn from the Regulation 114 Trust and deposited into the Supplemental Trust. The Regulation 114 Trust balance as of March 31, 2021 and December 31, 2020 was $221.2 million and $222.8 million.

The Supplemental Trust target balance is $603.0 million, less the amount of cash and securities in the Regulation 114 Trust in excess of its target balance (the “Supplemental Trust Target Balance”). If, at the end of any quarter, the Supplemental Trust balance exceeds the Supplemental Trust Target Balance, such excess may be distributed to HG Re. The distribution will be made first as an assignment of accrued interest on the BAM Surplus Notes and second in cash and/or fixed income securities.

As the BAM Surplus Notes are repaid over time, the BAM Surplus Notes will be replaced in the Supplemental Trust by cash and fixed income securities. The Supplemental Trust balance as of March 31, 2021 and December 31, 2020 was $597.9 million and $604.3 million.

As of March 31, 2021 and December 31, 2020, the Collateral Trusts held assets of $819.1 million and $827.1 million, which included $427.9 million and $434.5 million of cash and investments, $388.2 million and $388.2 million of BAM Surplus Notes and $3.0 million and $4.4 million of interest receivable on the BAM Surplus Notes.

BAM Surplus Notes

Through 2024, the interest rate on the BAM Surplus Notes is a variable rate equal to the one-year U.S. Treasury rate plus 300 basis points, set annually. During 2021, the interest rate on the BAM Surplus Notes is 3.1%. Beginning in 2025, the interest rate will be fixed at the higher of the then current variable rate or 8.0%. BAM is required to seek regulatory approval to pay interest and principal on the BAM Surplus Notes only to the extent that its remaining qualified statutory capital and other capital resources continue to support its outstanding obligations, its business plan and its “AA/stable” rating from Standard & Poor’s. No payment of principal or interest on the BAM Surplus Notes may be made without the approval of the NYDFS.

Under GAAP, if the terms of a debt instrument are amended, unless there is greater than a 10% change in the expected discounted future cash flows of such instrument, the instrument’s carrying value does not change. White Mountains has determined that the impact of the changes to the terms of the BAM Surplus Notes on the expected discounted future cash flows was less than 10%.

In December 2020, BAM made a $30.1 million cash payment of principal and interest on the BAM Surplus Notes held by HG Global. Of this payment, $21.5 million was a repayment of principal held in the Supplemental Trust, $0.2 million was a payment of accrued interest held inside the Supplemental Trust and $8.4 million was a payment of accrued interest held outside the Supplemental Trust.

In January 2020, BAM made a one-time $65 million cash payment of principal and interest on the BAM Surplus Notes held by HG Global. Of this payment, $47.9 million was a repayment of principal held in the Supplemental Trust, $0.9 million was a payment of accrued interest held inside the Supplemental Trust and $16.2 million was a payment of accrued interest held outside the Supplemental Trust.

As of March 31, 2021 and December 31, 2020, the principal balance on the BAM Surplus Notes for both periods was $388.2 million and total interest receivable on the BAM Surplus Notes was $158.8 million and $155.7 million.

Insured Obligations and Premiums

The following table presents a schedule of BAM’s insured obligations as of March 31, 2021 and December 31, 2020:


	March 31, 2021		December 31, 2020
Contracts outstanding	11,252		10,997
Remaining weighted average contract period outstanding (in years)	10.6		10.7
Contractual debt service outstanding (in millions):
Principal	$	77,689.3	$	75,287.7
Interest	36,710.5		36,448.8
Total debt service outstanding	$	114,399.8	$	111,736.5

Gross unearned insurance premiums (in millions)	$	243.7	$	237.5

The following table presents a schedule of BAM’s future premium revenues as of March 31, 2021:


Millions	March 31, 2021
April 1, 2021 - December 31, 2021	$	17.6

January 1, 2022 - March 31, 2022	5.7
April 1, 2022 - June 30, 2022	5.6
July 1, 2022 - September 30, 2022	5.6
October 1, 2022 - December 31, 2022	5.4
Total 2022	22.3

2023	21.0
2024	19.4
2025	18.0
2026	16.6
2027 and thereafter	128.8
Total gross unearned insurance premiums	$	243.7

The following table presents a schedule of written premiums and earned premiums included in White Mountains’s HG Global/BAM segment for the three months ended March 31, 2021 and 2020:


	Three Months Ended March 31,
Millions	2021		2020
Written premiums:
Direct	$	8.0	$	9.7
Assumed	4.5		—
Gross written premiums	$	12.5	$	9.7
Earned premiums:
Direct	$	5.3	$	4.5
Assumed	1.1		.9
Gross earned premiums	$	6.4	$	5.4

In November 2018, BAM entered into a 100% facultative quota share reinsurance agreement under which it assumed a portfolio of municipal bond guarantee contracts with a par value of $2.2 billion.

In September 2019, BAM entered into facultative quota share reinsurance agreements under which it assumed a portfolio of municipal bond guarantee contracts with a par value of $1.1 billion. In the second quarter of 2020, BAM assumed an additional municipal bond guarantee contract with a par value of $36.9 million through an endorsement to the facultative quota share reinsurance agreement.

In January 2021, BAM entered into a 100% facultative quota share reinsurance agreement under which it assumed a portfolio of municipal bond guarantee contracts with a par value of $0.8 billion. None of the contracts assumed were non-performing and no loss reserves have been established for any of the contracts, either as of the transaction dates or as of March 31, 2021. The agreements, which cover future claims exposure only, meet the risk transfer criteria under ASC 944-20, Insurance Activities and accordingly have been accounted for as reinsurance.

Earnings Per Share

3 Months Ended

Mar. 31, 2021

Earnings Per Share [Abstract]

Earnings Per Share

White Mountains calculates earnings per share using the two-class method, which allocates earnings between common shares and unvested restricted common shares. Both classes of shares participate equally in dividends and earnings on a per share basis. Basic earnings per share amounts are based on the weighted average number of common shares outstanding adjusted for unvested restricted common shares.

The following table presents the Company’s computation of earnings per share from continuing operations for the three months ended March 31, 2021 and 2020. See Note 19 — “Held for Sale and Discontinued Operations”.


	Three Months Ended
	March 31,
	2021		2020
Basic and diluted loss per share numerators (in millions):
Net loss attributable to White Mountains’s common shareholders	$	(75.3)	$	(128.8)
Less: total income from discontinued operations, net of tax	18.7		.9
Net loss from continuing operations attributable to White Mountains’s common shareholders	$	(94.0)	$	(129.7)


Allocation of losses to participating restricted common shares(1)	.9		1.3
Basic and diluted losses per share numerators	$	(93.1)	$	(128.4)
Basic loss per share denominators (in thousands):
Total average common shares outstanding during the period	3,100.2		3,178.0
Average unvested restricted common shares(2)	(32.4)		(33.8)
Basic losses per share denominator	3,067.8		3,144.2
Diluted loss per share denominator (in thousands):
Total average common shares outstanding during the period	3,100.2		3,178.0
Average unvested restricted common shares(2)	(32.4)		(33.8)

Diluted losses per share denominator	3,067.8		3,144.2




Basic and diluted losses per share (in dollars) - continuing operations:
Distributed earnings - dividends declared and paid	$	1.00	$	1.00
Undistributed losses	(31.33)		(41.82)
Basic and diluted losses per share	$	(30.33)	$	(40.82)

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

(2) Restricted shares outstanding vest either in equal annual installments or upon a stated date. See Note 12 — “Employee Share-Based Incentive Compensation Plans”.

The following table presents the undistributed net earnings (losses) from continuing operations for the three months ended March 31, 2021 and 2020. See Note 19 — “Held for Sale and Discontinued Operations”.


	Three Months Ended
	March 31,
Millions	2021		2020
Undistributed net losses - continuing operations:
Net loss attributable to White Mountains’s common shareholders, net of restricted common share amounts	$	(93.1)	$	(128.4)
Dividends declared, net of restricted common share amounts (1)	(3.1)		(3.1)
Total undistributed net losses, net of restricted common share amounts	$	(96.2)	$	(131.5)

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

Employee Share-Based Incentive Compensation Plans

3 Months Ended

Mar. 31, 2021

Share-based Payment Arrangement [Abstract]

Employee Share-Based Incentive Compensation Plans

White Mountains’s Long-Term Incentive Plan (the “WTM Incentive Plan”) provides for grants of various types of share-based and non-share-based incentive awards to key employees of White Mountains. As of March 31, 2021, White Mountains’s share-based compensation incentive awards consist of performance shares and restricted shares.

Performance Shares

Performance shares are designed to reward employees for meeting company-wide performance targets. 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 service period, are subject to the attainment of pre-specified performance goals, and are valued based on the market value of common shares at the time awards are paid. Performance shares earned under the WTM Incentive Plan are typically paid in cash but may be paid in common shares. Compensation expense is recognized for the vested portion of the awards over the related service periods. The level of payout ranges from zero to two times the number of shares initially granted, depending on White Mountains’s financial performance. Performance shares become payable at the conclusion of a performance cycle (typically 3 years) if pre-defined financial targets are met. The performance measures used for determining performance share payouts are growth in White Mountains’s adjusted book value per share and intrinsic value per share. Intrinsic value per share is generally calculated by adjusting adjusted book value per share for differences between the adjusted book value of certain assets and liabilities and White Mountains’s estimate of their underlying intrinsic values.

The following table presents the performance share activity for the three months ended March 31, 2021 and 2020 for performance shares granted under the WTM Incentive Plan:


	Three Months Ended March 31,
		2021	2020
Millions, except share amounts			Target Performance Shares Outstanding	Accrued Expense		Target Performance Shares Outstanding	Accrued Expense
Beginning of period			42,458	$	56.3	42,473	$	43.7
Shares paid (1)			(14,117)	(34.6)		(14,070)	(27.7)
New grants			13,000	—		14,055	—
Forfeitures and cancellations(2)			(557)	.4		—	.4
Expense recognized			—	16.1		—	(6.6)
End of period			40,784	$	38.2	42,458	$	9.8

(1) WTM performance share payments in 2021 for the 2018-2020 performance cycle, which were paid in cash in March 2021 at 200% of target. WTM performance share payments in 2020 for the 2017-2019 performance cycle, which were paid in cash in March 2020, ranged from 174% to 180% of target.

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

During the three months ended March 31, 2021, White Mountains granted 13,000 performance shares for the 2021-2023 performance cycle. During the three months ended March 31, 2020, White Mountains granted 14,055 performance shares for the 2020-2022 performance cycle.

All performance shares earned were settled in cash. If all the outstanding WTM performance shares had vested on March 31, 2021, the total additional compensation cost to be recognized would have been $38.1 million, based on accrual factors (common share price and payout assumptions) as of March 31, 2021.

The following table presents performance shares outstanding and accrued expense for performance shares awarded under the WTM Incentive Plan as of March 31, 2021 for each performance cycle:


	Three Months Ended March 31, 2021
Millions, except share amounts	Target Performance Shares Outstanding	Accrued Expense
Performance cycle:
2019 – 2021	14,850	$	24.9
2020 – 2022	13,555	12.7
2021 – 2023	13,000	1.2

Sub-total	41,405	38.8
Assumed forfeitures	(621)	(.6)
March 31, 2021	40,784	$	38.2

Restricted Shares

Restricted shares are grants of a specified number of common shares that generally vest at the end of a 34-month service period. The following table presents the unrecognized compensation cost associated with the outstanding restricted share awards for the three months ended March 31, 2021 and 2020:


	Three Months Ended March 31,
		2021	2020
Millions, except share amounts			Restricted Shares	Unamortized Issue Date Fair Value		Restricted Shares	Unamortized Issue Date Fair Value
Non-vested,
Beginning of period			43,105	$	15.2	43,395	$	16.7
Issued			13,000	15.6		14,055	15.1
Vested			(17,717)	—		(14,345)	—
Forfeited			(583)	(.6)		—	—
Expense recognized			—	(4.0)		—	(5.2)
End of period			37,805	$	26.2	43,105	$	26.6

During the three months ended March 31, 2021, White Mountains issued 13,000 restricted shares that vest on January 1, 2024. During the three months ended March 31, 2020, White Mountains issued 14,055 restricted shares that vest on January 1, 2023. The unamortized issue date fair value as of March 31, 2021 is expected to be recognized ratably over the remaining vesting periods.

Leases

3 Months Ended

Mar. 31, 2021

Leases [Abstract]

Leases

White Mountains has entered into lease agreements, primarily for office space. These leases are classified as operating leases, with lease expense recognized on a straight-line basis over the term of the lease. Lease incentives, such as free rent or landlord reimbursements for leasehold improvements, are recognized at lease inception and amortized on a straight-line basis over the term of the lease. Lease expense and the amortization of leasehold improvements are recognized within general and administrative expenses. Lease payments related to options to extend or renew the lease term are excluded from the calculation of lease liabilities unless White Mountains is reasonably certain of exercising those options.

As of March 31, 2021 and December 31, 2020, the right of use (“ROU”) asset was $40.3 million and $37.6 million and lease liabilities were $41.0 million and $38.3 million.

The following table summarizes net lease expense recognized in White Mountains’s consolidated statement of operations for the three months ended March 31, 2021 and 2020:


Millions	Three Months Ended March 31,
Lease Cost	2021		2020
Lease cost	$	1.9	$	2.0
Less: sublease income	.1		.1
Net lease cost	$	1.8	$	1.9

The following table presents the contractual maturities of the lease liabilities associated with White Mountains’s operating lease agreements as of March 31, 2021:


Millions	As of March 31, 2021
Remainder of 2021	$	5.7
2022	9.8
2023	8.5
2024	7.1
2025	5.4
Thereafter	12.2
Total undiscounted lease payments	48.7
Less: present value adjustment	7.7
Operating lease liability	$	41.0

The following tables present lease related assets and liabilities by reportable segment as of March 31, 2021 and December 31, 2020:


	As of March 31, 2021
Millions	HG/BAM		Ark		NSM		Kudu		Other Operations		Total		Weighted Average Incremental Borrowing Rate (1)
ROU lease asset	$	9.6	$	4.9	$	16.0	$	2.0	$	7.8	$	40.3	4.8%
Lease liability	$	9.6	$	4.9	$	16.0	$	2.0	$	8.5	$	41.0

(1) The present value of the remaining lease payments was determined by discounting the lease payments using the incremental borrowing rate.


	As of December 31, 2020
Millions	HG/BAM		NSM		Kudu		Other Operations		Total		Weighted Average Incremental Borrowing Rate (1)
ROU lease asset	$	10.1	$	17.1	$	2.0	$	8.4	$	37.6	4.6%
Lease liability	$	10.1	$	17.1	$	2.0	$	9.1	$	38.3

(1) The present value of the remaining lease payments was determined by discounting the lease payments using the incremental borrowing rate.

Non-controlling Interests

3 Months Ended

Mar. 31, 2021

Noncontrolling Interest [Abstract]

Non-controlling Interests

Non-controlling interests consist of the ownership interests of non-controlling shareholders in consolidated entities and are presented separately on the balance sheet.

The following table presents the balance of non-controlling interests included in White Mountains’s total equity and the related percentage of each consolidated entity’s total equity owned by non-controlling shareholders as of March 31, 2021 and December 31, 2020:


	March 31, 2021				December 31, 2020
$ in Millions	Non-controlling Percentage		Non-controlling Equity		Non-controlling Percentage		Non-controlling Equity
Non-controlling interests, excluding BAM
HG Global	3.1	%	$	11.6	3.1	%	$	13.5
Ark	28.0	%	211.0		—	%	—
NSM	3.4	%	16.0		3.4	%	17.0

Kudu	.7	%	2.3		.7	%	2.3


Other	various		2.0		various		2.4
Total, excluding BAM			242.9				35.2
BAM	100.0	%	(132.9)		100.0	%	(123.3)

Total non-controlling interests			$	110.0			$	(88.1)

Segment Information

3 Months Ended

Mar. 31, 2021

Segment Reporting [Abstract]

Segment Informartion

Segment Information

As of March 31, 2021, White Mountains conducted its operations through five segments: (1) HG Global/BAM, (2) Ark, (3) NSM, (4) Kudu and (5) Other Operations. A discussion of White Mountains’s consolidated investment operations is included after the discussion of operations by segment.

As a result of the Ark Transaction, White Mountains began consolidating Ark in its financial statements as of January 1, 2021.

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

The following tables present the financial information for White Mountains’s segments:


Millions	HG Global/ BAM		Ark		NSM		Kudu		Other Operations		Total
Three Months Ended March 31, 2021
Earned insurance premiums	$	6.4	$	104.6	$	—	$	—	$	—	$	111.0
Net investment income	4.5		.8		—		8.2		7.1		20.6
Net realized and unrealized investment (losses) gains	(17.9)		1.1		—		15.8		2.1		1.1
Net realized and unrealized investment losses from investment in MediaAlpha	—		—		—		—		(41.7)		(41.7)
Commission revenues	—		—		59.6		—		2.3		61.9

Other revenue	.3		2.6		15.2		.1		7.1		25.3
Total revenues	(6.7)		109.1		74.8		24.1		(23.1)		178.2

Loss and loss adjustment expenses	—		66.0		—		—		—		66.0
Insurance acquisition expenses	1.9		36.7		—		—		—		38.6

Cost of sales	—		—		—		—		4.0		4.0
General and administrative expenses	16.4		37.8		46.0		2.5		35.7		138.4
Broker commission expense	—		—		18.9		—		—		18.9
Change in fair value of contingent consideration earnout liabilities	—		—		—		—		—		—
Amortization of other intangible assets	—		—		8.6		.1		.5		9.2
Loss on assets held for sale	—		—		28.7		—		—		28.7
Interest expense	—		1.1		5.9		5.8		.3		13.1
Total expenses	18.3		141.6		108.1		8.4		40.5		316.9
Pre-tax (loss) income	$	(25.0)	$	(32.5)	$	(33.3)	$	15.7	$	(63.6)	$	(138.7)


Millions	HG Global/ BAM		NSM		Kudu		Other Operations		Total
Three Months Ended March 31, 2020
Earned insurance premiums	$	5.4	$	—	$	—	$	—	$	5.4
Net investment income	5.5		—		7.3		10.1		22.9
Net realized and unrealized investment gains (losses)	6.1		—		(24.8)		(168.0)		(186.7)
Net unrealized investment gains from investment in MediaAlpha	—		—		—		30.0		30.0
Commission revenues	—		53.0		—		2.1		55.1

Other revenue	.5		12.0		.1		1.5		14.1
Total revenues	17.5		65.0		(17.4)		(124.3)		(59.2)

Insurance acquisition expenses	1.7		—		—		—		1.7

Cost of sales	—		—		—		2.0		2.0
General and administrative expenses	14.7		39.6		2.5		17.5		74.3
Broker commission expense	—		18.3		—		—		18.3
Change in fair value of contingent consideration earnout liabilities	—		(.6)		—		—		(.6)
Amortization of other intangible assets	—		4.8		.1		.2		5.1
Interest expense	—		4.3		1.4		.3		6.0
Total expenses	16.4		66.4		4.0		20.0		106.8
Pre-tax income (loss)	$	1.1	$	(1.4)	$	(21.4)	$	(144.3)	$	(166.0)

In compliance with ASC 606, Revenues from Contracts with Customers, the following tables present White Mountains’s total revenues by revenue source for the three months ended March 31, 2021 and 2020:


Millions	HG Global/BAM		Ark		NSM		Kudu		Other Operations		Total
Three Months Ended March 31, 2021
Commission and other revenue
Specialty Transportation	$	—	$	—	$	20.7	$	—	$	—	$	20.7
Real Estate	—		—		9.8		—		—		9.8
Social Services	—		—		6.7		—		—		6.7
Pet	—		—		17.1		—		—		17.1
United Kingdom	—		—		13.1		—		—		13.1

Other	—		—		7.4		—		2.3		9.7
Total commission and other revenue	—		—		74.8		—		2.3		77.1

Product revenues	—		—		—		—		6.5		6.5
Revenues from contracts with customers	—		—		74.8		—		8.8		83.6

Other revenues (1)	(6.7)		109.1		—		24.1		(31.9)		94.6
Total revenues	$	(6.7)	$	109.1	$	74.8	$	24.1	$	(23.1)	$	178.2

(1) Other revenues consist of premiums, investment income, investment gains and losses and other revenues outside the scope of ASC 606, Revenues from Contracts with Customers.


Millions	HG Global/BAM		NSM		Kudu		Other Operations		Total
Three Months Ended March 31, 2020
Commission and other revenue
Specialty Transportation	$	—	$	20.3	$	—	$	—	$	20.3
Real Estate	—		11.3		—		—		11.3
Social Services	—		6.3		—		—		6.3
Pet	—		11.8		—		—		11.8
United Kingdom	—		10.0		—		—		10.0

Other	—		5.3		—		1.4		6.7
Total commission and other revenue	—		65.0		—		1.4		66.4

Product revenues	—		—		—		2.1		2.1
Revenues from contracts with customers	—		65.0		—		3.5		68.5

Other revenues (1)	17.5		—		(17.4)		(127.8)		(127.7)
Total revenues	$	17.5	$	65.0	$	(17.4)	$	(124.3)	$	(59.2)

(1) Other revenues consist of premiums, investment income, investment gains and losses and other revenues outside the scope of ASC 606, Revenues from Contracts with Customers.

- 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/disclosureRef
-Publisher FASB
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+ Details

Equity-Method Eligible Investments

3 Months Ended

Mar. 31, 2021

Equity Method Investments and Joint Ventures [Abstract]

Equity-Method Eligible Investments

White Mountains’s equity method eligible investments include White Mountains’s investment in MediaAlpha, certain other unconsolidated entities, including Kudu’s Participation Contracts, private equity funds and hedge funds in which White Mountains has the ability to exert significant influence over the investee’s operating and financial policies.

The following table presents the carrying values of White Mountains’s equity method eligible investments as of March 31, 2021 and December 31, 2020:


Millions	March 31, 2021		December 31, 2020
Investment in MediaAlpha	$	600.2	$	802.2

Other equity method eligible investments, at fair value	$	706.2	$	698.1

For the three months ended March 31, 2021 and 2020, White Mountains’s received dividend and income distributions from equity method eligible investments, including White Mountains’s investment in MediaAlpha, of $13.7 million, and $11.4 million, which were recorded within net investment income in the consolidated statement of operations.

The following table presents White Mountains’s significant equity method eligible investments as of March 31, 2021 and December 31, 2020:


	Basic Ownership Interest
Investee	March 31, 2021	December 31, 2020	Instrument Held
PassportCard/DavidShield	53.8%	53.8%	Common shares
New Market Solutions, LLC.	46.7%	46.7%	Units
durchblicker	45.0%	45.0%	Common shares
MediaAlpha	28.5%	35.0%	Common shares
Elementum Holdings, L.P.	29.7%	28.9%	Limited partnership interest
Compare.com	18.4%	18.4%	Common shares
Tuckerman Capital Funds	16.1 - 30.0%	14.9 - 62.0%	Limited and general partnership interests
Enlightenment Capital Funds	9.1 - 66.3%	9.7 - 66.7%	Limited and general partnership interests
Kudu Participation Contracts	3.2 - 35.6%	3.2 - 35.0%	Revenue and earnings participation contracts

On March 23, 2021, MediaAlpha completed a secondary offering of 8.05 million shares. In the secondary offering, White Mountains sold 3.6 million shares at $46.00 per share ($44.62 per share net of underwriting fees) for net proceeds of $160.3 million. Following the completion of the offering, White Mountains owns 16.9 million shares, representing a 28.5% basic ownership interest (26.3% fully-diluted/fully-converted basis). At the March 31, 2021, closing price of $35.43 per share, the fair value of White Mountains’s remaining investment in MediaAlpha was $600.2 million. For the three months ended March 31, 2021, White Mountains recognized $41.7 million in realized and unrealized investment losses associated with its investment in MediaAlpha.

For the three months ended March 31, 2021 and 2020, MediaAlpha was considered a significant subsidiary. The following tables present summarized financial information for MediaAlpha as of March 31, 2021 and 2020:


Millions	March 31, 2021		December 31, 2020
Balance sheet data:
Total assets	$	241.7	$	212.7
Total liabilities	$	331.1	$	315.8


	Three Months Ended
	March 31,
Millions	2021		2020
Income statement data:
Total revenues	$	173.6	$	119.4
Total expenses	$	173.4	$	110.6
Net income	$	.2	$	8.8

Fair Value of Financial Instruments

3 Months Ended

Mar. 31, 2021

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

White Mountains records its financial instruments at fair value with the exception of debt obligations, which are recorded as debt at face value less unamortized original issue discount.

The following table presents the fair value and carrying value of this financial instrument as of March 31, 2021 and December 31, 2020:


	March 31, 2021				December 31, 2020
Millions	Fair Value		Carrying Value		Fair Value		Carrying Value
Ark Subordinated Notes (1)	$	44.1	$	44.1	$	—	$	—
NSM Bank Facility	$	275.6	$	271.5	$	279.3	$	271.3
Other NSM debt	$	1.3	$	1.2	$	1.3	$	1.3
Kudu Credit Facility (2)	$	102.0	$	95.9	$	—	$	—
Kudu Bank Facility	$	—	$	—	$	89.3	$	86.3
Other Operations debt	$	18.3	$	17.0	$	18.8	$	17.5

(1) As of March 31, 2021, White Mountains measured the fair value of the Ark Bank Facility Notes at the carrying value as a result of the debt being acquired on January 1, 2021. See Note 7 — “Debt”.

(2) As of March 31, 2021, White Mountains measured the fair value of the Kudu Credit Facility debt at the carrying value, before unamortized issuance costs, as a result of the debt being refinanced on March 23, 2021.

The fair value estimates for the Ark Subordinated Notes, NSM Bank Facility, the Other NSM debt, the Kudu Credit Facility, the Kudu Bank Facility and Other Operations debt have been determined based on a discounted cash flow approach and are considered to be Level 3 measurements.

- Definition

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

+ References + Details

Commitments and Contingencies	3 Months Ended
Commitments and Contingencies	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Contingencies White Mountains is subject to litigation and arbitration in the normal course of business. White Mountains considers the requirements of ASC 450 when evaluating its exposure to 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 if there is a reasonable possibility that a loss may have been incurred. White Mountains does not have any current litigation that may have a material adverse effect on White Mountains’s financial condition, results of operations or cash flows. The following description presents significant legal contingencies, ongoing non-claims related litigation or arbitration as of March 31, 2021: Esurance On October 7, 2011, the Company completed the sale of its Esurance Holdings, Inc. and its subsidiaries and Answer Financial Inc. and its subsidiaries (collectively, “Esurance”) to The Allstate Corporation (“Allstate”) pursuant to a Stock Purchase Agreement dated as of May 17, 2011. Subject to specified thresholds and limits, the Company remains contingently liable to Allstate for specified matters related to the pre-closing period, including (a) losses of Esurance arising from extra-contractual claims and claims in excess of policy limits, (b) certain corporate reorganizations effected to remove entities from Esurance that were not being sold in the transaction, and (c) certain tax matters, including certain net operating losses being less than stated levels. Sirius Group Tax Contingency In the first quarter of 2021, White Mountains recorded a $17.6 million gain within discontinued operations as a result of reversing a liability arising from the tax indemnification provided in connection with the sale of Sirius International Insurance Group, Ltd. (“Sirius Group”) in 2016. The liability related to certain interest deductions claimed by Sirius Group that had been disputed by the Swedish Tax Agency (STA). In April 2021, the STA informed the Swedish Administrative Court of Appeal that, as a result of the Swedish Supreme Administrative Court having ruled that the Swedish interest disallowance rules violate the European Union’s freedom of establishment principle, Sirius Group should prevail in its appeal (and that the interest deductions should not be disallowed).

Held for Sale and Discontinued Operations

3 Months Ended

Mar. 31, 2021

Discontinued Operations and Disposal Groups [Abstract]

Held for Sale and Discontinued Operations

Sirius Group

As of December 31, 2020, White Mountains recorded a liability of $18.7 million, related to the tax indemnification provided in connection with the sale of Sirius Group in 2016. For the three months ended March 31, 2021, White Mountains recorded a gain of $17.6 million in discontinued operations to reverse the liability accrued as of December 31, 2020 and $1.1 million gain related to foreign currency translation. See Note 18 — “Commitments and Contingencies”.

Other

As of December 31, 2020, assets held for sale included a corporate aircraft with a carrying value of $1.7 million. On February 12, 2021, the corporate aircraft was sold for $2.1 million and White Mountains recorded $0.5 million of realized gains within other revenues in the Other Operations segment.

On April 12, 2021, NSM sold its Fresh Insurance motor business. White Mountains determined that the transaction qualified as a held for sale business in the first quarter 2021, however, it did not meet the criteria to be classified as discontinued operations. In the first quarter of 2021, NSM recorded a loss of $28.7 million related to the sale. As of March 31, 2021, assets held for sale included the net realizable value of Fresh Insurance’s motor business of $1.5 million, which was recorded in other assets in the NSM segment.

Earnings Per Share from Discontinued Operations

White Mountains calculates earnings per share using the two-class method, which allocates earnings between common and unvested restricted common shares. Both classes of shares participate equally in earnings on a per share basis. Basic earnings per share amounts are based on the weighted average number of common shares outstanding adjusted for unvested restricted common shares. Diluted earnings per share amounts are also impacted by the net effect of potentially dilutive common shares outstanding.

The following table presents the Company’s computation of earnings per share for discontinued operations for the three months ended March 31, 2021 and 2020:


	Three Months Ended
	March 31,
		2021		2020
Basic and diluted earnings per share numerators (in millions):
Net loss attributable to White Mountains’s common shareholders		$	(75.3)	$	(128.8)
Less: total loss from continuing operations, net of tax		(94.0)		(129.7)
Net income from discontinued operations attributable to White Mountains’s common shareholders		$	18.7	$	.9
Allocation of earnings to participating restricted common shares (1)		(.2)		—
Basic and diluted earnings per share numerators (2)		$	18.5	$	.9
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period		3,100.2		3,178.0
Average unvested restricted common shares (3)		(32.4)		(33.8)
Basic earnings per share denominator		3,067.8		3,144.2
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period		3,100.2		3,178.0
Average unvested restricted common shares (3)		(32.4)		(33.8)

Diluted earnings per share denominator		3,067.8		3,144.2

Basic and diluted (losses) earnings per share (in dollars) - discontinued operations:		$	6.03	$	.28

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

(2) Net earnings attributable to White Mountains’s common shareholders, net of restricted share amounts, is equal to undistributed earnings for the three months ended March 31, 2021 and 2020.

(3) Restricted common shares outstanding vest either in equal annual installments or upon a stated date. See Note 12 — “Employee Share-Based Incentive Compensation Plans”.

Basis of Presentation and Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company is an exempted Bermuda limited liability company whose principal businesses are conducted through its subsidiaries and other affiliates. The Company’s headquarters is located at 26 Reid Street, Hamilton, Bermuda HM 11, its principal executive office is located at 23 South Main Street, Suite 3B, Hanover, New Hampshire 03755-2053 and its registered office is located at Clarendon House, 2 Church Street, Hamilton, Bermuda HM 11. The Company’s website is located at www.whitemountains.com. The information contained on White Mountains’s website is not incorporated by reference into, and is not a part of, this report. The accompanying consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) and include the accounts of White Mountains Insurance Group, Ltd. (the “Company” or the “Registrant”), its subsidiaries (collectively with the Company, “White Mountains”) and other entities required to be consolidated under GAAP.
Consolidation Principles	Consolidation Principles Under GAAP, the Company is required to consolidate any entity in which it holds a controlling financial interest. A controlling financial interest is usually in the form of an investment representing the majority of the subsidiary’s voting interests. However, a controlling financial interest may also arise from a financial interest in a variable interest entity (“VIE”) through arrangements that do not involve ownership of voting interests. The Company consolidates a VIE if it determines that it is the primary beneficiary. The primary beneficiary is defined as the entity who holds a variable interest that gives it both the power to direct the VIE’s activities that most significantly impact its economic performance and the obligation to absorb losses of, or the right to receive returns from, the VIE that could potentially be significant to the VIE. Intercompany transactions have been eliminated in consolidation. These interim financial statements include all adjustments considered necessary by management to fairly state the financial position, results of operations and cash flows of White Mountains. These interim financial statements may not be indicative of financial results for the full year and should be read in conjunction with the Company’s 2020 Annual Report on Form 10-K.
Business Combinations	Business Combinations White Mountains accounts for purchases of businesses using the acquisition method, which requires the measurement of assets acquired, including goodwill and other intangible assets, and liabilities assumed, including contingent liabilities, at their estimated fair values as of the acquisition date. The acquisition date fair values represent management’s best estimates and are based upon established valuation techniques, reasonable assumptions and, where appropriate, valuations performed by independent third parties. In circumstances where additional information is required in order to determine the acquisition date fair value of balance sheet amounts, provisional amounts may be recorded as of the acquisition date and may be subject to subsequent adjustment throughout the measurement period, which is up to one year from the acquisition date. Measurement period adjustments are recognized in the period in which they are determined. The results of operations and cash flows of businesses acquired are included in the consolidated financial statements from the date of acquisition. White Mountains accounts for purchases of other intangible assets that do not meet the definition of a business as asset acquisitions. Asset acquisitions are recognized at the amount of consideration paid, which is deemed to equal fair value.
Use of Estimates	Use of Estimates 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.
Fair Value Measurements	Fair Value Measurements Fair value measurements are categorized into a hierarchy that distinguishes between inputs based on market data from independent sources (“observable inputs”) and a reporting entity’s internal assumptions based upon the best information available when external market data is limited or unavailable (“unobservable inputs”). Quoted prices in active markets for identical assets or liabilities have the highest priority (“Level 1”), followed by observable inputs other than quoted prices, including prices for similar but not identical assets or liabilities (“Level 2”) and unobservable inputs, including the reporting entity’s estimates of the assumptions that market participants would use, having the lowest priority (“Level 3”).
Reportable Segments	Reportable Segments White Mountains has determined its reportable segments based on the nature of the underlying businesses, the manner in which the Company’s subsidiaries and affiliates are organized and managed and the organization of the financial information provided to the chief operating decision maker to assess performance and make decisions regarding allocation of resources. As of March 31, 2021, White Mountains’s reportable segments were HG Global/BAM, Ark, NSM, Kudu and Other Operations. The HG Global/BAM segment consists of HG Global Ltd. and its wholly-owned subsidiaries (“HG Global”) and the consolidated results of Build America Mutual Assurance Company (“BAM”) (collectively, “HG Global/BAM”). BAM is the first and only mutual municipal bond insurance company in the United States. By insuring the timely payment of principal and interest, BAM provides market access to, and lowers interest expense for, issuers of municipal bonds used to finance essential public purposes such as schools, utilities and transportation facilities. BAM is owned by and operated for the benefit of its members, the municipalities that purchase BAM’s insurance for their debt issuances. HG Global was established to fund the startup of BAM and, through its wholly-owned subsidiary, HG Re Ltd. (“HG Re”), to provide up to 15%-of-par, first loss reinsurance protection for policies underwritten by BAM. For capital appreciation bonds, par is adjusted to the estimated equivalent par value for current interest paying bonds. HG Global, together with its subsidiaries, funded the initial capitalization of BAM through the purchase of $503.0 million of surplus notes issued by BAM, consisting of $203.0 million of Series A Notes and $300.0 million of Series B Notes (the “BAM Surplus Notes”). As of March 31, 2021 and December 31, 2020, White Mountains owned 96.9% of HG Global’s preferred equity and 88.4% of its common equity. White Mountains does not have an ownership interest in BAM. However, White Mountains is required to consolidate BAM’s results in its financial statements because BAM is a VIE for which White Mountains is the primary beneficiary. BAM’s results are attributed to non-controlling interests. The Ark segment consists of Ark Insurance Holdings Limited and its subsidiaries (collectively, “Ark”). Ark writes a diversified and balanced portfolio of reinsurance and insurance, including property, accident & health, energy, marine and political risks, through Lloyd’s Syndicates 4020 and 3902 (the “Syndicates”). Beginning in January 2021, Ark began writing certain classes of its business through Group Ark Insurance Limited (“GAIL”), Ark’s wholly-owned Bermuda-based insurance and reinsurance company. As of March 31, 2021, White Mountains owned 72.0% of Ark on a basic shares outstanding basis (63.0% on a fully-diluted, fully-converted basis, taking account of management’s equity incentives). If the additional $200.0 million of equity capital that White Mountains has agreed to contribute to Ark is contributed in full, White Mountains will own 77.1% of Ark on a basic shares outstanding basis (67.5% on a fully-diluted, fully-converted basis). The remaining shares are owned by employees. In the future, management rollover shareholders could earn additional shares in the company if and to the extent that White Mountains achieves certain multiple of invested capital return thresholds. If fully earned, these additional shares would represent 12.5% of the shares outstanding at closing. See Note 2 — “Significant Transactions”. The NSM segment consists of NSM Insurance HoldCo, LLC and its subsidiaries (collectively, “NSM”). NSM is a full-service managing general underwriting agency (“MGU”) and program administrator for specialty property and casualty insurance. The company places insurance in niche sectors such as specialty transportation, real estate, social services and pet. On behalf of its insurance carrier partners, NSM typically manages all aspects of the placement process, including product development, marketing, underwriting, policy issuance and claims. NSM earns commissions based on the volume and profitability of the insurance that it places. NSM does not take insurance risk. As of March 31, 2021 and December 31, 2020, White Mountains owned 96.6% of the basic units outstanding of NSM (89.6% on a fully diluted, fully converted basis). See Note 2 — “Significant Transactions”. The Kudu segment consists of Kudu Investment Management, LLC and its subsidiaries (collectively “Kudu”), a capital solutions provider for asset management firms. Kudu provides capital solutions for boutique asset managers for a variety of purposes including generational ownership transfers, management buyouts, acquisition and growth finance and legacy partner liquidity. Kudu also provides strategic assistance to investees from time to time. Kudu’s capital solutions typically are structured as minority preferred equity stakes with distribution rights, typically tied to gross revenues and designed to generate immediate strong, stable cash yields. As of March 31, 2021 and December 31, 2020, White Mountains owned 99.3% of the basic units outstanding (84.8% on a fully diluted, fully converted basis). See Note 2 — “Significant Transactions”. The Other Operations segment consists of the Company and its wholly-owned subsidiary, White Mountains Capital, LLC, (“WM Capital”) its other intermediate holding companies, its wholly-owned investment management subsidiary, White Mountains Advisors LLC (“WM Advisors”), investment assets managed by WM Advisors, its interests in MediaAlpha, Inc. (“MediaAlpha”), PassportCard Limited (“PassportCard”) and DavidShield Life Insurance Agency (2000) Ltd. (“DavidShield”) (collectively, “PassportCard/ DavidShield”), Elementum Holdings LP (“Elementum”), and certain other consolidated and unconsolidated entities and certain other assets.
Discontinued Operations and Assets Held for Sale	Discontinued Operations and Assets Held for Sale In the first quarter of 2021, White Mountains recorded a gain on sale of discontinued operations as a result of reversing a liability arising from the tax indemnification provided in connection with the sale of Sirius International Insurance Group, Ltd. (“Sirius Group”) in 2016. As of December 31, 2020, assets held for sale included a corporate aircraft, which was sold on February 12, 2021. On April 12, 2021, NSM sold the Fresh Insurance Services Group Limited (“Fresh Insurance”) motor business. As of March 31, 2021, assets held for sale included the net realizable value of Fresh Insurance’s motor business, which was recorded in other assets in the NSM segment. Note 19 — “Held for Sale and Discontinued Operations”.
Ark Insurance Operations	Ark Insurance Operations Ark writes a diversified and balanced portfolio of reinsurance and insurance, including property, accident & health, energy, marine and political risks, through the Syndicates. Beginning in January 2021, Ark began writing certain classes of its business through GAIL. For the years of account prior to White Mountains’s transaction with Ark, a significant proportion of the Syndicates’ underwriting capital was provided by other third-party insurance and reinsurance groups (“TPC Providers”) using whole account reinsurance contracts through Ark’s corporate member. The TPC Providers’ economic participation in the Syndicates for the remaining open years of account prior to White Mountains’s transaction with Ark is approximately 51% of the total net result of the Syndicates. Captions within results of operations and other comprehensive income are shown net of amounts relating to the TPC Providers share of the Syndicates’ results, including investment results. Ark’s premiums written comprise premiums on insurance contracts incepted during the year as well as premium adjustments related to prior accounting years. Insurance premiums are recognized in earnings over the loss exposure or coverage period in proportion to the level of protection provided. In most cases, such premiums are earned ratably over the term of the contract with unearned premiums calculated on a monthly pro-rata basis. Premiums earned are presented net of amounts ceded to reinsurers. Premiums receivable, representing amounts due from insureds, are presented net of an allowance for uncollectible premiums, including expected credit losses, both dispute and credit related. The allowance is based upon Ark’s ongoing review of amounts outstanding, historical loss data, including delinquencies and write-offs, current and forecasted economic conditions and other relevant factors. Credit risk is partially mitigated by Ark’s ability to cancel the policy if the policyholder does not pay the premium. Deferred acquisition costs comprise brokerage and taxes which are directly attributable to and vary with the production of business. These costs are deferred and amortized to the extent they related to successful contract acquisitions over the applicable premium recognition period. Losses and loss adjustment expenses (“LAE”) are charged against income as incurred. Unpaid losses and LAE, including estimates for amounts incurred and not reported (“IBNR”) are based on estimates of the ultimate costs of settling claims, including the effects of inflation and other societal and economic factors. 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 results of 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. Reinsurance recoverables represent amounts of paid losses and loss adjustment expenses, case reserves and IBNR amounts ceded to reinsurers under reinsurance treaties. Amounts recoverable from reinsurers are estimated in a manner consistent with the associated claim liability. Ark reports its reinsurance recoverables net of an allowance for estimated uncollectible reinsurance, including expected credit losses. The allowance is based upon its ongoing review of amounts outstanding, length of collection periods, changes in reinsurer credit standing, disputes, applicable coverage defenses and other relevant factors.
Derivatives	Derivatives From time to time, White Mountains holds derivative financial instruments for risk management purposes. White Mountains recognizes all derivatives as either assets or liabilities, measured at fair value, on the consolidated balance sheet. Changes in the fair value of derivative instruments that meet the criteria for hedge accounting are recognized in other comprehensive income and reclassified into current period pre-tax income when the hedged items are recognized therein. Changes in the fair value of derivative instruments that do not meet the criteria for hedge accounting are recognized in current period pre-tax income. As of March 31, 2021 and December 31, 2020, NSM holds an interest rate swap derivative instrument that meets the criteria for hedge accounting. See Note 9 — “Derivatives”.
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets Goodwill represents the excess of the amount paid to acquire subsidiaries over the fair value of identifiable net assets at the date of acquisition. Other intangible assets consist primarily of the Lloyds underwriting capacity, trade names, URL and online names, customer relationships and contracts, information technology platforms and insurance licenses.
Reinsurance Contracts Accounted For As Deposits	Reinsurance Contracts Accounted for as Deposits Reinsurance contracts that do not meet the risk transfer requirements necessary to be accounted for as reinsurance are accounted for using the deposit method. Under the deposit method, ceded premiums paid are not recognized through income but rather treated as a deposit. BAM entered into ceded reinsurance agreements with Fidus Re Ltd. (“Fidus Re”) during the second quarter of 2018 and the first quarter of 2021, which are both accounted for using the deposit method. See Note 10 — “Municipal Bond Guarantee Insurance”. The nonrefundable consideration paid by BAM to Fidus Re is charged to financing expense within general and administrative expenses. Ark has an aggregate excess of loss contract with Third Point Reinsurance Ltd. (“Third Point Re”) in the amount of $50.0 million, which is accounted for using the deposit method. Ark earns an annual crediting rate of 3% which is recorded within other revenue. As of March 31, 2021, the carrying value of Ark’s deposit in Third Point Re, including accrued interest, was $51.7 million and is recorded in other assets.
Cash and Restricted Cash	Cash and Restricted 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. Cash balances that are not immediately available for general corporate purposes, including fiduciary accounts held by NSM on behalf of insurance carriers, are classified as restricted.
Recently Adopted Changes in Accounting Principles and Recently Issued Accounting Pronouncements	Recently Adopted Changes in Accounting Principles Income Taxes On January 1, 2020, White Mountains adopted ASU 2019-12, Simplifying the Accounting for Income Taxes (ASC 740), which removes exceptions to standard guidance. Under the new guidance non-income-based taxes, such as franchise taxes, are reported within pre-tax income rather than being included in income taxes. In addition, the new guidance eliminated the exception to the incremental approach for inter-period tax allocation, which previously allowed consideration of the tax effect of items such as discontinued operations and items recognized through other comprehensive income. For periods subsequent to the adoption of ASU 2019-12, White Mountains has recorded both the tax expense related to BAM’s member surplus contributions (“MSC”) and the related valuation allowance on such taxes through the non-controlling interest equity. Prior to the adoption of ASU 2019-12, White Mountains recorded the tax expense related to BAM’s MSC directly to non-controlling interest equity, while the valuation allowance on such taxes was recorded through the income statement. Goodwill On January 1, 2020, White Mountains adopted ASU 2017-04, Simplifying the Test for Goodwill Impairment (ASC 350), which changed the guidance on goodwill impairment testing. Under the new guidance, the qualitative assessment of the recoverability of goodwill remains the same, but the second step of the two-step qualitative test, which required calculation of the implied fair value of goodwill, has been eliminated. Instead, an impairment charge is recognized when the carrying value of a reporting unit exceeds its fair value. Any excess of carrying value over fair value is written down as an impairment. White Mountains did not identify any impairment indicators associated with its reporting units and therefore did not recognize an impairment of goodwill during the quarter ended March 31, 2021. White Mountains’s adoption of ASU 2017-04 did not have any impact on White Mountains’s financial statements. Credit LossesOn January 1, 2020, White Mountains adopted ASU 2016-13, Measurement of Credit Losses on Financial Instruments (ASC 326), which establishes new guidance for the recognition of credit losses for financial assets measured at amortized cost. The new ASU requires reporting entities to estimate the credit losses expected over the life of a credit exposure using historical information, current information and reasonable and supportable forecasts that affect the collectability of the financial asset. White Mountains measures its portfolio of investment securities at fair value with changes therein recognized through current period earnings and, accordingly, adoption of ASU 2016-13 did not have any impact on White Mountains’s financial statements.

Significant Transactions (Tables)

3 Months Ended

Mar. 31, 2021

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Recognized Identified Assets Acquired and Liabilities Assumed

The following presents additional details of the assets acquired and liabilities assumed as of the January 1, 2021 acquisition date:


Millions	As of January 1, 2021
Investments	$	594.3
Cash	52.0		(1)
Reinsurance recoverables	433.4
Insurance premiums receivable	236.7
Ceded unearned premiums	170.2
Value of in-force business acquired	71.7
Other assets	88.9
Loss and loss adjustment expense reserves	(696.0)
Unearned insurance premiums	(326.1)
Debt	(46.4)

Ceded reinsurance payable	(528.3)
Other liabilities	(25.9)
Net tangible assets acquired	24.5
Goodwill	116.8
Other intangible assets - syndicate underwriting capacity	175.7
Deferred tax liability on other intangible assets	(33.4)
Net assets acquired	$	283.6

(1) Cash excludes the White Mountains cash contribution of $605.4 as part of the Ark transaction.

The following table presents a summary of the acquisition date fair values of goodwill and other intangible assets for

acquisitions completed from January 1, 2020 through March 31, 2021:

$ in Millions

Acquisition of subsidiary/ asset

Goodwill and

Other intangible asset (1)

Acquisition Date

Kingsbridge

131.7

April 7, 2020

Ark

292.5

January 1, 2021

Other Operations

15.2

July 2, 2020

(1) Acquisition date fair values include the effect of adjustments during the measurement period and excludes the effect of foreign currency translation subsequent to the acquisition date.

Loss and Loss Adjustment Expense Reserves (Tables)

3 Months Ended

Mar. 31, 2021

Insurance Loss Reserves [Abstract]

Schedule of Liability for Unpaid Claims and Claims Adjustment Expense

The following table summarizes the loss and LAE reserve activities of Ark’s insurance and reinsurance subsidiaries for the three months ended March 31, 2021:


Millions	Three Months Ended March 31, 2021
Gross beginning balance as of January 1, 2021	$	696.0
Less: beginning reinsurance recoverable on unpaid losses	(433.4)
Net loss and LAE reserves	262.6

Loss and LAE incurred relating to:
Current year losses	65.5
Prior year losses	.5
Total incurred losses and LAE	66.0

Foreign currency translation adjustment to loss and LAE reserves	.7

Loss and LAE paid relating to:
Current year losses	(5.2)
Prior year losses	(19.7)
Total loss and LAE payments	(24.9)

Net ending balance	304.4
Plus: ending reinsurance recoverable on unpaid losses	447.5
Gross ending balance as of March 31, 2021	$	751.9

Related Party Disclosures (Tables)

3 Months Ended

Mar. 31, 2021

Reinsurance Disclosures [Abstract]

Effects of Reinsurance

The following table summarizes the effects of reinsurance on written and earned premiums and on losses and LAE for Ark.


	Three Months Ended March 31, 2021
Millions
Written premiums:
Gross	$	404.5


Ceded	(62.1)
Net written premiums	$	342.4
Earned premiums:
Gross	$	162.6


Ceded	(58.0)
Net earned premiums	$	104.6
Losses and LAE:
Gross	$	115.6


Ceded	(49.6)
Net Losses and LAE	$	66.0

Investment Securities (Tables)

3 Months Ended

Mar. 31, 2021

Investments, Debt and Equity Securities [Abstract]

Pre-tax net investment income

The following table presents pre-tax net investment income for the three months ended March 31, 2021 and 2020:


	Three Months Ended
	March 31,
Millions		2021		2020
Fixed maturity investments		$	6.5	$	8.1
Short-term investments		1.6		.8
Common equity securities		—		3.8

Investment in MediaAlpha		—		2.4
Other long-term investments		13.8		8.1
Amount attributable to TPC Providers		(.9)		—
Total investment income		21.0		23.2
Third-party investment expenses		(.4)		(.3)
Net investment income, pre-tax		$	20.6	$	22.9

Schedule of net realized and unrealized investment gains and losses

The following table presents net realized and unrealized investment gains (losses) for the three months ended March 31, 2021 and 2020:


	Three Months Ended
	March 31,
Millions	2021		2020
Fixed maturity investments	$	(25.4)	$	2.2
Short-term investments	(1.3)		.4
Common equity securities	1.0		(140.8)
Investment in MediaAlpha	(41.7)		30.0
Other long-term investments	28.1		(48.5)
Amount attributable to TPC Providers	(1.3)		—
Net realized and unrealized investment losses (1)	(40.6)		(156.7)
Less: net losses on investment securities sold during the period	(.2)		(8.7)
Net realized and unrealized investment losses on investment securities held at the end of the period	$	(40.4)	$	(148.0)

(1) For the three months ended March 31, 2021 and 2020, includes $(0.2) and $(0.4) of realized and unrealized investment losses related to foreign currency exchange.

Net unrealized investment gains (losses) for Level 3 investments


	Three Months Ended
	March 31,
Millions	2021		2020



Other long-term investments	$	16.7	$	(9.4)
Total net unrealized investment gains (losses), pre-tax - Level 3 investments	$	16.7	$	(9.4)

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


	March 31, 2021
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains		Carrying Value
U.S. Government and agency obligations	$	220.1	$	2.1	$	(.6)	$	—	$	221.6
Debt securities issued by corporations	678.6		13.9		(5.7)		.1		686.9
Municipal obligations	269.4		15.4		(1.0)		—		283.8
Mortgage and asset-backed securities	225.8		5.4		(1.3)		—		229.9

Collateralized loan obligations	59.5		—		(.1)		—		59.4
Total fixed maturity investments	$	1,453.4	$	36.8	$	(8.7)	$	.1	$	1,481.6


	December 31, 2020
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Carrying Value
U.S. Government and agency obligations	$	173.2	$	3.1	$	—	$	176.3
Debt securities issued by corporations	522.8		24.7		(.1)		547.4
Municipal obligations	244.0		21.0		—		265.0
Mortgage and asset-backed securities	211.7		6.8		—		218.5


Total fixed maturity investments	$	1,151.7	$	55.6	$	(.1)	$	1,207.2


	March 31, 2021
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains (Losses)		Carrying Value
Common equity securities	$	117.6	$	1.1	$	(.2)	$	.1	$	118.6
Investment in MediaAlpha	$	—	$	600.2	$	—	$	—	$	600.2

Other long-term investments	$	965.5	$	125.8	$	(56.5)	$	(2.6)	$	1,032.2


	December 31, 2020
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains		Carrying Value
Common equity securities	$	—	$	—	$	—	$	—	$	—
Investment in MediaAlpha	$	—	$	802.2	$	—	$	—	$	802.2

Other long-term investments	$	767.4	$	95.8	$	(78.1)	$	1.7	$	786.8

Fair value measurements by level, investment securities


	March 31, 2021
Millions	Fair Value		Level 1		Level 2		Level 3
Fixed maturity investments:
U.S. Government and agency obligations	$	221.6	$	221.6	$	—	$	—

Debt securities issued by corporations:
Financials	183.1		—		183.1		—
Consumer	96.3		—		96.3		—
Technology	81.9		—		81.9		—
Healthcare	76.6		—		76.6		—
Industrial	74.2		—		74.2		—
Communications	53.4		—		53.4		—
Utilities	51.4		—		51.4		—
Energy	39.3		—		39.3		—
Materials	30.7		—		30.7		—

Total debt securities issued by corporations	686.9		—		686.9		—

Municipal obligations	283.8		—		283.8		—
Mortgage and asset-backed securities	229.9		—		229.9		—

Collateralized loan obligations	59.4		—		59.4		—
Total fixed maturity investments	1,481.6		221.6		1,260.0		—

Short-term investments	625.8		481.2		144.6		—

Common equity securities (1)	118.6		—		118.6		—
Investment in MediaAlpha	600.2		600.2		—		—














Other long-term investments	656.4		—		—		656.4
Other long-term investments — NAV (2)	375.8		—		—		—
Total other long-term investments	1,032.2		—		—		656.4
Total investments	$	3,858.4	$	1,303.0	$	1,523.2	$	656.4

(1) Consist of investments in listed funds that predominantly invest in international equities.


	December 31, 2020
Millions	Fair Value		Level 1		Level 2		Level 3
Fixed maturity investments:
U.S. Government and agency obligations	$	176.3	$	176.3	$	—	$	—

Debt securities issued by corporations:
Financials	133.9		—		133.9
Consumer	81.9		—		81.9		—
Industrial	66.9		—		66.9		—
Technology	66.7		—		66.7		—
Healthcare	51.5		—		51.5		—
Communications	44.5		—		44.5		—
Energy	35.8		—		35.8		—
Materials	33.9		—		33.9		—
Utilities	32.3		—		32.3		—

Total debt securities issued by corporations	547.4		—		547.4		—

Municipal obligations	265.0		—		265.0		—
Mortgage and asset-backed securities	218.5		—		218.5		—


Total fixed maturity investments	1,207.2		176.3		1,030.9		—

Short-term investments	142.9		142.9		—		—

Investment in MediaAlpha	802.2		802.2		—		—















Other long-term investments	614.2		—		—		614.2
Other long-term investments — NAV (1)	172.6		—		—		—
Total other long-term investments	786.8		—		—		614.2
Total investments	$	2,939.1	$	1,121.4	$	1,030.9	$	614.2

Debt securities issued by corporations, credit ratings

The following table presents the credit ratings of debt securities issued by corporations held in White Mountains’s investment portfolio as of March 31, 2021 and December 31, 2020:


	Fair Value at
Millions	March 31, 2021		December 31, 2020
AAA	$	12.7	$	10.6
AA	60.2		57.9
A	353.2		318.3
BBB	250.9		159.6
BB	1.0		1.0

Other	8.9		—
Debt securities issued by corporations (1)	$	686.9	$	547.4

Mortgage-backed, asset-backed securities

The following table presents the fair value of White Mountains’s mortgage and asset-backed securities and collateralized loan obligations as of March 31, 2021 and December 31, 2020:


	March 31, 2021						December 31, 2020
Millions	Fair Value		Level 2		Level 3		Fair Value		Level 2		Level 3
Mortgage-backed securities:
Agency:
FNMA	$	98.4	$	98.4	$	—	$	88.7	$	88.7	$	—
FHLMC	76.9		76.9		—		70.1		70.1		—
GNMA	36.7		36.7		—		40.6		40.6		—
Total agency (1)	212.0		212.0		—		199.4		199.4		—

Non-agency: Residential	.6		.6		—		—		—		—

Total non-agency	.6		.6		—		—		—		—
Total mortgage-backed securities	212.6		212.6		—		199.4		199.4		—
Other asset-backed securities:
Credit card receivables	11.3		11.3		—		11.3		11.3		—
Vehicle receivables	6.0		6.0		—		7.8		7.8		—

Total other asset-backed securities	17.3		17.3		—		19.1		19.1		—
Total mortgage and asset-backed securities	229.9		229.9		—		218.5		218.5		—
Collateralized loan obligations	59.4		59.4		—		—		—		—
Total mortgage and asset-backed securities and collateralized loan obligations	$	289.3	$	289.3	$	—	$	218.5	$	218.5	$	—

(1) Represents publicly traded mortgage-backed securities which carry the full faith and credit guaranty of the U.S. Government (i.e., GNMA) or are guaranteed

by a government sponsored entity (i.e., FNMA, FHLMC).

Schedule of carrying values for other long-term investments

The following table presents the carrying values of White Mountains’s other long-term investments as of March 31, 2021 and December 31, 2020:


	Carrying Value at
Millions	March 31, 2021		December 31, 2020
Kudu’s Participation Contracts	$	427.4	$	400.6
PassportCard/DavidShield	95.0		95.0
Elementum Holdings L.P.	56.7		55.1
Other unconsolidated entities (1)	43.3		42.4





Total unconsolidated entities (2)	622.4		593.1
Private equity funds and hedge funds	133.5		121.2

Lloyd’s trust deposits	99.2		—
Bank loan fund	89.2		—
ILS funds	53.8		51.4
Private debt investments (2)	21.0		21.1
Other	13.1		—
Total other long-term investments	$	1,032.2	$	786.8

(2) See Fair Value Measurements by Level table.

Other long-term investments

The following table presents investments and unfunded commitments in private equity funds and hedge funds by investment objective and sector as of March 31, 2021 and December 31, 2020:


	March 31, 2021				December 31, 2020
Millions	Fair Value		Unfunded Commitments		Fair Value		Unfunded Commitments
Private equity funds
Aerospace/Defense/Government	$	73.0	$	14.0	$	69.1	$	15.3
Financial services	43.2		35.3		23.5		30.4
Real estate	4.0		3.0		—		—
Manufacturing/Industrial	1.3		—		28.6		—

Total private equity funds	121.5		52.3		121.2		45.7
Hedge funds

European small/mid cap	12.0		—		—		—


Total hedge funds	12.0		—		—		—
Total private equity funds and hedge funds included in other long-term investments	$	133.5	$	52.3	$	121.2	$	45.7

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

The following table presents investments in private equity funds that were subject to lock-up periods as of March 31, 2021:


Millions	1 – 3 years	3 – 5 years	5 – 10 years	>10 years	Total
Private equity funds — expected lock-up period remaining	$6.8	$27.0	$74.5	$13.2	$121.5

Rollforward of fair value investments by level

The following tables present the changes in White Mountains’s fair value measurements by level for the three months ended March 31, 2021 and 2020:


					Level 3 Investments		Other Long-term Investments Measured at NAV (1)
Millions	Level 1 Investments		Level 2 Investments		Other Long-term Investments				Total
Balance at December 31, 2020	$	978.5	$	1,030.9	$	614.2	$	172.6	$	2,796.2	(2)
Net realized and unrealized (losses) gains	(43.2)		(22.9)		16.7		11.4		(38.0)		(3)

Amortization/Accretion	—		(1.4)		—		—		(1.4)
Purchases	53.4		426.4		17.5		94.5		591.8
Sales	(166.9)		(122.6)		(1.6)		(38.5)		(329.6)


Effect of Ark Transaction	—		68.2		9.6		135.8		213.6
Transfers in	—		—		—		—		—
Transfers out	—		—		—		—		—
Balance at March 31, 2021	$	821.8	$	1,378.6	$	656.4	$	375.8	$	3,232.6	(1)

(2) Excludes carrying value of $625.8 and $142.9 as of March 31, 2021 and December 31, 2020 classified as short-term investments.

(3) Excludes realized and unrealized losses associated with short-term investments of $(1.3) and includes amounts attributable to TPC Providers of $1.3 for the three months ended March 31, 2021.


							Level 3 Investments		Other Long-term Investments Measured at NAV (1)
Millions	Level 1 Investments		Level 2 Investments		Common equity securities		Other Long- term Investments and Investment in MediaAlpha Pre-IPO				Total
Balance at December 31, 2019	$	780.0	$	1,109.6	$	.1	$	654.0	$	202.3	$	2,746.0	(2)
Net realized and unrealized losses	(98.7)		(39.9)		—		(9.7)		(8.8)		(157.1)		(3)

Amortization/Accretion	—		(.8)		—		—		—		(.8)
Purchases	74.2		126.8		—		24.7		7.2		232.9
Sales	(109.9)		(105.4)		—		(8.1)		(56.0)		(279.4)


Transfers in	—		—		—		—		—		—
Transfers out	—		—		—		—		—		—
Balance at March 31, 2020	$	645.6	$	1,090.3	$	.1	$	660.9	$	144.7	$	2,541.6	(2)

(2) Excludes carrying value of $137.6 and $201.2 as of March 31, 2020 and December 31, 2019 classified as short-term investments.

(3) Excludes realized and unrealized losses associated with short-term investments of $0.4 for the three months ended March 31, 2020.

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

$ in Millions

March 31, 2021

Description

Valuation Technique(s) (1)

Fair Value (2)

Unobservable Inputs

Discount Rate (3)(4)

Terminal Cash Flow Exit Multiple (x) or Terminal Revenue Growth Rate (%) (4)

Kudu’s Participation Contracts (5)

Discounted cash flow

$427.4

18% - 23%

7x - 12x

PassportCard/DavidShield

Discounted cash flow

$95.0

23%

Elementum Holdings, L.P.

Discounted cash flow

$56.7

17%

Private debt instruments

Discounted cash flow

$17.0

4% - 8%

N/A

All other

Discounted cash flow

$19.8

20% - 24%

New Market Solutions, LLC

Recent transaction

$9.9

Transaction price:

$9.9

Noblr, Inc.

Recent transaction

$8.7

Transaction price:

$8.7

Zillion Insurance Services, Inc.

Recent transaction

$5.0

Transaction price:

$5.0

(1) Key inputs to the discounted cash flow analysis generally include projections of future revenue and earnings, discount rates and terminal exit multiples or growth rates.

(2) Includes the net unrealized investment gains (losses) associated with foreign currency; foreign currency effects based on observable inputs.

(5) In the first quarter of 2021, Kudu deployed a total of $10.9 in TIG Advisors LLC, an existing Kudu Participation Contract.

$ in Millions

December 31, 2020

Description

Valuation Technique(s) (1)

Fair Value (2)

Unobservable Inputs

Discount Rate (3)(4)

Terminal Cash Flow Exit Multiple (x) or Terminal Revenue Growth Rate (%) (4)

Kudu’s Participation Contracts (5)

Discounted cash flow

$400.6

18% - 23%

7x - 12x

PassportCard/DavidShield (6)

Discounted cash flow

$95.0

23%

Elementum Holdings, L.P.

Discounted cash flow

$55.1

17%

Private debt instruments

Discounted cash flow

$17.1

4% - 8%

N/A

All other

Discounted cash flow

$18.8

20% - 24%

New Market Solutions, LLC

Recent transaction

$9.9

Transaction price:

$9.9

Noblr, Inc.

Recent transaction

$8.7

Transaction price:

$8.7

Zillion Insurance Services, Inc.(7)

Recent transaction

$5.0

Transaction price:

$5.0

(1) Key inputs to the discounted cash flow analysis generally include projections of future revenue and earnings, discount rates and terminal exit multiples or growth rates.

(2) Includes the net unrealized investment gains (losses) associated with foreign currency; foreign currency effects based on observable inputs.

(5) In 2020, Kudu deployed a total of $118.2 in new Kudu Participation Contracts, including Creation Investments Capital, Sequoia Financial Group, Channel Capital and Ranger Investment Management.

(6) In 2020, White Mountains made an additional $15.0 investment in PassportCard/DavidShield. See Note 2 — “Significant Transactions”.

(7) In 2020, White Mountains made an additional $2.5 investment in Zillion Insurance Services, Inc.

Goodwill and Other Intangible Assets (Tables)

3 Months Ended

Mar. 31, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Intangible Assets and Goodwill


$ in Millions	Weighted Average Economic Life (in years)	March 31, 2021								December 31, 2020
		Acquisition Date Fair Value		Accumulated Amortization		Impairments and Amounts Allocated to Held for Sale		Net Carrying Value		Acquisition Date Fair Value		Accumulated Amortization		Impairments		Net Carrying Value
Goodwill:
Ark	N/A	$	116.8	$	—	$	—	$	116.8	$	—	$	—	$	—	$	—
NSM (1)	N/A	507.9		—		30.2		477.7		506.4		—		—		506.4
Kudu	N/A	7.6		—		—		7.6		7.6		—		—		7.6
Other Operations	N/A	11.3		—		—		11.3		11.5		—		—		11.5
Total goodwill		643.6		—		30.2		613.4		525.5		—		—		525.5

Other intangible assets:
Ark
Underwriting Capacity	N/A	175.7		—		—		175.7		—		—		—		—

NSM (1)
Customer relationships	8.9	136.4		41.7		3.5		91.2		136.2		36.7		3.5		96.0
Trade names	16	65.4		9.1		1.0		55.3		65.4		8.3		1.0		56.1
Information technology platform	0	3.1		1.4		1.7		—		3.1		1.4		1.7		—
Renewal rights	12	82.5		7.6		—		74.9		82.5		4.9				77.6
Other	3.4	1.7		1.1		—		.6		1.7		1.0				.7
Subtotal		289.1		60.9		6.2		222.0		288.9		52.3		6.2		230.4

Kudu
Trade names	7	2.2		.7		—		1.5		2.2		.6		—		1.6

Other Operations
Trade names	9.6	3.6		.4		—		3.2		3.6		.3		—		3.3
Customer relationships	10.7	14.2		1.8		—		12.4		14.2		1.4		—		12.8

Insurance Licenses	N/A	8.6		—		—		8.6		8.6		—		—		8.6
Other	5.4	.3		.1		—		.2		.3		.1		—		.2
Subtotal		26.7		2.3		—		24.4		26.7		1.8		—		24.9
Total other intangible assets		493.7		63.9		6.2		423.6		317.8		54.7		6.2		256.9
Total goodwill and other intangible assets		$	1,137.3	$	63.9	$	36.4	1,037.0		$	843.3	$	54.7	6.2		782.4
Goodwill and other intangible assets attributed to non-controlling interests								(108.4)								(28.1)
Goodwill and other intangible assets included in White Mountains’s common shareholders’ equity								$	928.6							$	754.3

The following tables present the change in goodwill and other intangible assets for the three months ended March 31, 2021 and 2020:


	Three Months Ended March 31,
	2021						2020
Millions	Goodwill		Other Intangible Assets		Total Goodwill and Other Intangible Assets		Goodwill		Other Intangible Assets		Total Goodwill and Other Intangible Assets
Beginning balance	$	525.5	$	256.9	$	782.4	$	394.7	$	260.0	$	654.7

Ark Transaction	116.8		175.7		292.5		—		—		—

Foreign currency translation	1.5		.2		1.7		(2.5)		(.5)		(3.0)

Loss on assets held for sale (1)	(30.2)		—		(30.2)		—		—		—
Measurement period adjustments (2)	(.2)		—		(.2)		.2		—		.2
Amortization	—		(9.2)		(9.2)		—		(5.1)		(5.1)
Ending balance	$	613.4	$	423.6	$	1,037.0	$	392.4	$	254.4	$	646.8

(1) Relates to the sale of NSM’s Fresh motor business recorded in the first quarter of 2021.This amounts excludes $1.5 of net proceeds related to the sale.

Schedule of Recognized Identified Assets Acquired and Liabilities Assumed

The following presents additional details of the assets acquired and liabilities assumed as of the January 1, 2021 acquisition date:


Millions	As of January 1, 2021
Investments	$	594.3
Cash	52.0		(1)
Reinsurance recoverables	433.4
Insurance premiums receivable	236.7
Ceded unearned premiums	170.2
Value of in-force business acquired	71.7
Other assets	88.9
Loss and loss adjustment expense reserves	(696.0)
Unearned insurance premiums	(326.1)
Debt	(46.4)

Ceded reinsurance payable	(528.3)
Other liabilities	(25.9)
Net tangible assets acquired	24.5
Goodwill	116.8
Other intangible assets - syndicate underwriting capacity	175.7
Deferred tax liability on other intangible assets	(33.4)
Net assets acquired	$	283.6

(1) Cash excludes the White Mountains cash contribution of $605.4 as part of the Ark transaction.

The following table presents a summary of the acquisition date fair values of goodwill and other intangible assets for

acquisitions completed from January 1, 2020 through March 31, 2021:

$ in Millions

Acquisition of subsidiary/ asset

Goodwill and

Other intangible asset (1)

Acquisition Date

Kingsbridge

131.7

April 7, 2020

Ark

292.5

January 1, 2021

Other Operations

15.2

July 2, 2020

(1) Acquisition date fair values include the effect of adjustments during the measurement period and excludes the effect of foreign currency translation subsequent to the acquisition date.

Debt (Tables)

3 Months Ended

Mar. 31, 2021

Debt Disclosure [Abstract]

Schedule of debt outstanding

The following table presents White Mountains’s debt outstanding as of March 31, 2021 and December 31, 2020:


Millions	March 31, 2021		Effective Rate	(1)	December 31, 2020		Effective Rate	(1)

Ark Alesco Notes, carrying value	$	30.0			$	—
Ark Dekania Note, carrying value	14.1				—
Ark Subordinated Notes, carrying value	44.1		4.6%		—
NSM Bank Facility	277.3		7.6%	(2)	277.4		7.5%	(2)
Unamortized issuance cost	(5.8)				(6.1)
NSM Bank Facility, carrying value	271.5				271.3
Other NSM debt, carrying value	1.2		2.3%		1.3		2.5%
Kudu Credit Facility	102.0		5.2%		—
Unamortized issuance cost	(6.1)				—
Kudu Credit Facility, carrying value	95.9				—
Kudu Bank Facility	—				89.2		8.3%
Unamortized issuance cost	—				(2.9)
Kudu Bank Facility, carrying value	—				86.3



Other Operations debt	17.5		7.6%		18.0		7.4%
Unamortized issuance cost	(.5)				(.5)
Other Operations, carrying value	17.0				17.5
Total debt	$	429.7			$	376.4

(1) Effective rate includes the effect of the amortization of debt issuance costs.

The following table presents the change in debt under the NSM Bank Facility for the three months ended March 31, 2021 and 2020:


NSM Bank Facility	Three Months Ended
	March 31,
Millions		2021		2020
Beginning balance		$	277.4	$	221.3
Term loans
Borrowings		—		—
Repayments		(.7)		(.6)
Foreign currency translation		.6		—
Revolving credit loan
Borrowings		—		—
Repayments		—		—
Ending balance		$	277.3	$	220.7

Schedule of Debt

The following table presents the NSM weighted average interest rate for the three months ended March 31, 2021 and 2020:


NSM Weighted Average Interest Rate	Three Months ended March 31,
	2021						2020
Millions	Weighted Average		Interest Expense (1)		Weighted Average Interest rate		Weighted Average		Interest Expense (1)		Weighted Average Interest rate
Term loan - hedged	$	147.6	$	3.4	9.2	%	$	148.4	$	3.0	8.1	%
Term loan - unhedged	129.8		2.5		7.7	%	72.6		1.2		6.6	%
Total NSM Facility	$	277.4	$	5.9	8.5	%	$	221.0	$	4.2	7.6	%

(1) Interest expense includes the amortization of debt issuance costs and the effect of the interest rate swap and excludes interest expense related to the Other NSM Debt.

- 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://fasb.org/us-gaap/role/ref/legacyRef
-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=120391452&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28541-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-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=120395691&loc=d3e23780-122690

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
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-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21538-112644

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

Municipal Bond Guarantee Insurance (Tables)

3 Months Ended

Mar. 31, 2021

Guarantees [Abstract]

Schedule of Municipal Bond Guarantee Insured Obligations

The following table presents a schedule of BAM’s insured obligations as of March 31, 2021 and December 31, 2020:


	March 31, 2021		December 31, 2020
Contracts outstanding	11,252		10,997
Remaining weighted average contract period outstanding (in years)	10.6		10.7
Contractual debt service outstanding (in millions):
Principal	$	77,689.3	$	75,287.7
Interest	36,710.5		36,448.8
Total debt service outstanding	$	114,399.8	$	111,736.5

Gross unearned insurance premiums (in millions)	$	243.7	$	237.5

Financial Guarantee Insurance Contracts, Premium Received over Contract Period

The following table presents a schedule of BAM’s future premium revenues as of March 31, 2021:


Millions	March 31, 2021
April 1, 2021 - December 31, 2021	$	17.6

January 1, 2022 - March 31, 2022	5.7
April 1, 2022 - June 30, 2022	5.6
July 1, 2022 - September 30, 2022	5.6
October 1, 2022 - December 31, 2022	5.4
Total 2022	22.3

2023	21.0
2024	19.4
2025	18.0
2026	16.6
2027 and thereafter	128.8
Total gross unearned insurance premiums	$	243.7

Schedule of Net Written Premiums

The following table presents a schedule of written premiums and earned premiums included in White Mountains’s HG Global/BAM segment for the three months ended March 31, 2021 and 2020:


	Three Months Ended March 31,
Millions	2021		2020
Written premiums:
Direct	$	8.0	$	9.7
Assumed	4.5		—
Gross written premiums	$	12.5	$	9.7
Earned premiums:
Direct	$	5.3	$	4.5
Assumed	1.1		.9
Gross earned premiums	$	6.4	$	5.4

Earnings Per Share (Tables)

3 Months Ended

Mar. 31, 2021

Earnings Per Share [Abstract]

Computation of earnings per share


	Three Months Ended
	March 31,
	2021		2020
Basic and diluted loss per share numerators (in millions):
Net loss attributable to White Mountains’s common shareholders	$	(75.3)	$	(128.8)
Less: total income from discontinued operations, net of tax	18.7		.9
Net loss from continuing operations attributable to White Mountains’s common shareholders	$	(94.0)	$	(129.7)


Allocation of losses to participating restricted common shares(1)	.9		1.3
Basic and diluted losses per share numerators	$	(93.1)	$	(128.4)
Basic loss per share denominators (in thousands):
Total average common shares outstanding during the period	3,100.2		3,178.0
Average unvested restricted common shares(2)	(32.4)		(33.8)
Basic losses per share denominator	3,067.8		3,144.2
Diluted loss per share denominator (in thousands):
Total average common shares outstanding during the period	3,100.2		3,178.0
Average unvested restricted common shares(2)	(32.4)		(33.8)

Diluted losses per share denominator	3,067.8		3,144.2




Basic and diluted losses per share (in dollars) - continuing operations:
Distributed earnings - dividends declared and paid	$	1.00	$	1.00
Undistributed losses	(31.33)		(41.82)
Basic and diluted losses per share	$	(30.33)	$	(40.82)

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

(2) Restricted shares outstanding vest either in equal annual installments or upon a stated date. See Note 12 — “Employee Share-Based Incentive Compensation Plans”.

Schedule of Undistributed Net Earnings (Losses) from Continuing Operations


	Three Months Ended
	March 31,
Millions	2021		2020
Undistributed net losses - continuing operations:
Net loss attributable to White Mountains’s common shareholders, net of restricted common share amounts	$	(93.1)	$	(128.4)
Dividends declared, net of restricted common share amounts (1)	(3.1)		(3.1)
Total undistributed net losses, net of restricted common share amounts	$	(96.2)	$	(131.5)

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

Employee Share-Based Incentive Compensation Plans (Tables)

3 Months Ended

Mar. 31, 2021

Share-based Payment Arrangement [Abstract]

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

The following table presents the performance share activity for the three months ended March 31, 2021 and 2020 for performance shares granted under the WTM Incentive Plan:


	Three Months Ended March 31,
		2021	2020
Millions, except share amounts			Target Performance Shares Outstanding	Accrued Expense		Target Performance Shares Outstanding	Accrued Expense
Beginning of period			42,458	$	56.3	42,473	$	43.7
Shares paid (1)			(14,117)	(34.6)		(14,070)	(27.7)
New grants			13,000	—		14,055	—
Forfeitures and cancellations(2)			(557)	.4		—	.4
Expense recognized			—	16.1		—	(6.6)
End of period			40,784	$	38.2	42,458	$	9.8

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

Share-based Compensation, Performance Shares Award Outstanding Activity

The following table presents performance shares outstanding and accrued expense for performance shares awarded under the WTM Incentive Plan as of March 31, 2021 for each performance cycle:


	Three Months Ended March 31, 2021
Millions, except share amounts	Target Performance Shares Outstanding	Accrued Expense
Performance cycle:
2019 – 2021	14,850	$	24.9
2020 – 2022	13,555	12.7
2021 – 2023	13,000	1.2

Sub-total	41,405	38.8
Assumed forfeitures	(621)	(.6)
March 31, 2021	40,784	$	38.2

Summary of restricted shares activity

The following table presents the unrecognized compensation cost associated with the outstanding restricted share awards for the three months ended March 31, 2021 and 2020:


	Three Months Ended March 31,
		2021	2020
Millions, except share amounts			Restricted Shares	Unamortized Issue Date Fair Value		Restricted Shares	Unamortized Issue Date Fair Value
Non-vested,
Beginning of period			43,105	$	15.2	43,395	$	16.7
Issued			13,000	15.6		14,055	15.1
Vested			(17,717)	—		(14,345)	—
Forfeited			(583)	(.6)		—	—
Expense recognized			—	(4.0)		—	(5.2)
End of period			37,805	$	26.2	43,105	$	26.6

Leases (Tables)

3 Months Ended

Mar. 31, 2021

Leases [Abstract]

Summary of Lease Expense

The following table summarizes net lease expense recognized in White Mountains’s consolidated statement of operations for the three months ended March 31, 2021 and 2020:


Millions	Three Months Ended March 31,
Lease Cost	2021		2020
Lease cost	$	1.9	$	2.0
Less: sublease income	.1		.1
Net lease cost	$	1.8	$	1.9

Schedule of Future Maturities of Operating Lease Liabilities, Lessee

The following table presents the contractual maturities of the lease liabilities associated with White Mountains’s operating lease agreements as of March 31, 2021:


Millions	As of March 31, 2021
Remainder of 2021	$	5.7
2022	9.8
2023	8.5
2024	7.1
2025	5.4
Thereafter	12.2
Total undiscounted lease payments	48.7
Less: present value adjustment	7.7
Operating lease liability	$	41.0

Schedule of Right-of-Use Assets and Lease Liabilities

The following tables present lease related assets and liabilities by reportable segment as of March 31, 2021 and December 31, 2020:


	As of March 31, 2021
Millions	HG/BAM		Ark		NSM		Kudu		Other Operations		Total		Weighted Average Incremental Borrowing Rate (1)
ROU lease asset	$	9.6	$	4.9	$	16.0	$	2.0	$	7.8	$	40.3	4.8%
Lease liability	$	9.6	$	4.9	$	16.0	$	2.0	$	8.5	$	41.0

(1) The present value of the remaining lease payments was determined by discounting the lease payments using the incremental borrowing rate.


	As of December 31, 2020
Millions	HG/BAM		NSM		Kudu		Other Operations		Total		Weighted Average Incremental Borrowing Rate (1)
ROU lease asset	$	10.1	$	17.1	$	2.0	$	8.4	$	37.6	4.6%
Lease liability	$	10.1	$	17.1	$	2.0	$	9.1	$	38.3

(1) The present value of the remaining lease payments was determined by discounting the lease payments using the incremental borrowing rate.

Non-controlling Interests (Tables)

3 Months Ended

Mar. 31, 2021

Noncontrolling Interest [Abstract]

Non-controlling Interests


	March 31, 2021				December 31, 2020
$ in Millions	Non-controlling Percentage		Non-controlling Equity		Non-controlling Percentage		Non-controlling Equity
Non-controlling interests, excluding BAM
HG Global	3.1	%	$	11.6	3.1	%	$	13.5
Ark	28.0	%	211.0		—	%	—
NSM	3.4	%	16.0		3.4	%	17.0

Kudu	.7	%	2.3		.7	%	2.3


Other	various		2.0		various		2.4
Total, excluding BAM			242.9				35.2
BAM	100.0	%	(132.9)		100.0	%	(123.3)

Total non-controlling interests			$	110.0			$	(88.1)

Segment Information (Tables)

3 Months Ended

Mar. 31, 2021

Segment Reporting [Abstract]

Schedule of Financial Information for White Mountains' Segments

The following tables present the financial information for White Mountains’s segments:


Millions	HG Global/ BAM		Ark		NSM		Kudu		Other Operations		Total
Three Months Ended March 31, 2021
Earned insurance premiums	$	6.4	$	104.6	$	—	$	—	$	—	$	111.0
Net investment income	4.5		.8		—		8.2		7.1		20.6
Net realized and unrealized investment (losses) gains	(17.9)		1.1		—		15.8		2.1		1.1
Net realized and unrealized investment losses from investment in MediaAlpha	—		—		—		—		(41.7)		(41.7)
Commission revenues	—		—		59.6		—		2.3		61.9

Other revenue	.3		2.6		15.2		.1		7.1		25.3
Total revenues	(6.7)		109.1		74.8		24.1		(23.1)		178.2

Loss and loss adjustment expenses	—		66.0		—		—		—		66.0
Insurance acquisition expenses	1.9		36.7		—		—		—		38.6

Cost of sales	—		—		—		—		4.0		4.0
General and administrative expenses	16.4		37.8		46.0		2.5		35.7		138.4
Broker commission expense	—		—		18.9		—		—		18.9
Change in fair value of contingent consideration earnout liabilities	—		—		—		—		—		—
Amortization of other intangible assets	—		—		8.6		.1		.5		9.2
Loss on assets held for sale	—		—		28.7		—		—		28.7
Interest expense	—		1.1		5.9		5.8		.3		13.1
Total expenses	18.3		141.6		108.1		8.4		40.5		316.9
Pre-tax (loss) income	$	(25.0)	$	(32.5)	$	(33.3)	$	15.7	$	(63.6)	$	(138.7)


Millions	HG Global/ BAM		NSM		Kudu		Other Operations		Total
Three Months Ended March 31, 2020
Earned insurance premiums	$	5.4	$	—	$	—	$	—	$	5.4
Net investment income	5.5		—		7.3		10.1		22.9
Net realized and unrealized investment gains (losses)	6.1		—		(24.8)		(168.0)		(186.7)
Net unrealized investment gains from investment in MediaAlpha	—		—		—		30.0		30.0
Commission revenues	—		53.0		—		2.1		55.1

Other revenue	.5		12.0		.1		1.5		14.1
Total revenues	17.5		65.0		(17.4)		(124.3)		(59.2)

Insurance acquisition expenses	1.7		—		—		—		1.7

Cost of sales	—		—		—		2.0		2.0
General and administrative expenses	14.7		39.6		2.5		17.5		74.3
Broker commission expense	—		18.3		—		—		18.3
Change in fair value of contingent consideration earnout liabilities	—		(.6)		—		—		(.6)
Amortization of other intangible assets	—		4.8		.1		.2		5.1
Interest expense	—		4.3		1.4		.3		6.0
Total expenses	16.4		66.4		4.0		20.0		106.8
Pre-tax income (loss)	$	1.1	$	(1.4)	$	(21.4)	$	(144.3)	$	(166.0)

Schedule of Reconciliation of Revenue from Segments to Consolidated


Millions	HG Global/BAM		Ark		NSM		Kudu		Other Operations		Total
Three Months Ended March 31, 2021
Commission and other revenue
Specialty Transportation	$	—	$	—	$	20.7	$	—	$	—	$	20.7
Real Estate	—		—		9.8		—		—		9.8
Social Services	—		—		6.7		—		—		6.7
Pet	—		—		17.1		—		—		17.1
United Kingdom	—		—		13.1		—		—		13.1

Other	—		—		7.4		—		2.3		9.7
Total commission and other revenue	—		—		74.8		—		2.3		77.1

Product revenues	—		—		—		—		6.5		6.5
Revenues from contracts with customers	—		—		74.8		—		8.8		83.6

Other revenues (1)	(6.7)		109.1		—		24.1		(31.9)		94.6
Total revenues	$	(6.7)	$	109.1	$	74.8	$	24.1	$	(23.1)	$	178.2

(1) Other revenues consist of premiums, investment income, investment gains and losses and other revenues outside the scope of ASC 606, Revenues from Contracts with Customers.


Millions	HG Global/BAM		NSM		Kudu		Other Operations		Total
Three Months Ended March 31, 2020
Commission and other revenue
Specialty Transportation	$	—	$	20.3	$	—	$	—	$	20.3
Real Estate	—		11.3		—		—		11.3
Social Services	—		6.3		—		—		6.3
Pet	—		11.8		—		—		11.8
United Kingdom	—		10.0		—		—		10.0

Other	—		5.3		—		1.4		6.7
Total commission and other revenue	—		65.0		—		1.4		66.4

Product revenues	—		—		—		2.1		2.1
Revenues from contracts with customers	—		65.0		—		3.5		68.5

Other revenues (1)	17.5		—		(17.4)		(127.8)		(127.7)
Total revenues	$	17.5	$	65.0	$	(17.4)	$	(124.3)	$	(59.2)

(1) Other revenues consist of premiums, investment income, investment gains and losses and other revenues outside the scope of ASC 606, Revenues from Contracts with Customers.

Equity-Method Eligible Investments (Tables)

3 Months Ended

Mar. 31, 2021

Equity Method Investments and Joint Ventures [Abstract]

Equity Method Investments

The following table presents the carrying values of White Mountains’s equity method eligible investments as of March 31, 2021 and December 31, 2020:


Millions	March 31, 2021		December 31, 2020
Investment in MediaAlpha	$	600.2	$	802.2

Other equity method eligible investments, at fair value	$	706.2	$	698.1

The following table presents White Mountains’s significant equity method eligible investments as of March 31, 2021 and December 31, 2020:


	Basic Ownership Interest
Investee	March 31, 2021	December 31, 2020	Instrument Held
PassportCard/DavidShield	53.8%	53.8%	Common shares
New Market Solutions, LLC.	46.7%	46.7%	Units
durchblicker	45.0%	45.0%	Common shares
MediaAlpha	28.5%	35.0%	Common shares
Elementum Holdings, L.P.	29.7%	28.9%	Limited partnership interest
Compare.com	18.4%	18.4%	Common shares
Tuckerman Capital Funds	16.1 - 30.0%	14.9 - 62.0%	Limited and general partnership interests
Enlightenment Capital Funds	9.1 - 66.3%	9.7 - 66.7%	Limited and general partnership interests
Kudu Participation Contracts	3.2 - 35.6%	3.2 - 35.0%	Revenue and earnings participation contracts

The following tables present summarized financial information for MediaAlpha as of March 31, 2021 and 2020:


Millions	March 31, 2021		December 31, 2020
Balance sheet data:
Total assets	$	241.7	$	212.7
Total liabilities	$	331.1	$	315.8


	Three Months Ended
	March 31,
Millions	2021		2020
Income statement data:
Total revenues	$	173.6	$	119.4
Total expenses	$	173.4	$	110.6
Net income	$	.2	$	8.8

Fair Value of Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2021

Fair Value Disclosures [Abstract]

Summary of the fair value and carrying value of financial instruments

The following table presents the fair value and carrying value of this financial instrument as of March 31, 2021 and December 31, 2020:


	March 31, 2021				December 31, 2020
Millions	Fair Value		Carrying Value		Fair Value		Carrying Value
Ark Subordinated Notes (1)	$	44.1	$	44.1	$	—	$	—
NSM Bank Facility	$	275.6	$	271.5	$	279.3	$	271.3
Other NSM debt	$	1.3	$	1.2	$	1.3	$	1.3
Kudu Credit Facility (2)	$	102.0	$	95.9	$	—	$	—
Kudu Bank Facility	$	—	$	—	$	89.3	$	86.3
Other Operations debt	$	18.3	$	17.0	$	18.8	$	17.5

Held for Sale and Discontinued Operations (Tables)

3 Months Ended

Mar. 31, 2021

Discontinued Operations and Disposal Groups [Abstract]

Schedule of Earnings Per Share for Discontinued Operations

The following table presents the Company’s computation of earnings per share for discontinued operations for the three months ended March 31, 2021 and 2020:


	Three Months Ended
	March 31,
		2021		2020
Basic and diluted earnings per share numerators (in millions):
Net loss attributable to White Mountains’s common shareholders		$	(75.3)	$	(128.8)
Less: total loss from continuing operations, net of tax		(94.0)		(129.7)
Net income from discontinued operations attributable to White Mountains’s common shareholders		$	18.7	$	.9
Allocation of earnings to participating restricted common shares (1)		(.2)		—
Basic and diluted earnings per share numerators (2)		$	18.5	$	.9
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period		3,100.2		3,178.0
Average unvested restricted common shares (3)		(32.4)		(33.8)
Basic earnings per share denominator		3,067.8		3,144.2
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period		3,100.2		3,178.0
Average unvested restricted common shares (3)		(32.4)		(33.8)

Diluted earnings per share denominator		3,067.8		3,144.2

Basic and diluted (losses) earnings per share (in dollars) - discontinued operations:		$	6.03	$	.28

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

(2) Net earnings attributable to White Mountains’s common shareholders, net of restricted share amounts, is equal to undistributed earnings for the three months ended March 31, 2021 and 2020.

(3) Restricted common shares outstanding vest either in equal annual installments or upon a stated date. See Note 12 — “Employee Share-Based Incentive Compensation Plans”.

- Definition

Tabular disclosure of information related to a disposal group. Includes, but is not limited to, a discontinued operation, disposal classified as held-for-sale or disposed of by means other than sale or disposal of an individually significant component.

+ References

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Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 13: http://fasb.org/us-gaap/role/ref/legacyRef
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+ Details

Basis of Presentation and Significant Accounting Policies (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
	Jan. 01, 2021	Mar. 31, 2021	Mar. 23, 2021	Dec. 31, 2020	Oct. 30, 2020	Mar. 31, 2020	Dec. 31, 2017	Dec. 31, 2012	Jul. 31, 2012
Marketing Technology (MediaAlpha)
Basis of Presentation
Ownership interest (as a percent)			28.50%		35.00%
Share price (in USD per share)		$ 35.43		$ 39.07	$ 19.00
Ark
Basis of Presentation
Investment, potential additional contribution of equity capital	$ 200.0	$ 200.0
Fully diluted ownership interest after additional funding		67.50%
Ownership interest after additional funding		77.10%
Percent of shares outstanding		12.50%
Ark
Basis of Presentation
Percent of underwriting capital provided by third parties						51.00%
NSM Insurance HoldCo, LLC
Basis of Presentation
Ownership interest (as a percent)		96.60%
Fully diluted ownership interest (as a percent)		89.60%
Asset Management (Kudu)
Basis of Presentation
Ownership interest (as a percent)		99.30%
Fully diluted ownership interest (as a percent)		84.80%
HG Global
Basis of Presentation
Percentage of par value of policy reinsured		15.00%
Surplus notes								$ 503.0	$ 503.0
HG Global \| Preferred Stock
Basis of Presentation
Ownership interest (as a percent)		96.90%		96.90%
HG Global \| Common equity securities
Basis of Presentation
Ownership interest (as a percent)		88.40%		88.40%
HG Global \| Series A BAM Surplus Note
Basis of Presentation
Surplus notes							$ 203.0		203.0
HG Global \| Series B BAM Surplus Note
Basis of Presentation
Surplus notes									$ 300.0
Ark
Basis of Presentation
Ownership interest (as a percent)		72.00%
Ark \| Ark
Basis of Presentation
Ownership interest (as a percent)		72.00%
Fully diluted ownership interest (as a percent)		63.00%
Investment, potential additional contribution of equity capital	$ 200.0
Fully diluted ownership interest after additional funding	67.50%
Ownership interest after additional funding	77.10%
Ark \| Ark
Basis of Presentation
Fully diluted ownership interest (as a percent)	63.00%
Ark \| Third Point Re
Basis of Presentation
Reinsurance recoverable, aggregate excess loss		$ 50.0
Annual crediting rate		3.00%
Carrying value of investment		$ 51.7

Significant Transactions - MediaAlpha (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended
	Mar. 23, 2021	Oct. 30, 2020	Dec. 31, 2020	Mar. 31, 2021
Secondary Offering \| Marketing Technology (MediaAlpha)
Other Significant Noncash Transactions [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	8,050,000.00
Sale of stock, price per share (in USD per share)	$ 46.00	$ 19.00
Sale of stock, price per share, net of underwriting fees (in USD per share)	$ 44.62	$ 17.67
Marketing Technology (MediaAlpha)
Other Significant Noncash Transactions [Line Items]
Proceeds from dividends received		$ 55.0	$ 55.0
Investment owned (in shares)	16,900,000	20,500,000
Ownership interest (as a percent)	28.50%	35.00%
Fully diluted ownership interest (as a percent)	26.30%	32.30%
Sale of stock, price per share, net of underwriting fees (in USD per share)		$ 17.67
Share price (in USD per share)		$ 19.00	$ 39.07	$ 35.43
Investment owned, balance			$ 802.2	$ 600.2
Marketing Technology (MediaAlpha) \| IPO
Other Significant Noncash Transactions [Line Items]
Sale of stock, number of shares issued in transaction (in shares)		3,600,000
Sale of stock, consideration received in transaction		$ 63.8
Investment owned (in shares)		20,500,000
Marketing Technology (MediaAlpha) \| Secondary Offering
Other Significant Noncash Transactions [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	3,600,000
Sale of stock, consideration received in transaction	$ 160.3
Investment owned (in shares)	16,900,000

Significant Transactions - Ark (Details) - USD ($) $ in Millions			3 Months Ended
	Jan. 01, 2021	Oct. 01, 2020	Mar. 31, 2021	Dec. 31, 2020
Other Significant Noncash Transactions [Line Items]
Goodwill and other intangible assets			$ 1,037.0	$ 782.4
Ark
Other Significant Noncash Transactions [Line Items]
Cash pre-funded/placed in escrow for Ark Transaction				366.3
Other Operations
Other Significant Noncash Transactions [Line Items]
Goodwill and other intangible assets			35.7	36.4
Cash pre-funded/placed in escrow for Ark Transaction			0.0	646.3
Ark
Other Significant Noncash Transactions [Line Items]
Goodwill and other intangible assets			292.5	0.0
Contingent consideration related to the Ark Transaction			$ 22.5	0.0
Ownership interest (as a percent)			72.00%
Ark \| Ark
Other Significant Noncash Transactions [Line Items]
Fully diluted ownership interest (as a percent)	63.00%
Ark \| Lloyd
Other Significant Noncash Transactions [Line Items]
Cash pre-funded/placed in escrow for Ark Transaction				$ 280.0
Ark
Other Significant Noncash Transactions [Line Items]
Merger agreement, equity capital contributed		$ 605.4
Equity capital, pre money valuation amount		300.0
Additional equity purchase from shareholders		$ 40.9
Assets acquired	$ 2,500.0
Goodwill and other intangible assets	292.5
Liabilities acquired	1,700.0
Contingent consideration related to the Ark Transaction	22.5
Noncontrolling interest acquired	220.2
Investment, potential additional contribution of equity capital	$ 200.0		$ 200.0
Ownership interest after additional funding			77.10%
Fully diluted ownership interest after additional funding			67.50%
Percent of shares outstanding			12.50%
Transaction costs			$ 25.3
Ark \| Ark
Other Significant Noncash Transactions [Line Items]
Percent of outstanding shares after performance obligations are satisfied	12.50%
Ownership interest (as a percent)			72.00%
Fully diluted ownership interest (as a percent)			63.00%
Investment, potential additional contribution of equity capital	$ 200.0
Ownership interest after additional funding	77.10%
Fully diluted ownership interest after additional funding	67.50%

Significant Transactions - Schedule of Assets Acquired and Liabilities Assumed, Ark (Details) - USD ($) $ in Millions	Mar. 31, 2021	Jan. 01, 2021	Dec. 31, 2020
Other Significant Transactions [Line Items]
Goodwill	$ 613.4		$ 525.5
Ark
Other Significant Transactions [Line Items]
Investments		$ 594.3
Cash		52.0
Reinsurance recoverables		433.4
Insurance premiums receivable		236.7
Ceded unearned premiums		170.2
Value of in-force business acquired		71.7
Other assets		88.9
Loss and loss adjustment expense reserves		(696.0)
Unearned insurance premiums		(326.1)
Debt		(46.4)
Ceded reinsurance payable		(528.3)
Other liabilities		(25.9)
Net tangible assets acquired		24.5
Goodwill		116.8
Other intangible assets - syndicate underwriting capacity		175.7
Deferred tax liability on other intangible assets		(33.4)
Net assets acquired		$ 283.6

Significant Transactions - Elementum (Details)	Mar. 31, 2021	Dec. 31, 2020
Elementum Holdings L.P.
Other Significant Noncash Transactions [Line Items]
Ownership interest (as a percent)	29.70%	28.90%

Significant Transactions - NSM (Details) £ in Millions						3 Months Ended		9 Months Ended
Significant Transactions - NSM (Details) £ in Millions	Apr. 07, 2020 USD ($)	Apr. 07, 2020 GBP (£)	Mar. 31, 2019 USD ($)	Dec. 03, 2018 USD ($)	May 18, 2018 USD ($) earnout_period	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2020 USD ($)	Apr. 07, 2020 GBP (£)
Other Significant Noncash Transactions [Line Items]
(Loss) gain on sale						$ 28,700,000
Goodwill						613,400,000			$ 525,500,000
Change in fair value of contingent consideration earnout liabilities						0	$ (600,000)
Change in Fair Value of Contingent Earnout Liability, Expense (Revenue) Recognized						0	(600,000)
Payment for Contingent Consideration Liability, Financing Activities						6,700,000	6,400,000
NSM Insurance HoldCo, LLC
Other Significant Noncash Transactions [Line Items]
Cash consideration to acquire businesses and interest in affiliates				$ 29,000,000.0
Fresh Insurance Services Group Limited
Other Significant Noncash Transactions [Line Items]
Ownership interest (as a percent)					100.00%
Equity method investment, aggregate cost					$ 49,600,000
Borrowings					$ 51,000,000.0
Purchase price adjustment								$ 700,000
Number of earnout periods \| earnout_period					2
KBK Insurance Group, Inc. & KBK Premium Services, Inc.
Other Significant Noncash Transactions [Line Items]
Cash consideration to acquire businesses and interest in affiliates				60,000,000.0
Borrowings				$ 30,100,000
Goodwill			$ 32,600,000
Intangible assets acquired			32,700,000
Specialty Insurance Distribution (NSM)
Other Significant Noncash Transactions [Line Items]
Contingent consideration earnout liabilities						7,900,000			$ 14,600,000
Specialty Insurance Distribution (NSM) \| Kingsbridge Group Limited
Other Significant Noncash Transactions [Line Items]
Equity method investment, aggregate cost	$ 132,200,000									£ 107.2
Borrowings	$ 52,400,000	£ 42.5
Percentage of voting interests acquired	100.00%									100.00%
Stock issued during period, value, acquisitions	$ 80,300,000
Acquisitions of businesses	111,500,000
Attribution of acquisition date fair value estimates between goodwill and other intangible assets	20,200,000
Contingent consideration related to the Ark Transaction	4,100,000					200,000
Pretax income	4,100,000
Foreign currency translation gain	$ 300,000
NSM Bank Facility \| Specialty Insurance Distribution (NSM)
Other Significant Noncash Transactions [Line Items]
Amount borrowed						$ 277,300,000
NSM Insurance HoldCo, LLC
Other Significant Noncash Transactions [Line Items]
Ownership interest (as a percent)						96.60%
Fully diluted ownership interest (as a percent)						89.60%
KBK Insurance Group, Inc. & KBK Premium Services, Inc.
Other Significant Noncash Transactions [Line Items]
Change in fair value of contingent consideration earnout liabilities			$ 5,900,000
Payment for Contingent Consideration Liability, Financing Activities						$ 6,700,000	$ 6,400,000
KBK Insurance Group, Inc. & KBK Premium Services, Inc. \| Specialty Insurance Distribution (NSM)
Other Significant Noncash Transactions [Line Items]
Contingent consideration earnout liabilities						$ 6,400,000

Significant Transactions - PassportCard/DavidShield (Details) - USD ($) $ in Millions	May 07, 2020	Jan. 24, 2018	Mar. 31, 2021	Dec. 31, 2020	May 06, 2020
DavidShield
Other Significant Noncash Transactions [Line Items]
Ownership interest (as a percent)		50.00%
PassportCard
Other Significant Noncash Transactions [Line Items]
Ownership interest (as a percent)		50.00%
PassportCard/DavidShield
Other Significant Noncash Transactions [Line Items]
Ownership interest (as a percent)	53.80%		53.80%	53.80%	50.00%
Payments to acquire businesses, gross		$ 41.8
Payments to acquire business, net		$ 28.3
Stock issued during period, value, acquisitions	$ 15.0
Maximum loss exposure			$ 104.2

Significant Transactions - Kudu (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020	Apr. 07, 2020	Mar. 31, 2020
Other Significant Noncash Transactions [Line Items]
Goodwill	$ 613,400,000	$ 525,500,000
Total commitment under revolving credit facility			$ 291,400,000	$ 234,000,000.0
Kudu
Other Significant Noncash Transactions [Line Items]
Ownership interest (as a percent)	99.30%
Fully diluted ownership interest (as a percent)	84.80%

Loss and Loss Adjustment Expense Reserves (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($)
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross beginning balance as of January 1, 2021	$ 696.0
Less: beginning reinsurance recoverable on unpaid losses	433.4
Net loss and LAE reserves	262.6
Loss and LAE incurred relating to:
Current year losses	65.5
Prior year losses	0.5
Total incurred losses and LAE	66.0
Foreign currency translation adjustment to loss and LAE reserves	0.7
Loss and LAE paid relating to:
Current year losses	(5.2)
Prior year losses	(19.7)
Total loss and LAE payments	(24.9)
Net ending balance	304.4
Plus: ending reinsurance recoverable on unpaid losses	447.5
Gross ending balance as of March 31, 2021	$ 751.9

Third Party Reinsurance - Schedule of Reinsurance (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earned premiums:
Earned insurance premiums	$ 111.0	$ 5.4
Losses and Loss Adjustment Expense [Abstract]
Reinsurance recoverables on unpaid losses	447.5
Reinsurance recoverables on paid losses	$ 1.5
Percent of reinsurance recoverables from insurers with excellent or higher credit quality	90.00%
Ark
Written premiums:
Direct	$ 404.5
Ceded	(62.1)
Net written premiums	342.4
Earned premiums:
Direct	162.6
Ceded	(58.0)
Earned insurance premiums	104.6
Losses and Loss Adjustment Expense [Abstract]
Gross	115.6
Ceded	(49.6)
Net Losses and LAE	66.0
Amount attributable to TPC Providers
Losses and Loss Adjustment Expense [Abstract]
Reinsurance recoverables on unpaid losses	331.0
All Entities Except TCP Providers
Losses and Loss Adjustment Expense [Abstract]
Reinsurance recoverables on unpaid losses	$ 116.5

Investment Securities - Schedule of Interest Income on Fixed Maturity Investments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Schedule of Investments [Line Items]
Total investment income	$ 21.0	$ 23.2
Investment Income, Investment Expense	(0.4)	(0.3)
Net investment income	20.6	22.9
Fixed maturity investments
Schedule of Investments [Line Items]
Total investment income	6.5	8.1
Short-term investments
Schedule of Investments [Line Items]
Total investment income	1.6	0.8
Common equity securities
Schedule of Investments [Line Items]
Total investment income	0.0	3.8
Marketing Technology (MediaAlpha)
Schedule of Investments [Line Items]
Total investment income	0.0	2.4
Other long-term investments
Schedule of Investments [Line Items]
Total investment income	13.8	8.1
Amount attributable to TPC Providers
Schedule of Investments [Line Items]
Total investment income	$ 0.9	$ 0.0

Investment Securities - Net Realized and Unrealized Investment Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Debt and Equity Securities, FV-NI [Line Items]
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	$ (40.6)	$ (156.7)
Less: net losses on investment securities sold during the period	(0.2)	(8.7)
MediaAlpha
Debt and Equity Securities, FV-NI [Line Items]
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	(41.7)	30.0
Investments Held
Debt and Equity Securities, FV-NI [Line Items]
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	(40.4)	(148.0)
Fixed maturity investments
Debt and Equity Securities, FV-NI [Line Items]
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	(25.4)	2.2
Short-term investments
Debt and Equity Securities, FV-NI [Line Items]
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	(1.3)	0.4
Common equity securities
Debt and Equity Securities, FV-NI [Line Items]
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	1.0	(140.8)
MediaAlpha
Debt and Equity Securities, FV-NI [Line Items]
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	(41.7)	30.0
Other long-term investments
Debt and Equity Securities, FV-NI [Line Items]
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	28.1	(48.5)
Gain (loss) on investments, exchange rate effect	(0.2)	(0.4)
Amount attributable to TPC Providers
Debt and Equity Securities, FV-NI [Line Items]
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	$ (1.3)	$ 0.0

Investment Securities - Investment gains (losses) for Level 3 (Details) - Level 3 - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Debt and Equity Securities, FV-NI [Line Items]
Debt securities, trading, unrealized gain (loss)	$ 16.7	$ (9.4)
Other long-term investments
Debt and Equity Securities, FV-NI [Line Items]
Debt securities, trading, unrealized gain (loss)	$ 16.7	$ (9.4)

Investment Securities - Investment Holdings Fixed Maturity Table (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Debt and Equity Securities, FV-NI [Line Items]
Net Foreign Currency Gains	$ 0.1
U.S. Government and agency obligations
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	220.1	$ 173.2
Gross Unrealized Gains	2.1	3.1
Gross Unrealized Losses	(0.6)	0.0
Net Foreign Currency Gains	0.0
Carrying Value	221.6	176.3
Debt securities issued by corporations
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	678.6	522.8
Gross Unrealized Gains	13.9	24.7
Gross Unrealized Losses	(5.7)	(0.1)
Net Foreign Currency Gains	0.1
Carrying Value	686.9	547.4
Municipal obligations
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	269.4	244.0
Gross Unrealized Gains	15.4	21.0
Gross Unrealized Losses	(1.0)	0.0
Net Foreign Currency Gains	0.0
Carrying Value	283.8	265.0
Mortgage and asset-backed securities
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	225.8	211.7
Gross Unrealized Gains	5.4	6.8
Gross Unrealized Losses	(1.3)	0.0
Net Foreign Currency Gains	0.0
Carrying Value	229.9	218.5
Total fixed maturity investments
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	1,453.4	1,151.7
Gross Unrealized Gains	36.8	55.6
Gross Unrealized Losses	(8.7)	(0.1)
Carrying Value	1,481.6	$ 1,207.2
Collateralized loan obligations
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	59.5
Gross Unrealized Gains	0.0
Gross Unrealized Losses	(0.1)
Net Foreign Currency Gains	0.0
Carrying Value	$ 59.4

Investment Securities - Investment Holding Common Equities/ Other Investments/ MediaAlpha (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Common equity securities
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	$ 117.6	$ 0.0
Gross Unrealized Gains	1.1	0.0
Gross Unrealized Losses	(0.2)	0.0
Net Foreign Currency Gains (Losses)	0.1	0.0
Common equity securities, at fair value	118.6	0.0
Marketing Technology (MediaAlpha)
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	0.0	0.0
Gross Unrealized Gains	600.2	802.2
Gross Unrealized Losses	0.0	0.0
Net Foreign Currency Gains (Losses)	0.0	0.0
Common equity securities, at fair value	600.2	802.2
Other long-term investments
Debt and Equity Securities, FV-NI [Line Items]
Cost or Amortized Cost	965.5	767.4
Gross Unrealized Gains	125.8	95.8
Gross Unrealized Losses	(56.5)	(78.1)
Net Foreign Currency Gains (Losses)	(2.6)	1.7
Common equity securities, at fair value	$ 1,032.2	$ 786.8

Investment Securities - Debt securities issued by corporation (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	$ 3,232.6	$ 2,796.2	$ 2,541.6	$ 2,746.0
Debt securities issued by corporations
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	686.9	547.4
AAA \| Debt securities issued by corporations
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	12.7	10.6
AA \| Debt securities issued by corporations
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	60.2	57.9
A \| Debt securities issued by corporations
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	353.2	318.3
BBB \| Debt securities issued by corporations
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	250.9	159.6
BB \| Debt securities issued by corporations
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	1.0	1.0
Other \| Debt securities issued by corporations
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	$ 8.9	$ 0.0

Investment Securities - Investment in MediaAlpha textual (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended
	Mar. 23, 2021	Oct. 30, 2020	Dec. 31, 2020	Mar. 31, 2021
Secondary Offering \| Marketing Technology (MediaAlpha)
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	8,050,000.00
Sale of stock, price per share (in USD per share)	$ 46.00	$ 19.00
Sale of stock, price per share, net of underwriting fees (in USD per share)	$ 44.62	17.67
Marketing Technology (MediaAlpha)
Subsidiary, Sale of Stock [Line Items]
Share price (in USD per share)		$ 19.00	$ 39.07	$ 35.43
Proceeds from dividends received		$ 55.0	$ 55.0
Investment owned (in shares)	16,900,000	20,500,000
Ownership interest (as a percent)	28.50%	35.00%
Fully diluted ownership interest (as a percent)	26.30%	32.30%
Investment owned, balance			$ 802.2	$ 600.2
Sale of stock, price per share, net of underwriting fees (in USD per share)		$ 17.67
Marketing Technology (MediaAlpha) \| IPO
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)		3,600,000
Sale of stock, consideration received in transaction		$ 63.8
Investment owned (in shares)		20,500,000
Marketing Technology (MediaAlpha) \| Secondary Offering
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	3,600,000
Sale of stock, consideration received in transaction	$ 160.3
Investment owned (in shares)	16,900,000

Investment Securities - Other long-term investments (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Debt and Equity Securities, FV-NI [Line Items]
Other Long-term Investments	$ 1,032.2	$ 786.8
Asset Management (Kudu)
Debt and Equity Securities, FV-NI [Line Items]
Other Long-term Investments	427.4	400.6
PassportCard/DavidShield
Debt and Equity Securities, FV-NI [Line Items]
Other Long-term Investments	95.0	95.0
Elementum Holdings L.P.
Debt and Equity Securities, FV-NI [Line Items]
Other Long-term Investments	56.7	55.1
Other unconsolidated entities
Debt and Equity Securities, FV-NI [Line Items]
Other Long-term Investments	43.3	42.4
Total unconsolidated entities
Debt and Equity Securities, FV-NI [Line Items]
Other Long-term Investments	622.4	593.1
Private equity funds and hedge funds
Debt and Equity Securities, FV-NI [Line Items]
Other Long-term Investments	133.5	121.2
Lloyd’s trust deposits
Debt and Equity Securities, FV-NI [Line Items]
Other Long-term Investments	99.2	0.0
Bank loan fund
Debt and Equity Securities, FV-NI [Line Items]
Other Long-term Investments	89.2	0.0
ILS funds
Debt and Equity Securities, FV-NI [Line Items]
Other Long-term Investments	53.8	51.4
Private debt instruments
Debt and Equity Securities, FV-NI [Line Items]
Other Long-term Investments	21.0	21.1
Other
Debt and Equity Securities, FV-NI [Line Items]
Other Long-term Investments	$ 13.1	$ 0.0

Investment Securities - Hedge Funds and Private Equity Funds (Details) $ in Millions	Mar. 31, 2021 USD ($) fund	Dec. 31, 2020 USD ($)
Private equity funds
Debt and Equity Securities, FV-NI [Line Items]
Number of investments	13
Hedge and private equity funds included in other long-term investments
Debt and Equity Securities, FV-NI [Line Items]
Largest single fund investment \| $	$ 23.5	$ 29.1
Hedge funds
Debt and Equity Securities, FV-NI [Line Items]
Number of investments	1

Investment Securities - Fair Value of Hedge Funds and Private Equity Funds (Details) $ in Millions	Mar. 31, 2021 USD ($) fund	Dec. 31, 2020 USD ($)
Hedge and private equity funds included in other long-term investments
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	$ 133.5	$ 121.2
Unfunded Commitments	$ 52.3	45.7
Hedge funds
Debt and Equity Securities, FV-NI [Line Items]
Number of investments \| fund	1
Private equity funds
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	$ 121.5	121.2
Unfunded Commitments	52.3	45.7
Private equity funds \| Aerospace/Defense/Government
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	73.0	69.1
Unfunded Commitments	14.0	15.3
Private equity funds \| Manufacturing/Industrial
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	1.3	28.6
Unfunded Commitments	0.0	0.0
Private equity funds \| Financial services
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	43.2	23.5
Unfunded Commitments	35.3	30.4
Private equity funds \| Real Estate
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	4.0	0.0
Unfunded Commitments	3.0	0.0
Hedge funds
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	12.0	0.0
Unfunded Commitments	0.0	0.0
Hedge funds \| European small/mid cap
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	12.0	0.0
Unfunded Commitments	$ 0.0	$ 0.0

Investment Securities - Investments In Private Equity Funds Subject to Lock-Up Periods (Details) - Private equity funds $ in Millions	Mar. 31, 2021 USD ($)
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	$ 121.5
1 – 3 years
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	6.8
3 – 5 years
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	27.0
5 – 10 years
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	74.5
Greater than 10 years
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	$ 13.2

Investment Securities - Lloyd's Trust Deposits, Bank Loan Fund, and Insurance-Linked Securities Funds (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	$ 3,232.6	$ 2,796.2	$ 2,541.6	$ 2,746.0
Minimum
Debt and Equity Securities, FV-NI [Line Items]
Redemptions and advanced redemption notice period	30 days
Maximum
Debt and Equity Securities, FV-NI [Line Items]
Redemptions and advanced redemption notice period	90 days
ILS funds
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	$ 53.8
Lloyds Bank
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	99.2
Bank loan fund
Debt and Equity Securities, FV-NI [Line Items]
Fair value investments	$ 89.2

Investment Securities - Fair Value Measurements (Details)	3 Months Ended
	Mar. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Percentage of investments recorded at fair value	73.00%

Investment Securities - Rollforward of Fair Value Measurements by Level (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Debt and Equity Securities, FV-NI [Line Items]
Beginning balance	$ 2,796.2	$ 2,746.0
Net realized and unrealized (losses) gains	(38.0)	(157.1)
Amortization/Accretion	(1.4)	(0.8)
Purchases	591.8	232.9
Sales	(329.6)	(279.4)
Transfers in	0.0	0.0
Transfers out	0.0	0.0
Ending balance	3,232.6	2,541.6
Ark
Debt and Equity Securities, FV-NI [Line Items]
Purchases	213.6
Short-term investments, at fair value	328.6		$ 0.0
Third Party Capital Providers
Debt and Equity Securities, FV-NI [Line Items]
Realized and unrealized losses	1.3
Level 1 Investments
Debt and Equity Securities, FV-NI [Line Items]
Beginning balance	978.5	780.0
Net realized and unrealized (losses) gains	(43.2)	(98.7)
Amortization/Accretion	0.0	0.0
Purchases	53.4	74.2
Sales	(166.9)	(109.9)
Transfers in	0.0	0.0
Transfers out	0.0	0.0
Ending balance	821.8	645.6
Level 1 Investments \| Ark
Debt and Equity Securities, FV-NI [Line Items]
Purchases	0.0
Level 2 Investments
Debt and Equity Securities, FV-NI [Line Items]
Beginning balance	1,030.9	1,109.6
Net realized and unrealized (losses) gains	(22.9)	(39.9)
Amortization/Accretion	(1.4)	(0.8)
Purchases	426.4	126.8
Sales	(122.6)	(105.4)
Transfers in	0.0	0.0
Transfers out	0.0	0.0
Ending balance	1,378.6	1,090.3
Level 2 Investments \| Ark
Debt and Equity Securities, FV-NI [Line Items]
Purchases	68.2
Other long-term investments \| Level 3 Investments
Debt and Equity Securities, FV-NI [Line Items]
Beginning balance	614.2	654.0
Net realized and unrealized (losses) gains	16.7	(9.7)
Amortization/Accretion	0.0	0.0
Purchases	17.5	24.7
Sales	(1.6)	(8.1)
Transfers in	0.0	0.0
Transfers out	0.0	0.0
Ending balance	656.4	660.9
Other long-term investments \| Level 3 Investments \| Ark
Debt and Equity Securities, FV-NI [Line Items]
Purchases	9.6
Hedge and private equity funds included in other long-term investments \| NAV
Debt and Equity Securities, FV-NI [Line Items]
Beginning balance	172.6	202.3
Net realized and unrealized (losses) gains	11.4	(8.8)
Amortization/Accretion	0.0	0.0
Purchases	94.5	7.2
Sales	(38.5)	(56.0)
Transfers in	0.0	0.0
Transfers out	0.0	0.0
Ending balance	375.8	144.7
Hedge and private equity funds included in other long-term investments \| NAV \| Ark
Debt and Equity Securities, FV-NI [Line Items]
Purchases	135.8
Short-term investments
Debt and Equity Securities, FV-NI [Line Items]
Short-term investments, at fair value	625.8	137.6	$ 142.9	$ 201.2
Realized and unrealized losses	$ (1.3)	0.4
Common equity securities \| Level 3 Investments
Debt and Equity Securities, FV-NI [Line Items]
Beginning balance		0.1
Net realized and unrealized (losses) gains		0.0
Amortization/Accretion		0.0
Purchases		0.0
Transfers in		0.0
Transfers out		0.0
Ending balance		$ 0.1

Investment Securities - Significant Unobservable Inputs (Details) $ / shares in Units, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($) $ / shares	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($) $ / shares
Quantitative information for Level 3 Fair Value Measurements Assets
Investments in kudu participation contracts	$ 11.0	$ 21.0
Kudu Investments \| Minimum \| Discount rate \| Standard Poors NR Rating
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value, discount rate	18.00%		18.00%
Kudu Investments \| Minimum \| Terminal Multiple \| Standard Poors NR Rating
Quantitative information for Level 3 Fair Value Measurements Assets
Terminal Cash Flow Exit Multiple	7		7
Kudu Investments \| Maximum \| Discount rate \| Standard Poors NR Rating
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value, discount rate	23.00%		23.00%
Kudu Investments \| Maximum \| Terminal Multiple \| Standard Poors NR Rating
Quantitative information for Level 3 Fair Value Measurements Assets
Terminal Cash Flow Exit Multiple	12		12
PassportCard/DavidShield
Quantitative information for Level 3 Fair Value Measurements Assets
Investments in kudu participation contracts			$ 15.0
Private debt instruments \| Minimum \| Discount rate \| Standard Poors NR Rating
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value, discount rate	4.00%		4.00%
Private debt instruments \| Maximum \| Discount rate \| Standard Poors NR Rating
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value, discount rate	8.00%		8.00%
All other \| Minimum \| Discount rate \| Standard Poors NR Rating
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value, discount rate	20.00%		20.00%
All other \| Maximum \| Discount rate \| Standard Poors NR Rating
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value, discount rate	24.00%		24.00%
New Market Solutions, LLC \| Measurement Input, Long-term Revenue Growth Rate \| Standard Poors NR Rating \| Recent Transaction
Quantitative information for Level 3 Fair Value Measurements Assets
Share price (in USD per share) \| $ / shares	$ 9.9
Zillion Insurance Services
Quantitative information for Level 3 Fair Value Measurements Assets
Investments in kudu participation contracts			$ 2.5
Kudu
Quantitative information for Level 3 Fair Value Measurements Assets
Investments in kudu participation contracts	$ 10.9		118.2
Level 3 \| Kudu Investments \| Standard Poors NR Rating \| Discounted cash flow
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	427.4		400.6
Level 3 \| PassportCard/DavidShield \| Standard Poors NR Rating \| Discounted cash flow
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	$ 95.0		$ 95.0
Level 3 \| PassportCard/DavidShield \| Discount rate \| Standard Poors NR Rating
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value, discount rate	23.00%		23.00%
Level 3 \| PassportCard/DavidShield \| Measurement Input, Long-term Revenue Growth Rate \| Standard Poors NR Rating
Quantitative information for Level 3 Fair Value Measurements Assets
Terminal Revenue Growth Rate	4.00%		4.00%
Level 3 \| Elementum Holdings L.P. \| Standard Poors NR Rating \| Discounted cash flow
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	$ 56.7		$ 55.1
Level 3 \| Elementum Holdings L.P. \| Discount rate \| Standard Poors NR Rating
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value, discount rate	17.00%		17.00%
Level 3 \| Elementum Holdings L.P. \| Measurement Input, Long-term Revenue Growth Rate \| Standard Poors NR Rating
Quantitative information for Level 3 Fair Value Measurements Assets
Terminal Revenue Growth Rate	4.00%		4.00%
Level 3 \| Private debt instruments \| Standard Poors NR Rating \| Discounted cash flow
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	$ 17.0		$ 17.1
Level 3 \| All other \| Standard Poors NR Rating \| Discounted cash flow
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	$ 19.8		$ 18.8
Level 3 \| All other \| Measurement Input, Long-term Revenue Growth Rate \| Standard Poors NR Rating
Quantitative information for Level 3 Fair Value Measurements Assets
Terminal Revenue Growth Rate	4.00%		4.00%
Level 3 \| New Market Solutions, LLC \| Standard Poors NR Rating \| Recent Transaction
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	$ 9.9		$ 9.9
Level 3 \| New Market Solutions, LLC \| Measurement Input, Long-term Revenue Growth Rate \| Standard Poors NR Rating \| Recent Transaction
Quantitative information for Level 3 Fair Value Measurements Assets
Share price (in USD per share) \| $ / shares			$ 9.9
Level 3 \| Noblr, Inc. \| Standard Poors NR Rating \| Recent Transaction
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	$ 8.7		$ 8.7
Level 3 \| Noblr, Inc. \| Measurement Input, Long-term Revenue Growth Rate \| Standard Poors NR Rating \| Recent Transaction
Quantitative information for Level 3 Fair Value Measurements Assets
Share price (in USD per share) \| $ / shares	$ 8.7
Level 3 \| Noblr, Inc. \| Recent Transaction \| Standard Poors NR Rating
Quantitative information for Level 3 Fair Value Measurements Assets
Share price (in USD per share) \| $ / shares			$ 8.7
Level 3 \| Zillion Insurance Services \| Standard Poors NR Rating \| Recent Transaction
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value			$ 5.0
Level 3 \| Zillion Insurance Services \| Measurement Input, Long-term Revenue Growth Rate \| Standard Poors NR Rating \| Recent Transaction
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	$ 5.0
Level 3 \| Zillion Insurance Services \| Recent Transaction \| Standard Poors NR Rating
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value			$ 5.0
Level 3 \| Zillion Insurance Services \| Zillion Insurance Services \| Standard Poors NR Rating \| Recent Transaction
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	$ 5.0

Goodwill and Other Intangible Assets - Schedule of Acquisition Date Fair Values, Accumulated Amortization and Net Carrying Values for Other Intangibles Assets and Goodwill, By Company (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill, fair value	$ 643.6		$ 525.5
Goodwill, impairment loss	30.2		0.0
Goodwill, net carrying value	613.4		525.5
Other intangible assets, acquisition date fair value	493.7		317.8
Other intangible assets, accumulated amortization	63.9		54.7
Impairment of intangible assets, including goodwill	36.4		6.2
Other intangible assets, impairments	6.2		6.2
Other intangible assets, net carrying value	423.6		256.9
Goodwill and other intangible assets	1,037.0		782.4
Intangible assets and goodwill, fair value	1,137.3		843.3
Goodwill
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill, impairment loss	30.2	$ 0.0
Goodwill, net carrying value	613.4	392.4	525.5	$ 394.7
Goodwill, foreign currency translation gain (loss)	1.5	(2.5)
Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets, foreign currency translation gain (loss)	0.2	$ (0.5)
Non-controlling interest
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and other intangible assets	108.4		28.1
Total
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and other intangible assets	928.6		754.3
Ark
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill, fair value	116.8		0.0
Goodwill, impairment loss	0.0		0.0
Goodwill, net carrying value	116.8		0.0
Ark \| Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets, acquisition date fair value	175.7		0.0
Other intangible assets, accumulated amortization	0.0		0.0
Other intangible assets, impairments	0.0		0.0
Other intangible assets, net carrying value	175.7		0.0
Specialty Insurance Distribution (NSM)
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill, fair value	507.9		506.4
Goodwill, impairment loss	30.2		0.0
Goodwill, net carrying value	477.7		506.4
Other intangible assets, acquisition date fair value	289.1		288.9
Other intangible assets, accumulated amortization	60.9		52.3
Other intangible assets, impairments	6.2		6.2
Other intangible assets, net carrying value	222.0		230.4
Specialty Insurance Distribution (NSM) \| Goodwill
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill, foreign currency translation gain (loss)	1.5		13.4
Specialty Insurance Distribution (NSM) \| Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets, foreign currency translation gain (loss)	$ 0.2		1.6
Specialty Insurance Distribution (NSM) \| Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets, weighted average useful life (in years)	8 years 10 months 24 days
Other intangible assets, acquisition date fair value	$ 136.4		136.2
Other intangible assets, accumulated amortization	41.7		36.7
Other intangible assets, impairments	3.5		3.5
Other intangible assets, net carrying value	$ 91.2		96.0
Specialty Insurance Distribution (NSM) \| Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets, weighted average useful life (in years)	16 years
Other intangible assets, acquisition date fair value	$ 65.4		65.4
Other intangible assets, accumulated amortization	9.1		8.3
Other intangible assets, impairments	1.0		1.0
Other intangible assets, net carrying value	55.3		56.1
Specialty Insurance Distribution (NSM) \| Information technology platform
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets, acquisition date fair value	3.1		3.1
Other intangible assets, accumulated amortization	1.4		1.4
Other intangible assets, impairments	1.7		1.7
Other intangible assets, net carrying value	$ 0.0		0.0
Specialty Insurance Distribution (NSM) \| Renewal rights
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets, weighted average useful life (in years)	12 years
Other intangible assets, acquisition date fair value	$ 82.5		82.5
Other intangible assets, accumulated amortization	7.6		4.9
Other intangible assets, impairments	0.0
Other intangible assets, net carrying value	$ 74.9		77.6
Specialty Insurance Distribution (NSM) \| Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets, weighted average useful life (in years)	3 years 4 months 24 days
Other intangible assets, acquisition date fair value	$ 1.7		1.7
Other intangible assets, accumulated amortization	1.1		1.0
Other intangible assets, impairments	0.0
Other intangible assets, net carrying value	0.6		0.7
Kudu
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill, fair value	7.6		7.6
Goodwill, impairment loss	0.0		0.0
Goodwill, net carrying value	$ 7.6		7.6
Kudu \| Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets, weighted average useful life (in years)	7 years
Other intangible assets, acquisition date fair value	$ 2.2		2.2
Other intangible assets, accumulated amortization	0.7		0.6
Other intangible assets, impairments	0.0		0.0
Other intangible assets, net carrying value	1.5		1.6
Other Operations
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill, fair value	11.3		11.5
Goodwill, impairment loss	0.0		0.0
Goodwill, net carrying value	11.3		11.5
Other intangible assets, acquisition date fair value	26.7		26.7
Other intangible assets, accumulated amortization	2.3		1.8
Other intangible assets, impairments	0.0		0.0
Other intangible assets, net carrying value	$ 24.4		24.9
Other Operations \| Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets, weighted average useful life (in years)	10 years 8 months 12 days
Other intangible assets, acquisition date fair value	$ 14.2		14.2
Other intangible assets, accumulated amortization	1.8		1.4
Other intangible assets, impairments	0.0		0.0
Other intangible assets, net carrying value	$ 12.4		12.8
Other Operations \| Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets, weighted average useful life (in years)	9 years 7 months 6 days
Other intangible assets, acquisition date fair value	$ 3.6		3.6
Other intangible assets, accumulated amortization	0.4		0.3
Other intangible assets, impairments	0.0		0.0
Other intangible assets, net carrying value	$ 3.2		3.3
Other Operations \| Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets, weighted average useful life (in years)	5 years 4 months 24 days
Other intangible assets, acquisition date fair value	$ 0.3		0.3
Other intangible assets, accumulated amortization	0.1		0.1
Other intangible assets, impairments			0.0
Other intangible assets, net carrying value	0.2		0.2
Other Operations \| Insurance Licenses
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets, acquisition date fair value	8.6		8.6
Other intangible assets, accumulated amortization	0.0		0.0
Other intangible assets, impairments	0.0		0.0
Other intangible assets, net carrying value	8.6		$ 8.6
Other Operations \| Other Operations
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets, impairments	$ 0.0

Goodwill and Other Intangible Assets - Summary of the Acquisition Date Fair Values of Goodwill and Other Intangible Assets (Details) - USD ($) $ in Millions	Jan. 01, 2021	Jul. 02, 2020	Apr. 07, 2020
Kingsbridge Group Limited \| Specialty Insurance Distribution (NSM)
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired			$ 131.7
Ark \| Specialty Insurance Distribution (NSM)
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired	$ 292.5
Other
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired		$ 15.2

Goodwill and Other Intangible Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, impairments	$ 6.2	$ 6.2
(Loss) gain on sale	28.7
Specialty Insurance Distribution (NSM)
Finite-Lived Intangible Assets [Line Items]
Other intangible assets, impairments	$ 6.2	$ 6.2

Goodwill and Other Intangible Assets - Schedule of Goodwill and Other Intangible Assets Rollforward (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill, beginning balance	$ 525,500,000
Goodwill, impairment loss	(30,200,000)		$ 0
Amortization of other intangible assets	(9,200,000)	$ (5,100,000)
Goodwill, ending balance	613,400,000		525,500,000
Fresh Insurance Services Group Limited
Acquired Finite-Lived Intangible Assets [Line Items]
Proceeds from sale of other assets	1,500,000
Goodwill
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill, beginning balance	525,500,000	394,700,000	394,700,000
Acquisitions of businesses	116,800,000	0
Goodwill, foreign currency translation gain (loss)	1,500,000	(2,500,000)
Goodwill, impairment loss	(30,200,000)	0
Measurement period adjustments	(200,000)	200,000
Goodwill, ending balance	613,400,000	392,400,000	525,500,000
Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets (excluding goodwill), beginning balance	256,900,000	260,000,000.0	260,000,000.0
Acquisitions of businesses	175,700,000	0
Other intangible assets, foreign currency translation gain (loss)	200,000	(500,000)
Measurement period adjustments	0	0
Amortization of other intangible assets	(9,200,000)	(5,100,000)
Other intangible assets (excluding goodwill), ending balance	423,600,000	254,400,000	256,900,000
Total Goodwill and Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets, gross (including goodwill), beginning balance	782,400,000	654,700,000	654,700,000
Acquisitions of businesses	292,500,000	0
Other intangible assets, foreign currency translation gain (loss)	1,700,000	(3,000,000.0)
Goodwill, impairment loss	(30,200,000)	0
Measurement period adjustments	(200,000)	200,000
Amortization of other intangible assets	(9,200,000)	(5,100,000)
Other intangible assets, gross (including goodwill), ending balance	$ 1,037,000,000.0	$ 646,800,000	$ 782,400,000

Debt - Summary of Debt Outstanding (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Debt Instrument
Total debt	$ 429.7	$ 376.4
Weighted average interest rate	7.10%	7.00%
Ark \| Ark Subordinated Debt
Debt Instrument
Amount borrowed	$ 44.1	$ 0.0
Effective percentage	4.60%
NSM Bank Facility
Debt Instrument
Effective percentage	8.50%	8.40%
NSM Bank Facility \| Book Value
Debt Instrument
Total debt	$ 271.5	$ 271.3
Other NSM debt
Debt Instrument
Total debt		1.3
Other NSM debt \| Book Value
Debt Instrument
Total debt	1.2	1.3
Kudu Credit Facility \| Book Value
Debt Instrument
Total debt	95.9	0.0
Kudu Bank Facility \| Book Value
Debt Instrument
Total debt	0.0	86.3
Ark Alesco Note \| Ark Subordinated Debt
Debt Instrument
Amount borrowed	30.0
Ark Dekania Note \| Ark Subordinated Debt
Debt Instrument
Amount borrowed	14.1
Term Loan \| NSM Bank Facility
Debt Instrument
Amount borrowed	277.3	277.4
Unamortized issuance cost	(5.8)	(6.1)
Total debt	$ 271.5	$ 271.3
Effective percentage	7.60%	7.50%
Term Loan \| Other NSM debt
Debt Instrument
Effective percentage	2.30%	2.50%
Term Loan \| Kudu Credit Facility
Debt Instrument
Amount borrowed	$ 102.0
Unamortized issuance cost	$ (6.1)
Effective percentage	5.20%
Term Loan \| Kudu Bank Facility
Debt Instrument
Amount borrowed		$ 89.2
Unamortized issuance cost		(2.9)
Total debt		$ 86.3
Effective percentage		8.30%
Term Loan \| Other Operations
Debt Instrument
Amount borrowed	$ 17.5	$ 18.0
Unamortized issuance cost	$ (0.5)	(0.5)
Total debt		$ 17.5
Effective percentage	7.60%	7.40%

Debt - Narrative (Details) £ in Millions			1 Months Ended	3 Months Ended
Debt - Narrative (Details) £ in Millions	Apr. 07, 2020 USD ($)	Apr. 07, 2020 GBP (£)	Mar. 31, 2007 USD ($)	Mar. 31, 2021 USD ($) credit_facility	Mar. 31, 2021 GBP (£)	Mar. 31, 2020 USD ($)	Mar. 31, 2021 EUR (€) credit_facility	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jun. 15, 2018 USD ($)	Mar. 31, 2007 EUR (€)
Debt Instrument
Total commitment under revolving credit facility	$ 291,400,000					$ 234,000,000.0
Debt covenant, maximum loan to value percent, period one				50.00%			50.00%
Debt covenant, maximum loan to value percent, period two				40.00%			40.00%
Debt covenant, maximum loan to value percent, period three				25.00%			25.00%
Debt covenant, maximum loan to value percent, period four				15.00%			15.00%
Debt covenant, maximum loan to value percent, period five				0.00%			0.00%
Debt covenant, maximum loan to value percent				29.50%			29.50%
Debt				$ 429,700,000				$ 376,400,000
Draw down of debt and revolving line of credit				$ 105,300,000		$ 12,000,000.0
Other
Debt Instrument
Secured credit facilities \| credit_facility				2			2
Specialty Insurance Distribution (NSM)
Debt Instrument
Debt				$ 272,700,000				272,600,000
Weighted Average Interest rate				8.50%		7.60%	8.50%
Specialty Insurance Distribution (NSM) \| Term loan - hedged
Debt Instrument
Weighted Average Interest rate				9.20%		8.10%	9.20%
Specialty Insurance Distribution (NSM) \| Term loan - unhedged
Debt Instrument
Weighted Average Interest rate				7.70%		6.60%	7.70%
NSM Bank Facility \| Specialty Insurance Distribution (NSM)
Debt Instrument
Amount borrowed				$ 277,300,000
Percentage of discounted future cash flows				10.00%	10.00%
Debt				$ 277,300,000		$ 220,700,000		277,400,000	$ 221,300,000
NSM Bank Facility \| Term Loan
Debt Instrument
Debt				271,500,000				271,300,000
Amount borrowed				277,300,000				277,400,000
NSM Bank Facility \| Term Loan \| Specialty Insurance Distribution (NSM)
Debt Instrument
Amount borrowed	276,400,000					224,000,000.0
Borrowings	$ 52,400,000	£ 42.5		0		0
NSM Bank Facility \| Term Loan \| Specialty Insurance Distribution (NSM) \| Interest Rate Swap
Debt Instrument
Total commitment under revolving credit facility										$ 151,000,000.0
Hedged liability, fair value										$ 151,000,000.0
NSM Bank Facility \| Term Loan \| Specialty Insurance Distribution (NSM) \| Interest Rate Swap \| Term loan - hedged
Debt Instrument
Debt				147,200,000
NSM Bank Facility \| Term Loan \| Specialty Insurance Distribution (NSM) \| Interest Rate Swap \| Term loan - unhedged
Debt Instrument
Debt				$ 130,100,000
NSM Bank Facility \| Term Loan \| Specialty Insurance Distribution (NSM) \| USD-LIBOR \| Minimum
Debt Instrument
Basis spread on variable rate	4.25%	4.25%		5.50%	5.50%
NSM Bank Facility \| Term Loan \| Specialty Insurance Distribution (NSM) \| USD-LIBOR \| Maximum
Debt Instrument
Basis spread on variable rate	4.75%	4.75%		6.00%	6.00%
Debt instrument, interest rate, increase (decrease)				1.25%	1.25%
NSM Bank Facility \| Term Loan \| Specialty Insurance Distribution (NSM) \| GBP-LIBOR \| Minimum
Debt Instrument
Basis spread on variable rate				6.00%	6.00%
NSM Bank Facility \| Term Loan \| Specialty Insurance Distribution (NSM) \| GBP-LIBOR \| Maximum
Debt Instrument
Basis spread on variable rate				6.50%	6.50%
Derivative, cap interest rate				1.25%			1.25%
NSM Bank Facility \| Revolving credit loan \| Specialty Insurance Distribution (NSM)
Debt Instrument
Total commitment under revolving credit facility	$ 15,000,000.0					10,000,000.0
Borrowings				$ 0		$ 0
NSM Bank Facility \| GBP Term Loan \| Specialty Insurance Distribution (NSM)
Debt Instrument
Borrowings				58,200,000	£ 42.5
Other NSM
Debt Instrument
Debt								1,300,000
Other NSM \| Term Loan \| Specialty Insurance Distribution (NSM)
Debt Instrument
Debt				1,400,000
Kudu Bank Facility \| Kudu
Debt Instrument
Total commitment under revolving credit facility				300,000,000.0
Debt				60,800,000
Kudu Bank Facility \| Term Loan
Debt Instrument
Debt								86,300,000
Amount borrowed								$ 89,200,000
Kudu Bank Facility \| Term Loan \| Kudu
Debt Instrument
Amount borrowed				198,000,000.0
Percentage of borrowing base				0.35
Kudu Bank Facility \| Line of Credit \| Kudu
Debt Instrument
Interest Reserve				$ 3,900,000
Kudu Bank Facility \| Line of Credit \| Kudu \| London Interbank Offered Rate (LIBOR)
Debt Instrument
Basis spread on variable rate				4.30%	4.30%
Kudu Bank Facility \| Line of Credit \| Kudu \| Base Rate
Debt Instrument
Basis spread on variable rate				0.25%	0.25%
Kudu Bank Facility \| Revolving credit loan \| Kudu
Debt Instrument
Total commitment under revolving credit facility				$ 102,000,000.0
Repayments on credit facility				92,200,000
First Credit Facility \| Other
Debt Instrument
Total commitment under revolving credit facility				16,300,000
First Credit Facility \| Term Loan \| Other
Debt Instrument
Total commitment under revolving credit facility				11,300,000
Repayments of lines of credit				600,000
Amount borrowed				8,800,000
First Credit Facility \| Delayed Draw Term Loans \| Other
Debt Instrument
Total commitment under revolving credit facility				3,000,000.0
First Credit Facility \| Revolving credit loan \| Other
Debt Instrument
Total commitment under revolving credit facility				2,000,000.0
Draw down of debt and revolving line of credit				300,000
Second Credit Facility \| Other
Debt Instrument
Total commitment under revolving credit facility				15,000,000.0
Second Credit Facility \| Term Loan \| Other
Debt Instrument
Total commitment under revolving credit facility				9,000,000.0
Repayments of lines of credit				200,000
Amount borrowed				8,700,000
Second Credit Facility \| Delayed Draw Term Loans \| Other
Debt Instrument
Total commitment under revolving credit facility				4,000,000.0
Second Credit Facility \| Revolving credit loan \| Other
Debt Instrument
Total commitment under revolving credit facility				2,000,000.0
Ark \| Term Loan
Debt Instrument
Total commitment under revolving credit facility				150,000,000.0
Line of credit				45,000,000.0
Ark Alesco Note \| Junior Notes \| Ark
Debt Instrument
Amount borrowed			$ 30,000,000.0
Debt				30,000,000.0
Ark Alesco Note \| Junior Notes \| London Interbank Offered Rate (LIBOR) \| Ark
Debt Instrument
Basis spread on variable rate			4.60%
Ark Dekania Note \| Junior Notes \| Ark
Debt Instrument
Amount borrowed \| €											€ 12,000,000.0
Debt				$ 14,100,000			€ 12,000,000.0
Ark Dekania Note \| Junior Notes \| EURIBOR \| Ark
Debt Instrument
Basis spread on variable rate			4.60%

Debt - Schedule of the Change in Debt under the NSM Bank Facility (Details) £ in Millions, $ in Millions			3 Months Ended
	Apr. 07, 2020 USD ($)	Apr. 07, 2020 GBP (£)	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)
Debt Instrument
Beginning balance			$ 376.4
Repayments			(93.7)	$ (1.0)
Ending balance			429.7
Term Loan \| NSM Bank Facility
Debt Instrument
Beginning balance			271.3
Ending balance			271.5
Specialty Insurance Distribution (NSM)
Debt Instrument
Beginning balance			272.6
Ending balance			272.7
Specialty Insurance Distribution (NSM) \| NSM Bank Facility
Debt Instrument
Beginning balance			277.4	221.3
Ending balance			277.3	220.7
Specialty Insurance Distribution (NSM) \| Term Loan \| NSM Bank Facility
Debt Instrument
Borrowings	$ 52.4	£ 42.5	0.0	0.0
Repayments			(0.7)	(0.6)
Foreign currency translation			0.6	0.0
Specialty Insurance Distribution (NSM) \| Revolving credit loan \| NSM Bank Facility
Debt Instrument
Borrowings			0.0	0.0
Repayments			$ 0.0	$ 0.0

Debt - Schedule of Weighted Average Interest Rates (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Debt Instrument
Interest expense	$ 13.1	$ 6.0
Specialty Insurance Distribution (NSM)
Debt Instrument
Weighted Average	277.4	221.0
Interest expense	$ 5.9	$ 4.2
Weighted Average Interest rate	8.50%	7.60%
Specialty Insurance Distribution (NSM) \| Term loan - hedged
Debt Instrument
Weighted Average	$ 147.6	$ 148.4
Interest expense	$ 3.4	$ 3.0
Weighted Average Interest rate	9.20%	8.10%
Specialty Insurance Distribution (NSM) \| Term loan - unhedged
Debt Instrument
Weighted Average	$ 129.8	$ 72.6
Interest expense	$ 2.5	$ 1.2
Weighted Average Interest rate	7.70%	6.60%

Income Taxes (Details)	3 Months Ended
Income Taxes (Details)	Mar. 31, 2021	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Effective income tax rate reconciliation, percent	6.90%	15.40%
Federal statutory income tax rate, percent	21.00%	21.00%

Derivatives - NSM Interest Rate Swap and Cap (Details)		3 Months Ended
Derivatives - NSM Interest Rate Swap and Cap (Details)	Aug. 18, 2020	Mar. 31, 2021 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)	Jun. 04, 2020 USD ($)	Jun. 04, 2020 GBP (£)	Apr. 07, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jun. 15, 2018 USD ($)
Derivative [Line Items]
Total commitment under revolving credit facility				$ 234,000,000.0				$ 291,400,000
Debt		$ 429,700,000			$ 376,400,000
NSM Bank Facility \| Term Loan
Derivative [Line Items]
Debt		271,500,000			271,300,000
Specialty Insurance Distribution (NSM)
Derivative [Line Items]
Debt		$ 272,700,000			272,600,000
Weighted Average Interest rate		8.50%		7.60%
Specialty Insurance Distribution (NSM) \| Term loan - hedged
Derivative [Line Items]
Weighted Average Interest rate		9.20%		8.10%
Specialty Insurance Distribution (NSM) \| Interest Rate Swap
Derivative [Line Items]
Derivative, fixed interest rate										2.97%
Derivative, variable interest rate		1.00%
Interest expense, net		$ 600,000		$ 500,000
Derivative, fair value, net		7,200,000			8,200,000
Change in fair value of derivative instruments		1,000,000.0		(3,200,000)
Specialty Insurance Distribution (NSM) \| Interest Rate Cap
Derivative [Line Items]
Derivative, fair value, net		100,000			100,000
Change in fair value of derivative instruments		$ 100,000
Premiums paid			$ 100,000
GBP-LIBOR rate		0.09%
Specialty Insurance Distribution (NSM) \| Interest Rate Cap \| GBP-LIBOR
Derivative [Line Items]
Derivative, cap interest rate		1.25%
Specialty Insurance Distribution (NSM) \| NSM Bank Facility
Derivative [Line Items]
Debt		$ 277,300,000		220,700,000	$ 277,400,000				$ 221,300,000
Amount borrowed		277,300,000
Specialty Insurance Distribution (NSM) \| NSM Bank Facility \| Term Loan
Derivative [Line Items]
Amount borrowed				$ 224,000,000.0				$ 276,400,000
Specialty Insurance Distribution (NSM) \| NSM Bank Facility \| Interest Rate Swap \| Term Loan
Derivative [Line Items]
Total commitment under revolving credit facility										$ 151,000,000.0
Specialty Insurance Distribution (NSM) \| NSM Bank Facility \| Interest Rate Swap \| Term Loan \| Term loan - hedged
Derivative [Line Items]
Debt		$ 147,200,000
Specialty Insurance Distribution (NSM) \| NSM Bank Facility \| Interest Rate Cap
Derivative [Line Items]
Debt instrument, term extension	1 year
Specialty Insurance Distribution (NSM) \| NSM Bank Facility \| Interest Rate Cap \| United Kingdom, Pounds
Derivative [Line Items]
Derivative, Notional Amount \| £							£ 42,500,000
Specialty Insurance Distribution (NSM) \| NSM Bank Facility \| Interest Rate Cap \| United States of America, Dollars
Derivative [Line Items]
Derivative, Notional Amount						$ 52,400,000

Municipal Bond Guarantee Insurance - Narrative (Details) - USD ($) $ in Millions		1 Months Ended					3 Months Ended	12 Months Ended
	Feb. 17, 2021	Jan. 31, 2021	Dec. 31, 2020	Jan. 31, 2020	Nov. 30, 2018	Apr. 30, 2018	Mar. 31, 2021	Dec. 31, 2012	Dec. 31, 2021	Sep. 30, 2019	Dec. 31, 2017	Jul. 31, 2012
Guarantor Obligations [Line Items]
Percentage of risk premium ceded							60.00%
Insurance-linked securities, term						12 years
Insurance-linked securities, callable term						5 years
Percent change in discounted future cash flows							10.00%
HG Global
Guarantor Obligations [Line Items]
Collateral held in supplement trust			$ 827.1				$ 819.1
Collateral Trusts, Investments And Cash			434.5				427.9
Interest receivable			155.7				158.8
BAM
Guarantor Obligations [Line Items]
Surplus notes			388.2				388.2
Interest receivable			$ 4.4				$ 3.0
HG Global
Guarantor Obligations [Line Items]
Percentage of par value of policy reinsured							15.00%
Capital invested								$ 594.5
Surplus notes								503.0				$ 503.0
Cash and Fixed Income Securities												100.0
Percent over a target trust balance							102.00%
Supplement Trust Target							$ 603.0
HG Global \| Preferred Stock
Guarantor Obligations [Line Items]
Ownership interest (as a percent)			96.90%				96.90%
HG Global \| Common equity securities
Guarantor Obligations [Line Items]
Ownership interest (as a percent)			88.40%				88.40%
HG Global \| Series B BAM Surplus Note
Guarantor Obligations [Line Items]
Surplus notes												300.0
HG Global \| Series A BAM Surplus Note
Guarantor Obligations [Line Items]
Surplus notes											$ 203.0	$ 203.0
Restricted Cash			$ 604.3				$ 597.9
HG Global \| BAM \| Maximum
Guarantor Obligations [Line Items]
Aggregate losses on ceded business				$ 75.0
HG Global \| Non-controlling interest
Guarantor Obligations [Line Items]
Capital invested								$ 14.5
HG Re
Guarantor Obligations [Line Items]
Percentage of par value of policy reinsured							15.00%
Restricted Cash			222.8				$ 221.2
BAM
Guarantor Obligations [Line Items]
Principal		$ 800.0	75,287.7				$ 77,689.3			$ 1,100.0
Additional municipal bond guarantee										$ 36.9
BAM \| Surplus Note
Guarantor Obligations [Line Items]
Repayments of unsecured debt			30.1	65.0
Accrued interest payment on surplus notes			8.4	16.2
BAM \| Supplemental Trust
Guarantor Obligations [Line Items]
Repayments of unsecured debt			21.5	47.9
Accrued interest payment on surplus notes			$ 0.2	$ 0.9
BAM \| US Treasury (UST) Interest Rate \| Surplus Note
Guarantor Obligations [Line Items]
Basis spread on variable rate							3.00%
BAM \| Fixed interest rate \| Surplus Note
Guarantor Obligations [Line Items]
Derivative, fixed interest rate (as a percent)							8.00%
BAM \| Forecast \| US Treasury (UST) Interest Rate \| Surplus Note
Guarantor Obligations [Line Items]
Effective percentage									3.10%
BAM \| Fidus Re Ltd.
Guarantor Obligations [Line Items]
Secured Debt	$ 150.0					$ 100.0
Aggregate losses on ceded business	135.0					165.0
Premium receivable, Premium expected to be collected	150.0					100.0
Percentage Of Financial Guaranty Policies Covered							41.00%
Principal					$ 2,200.0
Percentage of quota share reinsurance agreement		100.00%			100.00%
BAM \| Fidus Re Ltd. \| Maximum
Guarantor Obligations [Line Items]
Aggregate losses on ceded business	$ 301.7					$ 276.1
Fidus Re Ltd. \| BAM
Guarantor Obligations [Line Items]
Losses above retention, percentage of liability	90.00%					90.00%

Municipal Bond Guarantee Insurance - Schedule of Municipal Bond Guarantee Insured Obligations (Details) - BAM $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021 USD ($) Contract	Dec. 31, 2020 USD ($) Contract	Jan. 31, 2021 USD ($)	Sep. 30, 2019 USD ($)
Guarantor Obligations [Line Items]
Contracts outstanding \| Contract	11,252	10,997
Remaining weighted average contract period outstanding (in years)	10 years 7 months 6 days	10 years 8 months 12 days
Principal	$ 77,689.3	$ 75,287.7	$ 800.0	$ 1,100.0
Interest	36,710.5	36,448.8
Total debt service outstanding	114,399.8	111,736.5
Total gross unearned insurance premiums	$ 243.7	$ 237.5

Municipal Bond Guarantee Insurance - Schedule of Municipal Guarantee Insurance Contracts, Premium Received Over Contract Period (Details) - BAM - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Guarantor Obligations [Line Items]
April 1, 2021 - December 31, 2021	$ 17.6
January 1, 2022 - March 31, 2022	5.7
April 1, 2022 - June 30, 2022	5.6
July 1, 2022 - September 30, 2022	5.6
October 1, 2022 - December 31, 2022	5.4
Total 2022	22.3
2023	21.0
2024	19.4
2025	18.0
2026	16.6
2027 and thereafter	128.8
Total gross unearned insurance premiums	$ 243.7	$ 237.5

Municipal Bond Guarantee Insurance - Schedule of Net Written Premiums (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earned premiums:
Gross earned premiums	$ 111.0	$ 5.4
HG/BAM
Written premiums:
Direct	8.0	9.7
Assumed	4.5	0.0
Gross written premiums	12.5	9.7
Earned premiums:
Direct	5.3	4.5
Assumed	1.1	0.9
Gross earned premiums	$ 6.4	$ 5.4

Earnings Per Share - Basic and Diluted Earnings Per Share from Continuing Operations (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Basic and diluted loss per share numerators (in millions):
Net loss attributable to White Mountains’s common shareholders	$ (75.3)	$ (128.8)
Less: total income from discontinued operations, net of tax	18.7	0.9
Net loss from continuing operations attributable to White Mountains’s common shareholders	(94.0)	(129.7)
Allocation of (earnings) losses to participating restricted common shares	0.9	1.3
Basic and diluted losses per share numerators	$ (93.1)	$ (128.4)
Basic loss per share denominators (in thousands):
Total average common shares outstanding during the period (in shares)	3,100,200	3,178,000.0
Average unvested restricted common shares (in shares)	(32,400)	(33,800)
Basic earnings (losses) per share denominator (in shares)	3,067,800	3,144,200
Diluted loss per share denominator (in thousands):
Total average common shares outstanding during the period (in shares)	3,100,200	3,178,000.0
Average unvested restricted common shares (in shares)	(32,400)	(33,800)
Diluted earnings (losses) per share denominator (in shares)	3,067,800	3,144,200
Basic and diluted losses per share (in dollars) - continuing operations:
Distributed earnings - dividends declared and paid (in USD per share)	$ 1.00	$ 1.00
Undistributed earnings (losses) (in USD per share)	(31.33)	(41.82)
Basic and diluted earnings (losses) per share (in USD per share)	$ (30.33)	$ (40.82)

Earnings Per Share - Undistributed Net Earnings From Continuing Operations (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net loss attributable to White Mountains’s common shareholders, net of restricted common share amounts	$ (93.1)	$ (128.4)
Dividends declared net of restricted common share amounts	(3.1)	(3.1)
Total undistributed net losses, net of restricted common share amounts	$ (96.2)	$ (131.5)

Employee Share-Based Incentive Compensation Plans - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($) shares	Mar. 31, 2020 USD ($) shares	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Performance Share \| W T M Incentive Plan
Share-based compensation arrangement by share-based payment award
Vesting period	3 years
Performance cycle period	3 years
Performance shares (in shares)	41,405
New grants (in shares)	13,000	14,055
Additional compensation cost that would be recognized if all outstanding performance shares vested \| $	$ 38.1
Performance Share \| Minimum \| W T M Incentive Plan
Share-based compensation arrangement by share-based payment award
Share-based compensation arrangement by share-based payment award, multiplier	0
Performance Share \| Maximum \| W T M Incentive Plan
Share-based compensation arrangement by share-based payment award
Share-based compensation arrangement by share-based payment award, multiplier	2
Restricted Share Cliff Vesting in January 2023 \| W T M Incentive Plan
Share-based compensation arrangement by share-based payment award
Performance shares (in shares)	13,000
Restricted Share Cliff Vesting in January 2022 \| W T M Incentive Plan
Share-based compensation arrangement by share-based payment award
New grants (in shares)		14,055
Restricted Stock
Share-based compensation arrangement by share-based payment award
Vesting period	34 months
Restricted Stock \| W T M Incentive Plan
Share-based compensation arrangement by share-based payment award
Additional compensation cost that would be recognized if all outstanding performance shares vested \| $	$ 26.2	$ 26.6	$ 15.2	$ 16.7

Employee Share-Based Incentive Compensation Plans - Performance Shares (Details) - Performance Share - W T M Incentive Plan - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Target Performance Shares Outstanding
Beginning of period (in shares)	42,458	42,473
Shares paid (in shares)	(14,117)	(14,070)
New grants (in shares)	13,000	14,055
Forfeitures and cancellations (in shares)	(557)	0
Expense recognized (in shares)	0	0
End of period (in shares)	40,784	42,458
Accrued Expense
Beginning of period	$ 56.3	$ 43.7
Shares paid	(34.6)	(27.7)
New grants	0.0	0.0
Forfeitures and cancellations	0.4	0.4
Expense recognized	16.1	(6.6)
End of period	$ 38.2	$ 9.8
Performance Cycle 2018 to 2020
Accrued Expense
Percentage of target payout - minimum actual	200.00%
Performance Cycle 2017 to 2019
Accrued Expense
Percentage of target payout - minimum actual		174.00%
Percentage of target payout - maximum actual		180.00%

Employee Share-Based Incentive Compensation Plans - Performance Shares Granted Under the WTM Incentive Plan (Details) - Performance Share - W T M Incentive Plan - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Share-based compensation arrangement by share-based payment award
Target performance shares outstanding (in shares)	41,405
Assumed forfeitures (in shares)	(621)
Total target performance shares outstanding (in shares)	40,784	42,458	42,458	42,473
Accrued Expense	$ 38.8
Assumed forfeitures	(0.6)
Total Accrued Expense	$ 38.2	$ 56.3	$ 9.8	$ 43.7
2019 – 2021
Share-based compensation arrangement by share-based payment award
Target performance shares outstanding (in shares)	14,850
Accrued Expense	$ 24.9
2020 – 2022
Share-based compensation arrangement by share-based payment award
Target performance shares outstanding (in shares)	13,555
Accrued Expense	$ 12.7
2021 – 2023
Share-based compensation arrangement by share-based payment award
Target performance shares outstanding (in shares)	13,000
Accrued Expense	$ 1.2

Employee Share-Based Incentive Compensation Plans - Restricted Shares (Details) - W T M Incentive Plan - Restricted Stock - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Restricted Shares
Beginning of period (in shares)	43,105	43,395
Issued (in shares)	13,000	14,055
Vested (in shares)	(17,717)	(14,345)
Forfeited (in shares)	(583)	0
Expense recognized (in shares)	0	0
End of period (in shares)	37,805	43,105
Unamortized Issue Date Fair Value
Beginning of period	$ 15.2	$ 16.7
Issued	15.6	15.1
Vested	0.0	0.0
Forfeited	(0.6)	0.0
Expense recognized	(4.0)	(5.2)
End of period	$ 26.2	$ 26.6

Leases - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Leases [Abstract]
ROU lease asset	$ 40.3	$ 37.6
Operating lease liability	$ 41.0	$ 38.3

Leases - Schedule of Lease Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Leases [Abstract]
Lease cost	$ 1.9	$ 2.0
Less: sublease income	0.1	0.1
Net lease cost	$ 1.8	$ 1.9

Leases - Schedule of Future Minimum Payments on Operating Leases (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Remainder of 2021	$ 5.7
2022	9.8
2023	8.5
2024	7.1
2025	5.4
Thereafter	12.2
Total undiscounted lease payments	48.7
Less: present value adjustment	7.7
Operating lease liability	$ 41.0	$ 38.3

Leases - Schedule of Right-of-Use Assets and Lease Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
ROU lease asset	$ 40.3	$ 37.6
Lease liability	$ 41.0	$ 38.3
Operating lease, weighted average incremental borrowing rate, percent	4.80%	4.60%
HG/BAM
Lessee, Lease, Description [Line Items]
ROU lease asset	$ 9.6	$ 10.1
Lease liability	9.6	10.1
Ark
Lessee, Lease, Description [Line Items]
ROU lease asset	4.9
Lease liability	4.9
Specialty Insurance Distribution (NSM)
Lessee, Lease, Description [Line Items]
ROU lease asset	16.0	17.1
Lease liability	16.0	17.1
Asset Management (Kudu)
Lessee, Lease, Description [Line Items]
ROU lease asset	2.0	2.0
Lease liability	2.0	2.0
Other Operations
Lessee, Lease, Description [Line Items]
ROU lease asset	7.8	8.4
Lease liability	$ 8.5	$ 9.1

Non-controlling Interests (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Noncontrolling Interest [Line Items]
Total non-controlling interests	$ 110.0	$ (88.1)
Total Non-Controlling Excluding Reciprocals
Noncontrolling Interest [Line Items]
Total non-controlling interests	$ 242.9	$ 35.2
HG Global
Noncontrolling Interest [Line Items]
Noncontrolling equity percentage	3.10%	3.10%
Total non-controlling interests	$ 11.6	$ 13.5
Ark
Noncontrolling Interest [Line Items]
Noncontrolling equity percentage	28.00%	0.00%
Total non-controlling interests	$ 211.0	$ 0.0
Specialty Insurance Distribution (NSM)
Noncontrolling Interest [Line Items]
Noncontrolling equity percentage	3.40%	3.40%
Total non-controlling interests	$ 16.0	$ 17.0
Kudu
Noncontrolling Interest [Line Items]
Noncontrolling equity percentage	0.70%	0.70%
Total non-controlling interests	$ 2.3	$ 2.3
Other
Noncontrolling Interest [Line Items]
Total non-controlling interests	$ 2.0	$ 2.4
BAM
Noncontrolling Interest [Line Items]
Noncontrolling equity percentage	100.00%	100.00%
Total non-controlling interests	$ (132.9)	$ (123.3)

Segment Information - Narrative (Details)	3 Months Ended
Segment Information - Narrative (Details)	Mar. 31, 2021 numberOfSegments
Segment Reporting [Abstract]
Number of operating segments	5

Segment Information - Financial Information for White Mountain's Segments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Earned insurance premiums	$ 111.0	$ 5.4
Net investment income	20.6	22.9
Net realized and unrealized investment (losses) gains	1.1	(186.7)
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	(40.6)	(156.7)
Commission revenues	61.9	55.1
Other revenues	25.3	14.1
Total revenues	178.2	(59.2)
Loss and loss adjustment expenses	66.0
Insurance and reinsurance acquisition expenses	38.6
Cost of sales	4.0	2.0
General and administrative expenses	138.4	74.3
Loss on assets held for sale	28.7
Broker commission expenses	18.9	18.3
Change in fair value of contingent consideration earnout liabilities	0.0	(0.6)
Amortization of other intangible assets	9.2	5.1
Interest expense	13.1	6.0
Total expenses	316.9	106.8
Pre-tax loss from continuing operations	(138.7)	(166.0)
Marketing Technology (MediaAlpha)
Segment Reporting Information [Line Items]
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	(41.7)	30.0
HG Global/ BAM
Segment Reporting Information [Line Items]
Earned insurance premiums	6.4	5.4
Net investment income	4.5	5.5
Net realized and unrealized investment (losses) gains	(17.9)	6.1
Commission revenues	0.0	0.0
Other revenues	0.3	0.5
Total revenues	(6.7)	17.5
Loss and loss adjustment expenses	0.0
Insurance and reinsurance acquisition expenses	1.9
Cost of sales	0.0	0.0
General and administrative expenses	16.4	14.7
Loss on assets held for sale	0.0
Broker commission expenses	0.0	0.0
Change in fair value of contingent consideration earnout liabilities	0.0	0.0
Amortization of other intangible assets	0.0	0.0
Interest expense	0.0	0.0
Total expenses	18.3	16.4
Pre-tax loss from continuing operations	(25.0)	1.1
HG Global/ BAM \| Marketing Technology (MediaAlpha)
Segment Reporting Information [Line Items]
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	0.0	0.0
Ark
Segment Reporting Information [Line Items]
Earned insurance premiums	104.6	0.0
Net investment income	0.8	0.0
Net realized and unrealized investment (losses) gains	1.1	0.0
Commission revenues	0.0
Other revenues	2.6	0.0
Total revenues	109.1	0.0
Loss and loss adjustment expenses	66.0	0.0
Insurance and reinsurance acquisition expenses	36.7	0.0
Cost of sales	0.0
General and administrative expenses	26.6	0.0
Loss on assets held for sale	0.0
Broker commission expenses	0.0
Change in fair value of contingent consideration earnout liabilities	0.0
Amortization of other intangible assets	0.0
Interest expense	1.1	0.0
Total expenses	141.6	0.0
Pre-tax loss from continuing operations	(32.5)
Ark \| General and administrative expenses, including underwriting expense
Segment Reporting Information [Line Items]
General and administrative expenses	37.8
Ark \| Marketing Technology (MediaAlpha)
Segment Reporting Information [Line Items]
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	0.0
NSM
Segment Reporting Information [Line Items]
Earned insurance premiums	0.0	0.0
Net investment income	0.0	0.0
Net realized and unrealized investment (losses) gains	0.0	0.0
Commission revenues	59.6	53.0
Other revenues	15.2	12.0
Total revenues	74.8	65.0
Loss and loss adjustment expenses	0.0
Insurance and reinsurance acquisition expenses	0.0
Cost of sales	0.0	0.0
General and administrative expenses	46.0	39.6
Loss on assets held for sale	28.7	0.0
Broker commission expenses	18.9	18.3
Change in fair value of contingent consideration earnout liabilities	0.0	(0.6)
Amortization of other intangible assets	8.6	4.8
Interest expense	5.9	4.3
Total expenses	108.1	66.4
Pre-tax loss from continuing operations	(33.3)	(1.4)
NSM \| Marketing Technology (MediaAlpha)
Segment Reporting Information [Line Items]
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	0.0	0.0
Kudu
Segment Reporting Information [Line Items]
Earned insurance premiums	0.0	0.0
Net investment income	8.2	7.3
Net realized and unrealized investment (losses) gains	15.8	(24.8)
Commission revenues	0.0	0.0
Other revenues	0.1	0.1
Total revenues	24.1	(17.4)
Loss and loss adjustment expenses	0.0
Insurance and reinsurance acquisition expenses	0.0
Cost of sales	0.0	0.0
General and administrative expenses	2.5	2.5
Loss on assets held for sale	0.0
Broker commission expenses	0.0	0.0
Change in fair value of contingent consideration earnout liabilities	0.0	0.0
Amortization of other intangible assets	0.1	0.1
Interest expense	5.8	1.4
Total expenses	8.4	4.0
Pre-tax loss from continuing operations	15.7	(21.4)
Kudu \| Marketing Technology (MediaAlpha)
Segment Reporting Information [Line Items]
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	0.0	0.0
Other Operations
Segment Reporting Information [Line Items]
Earned insurance premiums	0.0	0.0
Net investment income	7.1	10.1
Net realized and unrealized investment (losses) gains	2.1	(168.0)
Commission revenues	2.3	2.1
Other revenues	7.1	1.5
Total revenues	(23.1)	(124.3)
Loss and loss adjustment expenses	0.0
Insurance and reinsurance acquisition expenses	0.0
Cost of sales	4.0	2.0
General and administrative expenses	35.7	17.5
Loss on assets held for sale	0.0
Broker commission expenses	0.0	0.0
Change in fair value of contingent consideration earnout liabilities	0.0	0.0
Amortization of other intangible assets	0.5	0.2
Interest expense	0.3	0.3
Total expenses	40.5	20.0
Pre-tax loss from continuing operations	(63.6)	(144.3)
Other Operations \| Marketing Technology (MediaAlpha)
Segment Reporting Information [Line Items]
Net realized and unrealized investment (losses) gains from investment in MediaAlpha	$ (41.7)	$ 30.0

Segment Information - Reconciliation of Revenue from Segments to Consolidated (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Revenues from contracts with customers	$ 83.6	$ 68.5
Other Revenue	94.6	(127.7)
Total revenues	178.2	(59.2)
HG Global/ BAM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Other Revenue	(6.7)	17.5
Total revenues	(6.7)	17.5
Ark
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0
Other Revenue	109.1
Total revenues	109.1	0.0
NSM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	74.8	65.0
Other Revenue	0.0	0.0
Total revenues	74.8	65.0
Kudu
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Other Revenue	24.1	(17.4)
Total revenues	24.1	(17.4)
Other Operations
Segment Reporting Information [Line Items]
Revenues from contracts with customers	8.8	3.5
Other Revenue	(31.9)	(127.8)
Total revenues	(23.1)	(124.3)
United Kingdom
Segment Reporting Information [Line Items]
Revenues from contracts with customers	13.1	10.0
United Kingdom \| HG Global/ BAM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
United Kingdom \| Ark
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0
United Kingdom \| NSM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	13.1	10.0
United Kingdom \| Kudu
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
United Kingdom \| Other Operations
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Specialty Transportation
Segment Reporting Information [Line Items]
Revenues from contracts with customers	20.7	20.3
Specialty Transportation \| HG Global/ BAM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Specialty Transportation \| Ark
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0
Specialty Transportation \| NSM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	20.7	20.3
Specialty Transportation \| Kudu
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Specialty Transportation \| Other Operations
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Real Estate
Segment Reporting Information [Line Items]
Revenues from contracts with customers	9.8	11.3
Real Estate \| HG Global/ BAM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Real Estate \| Ark
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0
Real Estate \| NSM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	9.8	11.3
Real Estate \| Kudu
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Real Estate \| Other Operations
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Social Services
Segment Reporting Information [Line Items]
Revenues from contracts with customers	6.7	6.3
Social Services \| HG Global/ BAM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Social Services \| Ark
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0
Social Services \| NSM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	6.7	6.3
Social Services \| Kudu
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Social Services \| Other Operations
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Pet
Segment Reporting Information [Line Items]
Revenues from contracts with customers	17.1	11.8
Pet \| HG Global/ BAM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Pet \| Ark
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0
Pet \| NSM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	17.1	11.8
Pet \| Kudu
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Pet \| Other Operations
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Other
Segment Reporting Information [Line Items]
Revenues from contracts with customers	9.7	6.7
Other \| HG Global/ BAM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Other \| Ark
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0
Other \| NSM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	7.4	5.3
Other \| Kudu
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Other \| Other Operations
Segment Reporting Information [Line Items]
Revenues from contracts with customers	2.3	1.4
Total commission and other revenue
Segment Reporting Information [Line Items]
Revenues from contracts with customers	77.1	66.4
Total commission and other revenue \| HG Global/ BAM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Total commission and other revenue \| Ark
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0
Total commission and other revenue \| NSM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	74.8	65.0
Total commission and other revenue \| Kudu
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Total commission and other revenue \| Other Operations
Segment Reporting Information [Line Items]
Revenues from contracts with customers	2.3	1.4
Product revenues
Segment Reporting Information [Line Items]
Revenues from contracts with customers	6.5	2.1
Product revenues \| HG Global/ BAM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Product revenues \| Ark
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0
Product revenues \| NSM
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Product revenues \| Kudu
Segment Reporting Information [Line Items]
Revenues from contracts with customers	0.0	0.0
Product revenues \| Other Operations
Segment Reporting Information [Line Items]
Revenues from contracts with customers	$ 6.5	$ 2.1

Equity-Method Eligible Investments - Carrying Values of Equity Method Eligible Investments Recorded within Other Long-Term Investments (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Investments in unconsolidated affiliates
Other long-term investments	$ 1,032.2	$ 786.8
Marketing Technology (MediaAlpha)
Investments in unconsolidated affiliates
Other long-term investments	600.2	802.2
Equity Method Investments
Investments in unconsolidated affiliates
Other long-term investments	$ 706.2	$ 698.1

Equity-Method Eligible Investments - Significant Equity Method Eligible Investments (Details)	Mar. 31, 2021	Dec. 31, 2020	May 07, 2020	May 06, 2020
PassportCard/DavidShield
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	53.80%	53.80%	53.80%	50.00%
New Market Solutions, LLC
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	46.70%	46.70%
durchblicker
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	45.00%	45.00%
MediaAlpha
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	28.50%	35.00%
Elementum Holdings L.P.
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	29.70%	28.90%
Compare.com
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	18.40%	18.40%
Minimum \| Tuckerman Capital Funds
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	16.10%	14.90%
Minimum \| Enlightenment Capital Funds
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	9.10%	9.70%
Minimum \| Kudu Investments
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	3.20%	3.20%
Maximum \| Tuckerman Capital Funds
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	30.00%	62.00%
Maximum \| Enlightenment Capital Funds
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	66.30%	66.70%
Maximum \| Kudu Investments
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	35.60%	35.00%

Equity-Method Eligible Investments - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended
	Mar. 23, 2021	Oct. 30, 2020	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Schedule of Equity Method Investments [Line Items]
Net realized and unrealized investment (losses) gains from investment in MediaAlpha			$ (40.6)		$ (156.7)
Marketing Technology (MediaAlpha)
Schedule of Equity Method Investments [Line Items]
Net realized and unrealized investment (losses) gains from investment in MediaAlpha			$ (41.7)		30.0
Secondary Offering \| Marketing Technology (MediaAlpha)
Schedule of Equity Method Investments [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	8,050,000.00
Sale of stock, price per share (in USD per share)	$ 46.00	$ 19.00
Sale of stock, price per share, net of underwriting fees (in USD per share)	$ 44.62	$ 17.67
Marketing Technology (MediaAlpha)
Schedule of Equity Method Investments [Line Items]
Proceeds from dividends received		$ 55.0		$ 55.0
Ownership interest (as a percent)	28.50%	35.00%
Investment owned (in shares)	16,900,000	20,500,000
Fully diluted ownership interest (as a percent)	26.30%	32.30%
Share price (in USD per share)		$ 19.00	$ 35.43	$ 39.07
Investment owned, balance			$ 600.2	$ 802.2
Sale of stock, price per share, net of underwriting fees (in USD per share)		$ 17.67
Marketing Technology (MediaAlpha) \| IPO
Schedule of Equity Method Investments [Line Items]
Sale of stock, number of shares issued in transaction (in shares)		3,600,000
Sale of stock, consideration received in transaction		$ 63.8
Investment owned (in shares)		20,500,000
Marketing Technology (MediaAlpha) \| Secondary Offering
Schedule of Equity Method Investments [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	3,600,000
Sale of stock, consideration received in transaction	$ 160.3
Investment owned (in shares)	16,900,000
Marketing Technology (MediaAlpha)
Schedule of Equity Method Investments [Line Items]
Proceeds from dividends received			$ 11.4		13.7
Ownership interest (as a percent)			28.50%	35.00%
Net realized and unrealized investment (losses) gains from investment in MediaAlpha			$ (41.7)		$ 30.0

Equity-Method Eligible Investments - Equity Method Investments Financial Data (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Total assets	$ 6,900.7		$ 4,831.4
Total liabilities	2,964.8		1,013.5
Total revenues	178.2	$ (59.2)
Net loss attributable to White Mountains’s common shareholders	(75.3)	(128.8)
MediaAlpha, Kudu and Tuckerman
Schedule of Equity Method Investments [Line Items]
Total assets	241.7		212.7
Total liabilities	331.1		$ 315.8
Total revenues	173.6	119.4
Total expenses	173.4	110.6
Net loss attributable to White Mountains’s common shareholders	$ 0.2	$ 8.8

- Definition

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Sum of the carrying amounts as of the balance sheet date of all liabilities that are recognized. Liabilities are probable future sacrifices of economic benefits arising from present obligations of an entity to transfer assets or provide services to other entities in the future.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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+ Details

Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Balance Sheet Grouping, Financial Statement Captions
Carrying value	$ 429.7	$ 376.4
Other NSM debt
Balance Sheet Grouping, Financial Statement Captions
Carrying value		1.3
Fair Value \| Ark Subordinated Debt
Balance Sheet Grouping, Financial Statement Captions
Debt, fair value	44.1	0.0
Fair Value \| NSM Bank Facility
Balance Sheet Grouping, Financial Statement Captions
Debt, fair value	275.6	279.3
Fair Value \| Other NSM debt
Balance Sheet Grouping, Financial Statement Captions
Debt, fair value	1.3	1.3
Fair Value \| Kudu Credit Facility
Balance Sheet Grouping, Financial Statement Captions
Debt, fair value	102.0	0.0
Fair Value \| Kudu Bank Facility
Balance Sheet Grouping, Financial Statement Captions
Debt, fair value	0.0	89.3
Fair Value \| Other Operations debt
Balance Sheet Grouping, Financial Statement Captions
Debt, fair value	18.3	18.8
Carrying Value \| Ark Subordinated Debt
Balance Sheet Grouping, Financial Statement Captions
Carrying value	44.1	0.0
Carrying Value \| NSM Bank Facility
Balance Sheet Grouping, Financial Statement Captions
Carrying value	271.5	271.3
Carrying Value \| Other NSM debt
Balance Sheet Grouping, Financial Statement Captions
Carrying value	1.2	1.3
Carrying Value \| Kudu Credit Facility
Balance Sheet Grouping, Financial Statement Captions
Carrying value	95.9	0.0
Carrying Value \| Kudu Bank Facility
Balance Sheet Grouping, Financial Statement Captions
Carrying value	0.0	86.3
Carrying Value \| Other Operations debt
Balance Sheet Grouping, Financial Statement Captions
Carrying value	$ 17.0	$ 17.5

Commitments and Contingencies (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Loss Contingencies [Line Items]
Net gain from sale of discontinued operations, net of tax	$ 18.7	$ 0.9
Sirius Group \| Discontinued Operations
Loss Contingencies [Line Items]
Net gain from sale of discontinued operations, net of tax	$ 17.6

Held for Sale and Discontinued Operations - Narrative (Details) - USD ($)		3 Months Ended
	Feb. 12, 2021	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain from sale of discontinued operations, net of tax		$ 18,700,000	$ 900,000
(Loss) gain on sale		(28,700,000)
Corporate Aircraft
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets Held-for-sale, Not Part of Disposal Group				$ 1,700,000
Proceeds from sale of property held-for-sale	$ 2,100,000
Realized gain on sale of corporate aircraft		500,000
Fresh Insurance Services Group Limited
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of other assets		1,500,000
Discontinued Operations \| Sirius Group
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain from sale of discontinued operations, net of tax		17,600,000
Contingent liability				$ 18,700,000
Discontinued Operations \| Sirius Group \| Foreign Currency Gain (Loss)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain from sale of discontinued operations, net of tax		$ 1,100,000

Held for Sale and Discontinued Operations - Earnings Per Share for Discontinued Operations (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Basic and diluted loss per share numerators (in millions):
Net loss attributable to White Mountains’s common shareholders	$ (75.3)	$ (128.8)
Less: total loss from continuing operations, net of tax	(94.0)	(129.7)
Net income from discontinued operations attributable to White Mountains’s common shareholders	18.7	0.9
Allocation of earnings to participating restricted common shares	0.9	1.3
Basic and diluted losses per share numerators	$ (93.1)	$ (128.4)
Basic loss per share denominators (in thousands):
Total average common shares outstanding during the period (in shares)	3,100,200	3,178,000.0
Average unvested restricted common shares (in shares)	(32,400)	(33,800)
Basic earnings (losses) per share denominator (in shares)	3,067,800	3,144,200
Diluted loss per share denominator (in thousands):
Total average common shares outstanding during the period (in shares)	3,100,200	3,178,000.0
Average unvested restricted common shares (in shares)	(32,400)	(33,800)
Diluted earnings (losses) per share denominator (in shares)	3,067,800	3,144,200
Basic and diluted earnings (losses) per share (in USD per share)	$ (30.33)	$ (40.82)
Discontinued Operations
Basic and diluted loss per share numerators (in millions):
Net loss attributable to White Mountains’s common shareholders	$ (75.3)	$ (128.8)
Less: total loss from continuing operations, net of tax	(94.0)	(129.7)
Net income from discontinued operations attributable to White Mountains’s common shareholders	18.7	0.9
Allocation of earnings to participating restricted common shares	(0.2)	0.0
Basic and diluted losses per share numerators	$ 18.5	$ 0.9
Basic loss per share denominators (in thousands):
Total average common shares outstanding during the period (in shares)	3,100,200	3,178,000.0
Average unvested restricted common shares (in shares)	(32,400)	(33,800)
Basic earnings (losses) per share denominator (in shares)	3,067,800	3,144,200
Diluted loss per share denominator (in thousands):
Total average common shares outstanding during the period (in shares)	3,100,200	3,178,000.0
Average unvested restricted common shares (in shares)	(32,400)	(33,800)
Diluted earnings (losses) per share denominator (in shares)	3,067,800	3,144,200
Basic and diluted earnings (losses) per share (in USD per share)	$ 6.03	$ 0.28