0000776867-20-000009 | 10-K | XBRL Viewer | White Mountains Insurance Group LTD

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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2019	Feb. 28, 2020	Jun. 30, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
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	80 South Main Street
Entity Address, City or Town	Hanover,
Entity Address, State or Province	NH
Entity Address, Postal Zip Code	03755-2053
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 Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
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 Public Float			$ 3,169,884,560
Entity Common Stock, Shares Outstanding		3,193,509
Documents Incorporated by Reference	Portions of the Registrant’s Definitive Proxy Statement to be filed with the Securities and Exchange Commission (“SEC”) pursuant to Regulation 14A under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), relating to the Registrant’s Annual General Meeting of Members scheduled to be held May 21, 2020 are incorporated by reference into Part III of this Form 10-K. With the exception of the portions of the Proxy Statement specifically incorporated herein by reference, the Proxy Statement is not deemed to be filed as part of this Form 10-K.
Entity Central Index Key	0000776867
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Assets
Other long-term investments	$ 856.0
Total investments	2,947.2	$ 2,542.9
Goodwill and other intangible assets	654.7	537.5
Total assets	3,983.2	3,362.6
Liabilities
Debt	283.5	192.7
Total liabilities	838.5	644.4
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 3,185,353 and 3,173,115 shares	3.2	3.2
Paid-in surplus	593.1	580.8
Retained earnings	2,672.4	2,264.9
Accumulated other comprehensive income (loss), after-tax:
Net unrealized foreign currency translation losses and interest rate swap	(7.2)	(5.8)
Total White Mountains’s common shareholders’ equity	3,261.5	2,843.1
Non-controlling interests
Non-controlling interests	(116.8)	(124.9)
Total equity	3,144.7	2,718.2
Total liabilities and equity	3,983.2	3,362.6
HG Global-BAM
Assets
Fixed maturity investments, at fair value	799.3	701.4
Short-term investments, at fair value	46.3	66.9
Total investments	845.6	768.3
Cash	24.2	12.5
Insurance premiums receivable	6.7	6.4
Deferred acquisition costs	22.1	19.0
Accrued investment income	5.4	4.9
Other assets	20.0	5.1
Total assets	924.0	816.2
Liabilities
Unearned insurance premiums	198.4	176.0
Accrued incentive compensation	21.7	20.4
Other liabilities	26.7	16.1
Total liabilities	246.8	212.5
NSM Holding Co LLC
Assets
Cash	89.7	66.2
Premium and commission receivable	70.8	44.0
Goodwill and other intangible assets	623.0	486.2
Other assets	41.7	27.2
Total assets	825.2	623.6
Liabilities
Debt	219.2	178.5
Premiums payable	102.3	77.2
Contingent consideration earnout liabilities	20.6	20.2
Other liabilities	59.0	38.9
Total liabilities	401.1	314.8
Kudu
Assets
Short-term investments, at fair value	0.1	0.0
Other long-term investments	266.5	0.0
Total investments	266.6	0.0
Cash	5.8	0.0
Accrued investment income	5.8	0.0
Goodwill and other intangible assets	9.6	0.0
Other assets	2.7	0.0
Total assets	290.5	0.0
Liabilities
Debt	53.6	0.0
Other liabilities	3.4	0.0
Total liabilities	57.0	0.0
MediaAlpha
Assets
Cash	0.0	5.7
Goodwill and other intangible assets	0.0	43.4
Accounts receivable from publishers and advertisers	0.0	37.0
Other assets	0.0	2.3
Total assets	0.0	88.4
Liabilities
Debt	0.0	14.2
Amounts due to publishers and advertisers	0.0	27.0
Other liabilities	0.0	5.7
Total liabilities	0.0	46.9
Other
Assets
Fixed maturity investments, at fair value	406.5	376.1
Short-term investments, at fair value	154.8	147.3
Common equity securities, at fair value	683.9	925.6
Other long-term investments	589.8	325.6
Total investments	1,835.0	1,774.6
Cash	41.3	25.9
Accrued investment income	5.7	5.5
Goodwill and other intangible assets	22.1	7.9
Other assets	36.4	17.2
Assets held for sale	3.0	3.3
Total assets	1,943.5	1,834.4
Liabilities
Debt	10.7	0.0
Accrued incentive compensation	55.1	38.9
Other liabilities	67.8	31.3
Total liabilities	$ 133.6	$ 70.2

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Cash restricted	$ 56.3	$ 50.0
Common shares, par value per share (in dollars per share)	$ 1.00	$ 1.00
Common shares, authorized shares	50,000,000	50,000,000
Common shares, issued shares	3,185,353	3,173,115
Common shares, outstanding shares	3,185,353	3,173,115
NSM Holding Co LLC
Cash restricted	$ 56.3	$ 50.0

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)		3 Months Ended								8 Months Ended	9 Months Ended	10 Months Ended	12 Months Ended
CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)	Sep. 28, 2017	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2018	Sep. 28, 2017	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues
Earned insurance premiums													$ 16,300,000	$ 13,900,000	$ 10,400,000
Net investment income													79,700,000	59,000,000.0	56,000,000.0
Net realized and unrealized investment gains													318,500,000
Net realized and unrealized investment gains (losses)													433,200,000	(108,300,000)	133,300,000
Commission revenues													249,100,000	389,200,000	167,000,000.0
Other revenue													47,600,000	15,300,000	7,100,000
Total revenues		$ 175,300,000	$ 155,500,000	$ 129,000,000.0	$ 433,600,000	$ 6,000,000.0	$ 198,700,000	$ 122,300,000	$ 42,100,000				893,400,000	369,100,000	373,800,000
Expenses
Loss and loss adjustment expenses															1,100,000
Insurance acquisition expense													5,700,000	5,300,000	4,100,000
Other underwriting expenses													400,000	400,000	400,000
Cost of sales													48,100,000	248,700,000	139,400,000
General and administrative expenses													327,800,000	233,500,000	208,000,000.0
Broker commission expense													64,800,000	28,400,000
Change in fair value of contingent consideration earnout liabilities													2,100,000	2,700,000
Amortization of other intangible assets													21,800,000	18,800,000	10,700,000
Interest expense on debt													17,600,000	9,500,000	2,300,000
Total expenses		118,800,000	104,400,000	113,200,000	151,900,000	150,100,000	154,400,000	134,700,000	108,100,000				488,300,000	547,300,000	366,000,000.0
Pre-tax income (loss)		56,500,000	51,100,000	15,800,000	281,700,000	(144,100,000)	44,300,000	(12,400,000)	(66,000,000.0)				405,100,000	(178,200,000)	7,800,000
Income tax (expense) benefit		(10,400,000)	(8,800,000)	100,000	(10,200,000)	3,600,000	3,600,000	(2,500,000)	(700,000)				(29,300,000)	4,000,000.0	7,800,000
Net income (loss) from continuing operations		46,100,000	42,300,000	15,900,000	271,500,000	(140,500,000)	47,900,000	(14,900,000)	(66,700,000)				375,800,000	(174,200,000)	15,600,000
Gain (loss) on sale of other discontinued operations, net of tax													800,000	(17,200,000)	557,000,000.0
Net income from discontinued operations, net of tax		(800,000)	900,000	0	700,000	0	(17,300,000)	0	100,000				0	0	20,500,000
Net income													376,600,000	(191,400,000)	593,100,000
Net loss attributable to non-controlling interests		15,600,000	5,500,000	4,600,000	12,200,000	3,000,000.0	10,200,000	18,400,000	18,600,000				37,900,000	50,200,000	34,100,000
Net income attributable to White Mountains’s common shareholders		$ 60,900,000	$ 48,700,000	$ 20,500,000	$ 284,400,000	$ (137,500,000)	$ 40,800,000	$ 3,500,000	$ (48,000,000.0)				414,500,000	(141,200,000)	627,200,000
Kudu
Revenues
Earned insurance premiums													0
Net investment income													14,700,000	0	0
Net realized and unrealized investment gains													6,300,000
Net realized and unrealized investment gains (losses)														0	0
Commission revenues													0
Other revenue													200,000	0	0
Total revenues													21,200,000	0	0
Expenses
Insurance acquisition expense													0
Other underwriting expenses													0
Cost of sales													0
General and administrative expenses													10,100,000	0	0
Broker commission expense													0
Amortization of other intangible assets													200,000	0	0
Interest expense on debt													100,000	0	0
Total expenses													10,400,000	0	0
Pre-tax income (loss)													10,800,000
HG Global-BAM
Revenues
Net investment income													21,600,000	16,700,000	12,300,000
Net realized and unrealized investment gains													27,100,000
Net realized and unrealized investment gains (losses)														(7,500,000)	600,000
Commission revenues													0
Other revenue													1,600,000	1,200,000	1,000,000.0
Total revenues													66,600,000	24,300,000	23,300,000
Expenses
Insurance acquisition expense													5,700,000	5,300,000	4,000,000.0
Other underwriting expenses													400,000	400,000	400,000
Cost of sales													0
General and administrative expenses													50,500,000	48,000,000.0	42,900,000
Broker commission expense													0
Amortization of other intangible assets													0
Interest expense on debt													0
Total expenses													56,600,000	53,700,000	47,300,000
Pre-tax income (loss)													10,000,000.0	(29,400,000)	(24,000,000.0)
NSM Holding Co LLC
Revenues
Earned insurance premiums													0
Net investment income													0
Net realized and unrealized investment gains													0
Commission revenues													193,400,000	89,600,000	0
Other revenue													39,700,000	12,000,000.0	0
Total revenues													233,100,000	101,600,000	0
Expenses
Insurance acquisition expense													0
Other underwriting expenses													0
Cost of sales													0
General and administrative expenses													132,200,000	59,400,000	0
Broker commission expense													64,800,000	28,400,000	0
Change in fair value of contingent consideration earnout liabilities													2,100,000	2,700,000	0
Amortization of other intangible assets													19,400,000	8,300,000	0
Interest expense on debt													16,700,000	8,000,000.0	0
Total expenses													235,200,000	106,800,000	0
Pre-tax income (loss)													(2,100,000)	(5,200,000)
MediaAlpha
Revenues
Commission revenues													48,800,000	295,500,000	163,200,000
Other revenue													0	1,600,000	0
Total revenues													48,800,000	297,100,000	163,200,000
Expenses
Cost of sales													40,600,000	245,000,000.0	135,900,000
General and administrative expenses													12,500,000	31,700,000	16,200,000
Amortization of other intangible assets													1,600,000	10,300,000	10,500,000
Interest expense on debt													200,000	1,200,000	1,000,000.0
Total expenses													54,900,000	288,200,000	163,600,000
Pre-tax income (loss)													(6,100,000)	8,900,000	(400,000)
Other
Revenues
Earned insurance premiums													0	0	1,000,000.0
Net investment income													43,400,000	42,300,000	43,700,000
Net realized and unrealized investment gains													285,100,000
Net realized and unrealized investment gains (losses)														(100,800,000)	132,700,000
Realized gain and unrealized investment gain from the MediaAlpha Transaction														0	0
Commission revenues													6,900,000	4,100,000	3,800,000
Other revenue													6,100,000	500,000	6,100,000
Total revenues													523,700,000	(53,900,000)	187,300,000
Expenses
Loss and loss adjustment expenses													0	0	1,100,000
Insurance acquisition expense													0	0	100,000
Other underwriting expenses													0
Cost of sales													7,500,000	3,700,000	3,500,000
General and administrative expenses													122,500,000	94,400,000	148,900,000
Broker commission expense													0
Amortization of other intangible assets													600,000	200,000	200,000
Interest expense on debt													600,000	300,000	1,300,000
Total expenses													131,200,000	98,600,000	155,100,000
Pre-tax income (loss)													392,500,000	(152,500,000)	32,200,000
NSM Holding Co LLC
Expenses
Change in fair value of contingent consideration earnout liabilities										$ 2,700,000			2,100,000
MediaAlpha \| MediaAlpha
Revenues
Total revenues												$ 359,200,000
MediaAlpha \| Other
Revenues
Realized gain and unrealized investment gain from the MediaAlpha Transaction													182,200,000
OneBeacon
Expenses
Gain (loss) on sale of other discontinued operations, net of tax	$ 554,600,000
Net income from discontinued operations, net of tax											$ 20,500,000
Tranzact
Expenses
Gain (loss) on sale of other discontinued operations, net of tax														3,200,000	3,200,000
Sirius Group
Expenses
Gain (loss) on sale of other discontinued operations, net of tax														(17,300,000)
Discontinued Operations
Expenses
Net income attributable to White Mountains’s common shareholders													414,500,000	(141,200,000)	627,200,000
Discontinued Operations \| OneBeacon
Revenues
Earned insurance premiums															807,600,000
Net investment income															39,700,000
Net realized and unrealized investment gains (losses)															38,800,000
Other revenue															7,700,000
Total revenues															893,800,000
Expenses
Loss and loss adjustment expenses															546,000,000.0
Other underwriting expenses															156,200,000
General and administrative expenses															21,200,000
Interest expense on debt															10,000,000.0
Total expenses															879,000,000.0
Gain (loss) on sale of other discontinued operations, net of tax															554,500,000
Net income from discontinued operations, net of tax															20,500,000
Discontinued Operations \| Tranzact
Revenues
Earned insurance premiums															0
Net investment income															0
Net realized and unrealized investment gains (losses)															0
Other revenue															0
Total revenues															0
Expenses
Loss and loss adjustment expenses															0
Other underwriting expenses															0
General and administrative expenses															0
Interest expense on debt															0
Total expenses															0
Gain (loss) on sale of other discontinued operations, net of tax															3,200,000
Net income from discontinued operations, net of tax															0
Discontinued Operations \| Sirius Group
Revenues
Earned insurance premiums															0
Net investment income															0
Net realized and unrealized investment gains (losses)															0
Other revenue															0
Total revenues															0
Expenses
Loss and loss adjustment expenses															0
Other underwriting expenses															0
General and administrative expenses															0
Interest expense on debt															0
Total expenses															0
Gain (loss) on sale of other discontinued operations, net of tax													$ 800,000	$ (17,200,000)	(700,000)
Net income from discontinued operations, net of tax															$ 0

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss) attributable to White Mountains’s common shareholders	$ 414.5	$ (141.2)	$ 627.2
Other comprehensive income, net of tax:
Other comprehensive (loss) income, net of tax	(1.4)	(4.8)	0.3
Comprehensive income from discontinued operations, net of tax	0.0	0.0	3.2
Comprehensive income (loss)	413.1	(146.0)	630.7
Comprehensive loss (income) attributable to non-controlling interests	0.0	0.3	(0.2)
Comprehensive income (loss) attributable to White Mountains’s common shareholders	$ 413.1	$ (145.7)	$ 630.5
Basic earnings (loss) per share
Continuing operations	$ 130.02	$ (36.67)	$ 11.56
Discontinued operations	0.25	(5.09)	134.50
Total consolidated operations	130.27	(41.76)	146.06
Diluted earnings (loss) per share
Continuing operations	130.02	(36.67)	11.56
Discontinued operations	0.25	(5.09)	134.50
Total consolidated operations	130.27	(41.76)	146.06
Dividends declared and paid per White Mountains’s common share	$ 1.00	$ 1.00	$ 1.00

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Total	Common Shares and Paid-in Surplus	Retained Earnings	AOCI, after tax	Parent	Non-controlling Interests	Total Equity	One Beacon Insurance Company [Member] Non-controlling Interests	One Beacon Insurance Company [Member] Total Equity	Star & Shield LLC [Member] Non-controlling Interests	Star & Shield LLC [Member] Total Equity	BAM Non-controlling Interests	BAM Total Equity	Foreign Currency Gain (Loss) AOCI, after tax	Foreign Currency Gain (Loss) Parent	Foreign Currency Gain (Loss) Non-controlling Interests	Foreign Currency Gain (Loss) Total Equity
Beginning balance at Dec. 31, 2016		$ 810.7	$ 2,776.6	$ (4.6)	$ 3,582.7	$ 133.3	$ 3,716.0
Increase (Decrease) in Shareholders' Equity
Net income (loss)	$ 593.1		627.2		627.2	(34.1)	593.1
Net change in foreign currency translation and interest rate swap														$ 0.4	$ 0.4	$ 0.1	$ 0.5
Net change in pension liability and other accumulated comprehensive items														$ 2.9	$ 2.9		$ 2.9
Comprehensive income (loss)	630.7		627.2	3.3	630.5	(34.0)	596.5
Dividends declared on common shares			(4.6)		(4.6)		(4.6)
Dividends to non-controlling interests						(19.3)	(19.3)
Issuances of common shares		1.7			1.7		1.7
Repurchases and retirements of common shares	(723.9)	(147.9)	(576.0)		(723.9)	(5.2)	(729.1)
Capital contributions from non-controlling interests		(4.6)			(4.6)	3.0	(1.6)					$ 27.2	$ 27.2
Issuance of shares of non-controlling interests		(4.1)			(4.1)	5.2	1.1
Amortization of restricted share and option awards		14.8			14.8	0.8	15.6
Deconsolidation of non-controlling interests		0.0						$ (238.3)	$ (238.3)	$ (4.4)	$ (4.4)
Ending balance at Dec. 31, 2017		670.6	2,823.2	(1.3)	3,492.5	(131.7)	3,360.8
Increase (Decrease) in Shareholders' Equity
Net income (loss)	(191.4)		(141.2)		(141.2)	(50.2)	(191.4)
Net change in foreign currency translation and interest rate swap				(4.5)	(4.5)	(0.3)	(4.8)
Comprehensive income (loss)	(146.0)		(141.2)	(4.5)	(145.7)	(50.5)	(196.2)
Dividends declared on common shares			(3.8)		(3.8)		(3.8)
Dividends to non-controlling interests						(8.0)	(8.0)
Issuances of common shares		2.0			2.0		2.0
Repurchases and retirements of common shares	(519.1)	(105.8)	(413.3)		(519.1)	0.0	(519.1)
Capital contributions from non-controlling interests												45.0	45.0
Amortization of restricted share and option awards		13.0			13.0	0.0	13.0
Acquisition of non-controlling interests		7.4			7.4	4.3	11.7
Dilution from equity units of subsidiary		(1.5)			(1.5)	1.5	0.0
Acquisition of non-controlling interests						14.5	14.5
Acquisition of subsidiary		(1.7)			(1.7)		(1.7)
Ending balance at Dec. 31, 2018	2,843.1	584.0	2,264.9	(5.8)	2,843.1	(124.9)	2,718.2
Increase (Decrease) in Shareholders' Equity
Net income (loss)	376.6		414.5		414.5	(37.9)	376.6
Net change in foreign currency translation and interest rate swap				(1.4)	(1.4)	0.0	(1.4)
Comprehensive income (loss)	413.1		414.5	(1.4)	413.1	(37.9)	375.2
Dividends declared on common shares			(3.2)		(3.2)		(3.2)
Dividends to non-controlling interests						(2.0)	(2.0)
Issuances of common shares		2.2			2.2		2.2
Repurchases and retirements of common shares	(4.9)	(1.1)	(3.8)		(4.9)		(4.9)
Capital contributions from non-controlling interests		(0.9)			(0.9)	2.4	1.5					$ 57.6	$ 57.6
Amortization of restricted share and option awards		10.6			10.6		10.6
Acquisition of non-controlling interests		1.5			1.5	0.0	1.5
Deconsolidation of non-controlling interests						(13.8)	(13.8)
Acquisition of non-controlling interests		0.0			0.0	1.8	1.8
Ending balance at Dec. 31, 2019	$ 3,261.5	$ 596.3	$ 2,672.4	$ (7.2)	$ 3,261.5	$ (116.8)	$ 3,144.7

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operations:
Net income (loss)	$ 376.6	$ (191.4)	$ 593.1
Charges (credits) to reconcile net income to net cash provided from (used for) operations:
Net realized and unrealized investment (gains) losses	(433.2)	108.3	(133.3)
Realized gain from the MediaAlpha Transaction	(67.5)	0.0	0.0
Amortization of restricted share and option awards	10.5	13.0	14.8
Amortization and depreciation	29.8	25.7	22.4
Deferred income tax expense (benefit)	24.8	(8.4)	(11.4)
Net income from discontinued operations	0.0	0.0	(20.5)
Net (gain) loss from sale of discontinued operations, net of tax	(0.8)	17.2	(557.0)
Other operating items:
Net change in unearned insurance premiums	35.8	39.2	54.5
Net change in deferred acquisition costs	(3.1)	(4.2)	(4.2)
Net change in restricted cash	6.3	(3.4)	0.0
Investments in asset management firms - Kudu	(118.4)	0.0	0.0
Net change in other assets and liabilities, net	18.7	(27.1)	(20.8)
Net cash used for continuing operations	(120.5)	(31.1)	(62.4)
Net cash provided from discontinued operations (See Note 20)	0.0	0.0	157.0
Net cash (used for) provided from operations	(120.5)	(31.1)	94.6
Cash flows from investing activities:
Net change in short-term investments	21.9	(39.0)	(1.7)
Sales of fixed maturity and convertible investments	334.3	1,848.5	2,124.4
Maturities, calls and paydowns of fixed maturity and convertible investments	119.3	141.0	213.4
Sales of common equity securities	467.2	169.9	424.1
Distributions and redemptions of other long-term investments	29.4	5.0	29.4
Sales of unconsolidated affiliates and consolidated subsidiaries, net of cash sold	0.0	0.0	1,131.0
Purchases of other long-term investments	(177.7)	(95.9)	(84.1)
Net settlement of investment cash flows and contributions with discontinued operations	0.0	0.0	167.7
Purchases of common equity securities	(29.8)	(328.3)	(881.2)
Purchases of fixed maturity and convertible investments	(539.2)	(970.2)	(2,365.2)
Purchases of consolidated subsidiaries, net of cash acquired of $12.8, $90.9, and $0.0 and including restricted cash of $0.0, $53.4, $0.0	(258.0)	(295.2)	(27.6)
Other investing activities, net	(27.3)	23.4	(14.7)
Net cash (used for) provided from investing activities — continuing operations	(59.9)	459.2	715.5
Net cash provided from investing activities — discontinued operations (See Note 20)	0.0	0.0	3.0
Net cash (used for) provided from investing activities	(59.9)	459.2	718.5
Cash flows from financing activities:
Draw down of debt and revolving line of credit	206.4	84.1	376.0
Repayment of debt and revolving line of credit	(22.9)	(15.4)	(365.0)
Cash dividends paid to the Company’s common shareholders	(3.2)	(3.8)	(4.6)
Acquisitions of additional shares from non-controlling interest	0.0	(1.7)	(0.7)
Distributions from discontinued operations	0.0	0.0	45.2
Common shares repurchased	0.0	(511.9)	(714.6)
Repurchase of shares from non-controlling interest shareholders	(21.1)	0.0	0.0
Proceeds from issuance of shares to non-controlling interest shareholders	62.7	0.0	0.0
Capital contributions from non-controlling interest shareholders	1.9	1.3	0.5
Distributions to non-controlling interest shareholders	(28.1)	(6.0)	(2.0)
Payments to contingent considerations related to purchases of consolidated subsidiaries	(7.6)	(2.6)	0.0
Capital contributions from BAM members	54.6	53.8	37.4
Fidus Re premium payment	(3.0)	(3.7)	0.0
Other financing activities, net	(9.2)	(8.4)	(9.3)
Net cash provided from (used for) financing activities — continuing operations	230.5	(414.3)	(637.1)
Net cash used for financing activities — discontinued operations (See Note 20)	0.0	0.0	(61.9)
Net cash provided from (used for) financing activities	230.5	(414.3)	(699.0)
Effect of exchange rate changes on cash	0.6	(0.6)	0.0
Net change in cash during the period - continuing operations	50.7	13.2	16.0
Cash balance at beginning of year	110.3	97.1	80.2
Add: cash held for sale at the beginning of period	0.0	0.0	0.9
Less: cash held for sale at the end of period		0.0	0.0
Cash balance at end of year	$ 161.0	$ 110.3	$ 97.1

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash acquired	$ 12.8	$ 90.9	$ 0.0
Restricted cash acquired	0.0	53.4	0.0
Cash restricted	56.3	50.0	0.0
Sirius Group
Held for sale and discontinued operations cash balance	$ 0.0	$ 0.0	$ 0.0

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Significant Accounting Policies Basis of Presentation The Company is an exempted Bermuda limited liability company whose principal businesses are conducted through its insurance 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 80 South Main Street, Hanover, New Hampshire 03755-2053 and its registered office is located at Clarendon House, 2 Church Street, Hamilton, Bermuda HM 11. 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. 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. See Note 16 — “Variable Interest Entities”. Intercompany transactions have been eliminated in consolidation. Certain amounts in the prior period financial statements have been reclassified to conform to the current presentation. 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. 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 December 31, 2019, White Mountains’s reportable segments were HG Global/BAM, NSM, Kudu and Other Operations. As a result of the MediaAlpha Transaction, White Mountains no longer consolidated MediaAlpha, and consequently it was no longer a reportable segment. See Note 14 — “Segment Information”. 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 reinsurance 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 million of Series A Notes and $300 million of Series B Notes (the “BAM Surplus Notes”). As of December 31, 2019 and 2018, 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 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, social services and real estate. On behalf of its insurance carrier partners, NSM 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 December 31, 2019 and 2018, White Mountains owned 96.4% and 95.5% of the basic units outstanding of NSM (88.4% and 85.0% on a fully diluted, fully converted basis). NSM was acquired by White Mountains in 2018. 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. On April 4, 2019, White Mountains acquired the ownership interests in Kudu held by certain funds managed by Oaktree Capital Management, L.P. (“Oaktree”) for cash consideration of $81.4 million. In addition, White Mountains assumed all of Oaktree’s unfunded capital commitments to Kudu, increasing White Mountains’s total capital commitment to $250.0 million (the “Kudu Transaction”). As a result of the Kudu Transaction, White Mountains’s basic unit ownership of Kudu increased from 49.5% to 99.1% (42.7% to 85.4% on a fully diluted, fully converted basis), and White Mountains began consolidating Kudu as a reportable segment in its financial statements during the second quarter of 2019. See Note 2 — “Significant Transactions". During the fourth quarter of 2019, White Mountains increased its total capital commitment to Kudu by $100.0 million to $350.0 million of which $129.0 million was undrawn as of December 31, 2019. Also during the fourth quarter of 2019, Kudu obtained a committed $125.0 million credit facility, of which $68.0 million was undrawn as of December 31, 2019. The Other Operations segment consists of the Company and its wholly-owned subsidiary, White Mountains Capital, Inc., 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 (for periods after the MediaAlpha Transaction), PassportCard Limited (“PassportCard”) and DavidShield Life Insurance Agency (2000) Ltd. (“DavidShield”) (collectively, “PassportCard/ DavidShield”), Elementum Holdings LP (“Elementum”) and Kudu (for periods prior to the Kudu Transaction), and certain other consolidated and unconsolidated entities and certain other strategic investments. The MediaAlpha segment consisted of QL Holdings LLC and its wholly-owned subsidiary QuoteLab, LLC (collectively “MediaAlpha”). MediaAlpha is a marketing technology company that enables the programmatic buying and selling of vertical-specific, performance-based media between advertisers (buyers of advertising inventory) and publishers (sellers of advertising inventory). MediaAlpha operates in insurance and non-insurance verticals and uses cost-per-click, cost-per-call and cost-per-lead pricing models. MediaAlpha’s media buying platform enables advertisers to create and automate data-driven bidding strategies designed to improve the efficiency and enhance overall performance of their marketing campaigns that target high-intent consumers at the time and place they are ready to purchase. MediaAlpha’s publisher platform is used by publishers to sell their media to advertisers through transparent, programmatic, auction-based marketplaces. On February 26, 2019, MediaAlpha completed the sale of a significant minority stake to Insignia Capital Group in connection with a recapitalization and cash distribution to existing equityholders (the “MediaAlpha Transaction”). White Mountains deconsolidated MediaAlpha as a result of the MediaAlpha Transaction and it was no longer a reportable segment. White Mountains’s consolidated statement of comprehensive income and its segment disclosures include MediaAlpha’s results of operations through the date of the MediaAlpha Transaction. See Note 2 — “Significant Transactions”. Discontinued Operations and Assets and Liabilities Held for Sale As of December 31, 2017, White Mountains classified its Guilford, Connecticut property, which consists of an office building and adjacent land, as held for sale. The property was valued at its estimated fair value, net of disposal costs. The related write-down of $3.7 million was recorded within general and administrative expenses during 2017. As of December 31, 2019 and 2018, the property has been measured at its estimated fair value, net of disposal costs of $3.0 million and $3.3 million. See Note 20 — “Held for Sale and Discontinued Operations”. Significant Accounting Policies Cash Cash includes amounts on hand and demand deposits with banks and other financial institutions. Amounts presented in the statement of cash flows are shown net of balances acquired and sold in the purchase or sale of the Company’s consolidated subsidiaries and exclude changes in amounts of restricted cash. Restricted cash consists primarily of amounts in fiduciary accounts held by NSM on behalf of insurance carriers. Short-Term Investments Short-term investments consist of interest-bearing money market funds and other securities, which at the time of purchase, mature or become available for use within one year. Short-term investments are carried at amortized or accreted cost, which approximated fair value as of December 31, 2019 and 2018. Investment Securities As of December 31, 2019 and 2018, White Mountains’s invested assets consisted of securities and other investments held for general investment purposes. White Mountains’s portfolio of fixed maturity investments, common equity securities and other long-term investments held for general investment purposes are generally classified as trading securities and are reported at fair value as of the balance sheet date. Changes in net unrealized investment gains (losses) are reported pre-tax in revenues. Realized investment gains (losses) are accounted for using the specific identification method and are reported pre-tax in revenues. Premiums and discounts on all fixed maturity investments are amortized and accreted to income over the anticipated life of the investment. White Mountains’s invested assets that are measured at fair value include fixed maturity investments, common equity securities and other long-term investments, including unconsolidated entities, non-controlling equity interests in the form of revenue and earnings participation contracts (“Kudu’s Participation Contracts”), private equity funds, hedge funds, insurance-linked securities (“ILS”) funds and private debt instruments. Whenever possible, White Mountains estimates fair value using valuation methods that maximize the use of quoted prices and other observable inputs. 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 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”). Assets and liabilities carried at fair value include substantially all of the investment portfolio and derivative instruments, both exchange traded and over the counter instruments. Valuation of assets measured at fair value require management to make estimates and apply judgment to matters that may carry a significant degree of uncertainty. In determining its estimates of fair value, White Mountains uses a variety of valuation approaches and inputs. Whenever possible, White Mountains estimates fair value using valuation methods that maximize the use of observable prices and other inputs. Where appropriate, assets and liabilities measured at fair value have been adjusted for the effect of counterparty credit risk. White Mountains uses outside pricing services and brokers to assist in determining fair values. The outside pricing services White Mountains uses have indicated that they will only provide prices where observable inputs are available. As of December 31, 2019, approximately 71% of the investment portfolio recorded at fair value was priced based upon quoted market prices or other observable inputs. Level 1 Measurements Investments valued using Level 1 inputs include fixed maturity investments, primarily investments in U.S. Treasuries and short-term investments, which include U.S. Treasury Bills, and common equity securities. For investments in active markets, White Mountains uses the quoted market prices provided by outside pricing services to determine fair value. Level 2 Measurements Investments valued using Level 2 inputs include fixed maturity investments which have been disaggregated into classes, including debt securities issued by corporations, municipal obligations and mortgage and asset-backed securities. Investments valued using Level 2 inputs also include certain passive exchange-traded funds (“ETFs”) that track U.S. stock indices such as the S&P 500 Index, but are traded on foreign exchanges, which White Mountains values using the fund manager’s published net asset value per share (“NAV”) to account for the difference in market close times. In circumstances where quoted market prices are unavailable or are not considered reasonable, White Mountains estimates the fair value using industry standard pricing methodologies and observable inputs such as benchmark yields, reported trades, broker-dealer quotes, issuer spreads, benchmark securities, bids, offers, credit ratings, prepayment speeds, reference data including research publications and other relevant inputs. Given that many fixed maturity investments do not trade on a daily basis, the outside pricing services evaluate a wide range of fixed maturity investments by regularly drawing parallels from recent trades and quotes of comparable securities with similar features. The characteristics used to identify comparable fixed maturity investments vary by asset type and take into account market convention. White Mountains’s process to assess the reasonableness of the market prices obtained from the outside pricing sources covers substantially all of its fixed maturity investments and includes, but is not limited to, the evaluation of pricing methodologies and a review of the pricing services’ quality control procedures on at least an annual basis, a comparison of its invested asset prices obtained from alternate independent pricing vendors on at least a semi-annual basis, monthly analytical reviews of certain prices and a review of the underlying assumptions utilized by the pricing services for select measurements on an ad hoc basis throughout the year. White Mountains also performs back-testing of selected investment sales activity to determine whether there are any significant differences between the market price used to value the security prior to sale and the actual sale price of the security on an ad-hoc basis throughout the year. Prices provided by the pricing services that vary by more than $0.5 million and 5% from the expected price based on these assessment procedures are considered outliers, as are prices that have not changed from period to period and prices that have trended unusually compared to market conditions. In circumstances where the results of White Mountains’s review process does not appear to support the market price provided by the pricing services, White Mountains challenges the vendor provided price. If White Mountains cannot gain satisfactory evidence to support the challenged price, White Mountains will rely upon its own internal pricing methodologies to estimate the fair value of the security in question. The valuation process described above is generally applicable to all of White Mountains’s fixed maturity investments. The techniques and inputs specific to asset classes within White Mountains’s fixed maturity investments for Level 2 securities that use observable inputs are as follows: Debt Securities Issued by Corporations: The fair value of debt securities issued by corporations is determined from a pricing evaluation technique that uses information from market sources and integrates relative credit information, observed market movements, and sector news. Key inputs include benchmark yields, reported trades, broker-dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, and reference data including sector, coupon, credit quality ratings, duration, credit enhancements, early redemption features and market research publications. Municipal Obligations: The fair value of municipal obligations is determined from a pricing evaluation technique that uses information from market makers, brokers-dealers, buy-side firms, and analysts along with general market information. Key inputs include benchmark yields, reported trades, issuer financial statements, material event notices and new issue data, as well as broker-dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, and reference data including type, coupon, credit quality ratings, duration, credit enhancements, geographic location and market research publications. Mortgage and Asset-Backed Securities: The fair value of mortgage and asset-backed securities is determined from a pricing evaluation technique that uses information from market sources and leveraging similar securities. Key inputs include benchmark yields, reported trades, underlying tranche cash flow data, collateral performance, plus new issue data, as well as broker-dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, and reference data including issuer, vintage, loan type, collateral attributes, prepayment speeds, default rates, recovery rates, cash flow stress testing, credit quality ratings and market research publications. Level 3 Measurements Fair value estimates for investments that trade infrequently and have few or no quoted market prices or other observable inputs are classified as Level 3 measurements. Investments valued using Level 3 fair value estimates are based upon unobservable inputs and include investments in certain fixed maturity investments, common equity securities and other long-term investments where quoted market prices or other observable inputs are unavailable or are not considered reliable or reasonable. Level 3 valuations are generated from techniques that use assumptions not observable in the market. These unobservable inputs reflect White Mountains’s assumptions of what market participants would use in valuing the investment. In certain circumstances, investment securities may start out as Level 3 when they are originally issued, but as observable inputs become available in the market, they may be reclassified to Level 2. Transfers of securities between levels are based on investments held as of the beginning of the period. Other Long-Term Investments As of December 31, 2019, White Mountains owned a portfolio of other long-term investments valued at $856 million, including unconsolidated entities, Kudu’s Participation Contracts, private equity funds, hedge funds, ILS funds and private debt instruments. As of December 31, 2019, $654 million of White Mountains’s other long-term investments, including unconsolidated entities, Kudu’s Participation Contracts and private debt instruments were classified as Level 3 investments in the GAAP fair value hierarchy, were not actively traded in public markets and did not have readily observable market prices. The determination of the fair value of these securities involves significant management judgment, and the use of valuation models and assumptions that are inherently subjective and uncertain. As of December 31, 2019, $202 million of White Mountains’s other long-term investments, including private equity funds, hedge funds and ILS funds, were valued at fair value using NAV as a practical expedient. Investments for which fair value is measured at NAV using the practical expedient are not classified within the fair value hierarchy. White Mountains may use a variety of valuation techniques to determine fair value depending on the nature of the investment, including a discounted cash flow analysis, market multiple approach, cost approach and/or liquidation analysis. On an ongoing basis, White Mountains also considers qualitative changes in facts and circumstances, which may impact the valuation of unconsolidated entities, including economic and market changes in relevant industries, changes to the entity’s capital structure, business strategy and key personnel, and any recent transactions relating to the unconsolidated entity. On a quarterly basis, White Mountains evaluates the most recent qualitative and quantitative information of the business and completes a fair valuation analysis for all Level 3 other long-term investments. Periodically, and at least on an annual basis, White Mountains uses a third-party valuation firm to complete an independent valuation analysis of significant unconsolidated entities. Other Long-term Investments - NAV White Mountains’s portfolio of other long-term investments includes investments in private equity funds, hedge funds and ILS funds. White Mountains employs a number of procedures to assess the reasonableness of the fair value measurements for its private equity funds, hedge funds and ILS funds, including obtaining and reviewing periodic and audited annual financial statements as well as discussing each fund’s pricing with the fund manager throughout the year. However, since the fund managers do not provide sufficient information to evaluate the pricing methods and inputs for each underlying investment, White Mountains considers the inputs to be unobservable. The fair value of White Mountains’s private equity fund, hedge fund and ILS fund investments are generally determined using the fund manager’s NAV. In the event that White Mountains believes the fair value of a private equity fund, hedge fund or ILS fund differs from the NAV reported by the fund manager due to illiquidity or other factors, White Mountains will adjust the reported NAV to more appropriately represent the fair value of its investment in the private equity fund, hedge fund or ILS fund. Derivatives White Mountains holds from time to time a variety of derivative financial instruments for risk management purposes. White Mountains recognizes all derivatives as either other assets or other liabilities, aside from the foreign currency forward contracts which are recognized within other long-term investments, measured at fair value, in the consolidated balance sheets. 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 December 31, 2019 and 2018, White Mountains holds an interest rate swap derivative instrument that meets the criteria for hedge accounting. In 2018, White Mountains held a foreign currency forward contract derivative instrument that did not meet the criteria for hedge accounting. The foreign currency forward contract was closed in the first quarter of 2018. From time to time, White Mountains holds warrants that it has received in the restructuring of certain of its common equity securities and fixed maturity investments. White Mountains accounts for its investments in warrants as derivatives. Receivables BAM’s receivables consist primarily of premiums receivable from customers for municipal bond insurance policies. NSM’s receivables consist of insurance premiums receivable from customers and commissions receivable from insurance carriers, net of a provision for amounts estimated to be uncollectible. MediaAlpha receivables consist of advertising fee receivables from publishers and advertisers. Incentive Compensation 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. Non-share based awards are recognized over the related service periods based on management’s best estimate of the amounts at which the awards are expected to be paid. Share-based compensation which is typically settled in cash, such as performance shares, is classified as a liability-type award. The compensation cost for liability-classified awards is measured initially at the grant date fair value and remeasured each reporting period until settlement. The compensation cost for equity-classified awards expected to be settled in shares, such as options and restricted shares, is measured at the original grant date fair value of the award. The compensation cost for all awards is recognized for the vested portion of the awards over the related service periods. See Note 10 — “Employee Share-Based Incentive Compensation Plans”. 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 trade names, URL and online names, customer relationships and contracts, information technology platforms and insurance licenses. Goodwill and other intangible assets with indefinite lives are not amortized, but rather are evaluated for impairment on an annual basis, or whenever indications of potential impairment exist. In the absence of any indications of potential impairment, the evaluation of goodwill and indefinite-lived intangible assets is performed no later than the interim period in which the anniversary of the acquisition date falls. White Mountains initially evaluates goodwill using a qualitative approach (step zero) to determine whether it is more likely than not that the implied fair value of goodwill is greater than its carrying value. If the results of the qualitative evaluation indicate that it is more likely than not that the carrying value of goodwill exceeds its implied fair value, White Mountains performs the two-step quantitative test for impairment. Other intangible assets with finite lives are measured at their acquisition date fair values, are amortized over their economic lives and presented net of accumulated amortization on the balance sheet. Other intangible assets with finite lives are reviewed for impairment when events occur or there are changes in circumstances indicating that their carrying value may exceed fair value. Impairment exists when the carrying value of other intangible assets exceeds fair value. Municipal Bond Guarantee Insurance All of the contracts issued by BAM are accounted for as insurance contracts under ASC 944-605, Financial Guarantee Insurance Contracts. Premiums are generally received upfront and an unearned premium revenue liability, equal to the amount of the premium received, is established at contract inception. Installment premiums are measured at the present value of contractual premiums, discounted at the risk-free rate, which is set at the inception of the insurance contract. Premium revenues are recognized in revenue over the period of the contracts in proportion to the amount of insurance protection provided using a constant rate. The constant rate is calculated based on the relationship between the par outstanding in a given reporting period compared with the sum of each of the par amounts outstanding for all periods. Deferred acquisition costs represent commissions, premium taxes, excise taxes and other costs which are directly attributable to and vary with the production of business. These costs are deferred and amortized to the extent they relate to successful contract acquisitions over the applicable premium recognition period as acquisition expenses. Deferred acquisition costs are limited to the amount expected to be recovered from future earned premiums and anticipated investment income. BAM’s obligation for outstanding contracts consists of the unearned premium reserve and any loss reserves. Loss reserves are recorded only to the extent that the present value of the expected amount of any losses to be paid, net of any expected recoveries, exceeds the associated unearned premium reserve. As of December 31, 2019 and 2018, BAM did not have any loss or loss adjustment expense reserves. Revenue Recognition NSM’s revenues consist primarily of commissions and broker revenues for placement of insurance policies and administrative fees for claims and other services provided to insurance carriers. Commission and broker revenues and service fees are measured based on the contractual rates with insurance carriers, net of any amounts expected to be uncollectible and any amounts associated with expected policy cancellations, adjustments, and are recognized when contractual performance obligations have been fulfilled. NSM’s primary contractual performance obligations are generally satisfied upon the issuance of an insurance policy by the carrier. Where NSM has significant performance obligations beyond the policy issuance date, NSM estimates the relative standalone selling price for the post-issuance services in order to allocate the transaction price using the price charged for the service when sold separately in similar circumstances to similar customers. Deferred revenues associated with unsatisfied performance obligations are recognized within other liabilities. Contingent commissions are based upon the overall profit and/or volume of the business placed with the insurance carrier during a calendar year and are determined after the contractual period has ended. NSM recognizes revenue on contingent commissions when management has determined that it is probable that the contingent commission requirements have been met. Kudu’s revenues are primarily generated from non-controlling equity interests in revenue and earnings participation contracts with asset management firms. The participation contracts are measured at fair value with the change therein recognized within unrealized investment gains and losses. Distributions from Kudu’s clients are recognized through investment income when Kudu’s right to receive payment has been established and can be reliably measured, which generally occurs on a quarterly basis in accordance with the terms of the underlying participation contracts. MediaAlpha recognized advertising and publishing fee revenues based on the contractual amount of the fees, adjusted for any amounts expected to be refunded or uncollectible, when it had satisfied its contractual performance obligations, which was generally at the time each transaction was executed. For transactions where MediaAlpha acted as the principal, such as the Open exchange, revenue amounts were reported gross. For transactions where MediaAlpha acted as an agent facilitating transactions between third parties, revenue amounts were reported at the net fee billed. Cost of Sales and Broker Commission Expense NSM’s broker commission expense consists of commissions paid to sub-agents and brokers. Broker commission expense is measured in accordance with contractual terms and recognized when incurred, which is generally at the policy issuance date. MediaAlpha’s cost of sales consisted primarily of revenue sharing payments to publisher partners and traffic acquisition costs to top tier search engines. Cost of sales were measured based on contract terms and recognized when the related revenue transactions are executed. Other Operations’s cost of sales consists of salaries and related expenses, professional services and marketing and advertising expenses directly related to sales generation. These expenses are recognized as incurred. Federal and Foreign Income Taxes A number of White Mountains’s subsidiaries file consolidated tax returns in the United States. Income earned or losses generated by companies outside the United States are generally subject to an overall effective tax rate lower than that imposed by the United States. Deferred tax assets and liabilities are recorded when a difference between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts for tax purposes exists, and for other temporary differences. The deferred tax asset or liability is recorded based on tax rates expected to be in effect when the difference reverses. The deferred tax asset is recognized when it is more likely than not that it will be realized. Foreign Currency Exchange The functional currency for White Mountains’s non-U.S. based subsidiaries are measured, in most instances, using functional currencies other than the U.S. dollar. Net foreign exchange gains and losses arising from the translation of functional currencies are generally reported in shareholders’ equity, in accumulated other comprehensive income or loss. White Mountains also invests in securities denominated in foreign currencies. Assets and liabilities recorded in these foreign currencies are translated into U.S. dollars at exchange rates in effect at the balance sheet date, and revenues and expenses are converted using the weighted average exchange rates for the period. As of December 31, 2019 and 2018, White Mountains had unrealized foreign currency translation losses of $2.4 million and $3.9 million recorded in accumulated other comprehensive income on its consolidated balance sheet. Non-controlling Interests Non-controlling interests consist of the ownership interests of non-controlling shareholders in consolidated subsidiaries, and are presented separately on the balance sheet. The portion of comprehensive income attributable to non-controlling interests is presented net of related income taxes in the statement of operations and comprehensive income. See Note 12 — “Common Shareholders’ Equity and Non-controlling Interests”. Recently Adopted Changes in Accounting Principles Leases On January 1, 2019, White Mountains adopted ASU 2016-02, Leases (ASC 842), which requires lessees to recognize lease assets and liabilities on the balance sheet for both operating and financing leases, with the exception of leases with an original term of 12 months or less. White Mountains elected the optional transition method that permits prospective adoption with recognition of a cumulative effect adjustment to the opening balance of retained earnings. As a result, White Mountains has presented comparative periods prior to adoption in accordance with previous lease accounting guidance. White Mountains also elected all available practical expedients permitted under ASC 842, which allowed White Mountains to carryforward its historical lease classification and not reassess leases for the definition of a lease under the new guidance. Upon adoption on January 1, 2019, White Mountains recognized $23.2 million for both the lease right-of-use (“ROU”) assets and lease liabilities. As of December 31, 2019, White Mountains recognized $22.6 million and $22.8 million of lease ROU assets and lease liabilities. Adoption of ASU 2016-02 did not result in an adjustment to opening retained earnings. Premium Amortization on Callable Debt Securities On January 1, 2019, White Mountains adopted ASU 2017-08, Premium Amortization on Purchased Callable Debt Securities (ASC 310-20), which changes the amortization period for certain purchased callable debt securities. Under the new guidance, for investments in callable debt securities held at a premium, the premium is amortized over the period to the earliest call date. The new guidance does not change the amortization period for callable debt securities held at a discount. Adoption of ASU 2017-08 did not have any impact on White Mountains’s financial statements. Revenue Recognition On January 1, 2018, White Mountains adopted ASU 2014-09, Revenue from Contracts with Customers (ASC 606), which modifies the guidance for revenue recognition. Under ASU 2014-09, revenue is recognized at an amount that reflects the consideration to which an entity expects to be entitled once it fulfills its performance obligations under the terms of its contract with the customer. The scope of the new guidance includes agent commissions and other non-insurance revenues. Adoption of ASU 2014-09 did not have any impact on White Mountains's financial statements. Share-Based Compensation On January 1, 2018, White Mountains adopted ASU 2017-09, Stock Compensation: Scope of Modification Accounting (ASC 718), which narrows the scope of transactions subject to modification accounting to changes in the terms of an award that result in a change in the award’s fair value, vesting conditions or classification. Adoption of ASU 2017-09 did not have any impact on White Mountains’s financial statements. Business Combinations On January 1, 2018, White Mountains adopted ASU 2017-01, Business Combinations: Clarifying the Definition of a Business (ASC 805), which clarifies the definition of a business and affects the determination of whether acquisitions or disposals are accounted for as assets or as a business. Under the new guidance, when substantially all of the fair value of the assets is concentrated in a single identifiable asset or group of similar assets, it is not a business. Adoption of ASU 2017-01 did not have any impact on White Mountains’s financial statements. Cash Flow Statement On January 1, 2018, White Mountains adopted ASU 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments (ASC 230), which addresses the classification and presentation of certain items, including debt prepayment and extinguishment costs, contingent consideration payments made after a business combination and distributions received from equity method investees, for which there was diversity in practice prior to the issuance of ASU 2016-15. Also on January 1, 2018, White Mountains adopted ASU 2016-18, Statement of Cash Flows: Restricted Cash (ASC 230), which modifies the guidance for the treatment of restricted cash amounts in the cash flow statement. The new guidance requires restricted cash to be included in the reconciliation of beginning and end-of-period amounts presented on the statement of cash flows and requires a description of the nature of the changes in restricted cash during the periods presented. Adoption of ASU 2016-15 and ASU 2016-18 did not have any impact on White Mountains's statement of cash flows. Financial Instruments - Recognition and Measurement On January 1, 2018, White Mountains adopted ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities (ASC 825-10), which modifies the guidance for financial instruments, including investments in equity securities. Under the new guidance, all equity securities with readily determinable fair values are required to be measured at fair value with changes therein recognized through current period earnings. In addition, the new ASU requires a qualitative assessment for equity securities without readily determinable fair values to identify impairment, and for impaired equity securities to be measured at fair value. White Mountains measures its portfolio of investment securities at fair value with changes therein recognized through current period earnings and, accordingly, adoption of ASU 2016-01 did not have any impact on White Mountains's financial statements. Recently Issued Accounting Pronouncements Income Taxes In December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for Income Taxes (ASC 740), which eliminates exceptions related to the approach for intra-period tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. ASU 2019-12 also clarifies and simplifies other aspects of the accounting for income taxes. Adoption of ASU 2019-12 is required for fiscal years beginning after December 15, 2020, with early adoption permitted. White Mountains did not elect to adopt the new guidance in 2019 and is currently evaluating the impact of adoption. VIE In October 2018, the FASB issued ASU 2018-17, Targeted Improvements to Related party Guidance for Variable Interest Entities (ASC 810), which changes the way indirect interests held through related parties under common control are evaluated, requiring consideration of such interests on a proportional basis for purposes of determining whether fees paid to decision makers and service providers are variable interests. The new guidance is effective for fiscal years beginning after December 15, 2019. White Mountains does not currently have any variable interests where the new guidance would affect the determination of the primary beneficiary and does not expect adoption to have any impact on its financial statements. Goodwill In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment (ASC 350), which changes the guidance on goodwill impairment testing. Under the new guidance, the qualitative assessment of the recoverability of goodwill remains the same. However, the second step required under the existing guidance has been eliminated. Goodwill is considered impaired if the carrying value exceeds the estimated fair value. The new guidance is effective for fiscal years beginning after December 15, 2019. White Mountains does not expect adoption to have any impact on its periodic evaluation of goodwill. Credit Losses In June 2016, the FASB issued 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. This differs from current GAAP, which delays recognition until it is probable a loss has been incurred. The new guidance is expected to accelerate recognition of credit losses. The types of assets within the scope of the new guidance include loans and trade receivables such as premium receivables and reinsurance recoverables on paid losses. ASU 2016-13 is effective for annual periods beginning after January 1, 2020, including interim periods. White Mountains measures its portfolio of investment securities at fair value with changes therein recognized through current period earnings and does not expect adoption to have any effect on its financial statements.

Significant Transactions	12 Months Ended
Significant Transactions	Dec. 31, 2019
Significant Transactions [Abstract]
Significant Transactions	Significant Transactions Acquisitions Elementum On May 31, 2019, White Mountains acquired a 30.0% limited partnership interest in Elementum, a third-party registered investment adviser specializing in natural catastrophe ILS, for $55.1 million (the “Elementum Transaction”). Elementum manages separate accounts and pooled investment vehicles across various ILS sectors, including catastrophe bonds, collateralized reinsurance investments and industry loss warranties, on behalf of third-party clients. As part of the Elementum Transaction, White Mountains also committed to invest $50.0 million in ILS funds managed by Elementum. As of December 31, 2019, White Mountains has invested $40.0 million into three Elementum-managed funds. White Mountains has elected to use the fair value option for its investment in Elementum. Both the investment in Elementum and the investments in ILS funds managed by Elementum are included within other long-term investments. NSM On May 11, 2018, White Mountains acquired a 95.0% basic unit ownership interest in NSM (83.6% on a fully diluted, fully converted basis). White Mountains funded the acquisition through a combination of cash on hand and new borrowings by NSM. White Mountains paid $274.2 million of cash consideration for its equity interest in NSM, and NSM borrowed $100.0 million in new debt as part of the transaction. During the third quarter of 2018, White Mountains recorded a purchase price adjustment of an additional $2.1 million of consideration, which was paid in the fourth quarter of 2018. White Mountains recognized total assets acquired related to NSM of $495.2 million, including $383.0 million of goodwill and other intangible assets, total liabilities assumed of $204.6 million, including contingent consideration earnout liabilities related to NSM’s previous acquisitions of its U.K.-based operations, of $10.2 million, and non-controlling interest of $14.4 million reflecting acquisition date fair values. In connection with the acquisition, White Mountains incurred transaction costs of $6.3 million in the Other Operations segment, which were expensed in 2018. On May 18, 2018, NSM acquired 100% of Fresh Insurance Services Group Limited (“Fresh Insurance”). Fresh Insurance 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 three months ended March 31, 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, ending in February 2020 and February 2022. NSM recognized total assets acquired related to Fresh Insurance of $72.6 million, including $54.6 million of goodwill and other intangible assets, and total liabilities assumed of $22.3 million, reflecting acquisition date fair values. In connection with the acquisition, NSM recorded a contingent consideration earnout liability of $7.5 million. 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 and NSM borrowed $30.1 million to fund the transaction. White Mountains recognized $59.4 million of goodwill and other intangible assets, reflecting acquisition date fair values, for which the relative fair values of goodwill and other intangible assets had not yet been finalized as of December 31, 2018. During 2019, NSM determined that the relative values of goodwill and other intangible assets recorded in connection with the KBK transaction were $32.6 million and $32.7 million, reflecting acquisition date fair values. The purchase price is subject to additional adjustments based upon growth in EBITDA during three earn out periods ending in December 2019, December 2020 and December 2021. During the three months ended March 31, 2019, NSM recorded a purchase price adjustment of $5.9 million relating to the fair value of the contingent consideration earnout liability in connection with the acquisition. On April 1, 2019, NSM acquired 100% of Embrace Pet Insurance (“Embrace”), a nationwide provider of pet health insurance for dogs and cats. NSM paid $71.5 million of cash consideration, net of cash acquired, for Embrace. White Mountains contributed $58.2 million to NSM and NSM borrowed $20.4 million to fund the transaction. White Mountains recognized $52.2 million of goodwill and $15.4 million of other intangible assets, reflecting acquisition date fair values. On June 28, 2019, NSM acquired the renewal rights on its U.S. collector car business (the “Renewal Rights”) from American International Group, Inc. (“AIG”) for $82.5 million. The acquisition satisfied NSM’s obligation to acquire the Renewal Rights from AIG. See Note 19 — “Commitments and Contingencies”. White Mountains contributed $59.1 million to NSM and NSM borrowed $22.5 million to fund the transaction. White Mountains recognized $82.5 million of other intangible assets, reflecting the acquisition date fair value. See Note 4 — “Goodwill and Other Intangible Assets”. The contingent consideration earnout liabilities related to the NSM, Fresh Insurance and KBK acquisitions are subject to adjustments based upon EBITDA, EBITDA projections, and present value factors for acquired entities. For the year ended December 31, 2019, NSM recognized pre-tax expense of $2.1 million for the change in the fair value of its contingent consideration earnout liabilities. For the period from May 11, 2018 through December 31, 2018, NSM recognized pre-tax expense of $2.7 million 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 December 31, 2019 and 2018, NSM recognized total contingent consideration earnout liabilities of $20.6 million and $20.2 million. 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. Kudu On February 5, 2018, White Mountains entered into an agreement to fund up to $125.0 million in Kudu in exchange for a 49.5% basic unit ownership interest in Kudu (42.7% on a fully diluted, fully converted basis). On April 4, 2019, White Mountains acquired the ownership interests in Kudu held by certain funds managed by Oaktree for cash consideration of $81.4 million. In addition, White Mountains assumed all of Oaktree’s unfunded capital commitments to Kudu, increasing White Mountains’s total capital commitment to $250.0 million. White Mountains recognized total assets acquired of $155.5 million, including $7.6 million of goodwill and $2.2 million of other intangible assets, total liabilities assumed of $0.8 million and non-controlling interest of $1.5 million. As a result of the Kudu Transaction, White Mountains’s basic unit ownership of Kudu increased from 49.5% to 99.1% (42.7% to 85.4% on a fully diluted, fully converted basis), and White Mountains began consolidating Kudu as a reportable segment in its financial statements during the second quarter of 2019. White Mountains’s consolidated financial statements and its segment disclosures include Kudu’s results for the period from April 4, 2019 to December 31, 2019. For periods prior to the Kudu Transaction, White Mountains determined that Kudu was a VIE, but White Mountains was not the primary beneficiary. In those periods, White Mountains elected to use the fair value option. During the fourth quarter of 2019, White Mountains increased its total capital commitment to Kudu by $100.0 million to $350.0 million of which $129.0 million is undrawn as of December 31, 2019. Also during the fourth quarter of 2019, Kudu obtained a committed $125.0 million credit facility, of which $68.0 million was undrawn as of December 31, 2019. See Note 5 — “Debt”. Dispositions MediaAlpha On February 26, 2019, MediaAlpha completed the MediaAlpha Transaction. White Mountains received net cash proceeds of $89.3 million from the MediaAlpha Transaction. White Mountains recognized a realized gain of $67.5 million and reduced its ownership interest to 48.3% of the basic units outstanding of MediaAlpha (42.0% on a fully diluted, fully converted basis) as a result of the MediaAlpha Transaction. White Mountains’s remaining ownership interest in MediaAlpha no longer meets the criteria for a controlling ownership interest and, accordingly, White Mountains deconsolidated MediaAlpha on February 26, 2019. White Mountains’s consolidated statement of operations and comprehensive income and its segment disclosures include MediaAlpha’s results of operations for the period from January 1, 2019 through February 26, 2019. Upon deconsolidation, White Mountains’s investment in MediaAlpha met the criteria to be accounted for under the equity method or under the fair value option. See Note 15 — “Equity-Method Eligible Investments”. White Mountains elected the fair value option and the investment in MediaAlpha was initially measured at its estimated fair value of $114.7 million as of the transaction date, with the change in fair value of $114.7 million recognized as an unrealized investment gain. White Mountains recognized a total of $182.2 million of realized gain and unrealized investment gain on the MediaAlpha Transaction. OneBeacon On September 28, 2017, Intact Financial Corporation completed its acquisition of OneBeacon Insurance Group, Ltd. in an all-cash transaction for $18.10 per share (the “OneBeacon Transaction”). White Mountains received $1.3 billion in cash proceeds from the OneBeacon Transaction and recorded a net gain of $554.6 million, net of transaction costs, and other comprehensive income of $2.9 million. As a result of the OneBeacon Transaction, OneBeacon’s results have been reported as discontinued operations within White Mountains’s GAAP financial statements. See Note 20 — “Held for Sale and Discontinued Operations”. Tranzact On July 21, 2016, White Mountains completed the disposition of Tranzact Holdings, LLC (“Tranzact”) to an affiliate of Clayton, Dubilier & Rice, LLC and received net proceeds of $221.3 million. During 2017, White Mountains recorded a $3.2 million increase to the gain from sale of Tranzact in discontinued operations as a result of a change in state tax expense. Sirius Group On April 18, 2016, White Mountains completed the disposition of Sirius International Insurance Group, Ltd. (“Sirius Group”) to CM International Pte. Ltd. and CM Bermuda Limited (collectively “CMI”) for approximately $2.6 billion. During 2017, White Mountains recorded a $0.7 million reduction to the gain from sale of Sirius Group as a result of a change to the valuation of the accrued incentive compensation payable to Sirius Group employees. During 2019 and 2018, White Mountains recorded a gain (loss) of $0.8 million and $(17.3) million within net gain (loss) on sale of discontinued operations for a contingency related to the sale of Sirius Group. See Note 19 — “Commitments and Contingencies”.

Investment Securities

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Investment Securities

Investments Securities

White Mountains’s portfolio of investment securities held for general investment purposes consists of fixed maturity investments, short-term investments, common equity securities and other long-term investments, which are substantially all 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 amortized or accreted cost, which approximated fair value as of as of December 31, 2019 and 2018.

Other long-term investments consist primarily of unconsolidated entities, Kudu’s Participation Contracts, private equity funds, hedge funds, 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 and dividend income from its common equity securities and other long-term investments.

The following table presents pre-tax net investment income for 2019, 2018 and 2017:



	Year Ended December 31,
Millions	2019			2018			2017
Fixed maturity investments	$	32.4		$	35.1		$	44.9
Short-term investments	5.0			8.0			1.8
Common equity securities	13.5			15.1			10.6
Other long-term investments	30.1			3.8			1.2
Total investment income	81.0			62.0			58.5
Third-party investment expenses	(1.3		)	(3.0		)	(2.5		)
Net investment income, pre-tax	$	79.7		$	59.0		$	56.0

Net Realized and Unrealized Investment Gains (Losses)

The following table presents net realized and unrealized investment gains (losses) for 2019, 2018 and 2017:



	Year Ended December 31,
Millions	2019			2018			2017
Net realized investment gains (losses), pre-tax ⁽¹⁾	$	96.6		$	(12.9	)	$	24.1
Net unrealized investment gains (losses), pre-tax ⁽²⁾	336.6			(95.4		)	109.2
Net realized and unrealized investment gains (losses), pre-tax	433.2			(108.3		)	133.3
Income tax (expense) benefit attributable to net realized and unrealized investment gains (losses)	(87.0		)	18.2			(12.9		)
Net realized and unrealized investment gains (losses), after-tax	$	346.2		$	(90.1	)	$	120.4

⁽¹⁾ Excludes $67.5 realized gain associated with the MediaAlpha Transaction, which is recorded in a separate line item in the statement of operations titled Realized gain and unrealized investment gain from the MediaAlpha Transaction. See Note 2 — “Significant Transactions.”

⁽²⁾ Includes $114.7 unrealized investment gain associated with the MediaAlpha Transaction, which is recorded in a separate line item in the statement of operations titled Realized gain and unrealized investment gain from the MediaAlpha Transaction. See Note 2 — “Significant Transactions.”

For the years ended December 31, 2019, 2018 and 2017, all of White Mountains’s net realized and unrealized investment gains (losses) were recorded in the consolidated statements of operations. There were no investment gains (losses) recorded in other comprehensive income.

Net Realized Investment Gains (Losses)

The following tables present net realized investment gains (losses) for the years ended 2019, 2018 and 2017:



	Year Ended December 31, 2019
Millions	Net Realized Gains			Net Foreign Exchange Gains (Losses)		Total Net Realized Gains Reflected in Earnings
Fixed maturity investments	$	4.9		$	—	$	4.9
Short-term investments	.2			—		.2
Common equity securities	85.9			—		85.9
Other long-term investments ⁽¹⁾	5.6			—		5.6
Net realized investment gains, pre-tax	96.6			—		96.6
Income tax expense attributable to net realized investment gains	(10.6		)	—		(10.6		)
Net realized investment gains, after-tax	$	86.0		$	—	$	86.0



	Year Ended December 31, 2018
Millions	Net Realized (Losses) Gains			Net Foreign Exchange Gains (Losses)			Total Net Realized (Losses) Gains Reflected in Earnings
Fixed maturity investments	$	(29.8	)	$	18.2		$	(11.6	)
Short-term investments	(.8		)	—			(.8		)
Common equity securities	6.6			—			6.6
Other long-term investments	.1			(7.2		)	(7.1		)
Net realized investment (losses) gains, pre-tax	(23.9		)	11.0			(12.9		)
Income tax benefit attributable to net realized investment (losses) gains	9.1			—			9.1
Net realized investment (losses) gains, after-tax	$	(14.8	)	$	11.0		$	(3.8	)



	Year Ended December 31, 2017
Millions	Net Realized (Losses) Gains			Net Foreign Exchange Gains (Losses)			Total Net Realized Gains (Losses) Reflected in Earnings
Fixed maturity investments	$	(1.6	)	$	4.1		$	2.5
Short-term investments	(.3		)	—			(.3		)
Common equity securities	18.1			6.0			24.1
Other long-term investments	19.1			(21.3		)	(2.2		)
Net realized investment gains (losses), pre-tax	35.3			(11.2		)	24.1
Income tax expense attributable to net realized investment gains (losses)	(8.9		)	—			(8.9		)
Net realized investment gains (losses), after-tax	$	26.4		$	(11.2	)	$	15.2

White Mountains recognized gross realized investment gains of $104.0 million, $49.4 million and $61.5 million and gross realized investment losses of $7.4 million, $62.3 million and $37.4 million on sales of investment securities during 2019, 2018 and 2017

Net Unrealized Investment Gains (Losses)

The following tables present net unrealized investment gains (losses) and changes in the carrying value of investments measured at fair value for the years ended 2019, 2018 and 2017:



	Year Ended December 31, 2019
Millions	Net Unrealized Gains			Net Foreign Exchange Losses			Total Net Unrealized Gains Reflected in Earnings
Fixed maturity investments	$	38.6		$	—		$	38.6
Common equity securities	109.8			—			109.8
Other long-term investments ⁽¹⁾	188.5			(.3		)	188.2
Net unrealized investment gains (losses), pre-tax	336.9			(.3		)	336.6
Income tax expense attributable to net unrealized investment gains	(76.4		)	—			(76.4		)
Net unrealized investment gains (losses), after-tax	$	260.5		$	(.3	)	$	260.2

⁽¹⁾ Includes $114.7 unrealized investment gain associated with the MediaAlpha Transaction, which is recorded in a separate line item in the statement of operations titled Realized gain and unrealized investment gain from the MediaAlpha Transaction. See Note 2 — “Significant Transactions.”



	Year Ended December 31, 2018
Millions	Net Unrealized (Losses) Gains			Net Foreign Exchange (Losses) Gains			Total Net Unrealized (Losses) Gains Reflected in Earnings
Fixed maturity investments	$	(8.3	)	$	(14.8	)	$	(23.1	)
Common equity securities	(105.5		)	—			(105.5		)
Other long-term investments	30.2			3.0			33.2
Net unrealized investment losses, pre-tax	(83.6		)	(11.8		)	(95.4		)
Income tax benefit attributable to net unrealized investment losses	9.1			—			9.1
Net unrealized investment losses, after-tax	$	(74.5	)	$	(11.8	)	$	(86.3	)



	Year Ended December 31, 2017
Millions	Net Unrealized Gains (Losses)			Net Foreign Exchange Gains (Losses)			Total Net Unrealized Gains (Losses) Reflected in Earnings
Fixed maturity investments	$	13.8		$	12.7		$	26.5
Common equity securities	99.3			—			99.3
Other long-term investments	(15.6		)	(1.0		)	(16.6		)
Net unrealized investment gains, pre-tax	97.5			11.7			109.2
Income tax expense attributable to net unrealized investment gains	(4.0		)	—			(4.0		)
Net unrealized investment gains, after-tax	$	93.5		$	11.7		$	105.2

The following table presents total gains (losses) included in earnings attributable to net unrealized investment gains (losses) for Level 3 investments for the years ended December 31, 2019, 2018 and 2017 for investments held as of December 31, 2019, 2018 and 2017:



	Year Ended December 31,
Millions	2019		2018		2017
Other long-term investments	$	181.9	$	22.6	$	(15.4	)

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 December 31, 2019 and 2018.



	December 31, 2019
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Carrying Value
U.S. Government and agency obligations	$	231.7	$	1.0	$	(.2	)	$	232.5
Debt securities issued by corporations	454.9		12.5		(.2		)	467.2
Municipal obligations	284.7		12.5		(.1		)	297.1
Mortgage and asset-backed securities	206.6		2.7		(.3		)	209.0
Total fixed maturity investments	$	1,177.9	$	28.7	$	(.8	)	$	1,205.8



	December 31, 2018
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Carrying Value
U.S. Government and agency obligations	$	154.0	$	.1	$	(.9	)	$	153.2
Debt securities issued by corporations	519.0		1.0		(9.5		)	510.5
Municipal obligations	279.0		2.4		(1.1		)	280.3
Mortgage and asset-backed securities	136.1		.1		(2.7		)	133.5
Total fixed maturity investments	$	1,088.1	$	3.6	$	(14.2	)	$	1,077.5

The weighted average duration of White Mountains’s fixed income portfolio was approximately 2.8 years when including short-term investments and approximately 3.3 years when excluding short-term investments as of December 31, 2019.

The following table presents the cost or amortized cost and carrying value of White Mountains’s fixed maturity investments by contractual maturity as of December 31, 2019. Actual maturities could differ from contractual maturities because borrowers may have the right to call or prepay certain obligations with or without call or prepayment penalties.



	December 31, 2019
Millions	Cost or Amortized Cost		Carrying Value
Due in one year or less	$	190.0	$	190.8
Due after one year through five years	481.6		489.3
Due after five years through ten years	165.3		173.2
Due after ten years	134.4		143.5
Mortgage and asset-backed securities	206.6		209.0
Total	$	1,177.9	$	1,205.8

The following tables present the cost or amortized cost, gross unrealized investment gains (losses), net foreign currency losses, and carrying values of White Mountains’s common equity securities and other long-term investments as of December 31, 2019 and 2018:



	December 31, 2019
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Net Foreign Currency Losses			Carrying Value
Common equity securities	$	553.3	$	130.6	$	—		$	—		$	683.9
Other long-term investments	$	667.4	$	255.2	$	(64.1	)	$	(2.2	)	$	856.3



	December 31, 2018
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Net Foreign Currency Losses			Carrying Value
Common equity securities	$	904.7	$	51.0	$	(30.1	)	$	—		$	925.6
Other long-term investments	$	330.3	$	52.2	$	(54.9	)	$	(2.0	)	$	325.6

Proceeds from the sales and maturities of investments, excluding short-term investments, totaled $1.0 billion, $2.2 billion and $2.8 billion for the years ended December 31, 2019, 2018 and 2017.

Investments Held on Deposit or as Collateral

As of December 31, 2019 and 2018, investments of $319.9 million and $254.3 million, were held in trusts required to be maintained in relation to HG Global’s reinsurance agreements with BAM. White Mountains’s insurance subsidiaries are required to maintain deposits with certain insurance regulatory agencies in order to maintain their insurance licenses. The fair value of such deposits, which represent state deposits and are included within the investment portfolio, totaled $9.9 million and $6.1 million as of December 31, 2019 and 2018.

Fair Value Measurements as of December 31, 2019

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”). As of December 31, 2019 and 2018, White Mountains used quoted market prices or other observable inputs to determine fair value for approximately 71% and 87% of the investment portfolio. See Note 1 — “Basis of Presentation and Significant Accounting Policies”.

Fair Value Measurements by Level

The following tables present White Mountains’s fair value measurements for investments as of December 31, 2019 and 2018 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, foreign governments, 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 and common equity securities by industry sector because investors often reference commonly used benchmarks and their subsectors to monitor risk and performance. Accordingly, White Mountains has further disaggregated these asset classes 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 and S&P 500 indices.



	December 31, 2019
Millions	Fair Value		Level 1		Level 2		Level 3
Fixed maturity investments:
U.S. Government and agency obligations	$	232.5	$	232.5	$	—	$	—
Debt securities issued by corporations:
Financials	144.8		—		144.8		—
Industrial	59.0		—		59.0		—
Healthcare	52.6		—		52.6		—
Consumer	50.9		—		50.9		—
Energy	44.9		—		44.9		—
Technology	41.2		—		41.2		—
Communications	31.3		—		31.3		—
Utilities	25.0		—		25.0		—
Materials	17.5		—		17.5		—
Total debt securities issued by corporations	467.2		—		467.2		—

Municipal obligations	297.1		—		297.1		—
Mortgage and asset-backed securities	209.0		—		209.0		—
Total fixed maturity investments	1,205.8		232.5		973.3		—

Short-term investments ⁽¹⁾	201.2		189.4		11.8		—

Common equity securities:

Exchange traded funds ⁽²⁾	536.4		521.6		14.8		—
Other ⁽³⁾	147.5		25.9		121.5		0.1
Total common equity securities	683.9		547.5		136.3		0.1
Other long-term investments	654.0		—		—		654.0
Other long-term investments — NAV⁽⁴⁾	202.3		—		—		—
Total investments	$	2,947.2	$	969.4	$	1,121.4	$	654.1

⁽¹⁾Short-term investments are measured at amortized cost, which approximates fair value.

⁽²⁾ ETFs traded on foreign exchanges are priced using the fund’s published NAV to account for the difference in market close times and are therefore designated a Level 2 measurement.

⁽³⁾Primarily consists of two investments in unit trusts that predominantly invest in international equities and an open-end mutual fund that invests in domestic large-cap companies.

⁽⁴⁾ Consists of private equity funds, one hedge 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, 2018
Millions	Fair Value		Level 1		Level 2		Level 3
Fixed maturity investments:
U.S. Government and agency obligations	$	153.2	$	153.2	$	—	$	—

Debt securities issued by corporations:
Financials	143.4		—		143.4		—
Consumer	68.5		—		68.5		—
Technology	60.5		—		60.5		—
Energy	57.6		—		57.6		—
Healthcare	55.0		—		55.0		—
Industrial	47.6		—		47.6		—
Communications	31.8		—		31.8		—
Materials	26.3		—		26.3		—
Utilities	19.8		—		19.8		—
Total debt securities issued by corporations	510.5		—		510.5		—

Municipal obligations	280.3		—		280.3		—
Mortgage and asset-backed securities	133.5		—		133.5		—
Total fixed maturity investments	1,077.5		153.2		924.3		—

Short-term investments ⁽¹⁾	214.2		204.4		9.8		—

Common equity securities:
Exchange traded funds ⁽²⁾	675.3		617.0		58.3		—
Healthcare	14.0		14.0		—		—
Financials	13.5		13.5		—		—
Communications	12.7		12.7		—		—
Industrial	11.4		11.4		—		—
Technology	7.4		7.4		—		—
Consumer	6.2		6.2		—		—
Energy	4.1		4.1		—		—
Materials	3.1		3.1		—		—
Other ⁽³⁾	177.9		—		177.9		—
Total common equity securities	925.6		689.4		236.2		—
Other long-term investments	138.7		—		—		138.7
Other long-term investments — NAV ⁽⁴⁾	186.9		—		—		—
Total investments	$	2,542.9	$	1,047.0	$	1,170.3	$	138.7

⁽¹⁾Short-term investments are measured at amortized cost, which approximates fair value.

⁽²⁾ETFs traded on foreign exchanges are priced using the fund’s published NAV to account for the difference in market close times and are therefore designated a Level 2 measurement.

⁽³⁾Consists of two investments in unit trusts that predominantly invest in international equities.

⁽⁴⁾Consists of private equity funds, one hedge fund, White Mountains’s non-controlling equity interest in Kudu prior to consolidation and one unconsolidated entity 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 ratings of debt securities issued by corporations held in White Mountains’s investment portfolio as of December 31, 2019 and 2018:



	Fair Value at December 31,
Millions	2019		2018
AAA	$	9.5	$	8.9
AA	73.9		88.7
A	288.5		270.5
BBB	95.3		142.4
Debt securities issued by corporations ⁽¹⁾	$	467.2	$	510.5


⁽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

The following table presents the fair value of White Mountains’s mortgage and asset-backed securities as of December 31, 2019 and 2018:



	December 31, 2019						December 31, 2018
Millions	Fair Value		Level 2		Level 3		Fair Value		Level 2		Level 3
Mortgage-backed securities:
Agency:
FNMA	$	88.6	$	88.6	$	—	$	53.6	$	53.6	$	—
FHLMC	60.5		60.5		—		38.1		38.1		—
GNMA	30.8		30.8		—		23.7		23.7		—
Total agency ⁽¹⁾	179.9		179.9		—		115.4		115.4		—
Total mortgage-backed securities	179.9		179.9		—		115.4		115.4		—
Other asset-backed securities:
Vehicle receivables	15.1		15.1		—		9.2		9.2		—
Credit card receivables	14.0		14.0		—		8.9		8.9		—
Total other asset-backed securities	29.1		29.1		—		18.1		18.1		—
Total mortgage and asset-backed securities	$	209.0	$	209.0	$	—	$	133.5	$	133.5	$	—


⁽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).

Other Long-Term Investments

The following table presents the carrying values of White Mountains’s other long-term investments as of December 31, 2019 and 2018:



	Carrying Value at
Millions	December 31, 2019		December 31, 2018
Kudu’s Participation Contracts ⁽¹⁾⁽²⁾	$	266.5	$	—
MediaAlpha ⁽¹⁾⁽³⁾	180.0		—
PassportCard/DavidShield ⁽¹⁾	90.0		75.0
Elementum ⁽¹⁾	55.1		—
Other unconsolidated entities ⁽¹⁾⁽⁴⁾	31.2		60.0
Kudu ⁽⁵⁾	—		30.7
Total unconsolidated entities ⁽¹⁾	622.8		165.7
Private equity funds and hedge funds	161.1		146.1
Insurance-linked securities funds	41.2		—
Other	31.2		13.8
Total other long-term investments	$	856.3	$	325.6

⁽¹⁾See Fair Value Measurements by Level table.

⁽²⁾ Includes Kudu’s non-controlling equity interests in the form of revenue and earnings participation contracts. As of December 31, 2019, White Mountains consolidates Kudu. See Note 2 — “Significant Transactions”.

⁽³⁾ The MediaAlpha Transaction was completed on February 26, 2019. See Note 2 — “Significant Transactions”.

⁽⁴⁾Includes White Mountains’s non-controlling equity interests in certain private common equity securities, limited liability companies and convertible preferred securities.

⁽⁵⁾ Includes White Mountains’s non-controlling equity interest in Kudu prior to consolidation. See Note 2 — “Significant Transactions”.

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 NAV of the funds. As of December 31, 2019, White Mountains held investments in 12 private equity funds and one hedge fund. The largest investment in a single fund was $54.6 million as of December 31, 2019 and $54.3 million as of December 31, 2018.

The following table presents investments and unfunded commitments in private equity funds and hedge funds by investment objective and sector as of December 31, 2019 and 2018:



	December 31, 2019				December 31, 2018
Millions	Fair Value		Unfunded Commitments		Fair Value		Unfunded Commitments

Private equity funds
Manufacturing/Industrial	$	57.7	$	4.1	$	42.9	$	10.5
Aerospace/Defense/Government	33.8		23.3		27.6		34.9
Financial services	15.0		22.8		8.3		13.6
Direct lending	—		—		13.0		17.7
Total private equity funds	106.5		50.2		91.8		76.7

Hedge funds
Long/short banks and financial	54.6		—		54.3		—
Total hedge funds	54.6		—		54.3		—
Total private equity funds and hedge funds included in other long-term investments	$	161.1	$	50.2	$	146.1	$	76.7

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 December 31, 2019:



Millions	1 – 3 years		3 – 5 years		5 – 10 years		>10 years		Total
Private equity funds — expected lock-up period remaining	$	4.8	$	51.9	$	40.2	$	9.6	$	106.5

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 December 31, 2019 and 2018, 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. As of December 31, 2019, White Mountains held one active hedge fund with a fair value of $54.6 million. The hedge fund is subject to a semi-annual restriction on redemptions and an advance notice period requirement of 45 days. On February 13, 2020, White Mountains submitted a notice to redeem its full interest in the hedge fund as of March 31, 2020 and expects to receive the proceeds, subject to any audit holdback, in the second quarter of 2020.

Insurance-Linked Securities Funds

White Mountains’s other long-term investments include ILS funds. The fair value of these investments are generally estimated using the NAV of the funds. As of December 31, 2019, White Mountains held investments in three ILS funds with a fair value of $41.2 million. Also as of December 31, 2019, White Mountains had made an in-transit cash contribution of $4.8 million, which was recorded within other assets, in support of its remaining $10.0 million commitment to invest $50.0 million in ILS funds managed by Elementum. The cash was invested in the ILS fund on January 1, 2020 and will be recorded within other long-term investments in the first quarter of 2020

Investments in ILS funds are generally subject to restrictions, including lock-up periods where no redemptions or withdrawals are allowed, 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 an ILS fund less certain due to the potential for loss development. In such circumstances, the impacted investments may be subject to additional lock-up provisions.

As of December 31, 2019, White Mountains holds one ILS fund subject to a lock-up period that expires on June 1, 2020. White Mountains’s ILS funds are subject to monthly and annual restrictions on redemptions and advance redemption notice period requirements that range between 30 and 90 days. 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.

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 December 31, 2019 and 2018 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 years ended December 31, 2019 and 2018:



							Level 3 Investments					Other Long-term Investments Measured at NAV ⁽³⁾
Millions	Level 1 Investments			Level 2 Investments			Common Equity Securities		Other Long-term Investments⁽²⁾			Other Long-term Investments Measured at NAV ⁽³⁾			Total
Balance at December 31, 2018	$	842.6		$	1,160.5		$	—	$	138.7		$	186.9		$	2,328.7		⁽¹⁾
Net realized and unrealized gains	163.0			76.1			—		181.2			12.7			433.0			⁽²⁾⁴⁾
Amortization/accretion	.2			(1.8		)	—		—			—			(1.6		)
Purchases	165.3			404.5			.1		185.4			110.8			866.1
Sales	(391.1		)	(529.7		)	—		—			(29.5		)	(950.3		)
Effect of Kudu Transaction	—			—			—		141.8			(71.7		)	70.1
Transfers in	—			—			—		10.9			4.0			14.9
Transfers out	—			—			—		(4.0		)	(10.9		)	(14.9		)
Balance at December 31, 2019	$	780.0		$	1,109.6		$	.1	$	654.0		$	202.3		$	2,746.0		⁽¹⁾

⁽¹⁾Excludes carrying value of $201.2 and $214.2 as of December 31, 2019 and 2018 classified as short-term investments.


⁽²⁾	Includes $114.7 unrealized investment gain associated with the MediaAlpha Transaction, which is recorded in a separate line item in the statement of operations titled Realized gain and unrealized investment gain from the MediaAlpha Transaction. See Note 2 — “Significant Transactions”.

⁽³⁾Includes private equity funds, hedge funds, ILS funds and unconsolidated entities 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”.

⁽⁴⁾ Excludes realized and unrealized losses associated with short-term investments of $0.2 for the year ended December 31, 2019.



							Level 3 Investments		Other Long-term Investments Measured at NAV ⁽³⁾
Millions	Level 1 Investments			Level 2 Investments			Other Long- term Investments		Other Long-term Investments Measured at NAV ⁽³⁾			Total
Balance at December 31, 2017	$	890.4		$	2,105.4		$	77.2	$	135.3		$	3,208.3		⁽¹⁾⁽²⁾
Net realized and unrealized (losses) gains	(64.9		)	(64.4		)	16.2		13.3			(99.8		)	⁽⁴⁾
Amortization/accretion	.2			(2.7		)	—		—			(2.5		)
Purchases	514.7			783.8			45.3		50.5			1,394.3
Sales	(497.8		)	(1,661.6		)	—		(12.2		)	(2,171.6		)
Transfers in	—			—			—		—			—
Transfers out	—			—			—		—			—
Balance at December 31, 2018	$	842.6		$	1,160.5		$	138.7	$	186.9		$	2,328.7		⁽²⁾

⁽¹⁾Excludes carrying value of $(3.7) as of December 31, 2017 associated with foreign currency forward contracts.

⁽²⁾Excludes carrying value of $214.2 and $176.1 as of December 31, 2018 and 2017 classified as short-term investments.


⁽³⁾	Includes private equity funds, hedge funds and unconsolidated entities 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”.

⁽⁴⁾Excludes realized and unrealized losses associated with foreign currency forward contracts, foreign currency on cash and open trades and short-term investments of $3.5, $4.2 and $0.8 for the year ended December 31, 2018.

Fair Value Measurements — Transfers Between Levels - For Years Ended December 31, 2019 and 2018

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 2019 and 2018, 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.

Significant Unobservable Inputs

The following tables present significant unobservable inputs used in estimating the fair value of other long-term investments, other than private equity funds, hedge funds and ILS funds, classified within Level 3 as of December 31, 2019 and 2018. The fair value of investments in private equity funds, hedge funds and ILS funds are generally estimated using the NAV of the funds.



$ in Millions	December 31, 2019
Description	Valuation Technique(s)	Fair Value ⁽¹⁾	Unobservable Inputs
			Discount Rate ⁽²⁾	Terminal Cash Flow Exit Multiple (x) or Terminal Revenue Growth Rate (%) ⁽²⁾
Kudu’s Participation Contracts	Discounted cash flow	$266.5	15% - 22%	6x - 12x
MediaAlpha	Discounted cash flow	$180.0	15%	4%
PassportCard/DavidShield	Discounted cash flow	$90.0	22%	4%
Elementum Holdings, L.P.	Discounted cash flow	$55.1	20%	4%
Private debt instruments	Discounted cash flow	$23.7	4% - 9%	N/A
All other	Discounted cash flow	$23.7	25% - 32%	4%

Compare.com	Estimated net realizable value	$2.5	Net asset value:	$2.5

⁽¹⁾Includes the net unrealized investment gains (losses) associated with foreign currency; foreign currency effects based on observable inputs.

⁽²⁾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.



$ in Millions	December 31, 2018
Description	Valuation Technique(s)	Fair Value ⁽¹⁾	Unobservable Inputs
			Discount Rate ⁽²⁾	Terminal Revenue Exit Multiple (x) ⁽²⁾
PassportCard/DavidShield	Discounted cash flow	$75.0	18%	1x
Compare.com	Discounted cash flow	$16.9	22%	3x
Private debt instrument	Discounted cash flow	$10.0	9%	N/A
All other	Discounted cash flow	$30.0	23%	2x - 4x

Galvanic Applied Sciences	Multiple of EBITDA	$3.1	EBITDA multiple:	6x

⁽¹⁾Includes the net unrealized investment gains (losses) associated with foreign currency; foreign currency effects based on observable inputs.

⁽²⁾Increases (decreases) to the discount rates in isolation would result in lower (higher) fair value measurements, while increases (decreases) to the terminal revenue exit multiples in isolation would result in higher (lower) fair value measurements.

Goodwill and Other Intangible Assets

12 Months Ended

Dec. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Other Intangible Assets

White Mountains accounts for business combinations 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 estimated acquisition date fair values, 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 economic lives, acquisition date fair values, accumulated amortization and net carrying values for other intangible assets and goodwill, by company as of December 31, 2019 and 2018:



$ in Millions	Weighted Average Economic Life (in years)	December 31, 2019									December 31, 2018
$ in Millions	Weighted Average Economic Life (in years)	Acquisition Date Fair Value		Accumulated Amortization		Impairments		Net Carrying Value			Acquisition Date Fair Value		Accumulated Amortization		Net Carrying Value
Goodwill:
NSM ⁽¹⁾⁽²⁾	N/A	$	381.6	$	—	$	—	$	381.6		$	354.3	$	—	$	354.3
Kudu	N/A	7.6		—		—		7.6			—		—		—
MediaAlpha	N/A	—		—		—		—			18.3		—		18.3
Other Operations ⁽³⁾	N/A	13.1		—		7.6		5.5			7.3		—		7.3
Total goodwill		402.3		—		7.6		394.7			379.9		—		379.9
Other intangible assets:
NSM ⁽¹⁾⁽²⁾
Customer relationships	9	121.7		19.8		1.4		100.5			85.3		6.0		79.3
Trade names	19	61.9		5.3		.4		56.2			51.2		1.8		49.4
Information technology platform	5	3.9		1.4		.6		1.9			3.7		.5		3.2
Renewal rights	12	82.5		.7		—		81.8			—		—		—
Other	3	1.7		.7		—		1.0			—		—		—
Subtotal		271.7		27.9		2.4		241.4			140.2		8.3		131.9
Kudu
Trade names	7	2.2		.2		—		2.0			—		—		—
MediaAlpha
Customer relationships	9	—		—		—		—			26.8		4.9		21.9
Information technology platform	5	—		—		—		—			33.3		30.9		2.4
Other	3	—		—		—		—			9.8		9.0		.8
Subtotal		—		—		—		—			69.9		44.8		25.1
Other Operations
Trade names	10	1.7		.5		.2		1.0			.6		.2		.4
Customer Relationships	11	7.2		.4		—		6.8			—		—		—
Information technology platform	5	.5		.3		.2		—			.5		.3		.2
Insurance licenses	N/A	8.6		—		—		8.6			—		—		—
Other	5	.2		—		—		.2			—		—		—
Subtotal		18.2		1.2		.4		16.6			1.1		.5		.6
Total other intangible assets		292.1		29.3		2.8		260.0			211.2		53.6		157.6
Total goodwill and other intangible assets		$	694.4	$	29.3	$	10.4	654.7			$	591.1	$	53.6	537.5
Goodwill and other intangible assets attributed to non-controlling interests								(23.4		)					(40.6		)
Goodwill and other intangible assets included in White Mountains’s common shareholders’ equity								$	631.3						$	496.9

⁽¹⁾As of December 31, 2019, NSM’s goodwill and intangible assets includes $1.4 and $0.7 of the effect of foreign currency translation. As of December 31, 2018, NSM’s goodwill and intangible assets includes $(2.2) and $(0.7) of the effect of foreign currency translation.

⁽²⁾The relative fair values of goodwill and other intangible assets recognized in connection with the acquisition of KBK had not yet been determined at December 31, 2018. The attribution of acquisition date fair value estimates between goodwill and other intangible assetsfor KBK was completed during 2019.

⁽³⁾As of December 31, 2019 and 2018, Other Operations’ goodwill includes $0.0 and $(0.3) 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 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 during 2019 and 2018:



$ in Millions
Acquisition of Subsidiary/ Asset	Goodwill and Other Intangible Assets⁽¹⁾		Acquisition Date
NSM	$	383.0	May 11, 2018
Fresh Insurance	54.6		May 18, 2018
KBK⁽³⁾	65.3		December 3, 2018
Embrace⁽²⁾	67.6		April 1, 2019
Renewal Rights ⁽³⁾	82.5		June 28, 2019
Total NSM segment	$	653.0
Kudu Transaction	$	9.8	April 4, 2019
Other Operations	$	22.6	Various

⁽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.

⁽²⁾Excludes $3.4 of software classified within other assets.

⁽³⁾NSM’s purchase of the Renewal Rights from AIG was an asset acquisition. NSM’s purchase of KBK was accounted for as a business combination but did not include acquisition of the legal entity.

On an annual basis beginning no later than the interim period included in the one-year anniversary of an acquisition, White Mountains evaluates goodwill for potential impairment. During 2019, White Mountains recognized impairments of goodwill of $7.6 million and other intangible assets of $2.8 million, of which $7.6 million of goodwill and $0.4 million of other intangible assets related to Other Operations and $2.4 million of other intangible assets related to Fresh Insurance. There were no impairments during 2018 or 2017.

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



	December 31,
	2019									2018
Millions	Goodwill			Other Intangible Assets			Total Goodwill and Other Intangible Assets			Goodwill			Other Intangible Assets			Total Goodwill and Other Intangible Assets
Beginning balance	$	379.9		$	157.6		$	537.5		$	25.9		$	36.2		$	62.1
Acquisitions of businesses ⁽¹⁾	64.8			34.6			99.4			356.5			140.9			497.4
Acquisition of collector car renewal rights	—			82.5			82.5			—			—			—
Dispositions of businesses ⁽²⁾	(18.3		)	(23.5		)	(41.8		)	—			—			—
Attribution of acquisition date fair value estimates between goodwill and other intangible assets⁽³⁾	(26.8		)	26.8			—			—			—			—
Impairments ⁽⁴⁾	(7.6		)	(2.8		)	(10.4		)	—			—			—
Measurement period adjustments⁽⁵⁾	.9			5.9			6.8			—			—			—
Foreign currency translation	1.8			.7			2.5			(2.5		)	(.7		)	(3.2		)
Amortization	—			(21.8		)	(21.8		)	—			(18.8		)	(18.8		)
Ending balance	$	394.7		$	260.0		$	654.7		$	379.9		$	157.6		$	537.5

⁽¹⁾During 2019, amounts include acquisitions related to Kudu, Other Operations and Embrace. During 2018, amounts include acquisitions related to NSM, Fresh Insurance and KBK. See Note 2 — “Significant Transactions”.

⁽²⁾Dispositions relate to the MediaAlpha Transaction. See Note 2 — “Significant Transactions”.


⁽³⁾	The determination of the relative fair values of goodwill and other intangible assets recognized in connection with the acquisition of KBK was completed in 2019. The attribution is net of a $5.9 measurement period adjustment for contingent consideration.

⁽⁴⁾ Impairments of $7.6 and $0.4 of goodwill and other intangible assets relate to Other Operations and $2.4 of impairments to other intangible relate to Fresh Insurance.


⁽⁵⁾	Measurement period adjustments relate to updated information about acquisition date fair values of assets acquired and liabilities assumed.

Amortization expense was $21.8 million, $18.8 million and $10.7 million for the years ended December 31, 2019, 2018 and 2017.

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



Millions	Amortization Expense
2020	$	23.9
2021	30.5
2022	29.7
2023	28.4
2024 and years after	138.9
Total ⁽¹⁾	$	251.4

⁽¹⁾Excludes indefinite-lived intangible assets of $8.6.

Debt

12 Months Ended

Dec. 31, 2019

Debt Disclosure [Abstract]

Debt

The following table presents White Mountains’s debt outstanding as of December 31, 2019 and 2018:



	December 31,			Effective	December 31,			Effective
$ in Millions	2019			Rate ⁽¹⁾	2018			Rate ⁽¹⁾
NSM Bank Facility	$	221.3		7.5%	$	180.4		7.4%
Unamortized issuance cost	(3.9		)		(3.8		)
NSM Bank Facility, carrying value	217.4				176.6
Other NSM debt	1.8			3.0%	1.9			2.2%
Kudu Bank Facility	57.0			8.3%	—
Unamortized issuance cost	(3.4		)		—
Kudu Bank Facility, carrying value	53.6				—
MediaAlpha Bank Facility	—				14.3			7.1%
Unamortized issuance cost	—				(.1		)
MediaAlpha Bank Facility, carrying value	—				14.2
Other Operations debt	11.1			8.3%	—
Unamortized issuance cost	(.4		)		—
Other Operations debt, carrying value	10.7				—
Total debt	$	283.5			$	192.7

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

The following table presents a schedule of contractual repayments of White Mountains’s debt as of December 31, 2019:



Millions	December 31, 2019
Due in one year or less	$	2.8
Due in two to three years	7.0
Due in four to five years	226.2
Due after five years	55.2
Total	$	291.2

WTM Bank Facility

White Mountains had a revolving credit facility with a syndicate of lenders administered by Wells Fargo Bank, N.A., which had a total commitment of $425.0 million (the “WTM Bank Facility”). White Mountains terminated the WTM Bank Facility on May 8, 2018. White Mountains recorded $0.3 million and $0.6 million of interest expense on the WTM Bank Facility for the years ended December 31, 2018 and 2017.

NSM Bank Facility

On May 11, 2018, NSM entered into a secured credit facility (the “NSM Bank Facility”) with Ares Capital Corporation in order to refinance NSM’s existing debt and to fund the acquisitions of subsidiaries. The NSM Bank Facility has a total commitment of $234.0 million, which is comprised of term loans of $224.0 million and a revolving credit loan of $10.0 million. The term loans under the NSM Bank Facility mature on May 11, 2024, and the revolving loan under the NSM Bank Facility matures on May 11, 2023. During 2019, NSM repaid $2.0 million on the term loans and $6.5 million on the revolving credit loan. During 2019, NSM borrowed $42.9 million of incremental term loans, which included $20.4 million and $22.5 million for the funding of the acquisitions of Embrace and the Renewal Rights from AIG, respectively, and repaid $2 million of the term loans. Additionally, during 2019, NSM borrowed $6.5 million on the revolving credit loans under the NSM Bank Facility. During the period from May 11, 2018 through December 31, 2018, NSM repaid $0.8 million on the term loans and $2.0 million on the revolving credit loan. As of December 31, 2019, the term loans had an outstanding balance of $221.3 million and the revolving credit loans were undrawn.

Interest on the NSM Bank Facility accrues at a floating interest rate equal to the three-month LIBOR or the Prime Rate, as published by the Wall Street Journal plus, in each case, an applicable margin. The margin over LIBOR may vary between 4.25% and 4.75%, and the margin over the Prime Rate may vary between 3.25% and 3.75%, in each case, depending on the consolidated total leverage ratio of the borrower.

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 variable rate term loans. 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 then-current LIBOR. As of December 31, 2019, the variable rate received by NSM under the swap agreement was 1.71%. As of December 31, 2019, the interest rate, including the effect of the swap, for the outstanding term loans of $148.7 million that are hedged by the swap was 7.47%. The effective interest on the outstanding term loans of $72.6 million that are unhedged was 6.21%. The effective interest rate on the total outstanding term loans under the NSM Bank Facility of $221.3 million was 7.06%, excluding the effect of debt issuance costs. See Note 7 - “Derivatives”.

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.-based operations. As of December 31, 2019, the secured term loan had an outstanding balance of $1.8 million and a maturity date of May 11, 2024.

Kudu Bank Facility

On December 23, 2019, Kudu entered into a secured credit facility (the “Kudu Bank Facility”) with Monroe Capital Management Advisors, LLC to provide funding for distributions to unitholders and fund new investments and related transaction expenses. The Kudu Bank Facility has a maximum borrowing capacity of $125.0 million, which is comprised of a revolving credit loan of $5.0 million, an initial term loan of $57.0 million and a delayed-draw term loan of $63.0 million. The term loans and revolving credit loans, under the Kudu Bank Facility, mature in 2025. During 2019, Kudu borrowed $57.0 million in term loans under the Kudu Bank Facility and made no repayments. As of December 31, 2019, the term loans had an outstanding balance of $57.0 million and the revolving credit loan was undrawn.

Interest on the Kudu Bank Facility accrues at a floating interest rate equal to one-month LIBOR plus 1.0% or the Prime Rate plus, in each case, an applicable margin. The margin over LIBOR may vary between 5.50% and 6.25% and the margin over the Base Rate may vary between 4.50% and 5.25%, depending on the consolidated total leverage ratio of the borrower.

The Kudu 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.

MediaAlpha Bank Facility

On May 12, 2017, MediaAlpha entered into a secured credit facility (the “MediaAlpha Bank Facility”) with Western Alliance Bank, which had a total commitment of $20.0 million and had a maturity date of May 12, 2020. The MediaAlpha Bank Facility consists of a $18.4 million term loan facility, which had an outstanding balance of $14.3 million as of December 31, 2018, and a revolving loan facility for $10.0 million, which was undrawn as of December 31, 2018. The MediaAlpha Bank Facility replaced MediaAlpha’s previous credit facility with Opus Bank, which had a total commitment of $20.0 million.

During 2018, under the MediaAlpha Bank Facility, MediaAlpha repaid $3.6 million on the term loan and borrowed $3.0 million and repaid $9.0 million on the revolving loan. In 2017, under the MediaAlpha Bank Facility, MediaAlpha borrowed $20.0 million and repaid $2.1 million on the term loan and borrowed $6.0 million on the revolving loan. During 2017, under the previous MediaAlpha Bank Facility, MediaAlpha repaid $12.9 million.

MediaAlpha recorded $1.2 million and $1.0 million of interest expense on the MediaAlpha Bank Facility for the years ended December 31, 2018 and 2017.

Other Operations Debt

As of December 31, 2019, debt in White Mountains’s Other Operations segment consisted of a secured credit facility that had 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.

Compliance

As of December 31, 2019, White Mountains was in compliance with all of the covenants under all of its debt facilities.

Interest

Total interest expense incurred by White Mountains for its indebtedness was $17.6 million, $9.5 million and $2.3 million for the periods ended December 31, 2019, 2018 and 2017. Total interest paid by White Mountains for its indebtedness was $16.3 million, $8.8 million, and $1.4 million for the periods ended December 31, 2019, 2018 and 2017.

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Taxes

The Company and its Bermuda domiciled subsidiaries are not subject to Bermuda income tax under current Bermuda law. In the event there is a change in the current law such that taxes are imposed, the Company and its Bermuda domiciled subsidiaries would be exempt from such tax until March 31, 2035, pursuant to the Bermuda Exempted Undertakings Tax Protection Act of 1966. The Company has subsidiaries and branches that operate in various other jurisdictions around the world and 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 Barbados, Ireland, Israel, Luxembourg, the United Kingdom and the United States.

The following table presents the total income tax (expense) benefit for the years ended December 31, 2019, 2018 and 2017:



	Year Ended December 31,
Millions	2019			2018			2017
Current income tax benefit (expense):
U.S. federal	$	.9		$	(.1	)	$	(.3	)
State	(3.7		)	(1.4		)	(1.3		)
Non-U.S.	(1.7		)	(2.9		)	(2.0		)
Total current income tax (expense) benefit	(4.5		)	(4.4		)	(3.6		)
Deferred income tax (expense) benefit:
U.S. federal	(14.9		)	8.3			11.4
State	(10.4		)	—			—
Non-U.S.	.5			.1			—
Total deferred income tax (expense) benefit	(24.8		)	8.4			11.4
Total income tax (expense) benefit	$	(29.3	)	$	4.0		$	7.8

Effective Rate Reconciliation

The following table presents a reconciliation of taxes calculated for 2019 and 2018 using the 21% U.S. federal statutory rate and for 2017 using the 35% U.S. federal statutory rate (the tax rate at which the majority of White Mountains’s worldwide operations are taxed) to the income tax (expense) benefit on pre-tax income (loss):



	Year Ended December 31,
Millions	2019			2018			2017
Tax (expense) benefit at the U.S. statutory rate	$	(85.1	)	$	37.4		$	(2.7	)
Differences in taxes resulting from:
Change in valuation allowance	63.6			(31.0		)	42.6
Non-U.S. earnings, net of foreign taxes	27.1			(2.9		)	21.5
State taxes	(17.5		)	4.0			.6
Tax rate changes	(5.7		)	1.7			(44.3		)
Member’s surplus contributions	(3.6		)	(2.6		)	(3.0		)
Withholding tax	(1.6		)	(2.7		)	(2.0		)
Tax exempt interest and dividends	1.1			.6			.5
Tax reserve adjustments	(.7		)	(.8		)	(.3		)
Officer compensation	—			—			(4.1		)
Other, net	(6.9		)	.3			(1.0		)
Total income tax (expense) benefit on pre-tax income (loss)	$	(29.3	)	$	4.0		$	7.8

The non-U.S. component of pre-tax income (loss) was $100.4 million, $(30.1) million and $71.3 million for the years ended December 31, 2019, 2018 and 2017.

Tax Payments and Receipts

Net income tax payments (primarily to the United States) totaled $3.7 million, $3.5 million, and $2.0 million for the years ended December 31, 2019, 2018 and 2017.

Deferred Tax Assets and Liabilities

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

The following table presents an outline of the significant components of White Mountains’s U.S. federal, state and non-U.S. deferred tax assets and liabilities:



	December 31,
Millions	2019			2018
Deferred tax assets related to:
U.S. federal and state net operating and capital loss carryforwards	$	92.3		$	95.5
Non-U.S. net operating loss carryforwards	41.7			36.6
Incentive compensation	15.0			14.1
Investment basis difference	—			11.1
Net unrealized investment losses	—			9.5
Accrued interest	5.1			—
Deferred acquisition costs	4.3			3.5
Tax credit carryforwards	4.2			4.2
Other items	3.4			5.8
Total gross deferred tax assets	166.0			180.3
Less: valuation allowances	77.9			139.9
Total net deferred tax assets	88.1			40.4
Deferred tax liabilities related to:
Net unrealized investment gains	66.3			—
Member’s surplus contributions	43.2			32.8
Investment basis difference	6.6			—
Other items	4.6			5.4
Total deferred tax liabilities	120.7			38.2
Net deferred tax (liability) asset	$	(32.6	)	$	2.2

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

Tax Cuts and Jobs Act of 2017

On December 22, 2017, the Tax Cuts and Jobs Act of 2017 (the “TCJA”) was enacted. Substantially all of the provisions of the TCJA are effective for taxable years beginning after December 31, 2017. The TCJA includes significant changes to the Internal Revenue Code of 1986 (the “Code”), including amendments which significantly change the taxation of individuals and business entities. The more significant changes in the TCJA that impact White Mountains are reductions in the corporate federal income tax rate from 35% to 21% and several technical provisions including, among others, limiting the utilization of net operating losses arising after December 31, 2017 to 80% of taxable income with an indefinite carryforward.

The TCJA did not have a material impact on White Mountains’s financial statements in 2017 due to a full valuation allowance previously having been recorded against its U.S. deferred tax assets. Under U.S. GAAP, specifically ASC Topic 740, Income Taxes, the tax effects of changes in tax laws must be recognized in the period in which the law is enacted, or December 22, 2017 for the TCJA. ASC 740 also requires deferred tax assets and liabilities to be measured at the enacted tax rate expected to apply when temporary differences are to be realized or settled. Thus, at the date of enactment, White Mountains’s deferred taxes were re-measured based upon the new tax rate. For White Mountains, a change in deferred taxes was recorded as an adjustment to our deferred tax provision for $43.1 million of federal tax expense, which was offset by a change in the valuation allowance.

The staff of the U.S. Securities and Exchange Commission has recognized the complexity of reflecting the impacts of the TCJA and on December 22, 2017 issued guidance in Staff Accounting Bulletin 118 (“SAB 118”) which clarifies accounting for income taxes under ASC 740 if information is not yet available or complete and provides for up to a one-year period in which to complete the required analyses and accounting (the measurement period). SAB 118 describes three scenarios associated with a company’s status of accounting for income tax reform: (1) a company is complete with its accounting for certain effects of tax reform, (2) a company is able to determine a reasonable estimate for certain effects of tax reform and records that estimate as a provisional amount, or (3) a company is not able to determine a reasonable estimate and therefore continues to apply ASC 740, based on the provisions of the tax laws that were in effect immediately prior to the TCJA being enacted. White Mountains completed its accounting for the effects of the TCJA, which have been reflected in the December 31, 2017 financial statements.

Valuation Allowance

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

Of the $77.9 million valuation allowance as of December 31, 2019, $34.9 million related to deferred tax assets on net operating losses in U.S. subsidiaries and other federal and state deferred tax benefits, $22.6 million related to deferred tax assets on net operating losses and net investment unrealized gains and losses in Luxembourg subsidiaries, $17.3 million related to net operating losses and other deferred tax benefits in Israeli subsidiaries and $3.1 million related to net operating losses and other deferred tax benefits in U.K. subsidiaries. Of the $139.9 million valuation allowance as of December 31, 2018, $102.6 million related to deferred tax assets on net operating losses in U.S. subsidiaries and other federal and state deferred tax benefits, $21.1 million related to deferred tax assets on net operating losses and net investment unrealized gains and losses in Luxembourg subsidiaries, $14.5 million related to net operating losses in Israeli subsidiaries and $1.7 million related to net operating losses and other deferred tax benefits in U.K. subsidiaries.

United States

During 2019 and 2018, White Mountains recorded income tax (benefit) expense of $(63.2) million to release and $22.7 million to establish a valuation allowance against deferred tax assets of Guilford Holdings, Inc. and subsidiaries (“Guilford”), which includes Kudu, White Mountains’s investment in MediaAlpha, WM Capital, WM Advisors and certain other entities and investments that are included in the Other Operations segment. During 2019, Guilford was in a net deferred tax liability position due to unrealized gains. Guilford recorded a tax benefit due to a release in the full valuation allowance from 2018. During 2018, Guilford had a full valuation allowance recorded against its deferred tax assets, as White Mountains management was unsure it would generate sufficient taxable income to utilize the deferred tax assets.

During 2019 and 2018, White Mountains recorded income tax (benefit) expense of $(4.5) million to release and $1.5 million to establish a valuation allowance against deferred tax assets of BAM. During 2019 and 2018, BAM had income in equity that was available to offset its loss from continuing operations. As a result, BAM recorded an income tax benefit of $10.5 million and $8.7 million, in continuing operations, with an offsetting tax expense in paid-in surplus. Also, during 2019 and 2018, BAM continued to have a full valuation allowance recorded against its deferred tax assets, as White Mountains management is unsure it will generate sufficient taxable income to utilize the deferred tax assets.

During 2019 and 2018, White Mountains recorded income tax expense of $0.1 million and $2.8 million to establish a valuation allowance against a deferred tax asset related to foreign tax credits at White Mountains Catskill Holdings, Inc., as White Mountains management is unsure it will generate sufficient taxable income to utilize the deferred tax asset.

Non-U.S. Jurisdictions

During 2019 and 2018, White Mountains recorded income tax expense of $1.1 million and $1.2 million to establish a valuation allowance against most of the deferred tax assets which primarily relate to losses on the write-down of foreign subsidiaries and the unrealized losses on investments held in Luxembourg-domiciled subsidiaries.

During 2019 and 2018, White Mountains recorded income tax expense of $1.6 million and $2.1 million to establish a full valuation allowance against deferred tax assets at certain Israel-domiciled subsidiaries, as White Mountains management does not currently anticipate sufficient taxable income to utilize the deferred tax assets.

During 2019 and 2018, White Mountains recorded income tax expense of $1.3 million and $0.7 million to establish a full valuation allowance against deferred tax assets at certain U.K.-domiciled subsidiaries, as White Mountains management does not currently anticipate sufficient taxable income to utilize the deferred tax assets.

Net Operating Loss and Capital Loss Carryforwards

The following table presents net operating loss and capital loss carryforwards as of December 31, 2019, the expiration dates and the deferred tax assets thereon:



	December 31, 2019
Millions	United States			Luxembourg			United Kingdom			Israel			Total
2019-2023	$	.1		$	—		$	—		$	—		$	.1
2024-2028	—			—			—			—			—
2029-2038	302.6			58.0			—			—			360.6
No expiration date	117.4			28.5			18.7			73.6			238.2
Total	$	420.1		$	86.5		$	18.7		$	73.6		$	598.9
Gross deferred tax asset	$	88.0		$	21.6		$	3.2		$	16.9		$	129.7
Valuation allowance	(63.5		)	(21.5		)	(3.0		)	(16.9		)	(104.9		)
Net deferred tax asset	$	24.5		$	.1		$	.2		$	—		$	24.8

As of December 31, 2019, there are U.S. foreign tax credit carryforwards available of $3.8 million, which begin to expire in 2028. As of December 31, 2019, there are U.S. alternative minimum tax credit carryforwards of $0.4 million, which are refundable under provisions of the TCJA.

Uncertain Tax Positions

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

The following table presents a reconciliation of the beginning and ending amount of unrecognized tax benefits from 2017 to 2019:



Millions	Permanent Differences ⁽¹⁾		Temporary Differences ⁽²⁾		Interest and Penalties ⁽³⁾		Total
Balance at December 31, 2016	$	—	$	—	$	—	$	—
Changes in prior year tax positions	.1		—		—		.1
Tax positions taken during the current year	.2		—		—		.2
Balance at December 31, 2017	.3		—		—		.3
Changes in prior year tax positions	.8		—		—		.8
Balance at December 31, 2018	1.1		—		—		1.1
Tax positions taken during the current year	1.3		—		—		1.3
Balance at December 31, 2019	$	2.4	$	—	$	—	$	2.4


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


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


⁽³⁾	Net of tax benefit.

White Mountains classifies all interest and penalties on unrecognized tax benefits as part of income tax expense. During the years ended December 31, 2019, 2018 and 2017, White Mountains did not recognize any net interest (income) expense. There was no accrued interest as of December 31, 2019 and 2018.

Tax Examinations

With few exceptions, White Mountains is no longer subject to U.S. federal, state, or non-U.S. income tax examinations by tax authorities for years before 2013.

Derivatives	12 Months Ended
Derivatives	Dec. 31, 2019
Derivative [Line Items]
Derivatives	Derivatives
Interest Rate Swap
Derivative [Line Items]
Derivatives	NSM Interest Rate Swap On May 11, 2018, NSM entered into the NSM Bank Facility. Interest on the NSM Bank Facility accrues at a floating interest rate equal to the three-month LIBOR or the Prime Rate, as published by the Wall Street Journal plus, in each case, an applicable margin. The margin over LIBOR may vary between 4.25% and 4.75%, and the margin over the Prime Rate may vary between 3.25% and 3.75%, in each case, depending on the consolidated total leverage ratio of the borrower. 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 variable rate term loans. 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 LIBOR. As of December 31, 2019, the variable rate received by NSM under the swap agreement was 1.71%. 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 December 31, 2019, the interest rate, including the effect of the swap, for the outstanding term loans of $148.7 million that are hedged by the swap was 7.47%, excluding the effect of debt issuance costs. 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 will evaluate the effectiveness of the hedging relationship on an ongoing basis. For the twelve months ending December 31, 2019, NSM recognized net interest expense of $1.1 million for the periodic net settlement payments on the swap. For the period from May 11, 2018 through December 31, 2018, NSM recognized net interest expense of $0.7 million for the periodic net settlement payments on the swap. As of December 31, 2019 and 2018, the estimated fair value of the swap and the accrual of the periodic net settlement payments recorded in other liabilities was $6.6 million and $2.7 million. There was no ineffectiveness in the hedge for the twelve months ending December 31, 2019 and for the period from May 11, 2018 through December 31, 2018. For the twelve months ending December 31, 2019, the $(3.9) million change in the fair value is included within accumulated other comprehensive income (loss). For the period from May 11, 2018 through December 31, 2018, the $(2.7) million change in the fair value of the swap is included within accumulated other comprehensive income (loss).
Forward Contracts
Derivative [Line Items]
Derivatives	Foreign Currency Forward Contracts White Mountains’s investment portfolio includes investments denominated in GBP, Euros, Japanese Yen and other foreign currencies. White Mountains previously entered into foreign currency forward contracts to manage its foreign currency exposure related to certain of these investments. The foreign currency forward contracts did not meet the criteria to be accounted for as a hedge. Mismatches between currency driven movements in foreign denominated investments and foreign currency forward contracts may result in net foreign currency positions being outside pre-defined ranges and/or may result in net foreign currency gains (losses). White Mountains’s foreign currency forward contracts were traded over-the-counter. The fair value of the foreign currency forward contracts was estimated using over-the-counter quotes for similar instruments and accordingly, the measurements were classified as Level 2 measurements. During the fourth quarter of 2017, White Mountains closed the foreign currency forward contracts associated with certain of its non-U.S. common equity securities. In conjunction with the liquidation of the GBP investment grade corporate bond mandate in the first quarter of 2018, White Mountains closed the associated foreign currency forward contract. As of December 31, 2019 and 2018, White Mountains no longer had any open foreign currency forward contracts. The derivative (losses) recognized in net realized and unrealized investment gains (losses) for the years ended December 31, 2018 and 2017 were $(3.5) million and $(23.8) million. White Mountains did not hold or provide any collateral under its foreign currency forward contracts.

Municipal Bond Guarantee Insurance

12 Months Ended

Dec. 31, 2019

Insurance [Abstract]

Municipal Bond Guarantee Insurance

In 2012, HG Global was capitalized with $594.5 million from White Mountains and $14.5 million from non-controlling interests to fund the initial capitalization of BAM, a newly formed mutual municipal bond insurer. As of December 31, 2019, White Mountains owned 96.9% of HG Global’s preferred equity and 88.4% of its common equity. HG Global, together with its subsidiaries, provided the initial capitalization of BAM through the purchase of $503.0 million of BAM Surplus Notes. At inception, BAM and HG Re also entered into a first loss reinsurance treaty (“FLRT”). 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 60% of the risk premium charged for insuring the municipal bond, which is net of a ceding commission.

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. At the same time HG Global and BAM also changed the payment terms of the Series B Notes, so that payments reduce principal and accrued interest on a pro rata basis, consistent with the payment terms on the Series A Notes. The terms of the Series B Notes had previously stipulated that payments would first reduce interest owed, then reduce principal owed once all accrued interest had been paid. The New York State Department of Financial Services (“NYDFS”) approved the change during 2017. In connection with the contribution and change in payment terms of the Series B Notes, 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 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.

Effective January 1, 2014, HG Global and BAM agreed to change the interest rate on the BAM Surplus Notes for the five years ending December 31, 2018 from a fixed rate of 8.0% to a variable rate equal to the one-year U.S. treasury rate plus 300 basis points, set annually. In 2018, BAM exercised its option to extend the variable rate period for an additional three years and during 2020, the interest rate will be 4.6%. In January 2020, HG Global and BAM agreed to amend the BAM Surplus Notes to extend the end of the variable interest rate period until December 31, 2024. See Note 21 — “Subsequent Event”. At the end of the variable rate period, the interest rate will be fixed at the higher of the then current variable rate or 8.0%. BAM is required to seek regulatory approval to pay interest and principal on 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 a greater than 10% change in the expected discounted future cash flows of such instrument, a change in the instrument’s carrying value is not permitted. 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 not greater than 10%.

In December 2019, BAM made a $32.0 million cash payment of principal and interest on the BAM Surplus Notes held by HG Global. Of this payment, $23.7 million was a repayment of principal held in the Supplemental Trust, $0.3 million was a payment of accrued interest held in the Supplemental Trust and $8.0 million was a payment of accrued interest held outside the Supplemental Trust. During 2018, BAM made a $23.0 million cash payment of principal and interest on the BAM Surplus Notes. Of this payment, $17.7 million was a repayment of principal held in the Supplemental Trust, $0.7 million was a payment of accrued interest held in the Supplemental Trust and $4.6 million was a payment of accrued interest held outside the Supplemental Trust. During 2017, BAM made a $5.0 million cash payment principal and interest on the BAM Surplus Notes. Of this payment, $4.0 million was a repayment of principal held in the Supplemental Trust, $0.1 million was a payment of accrued interest held in the Supplemental Trust and $0.9 million was a payment of accrued interest held outside the Supplemental Trust.

As of December 31, 2019 and 2018, the Collateral Trusts held assets of $786.7 million and $757.4 million, which included $457.6 million and $481.3 million of BAM Surplus Notes. As of December 31, 2019 and 2018, HG Global has accrued $162.7 million and $143.7 million of interest receivable on the BAM Surplus Notes.

The following table presents a schedule of BAM’s insured obligations as of December 31, 2019 and 2018:



	December 31, 2019		December 31, 2018
Contracts outstanding	8,987		7,525
Remaining weighted average contract period (in years)	10.7		10.7
Contractual debt service outstanding (in millions):
Principal	$	62,250.5	$	52,201.6
Interest and capital appreciation	31,799.7		26,560.3
Total debt service outstanding	$	94,050.2	$	78,761.9

Gross unearned insurance premiums	$	198.4	$	176.0

The following table presents a schedule of BAM’s future premium revenues as of December 31, 2019:



Millions	December 31, 2019
January 1, 2020 - March 31, 2020	$	4.8
April 1, 2020 - June 30, 2020	4.8
July 1, 2020 - September 30, 2020	4.6
October 1, 2020 - December 31, 2020	4.5
	18.7
2021	17.3
2022	16.3
2023	15.2
2024	14.2
2025 and thereafter	116.7
Total gross unearned insurance premiums	$	198.4

The following table presents a schedule of net written premiums and net earned premiums included in White Mountains’s HG Global/BAM segment for the years ended December 31, 2019, 2018 and 2017:



Millions	December 31, 2019		December 31, 2018		December 31, 2017
Written premiums:
Direct	$	28.1	$	44.8	$	63.2
Assumed	10.6		8.1		—
Gross written premiums	$	38.7	$	52.9	$	63.2
Earned premiums:
Direct	$	13.6	$	13.6	$	9.4
Assumed	2.7		.3		—
Gross earned premiums	$	16.3	$	13.9	$	9.4

In April 2018, BAM entered into a collateralized financial guarantee excess of loss reinsurance agreement with Fidus Re, Ltd. (“Fidus Re”), a Bermuda based special purpose insurer created solely to provide reinsurance protection to BAM. Fidus Re was capitalized by the issuance of $100.0 million of insurance linked securities. 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 twelve years and are callable five years after the date of issuance. Fidus Re reinsures 90% of aggregate losses exceeding $165.0 million on a portion of BAM’s financial guarantee portfolio up to a total reimbursement of $100.0 million. The aggregate loss limit under the agreement is $276.1 million. 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.

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 November 2018, BAM entered into a 100% quota share facultative reinsurance agreement under which it assumed a portfolio of municipal bond guarantee contracts with a par value of $2.2 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 December 31, 2019. The agreement, which covers future claims exposure only, meets the risk transfer criteria under ASC 944-20, Insurance Activities and accordingly has been accounted for as reinsurance.

Earnings Per Share

12 Months Ended

Dec. 31, 2019

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 years ended December 31, 2019, 2018 and 2017. See Note 20 — “Held for Sale and Discontinued Operations”.



	Year Ended December 31,
	2019			2018			2017
Basic and diluted earnings per share numerators (in millions):
Net income (loss) attributable to White Mountains’s common shareholders	$	414.5		$	(141.2	)	$	627.2
Less: total income (loss) from discontinued operations, net of tax	.8			(17.2		)	577.5
Net income (loss) from continuing operations attributable to White Mountains’s common shareholders	413.7			(124.0		)	49.7
Allocation of (earnings) losses to participating restricted common shares⁽¹⁾	(5.3		)	1.4			(.7		)
Basic and diluted earnings (losses) per share numerators	$	408.4		$	(122.6	)	$	49.0
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period	3,181.6			3,382.5			4,293.8
Average unvested restricted common shares⁽²⁾	(40.5		)	(40.1		)	(54.3		)
Basic earnings (losses) per share denominator	3,141.1			3,342.4			4,239.5
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period	3,181.6			3,382.5			4,293.8
Average unvested restricted common shares⁽²⁾	(40.5		)	(40.1		)	(54.3		)
Diluted earnings (losses) per share denominator	3,141.1			3,342.4			4,239.5
Basic and diluted earnings per share (in dollars) - continuing operations:
Distributed earnings - dividends declared and paid	$	1.00		$	1.00		$	1.00
Undistributed earnings (losses)	129.02			(37.67		)	10.56
Basic and diluted earnings (losses) per share	$	130.02		$	(36.67	)	$	11.56

⁽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 10 — “Employee Share-Based Incentive Compensation Plans”.

The following table presents the undistributed net earnings (losses) from continuing operations for the years ended December 31, 2019, 2018 and 2017. See Note 20 — “Held for Sale and Discontinued Operations”.



	Year Ended December 31,
Millions		2019			2018			2017
Undistributed net earnings - continuing operations:
Net income (loss) attributable to White Mountains’s common shareholders, net of restricted common share amounts		$	408.4		$	(122.6	)	$	49.0
Dividends declared, net of restricted common share amounts ⁽¹⁾		(3.2		)	(3.7		)	(4.5		)
Total undistributed net earnings (losses), net of restricted common share amounts		$	405.2		$	(126.3	)	$	44.5

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

Employee Share-Based Incentive Compensation Plans

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Employee Share-Based Incentive Compensation Plans

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

Incentive Compensation Plans

White Mountains’s Long-Term Incentive Plan (the “WTM Incentive Plan”) provides for grants of various types of share-based and non-share-based incentive awards to key employees and directors of White Mountains. The WTM Incentive Plan was adopted by the Board, was approved by the Company’s sole shareholder in 1985 and was subsequently amended by its shareholders in 1995, 2001, 2003, 2005, 2010, 2013 and 2019. Share-based incentive awards that may be granted under the plan include performance shares, restricted shares, incentive stock options and non-qualified stock options (“Non-Qualified Options”).

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 three 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 performance share activity for the years ended December 31, 2019, 2018 and 2017 for performance shares granted under the WTM Incentive Plan:



	Year Ended December 31,
	2019					2018					2017
$ in Millions	Target Performance Shares Outstanding		Accrued Expense			Target Performance Shares Outstanding		Accrued Expense			Target Performance Shares Outstanding		Accrued Expense
Beginning of period	40,616		$	31.7		50,515		$	45.8		80,353		$	42.4
Shares paid or expired ⁽¹⁾	(13,715	)	(18.1		)	(23,186	)	(28.4		)	(30,838	)	(21.9		)
New grants	15,600		—			14,105		—			17,710		—
Forfeitures ⁽²⁾	(28	)	(.1		)	(818	)	.1			(16,710	)	(9.3		)
Expense recognized	—		30.2			—		14.2			—		34.6
End of period ⁽³⁾	42,473		$	43.7		40,616		$	31.7		50,515		$	45.8

⁽¹⁾

WTM performance shares payments in 2019 for the 2016-2018 performance cycle, which were paid in March 2019 ranged from 139% to 166% of target. WTM performance share payments in 2018 for the 2015-2017 performance cycle, which were paid in March 2018 ranged from 145% to 147% of target. WTM performance share payments in 2017 for the 2014-2016 performance cycle, which were paid in March 2017 ranged from 34% to 76% of target.


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


⁽³⁾	Outstanding performance share awards as of December 31, 2017 exclude 2,195 unvested performance shares awards for employees of Sirius Group, which are included in discontinued operations.

For the 2016-2018, 2015-2017 and 2014-2016 performance cycles, all performance shares earned were settled in cash. If the outstanding performance shares had vested on December 31, 2019, the total additional compensation cost to be recognized would have been $17.2 million, based on accrual factors as of December 31, 2019 (common share price and payout assumptions).

The following table presents performance shares outstanding and accrued expense for performance shares awarded under the WTM Incentive Plan as of December 31, 2019 for each performance cycle:



$ in Millions	Target Performance Shares Outstanding		Accrued Expense
Performance cycle:
2019 – 2021	15,600		$	6.0
2018 – 2020	13,450		10.5
2017 – 2019	14,070		27.8
Sub-total	43,120		44.3
Assumed forfeitures	(647	)	(.6		)
Total	42,473		$	43.7

For the 2019-2021 performance cycle, the targeted performance goal for full payment of outstanding performance shares granted under the WTM Incentive Plan is 7% average growth in adjusted book value per share and intrinsic value per share. Average growth of 2% or less would result in no payout and average growth of 12% or more would result in a payout of 200%.

For the 2018-2020 performance cycle, the targeted performance goal for full payment of outstanding performance shares granted under the WTM Incentive Plan is 6% average growth in adjusted book value per share and intrinsic value per share. Average growth of 2% or less would result in no payout and average growth of 10% or more would result in a payout of 200%.

For the 2017-2019 performance cycle, the targeted performance goal for full payment of outstanding performance shares granted under the WTM Incentive Plan to non-investment personnel is 5% average growth in adjusted book value per share and intrinsic value per share. Average growth of 1% or less would result in no payout and average growth of 9% or more would result in a payout of 200%.

For investment personnel, for the period ended December 31, 2017, the targeted performance goals for full payment of outstanding performance shares granted under the WTM Incentive Plan are based one-third on average growth in adjusted book value per share and intrinsic value per share (as described above) and two-thirds on achieving a total return on invested assets as measured against metrics based on the 10-year U.S. Treasury Note. For periods after December 31, 2017, the targeted performance goals for full payment of outstanding performance shares granted under the WTM Incentive Plan to investment personnel are based on the same performance goals described above for non-investment personnel.

Restricted Shares

Restricted shares are grants of a specified number of common shares that generally vest at the end of a three-year service period. The following table presents the unrecognized compensation cost associated with the outstanding restricted share awards under the WTM Incentive Plan for the years ended December 31, 2019, 2018 and 2017:



	Year Ended December 31,
	2019					2018					2017
$ in Millions	Restricted Shares		Unamortized Issue Date Fair Value			Restricted Shares		Unamortized Issue Date Fair Value			Restricted Shares		Unamortized Issue Date Fair Value
Non-vested,
Beginning of period	41,510		$	12.5		53,755		$	14.3		70,620		$	19.7
Issued	15,600		14.5			14,105		11.4			17,985		16.3
Vested	(13,715	)	—			(25,381	)	—			(28,846	)	—
Forfeited	—		—			(969	)	(.2		)	(6,004	)	(3.5		)
Expense recognized	—		(10.3		)	—		(13.0		)	—		(18.2		)
End of period ⁽¹⁾	43,395		$	16.7		41,510		$	12.5		53,755		$	14.3


⁽¹⁾	Outstanding restricted share awards as of December 31, 2017 include 2,195 unvested restricted shares for employees of Sirius Group.

During 2019, White Mountains issued 15,600 restricted shares that vest on January 1, 2022. During 2018, White Mountains issued 13,450 restricted shares that vest on January 1, 2021, 290 restricted shares that vest on January 1, 2019 and 365 restricted shares that vest on January 1, 2018. During 2017, White Mountains issued 17,485 restricted shares that vest on January 1, 2020, 250 restricted shares that vest on January 1, 2019 and 250 restricted shares that vest on January 1, 2018. The unrecognized compensation cost as of December 31, 2019 is expected to be recognized ratably over the remaining vesting periods.

Non-Qualified Options

As of January 20, 2017, the 125,000 Non-Qualified Options issued to the Company’s former Chairman and CEO had been exercised. During the first quarter of 2017, 40,000 Non-Qualified Options, with an intrinsic value of $4.4 million, were exercised in exchange for 5,142 common shares with an equal total market value. Intrinsic value represents the difference between the market price of the Company’s common shares at the date of exercise and the fixed strike price of $742 per common share. The Non-Qualified Options were fully amortized as of 2011.

Leases

12 Months Ended

Dec. 31, 2019

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.

On January 1, 2019, White Mountains adopted ASU 2016-02, Leases (ASC 842). See Note 1 — “Basis of Presentation and Significant Accounting Policies” — Basis of Presentation and Significant Accounting Policies. Prior to adoption of ASU 2016-02, White Mountains recognized lease expense for operating leases on a straight-line basis, but did not recognize lease assets or liabilities on its consolidated balance sheet. Upon adoption on January 1, 2019, White Mountains recognized lease ROU assets of $23.2 million and lease liabilities of $23.2 million. As of December 31, 2019, the ROU asset was $22.6 million and lease liabilities were $22.8 million.

The following table summarizes net lease expense recognized in White Mountains’s consolidated statement of operations for the year ended December 31, 2019:



Millions Lease Cost	December 31, 2019
Lease cost	$	7.2
Less: sublease income	.4
Net lease cost	$	6.8

The following table presents the contractual maturities of the lease liabilities associated with White Mountains’s operating lease agreements as of December 31, 2019:



Millions	As of December 31, 2019
2020	$	5.9
2021	4.9
2022	4.5
2023	3.9
2024	3.1
Thereafter	3.4
Total undiscounted lease payments	25.7
Less: present value adjustment	(2.9		)
Operating lease liability	$	22.8

The following table presents lease related assets and liabilities by reportable segment as of December 31, 2019:



	As of December 31, 2019
$ in Millions	HG/BAM		NSM		Kudu		Other Operations		Total		Weighted Average Incremental Borrowing Rate ⁽¹⁾
ROU lease asset	$	10.4	$	4.8	$	2.3	$	5.1	$	22.6	4.6%
Lease liability	$	10.4	$	4.8	$	2.3	$	5.3	$	22.8	4.6%

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

Common Shareholders’ Equity and Non-controlling Interests

12 Months Ended

Dec. 31, 2019

Stockholders' Equity Note [Abstract]

Common Shareholder's Equity

Common Shareholders’ Equity and Non-controlling Interests

Common Shares Repurchased and Retired

During the past several years, White Mountains’s board of directors authorized the Company to repurchase its common shares, from time to time, subject to market conditions. Shares may be repurchased on the open market or through privately negotiated transactions. The repurchase authorizations do not have a stated expiration date. As of December 31, 2019, White Mountains may repurchase an additional 635,705 shares under these board authorizations. In addition, from time to time White Mountains has also repurchased its common shares through tender offers that were separately authorized by its board of directors.

During 2019, the Company repurchased 5,679 common shares for $4.9 million at an average share price of $858 pursuant to employee benefit plans.

During 2018, the Company repurchased 592,458 common shares for $519.1 million at an average share price of $877, which were comprised of 582,493 common shares repurchased under the board authorizations for $511.0 million at an average share price of $877 and 9,965 common shares repurchased pursuant to employee benefit plans. Shares repurchased pursuant to employee benefit plans do not fall under the board authorizations referred to above.

During 2017, the Company repurchased 832,725 common shares for $723.9 million at an average share price of $869, which were comprised of 821,732 common shares repurchased under the board authorizations for $713.1 million at an average share price of $870 and 10,993 common shares repurchased pursuant to employee benefit plans.

Common Shares Issued

During 2019, the Company issued a total of 17,917 common shares, which consisted of 15,600 restricted shares issued to key personnel and 2,317 shares issued to directors of the Company.

During 2018, the Company issued a total of 16,377 common shares, which consisted of 14,105 restricted shares to key personnel and 2,272 shares issued to directors of the Company.

During 2017, the Company issued a total of 25,086 common shares, which consisted of 17,985 restricted shares to key personnel, 5,142 shares issued to the Company’s former Chairman and CEO as a result of exercised options, and 1,959 shares issued to directors of the Company.

Dividends on Common Shares

For the years ended December 31, 2019, 2018 and 2017, the Company declared and paid cash dividends totaling $3.2 million, $3.8 million and $4.6 million (or $1.00 per common share).

Non-controlling Interests

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

The following table 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 December 31, 2019 and 2018:



	December 31, 2019					December 31, 2018
$ in Millions	Non-controlling Percentage		Non-controlling Equity			Non-controlling Percentage		Non-controlling Equity
Non-controlling interests, excluding BAM
HG Global	3.1	%	$	14.4		3.1	%	$	14.5
NSM	3.6		14.9			4.5		13.6
Other NSM	13.4		(.1		)	13.4		.3
Kudu	—		2.2			—		—
MediaAlpha	—		—			39.0		16.2
Other Operations	various		(1.5		)	various		1.1
Total, excluding BAM			29.9					45.7

BAM	100.0		(146.7		)	100.0		(170.6		)
Total non-controlling interests			$	(116.8	)			$	(124.9	)

Statutory Capital and Surplus	12 Months Ended
Statutory Capital and Surplus	Dec. 31, 2019
Insurance [Abstract]
Statutory Capital and Surplus	Statutory Capital and Surplus White Mountains’s insurance operations are subject to regulation and supervision in each of the jurisdictions where they are domiciled and licensed to conduct business. Generally, regulatory authorities have broad supervisory and administrative powers over such matters as licenses, standards of solvency, premium rates, policy forms, investments, security deposits, methods of accounting, form and content of financial statements, minimum capital and surplus requirements, dividends and other distributions to shareholders, periodic examinations and annual and other report filings. In general, such regulation is for the protection of policyholders rather than shareholders. The Insurance Act 1978 of Bermuda and related regulations, as amended (“Insurance Act”), regulates the insurance business of Bermuda-domiciled insurers. Under the Insurance Act, insurers are required to maintain available statutory capital and surplus at a level equal to or in excess of its enhanced capital requirement which is established by reference to either a Bermuda Solvency Capital Requirement (“BSCR”) model or an approved internal capital model. Generally, the Bermuda Monetary Authority (“BMA”) has broad supervisory and administrative powers over such matters as licenses, standards of solvency, investments, methods of accounting, form and content of financial statements, minimum capital and surplus requirements, and annual and other report filings. HG Global/BAM HG Re is a Special Purpose Insurer under Bermuda insurance regulations and is subject to regulation and supervision by the BMA. As of December 31, 2019, HG Re had statutory capital and surplus of $745.4 million. As a Special Purpose Insurer, HG Re has a nominal minimum regulatory capital requirement of $1. BAM is domiciled in New York and is subject to regulation by the NYDFS. New York financial guarantee insurance law establishes single risk and aggregate limits with respect to insured obligations insured by financial guarantee insurers. BAM’s statutory net loss for the years ended December 31, 2019, 2018 and 2017 was $38.3 million, $34.6 million and $25.4 million. BAM’s members’ surplus, as reported to regulatory authorities as of December 31, 2019, was $402.4 million, which exceeds the minimum members’ surplus necessary for BAM to maintain its New York State financial guarantee insurance license of $66.0 million. Dividend Capacity There are no restrictions under Bermuda law or the law of any other jurisdiction on the payment of dividends from retained earnings by White Mountains, provided that after the payment of any dividend, the Company would continue to be able to pay its liabilities as they become due and the realizable value of the Company’s assets would remain greater that its liabilities. Following is a description of the dividend capacity of White Mountains’s reinsurance and other operating subsidiaries: HG Global/BAM As of December 31, 2019, HG Global had $619.0 million face value of preferred shares outstanding, of which White Mountains owned 96.9%. Holders of the HG Global preferred shares receive cumulative dividends at a fixed annual rate of 6.0% on a quarterly basis, when and if declared by HG Global. HG Global declared and paid preferred dividends of $2.0 million in 2019. As of December 31, 2019, HG Global had accrued $341.7 million of dividends payable to holders of its preferred shares, $330.2 million of which is payable to White Mountains and eliminated in consolidation. As of December 31, 2019, HG Global and its subsidiaries had $3.0 million of cash outside of HG Re. HG Re is a Special Purpose Insurer subject to regulation and supervision by the BMA, but does not require regulatory approval to pay dividends. However, HG Re’s dividend capacity is limited to amounts held outside of the Collateral Trusts pursuant to the FLRT with BAM. As of December 31, 2019, HG Re had $745.4 million of statutory capital and surplus and $786.7 million of assets held in the Collateral Trusts pursuant to the FLRT with BAM. 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 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. 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. As of December 31, 2019, HG Re had $6.3 million of cash and investments and $111.2 million of accrued interest on the BAM Surplus Notes held outside the Collateral Trusts. 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, 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. In December 2019, BAM made a $32.0 million cash payment of principal and interest on the BAM Surplus Notes held by HG Global. Of this payment, $23.7 million was a repayment of principal held in the Supplemental Trust, $0.3 million was a payment of accrued interest held in the Supplemental Trust and $8.0 million was a payment of accrued interest held outside the Supplemental Trust. During 2018, BAM made a $23.0 million cash payment of principal and interest on the BAM Surplus Notes. Of this payment, $17.7 million was a repayment of principal held in the Supplemental Trust, $0.7 million was a payment of accrued interest held in the Supplemental Trust and $4.6 million was a payment of accrued interest held outside the Supplemental Trust. In January 2020, BAM made an additional $65.0 million special cash payment of principal and interest on the BAM Surplus Notes. See Note 21 — “Subsequent Event”. NSM During 2019, NSM did not make any distributions to unitholders. As of December 31, 2019, NSM had $33.4 million of net unrestricted cash. Kudu In December 2019, Kudu entered into a secured credit facility to provide funding for distributions to unitholders and fund new investments and related transaction expenses. At closing, Kudu drew an initial term loan of $57.0 million to pay transaction expenses and to distribute $53.7 million to unitholders, of which $53.3 million was paid to White Mountains. As of December 31, 2019, Kudu had $5.9 million of net unrestricted cash and short-term investments. Other Operations During 2019, White Mountains paid a $3.2 million common share dividend. As of December 31, 2019, the Company and its intermediate holding companies had $602.6 million of net unrestricted cash, short-term investments and fixed maturity investments, $683.9 million of common equity securities and $202.3 million of private equity funds, hedge funds and ILS funds.

Segment Information

12 Months Ended

Dec. 31, 2019

Segment Reporting [Abstract]

Segment Information

As of December 31, 2019, White Mountains conducted its operations through four segments: (1) HG Global/BAM, (2) NSM, (3) Kudu and (4) Other Operations. In addition, MediaAlpha was consolidated as a reportable segment until the date of the MediaAlpha Transaction. A discussion of White Mountains’s consolidated investment operations is included after the discussion of operations by segment.

As a result of the Kudu Transaction, White Mountains began consolidating Kudu in its financial statements in the second quarter of 2019. White Mountains’s segment disclosures for the year ended December 31, 2019 include Kudu’s results of operations for the period from April 4, 2019, the date of the Kudu Transaction, to December 31, 2019. See Note 2 — “Significant Transactions”.

As a result of the MediaAlpha Transaction, White Mountains no longer consolidated MediaAlpha, and consequently it was no longer a reportable segment. White Mountains’s segment disclosures for the year ended December 31, 2019 include MediaAlpha’s results of operations for the period from January 1, 2019 to February 26, 2019, the date of the MediaAlpha Transaction. See Note 2 — “Significant Transactions”.

As a result of the OneBeacon Transaction, the results of operations for OneBeacon for the year ended December 31, 2017 have been classified as discontinued operations, and are now presented separately, net of related income taxes, in the statement of comprehensive income. See Note 19 — “Held for Sale and Discontinued Operations”.

White Mountains has made its segment determination based on consideration of the following criteria: (i) the nature of the business activities of each of the Company’s subsidiaries and affiliates; (ii) the manner in which the Company’s subsidiaries and affiliates are organized; (iii) the existence of primary managers responsible for specific subsidiaries and affiliates; and (iv) the organization of information provided to the chief operating decision makers and the Board of Directors. 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 ⁽¹⁾		NSM			Kudu ⁽²⁾		MediaAlpha ⁽³⁾			Other Operations		Total
Year Ended December 31, 2019
Earned insurance premiums	$	16.3	$	—		$	—	$	—		$	—	$	16.3
Net investment income	21.6		—			14.7		—			43.4		79.7
Net realized and unrealized investment gains	27.1		—			6.3		—			285.1		318.5
Gain from deconsolidation of MediaAlpha	—		—			—		—			182.2		182.2
Advertising and commission revenues ⁽⁴⁾	—		193.4			—		48.8			6.9		249.1
Other revenues	1.6		39.7			.2		—			6.1		47.6
Total revenues	66.6		233.1			21.2		48.8			523.7		893.4
Insurance acquisition expenses	5.7		—			—		—			—		5.7
Other underwriting expenses	.4		—			—		—			—		.4
Cost of sales	—		—			—		40.6			7.5		48.1
General and administrative expenses	50.5		132.2			10.1		12.5			122.5		327.8
Broker commission expense	—		64.8			—		—			—		64.8
Change in fair value of contingent consideration earnout liabilities	—		2.1			—		—			—		2.1
Amortization of other intangible assets	—		19.4			.2		1.6			.6		21.8
Interest expense	—		16.7			.1		.2			.6		17.6
Total expenses	56.6		235.2			10.4		54.9			131.2		488.3
Pre-tax income (loss)	$	10.0	$	(2.1	)	$	10.8	$	(6.1	)	$	392.5	$	405.1


⁽¹⁾	BAM manages its affairs on a statutory accounting basis. BAM’s statutory surplus includes the BAM Surplus Notes and is not reduced by accruals of interest expense on the BAM Surplus Notes. BAM’s statutory surplus is reduced only after a payment of principal or interest has been approved by the NYDFS.


⁽²⁾	Kudu’s results are from April 4, 2019, the date of the Kudu Transaction, to December 31, 2019.


⁽³⁾	MediaAlpha’s results are from January 1, 2019 to February 26, 2019, the date of the MediaAlpha Transaction.


⁽⁴⁾	Approximately 17% of NSM’s commission revenue was associated with one single carrier.



Millions	HG Global/BAM ⁽¹⁾			NSM			MediaAlpha		Other Operations			Total
Year Ended December 31, 2018
Earned insurance premiums	$	13.9		$	—		$	—	$	—		$	13.9
Net investment income	16.7			—			—		42.3			59.0
Net realized and unrealized investment losses	(7.5		)	—			—		(100.8		)	(108.3		)
Advertising and commission revenues ⁽²⁾	—			89.6			295.5		4.1			389.2
Other revenues	1.2			12.0			1.6		.5			15.3
Total revenues	24.3			101.6			297.1		(53.9		)	369.1
Insurance acquisition expenses	5.3			—			—		—			5.3
Other underwriting expenses	.4			—			—		—			.4
Cost of sales	—			—			245.0		3.7			248.7
General and administrative expenses	48.0			59.4			31.7		94.4			233.5
Broker commission expense	—			28.4			—		—			28.4
Change in fair value of contingent consideration earnout liabilities	—			2.7			—		—			2.7
Amortization of other intangible assets	—			8.3			10.3		.2			18.8
Interest expense	—			8.0			1.2		.3			9.5
Total expenses	53.7			106.8			288.2		98.6			547.3
Pre-tax (loss) income	$	(29.4	)	$	(5.2	)	$	8.9	$	(152.5	)	$	(178.2	)


⁽¹⁾	BAM manages its affairs on a statutory accounting basis. BAM’s statutory surplus includes the BAM Surplus Notes and is not reduced by accruals of interest expense on the BAM Surplus Notes. BAM’s statutory surplus is reduced only after a payment of principal or interest has been approved by the NYDFS.


⁽²⁾	As of December 31, 2018, approximately 29% of MediaAlpha’s advertising revenue was associated with one customer.As of December 31, 2018, approximately 33% of NSM’s commission revenue was associated with one single carrier.



Millions	HG Global/BAM ⁽¹⁾			MediaAlpha			Other Operations		Total
Year Ended December 31, 2017
Earned insurance premiums	$	9.4		$	—		$	1.0	$	10.4
Net investment income	12.3			—			43.7		56.0
Net realized and unrealized investment gains	.6			—			132.7		133.3
Advertising and commission revenues⁽²⁾	—			163.2			3.8		167.0
Other revenues	1.0			—			6.1		7.1
Total revenues	23.3			163.2			187.3		373.8
Losses and LAE	—			—			1.1		1.1
Insurance acquisition expenses	4.0			—			.1		4.1
Other underwriting expenses	.4			—			—		.4
Cost of sales	—			135.9			3.5		139.4
General and administrative expenses	42.9			16.2			148.9		208.0
Amortization of other intangible assets	—			10.5			.2		10.7
Interest expense	—			1.0			1.3		2.3
Total expenses	47.3			163.6			155.1		366.0
Pre-tax (loss) income	$	(24.0	)	$	(.4	)	$	32.2	$	7.8


⁽¹⁾	BAM manages its affairs on a statutory accounting basis. BAM’s statutory surplus includes the BAM Surplus Notes and is not reduced by accruals of interest expense on the BAM Surplus Notes. BAM’s statutory surplus is reduced only after a payment of principal or interest has been approved by the NYDFS.


⁽²⁾	As of December 31, 2017, approximately 27% of MediaAlpha’s advertising revenue was associated with one customer.



Millions Selected Balance Sheet Data	HG Global/BAM				NSM		Kudu		MediaAlpha		Other Operations				Held for Sale		Total
December 31, 2019:
Total investments	$	845.6			$	—	$	266.6	$	—	$	1,835.0			$	—	$	2,947.2
Total assets	$	924.0		⁽¹⁾	$	825.2	$	290.5	$	—	$	1,940.5		⁽²⁾	$	3.0	$	3,983.2
Total liabilities	$	246.8		⁽²⁾	$	401.1	$	57.0	$	—	$	133.6			$	—	$	838.5
Total White Mountains’s common shareholders’ equity	$	809.5		⁽²⁾	$	409.3	$	231.3	$	—	$	1,808.4		⁽²⁾	$	3.0	$	3,261.5
Non-controlling interest	$	(132.3	)		$	14.8	$	2.2	$	—	$	(1.5	)		$	—	$	(116.8	)
December 31, 2018:
Total investments	$	768.3			$	—	$	—	$	—	$	1,774.6			$	—	$	2,542.9
Total assets	$	816.2		⁽¹⁾	$	623.6	$	—	$	88.4	$	1,831.1		⁽²⁾	$	3.3	$	3,362.6
Total liabilities	$	212.5		⁽²⁾	$	314.8	$	—	$	46.9	$	70.2			$	—	$	644.4
Total White Mountains’s common shareholders’ equity	$	759.8		⁽²⁾	$	294.9	$	—	$	25.3	$	1,759.8		⁽²⁾	$	3.3	$	2,843.1
Non-controlling interest	$	(156.1	)		$	13.9	$	—	$	16.2	$	1.1			$	—	$	(124.9	)


⁽¹⁾	As of December 2019 and 2018, total assets in the HG Global/BAM segment reflected the elimination of $457.6 and $481.3 of BAM Surplus Notes issued to HG Global and its subsidiaries, and $162.7 and $143.7 in accrued interest related to the BAM Surplus Notes.

⁽²⁾

HG Global preferred dividends payable to White Mountains’s subsidiaries is eliminated in White Mountains’s consolidated financial statements. For segment reporting, the HG Global preferred dividends payable to White Mountains’s subsidiaries included within the HG Global/BAM segment are eliminated against the offsetting receivable included within the Other Operations segment and therefore added back to White Mountains’s common shareholders’ equity within the HG Global/BAM segment. As of December 31, 2019 and 2018, the HG Global preferred dividends payable to White Mountains’s subsidiaries was $330.3 and $278.5.

In compliance with ASC 606, Revenues from Contracts with Customers, the following tables present White Mountains’s total revenues by revenue source:



Millions	HG Global/BAM		NSM		Kudu ⁽²⁾		MediaAlpha ⁽³⁾		Other Operations		Total
Year Ended December 31, 2019
Commission and Other Revenue
Specialty Transportation	$	—	$	77.6	$	—	$	—	$	—	$	77.6
Real Estate	—		34.7		—		—		—		34.7
Social Services	—		25.9		—		—		—		25.9
Pet	—		30.0		—		—		—		30.0
United Kingdom	—		45.9		—		—		—		45.9
Other	—		19.0		—		—		6.9		25.9
Total Commission and Other Revenue	—		233.1		—		—		6.9		240.0
Advertising revenues	—		—		—		48.8		—		48.8
Products	—		—		—		—		5.5		5.5
Total revenues from contracts with customers	—		233.1		—		48.8		12.4		294.3
Other revenues⁽¹⁾	66.6		—		21.2		—		511.3		599.1
Total revenues	$	66.6	$	233.1	$	21.2	$	48.8	$	523.7	$	893.4


⁽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.


⁽²⁾	Kudu’s results are from April 4, 2019, the date of the Kudu Transaction, to December 31, 2019.


⁽³⁾	MediaAlpha’s results are from January 1, 2019 to February 26, 2019, the date of the MediaAlpha Transaction.



Millions	HG Global/BAM		NSM		MediaAlpha		Other Operations			Total
Year Ended December 31, 2018
Commission and Other Revenue
Specialty Transportation	$	—	$	28.3	$	—	$	—		$	28.3
Real Estate	—		17.8		—		—			17.8
Social Services	—		14.7		—		—			14.7
United Kingdom	—		28.0		—		—			28.0
Other	—		12.8		—		4.1			16.9
Total Commission and Other Revenue	—		101.6		—		4.1			105.7
Advertising revenues	—		—		295.5		—			295.5
Total revenues from contracts with customers	—		101.6		295.5		4.1			401.2
Other revenues⁽¹⁾	24.3		—		1.6		(58.0		)	(32.1		)
Total revenues	$	24.3	$	101.6	$	297.1	$	(53.9	)	$	369.1

⁽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		MediaAlpha		Other Operations		Total
Year Ended December 31, 2017
Commission and Other Revenue
Other	$	—	$	—	$	.4	$	.4
Total Commission and Other Revenue	—		—		.4		.4
Advertising revenues	—		163.2		—		163.2
Total revenues from contracts with customers	—		163.2		.4		163.6
Other revenues⁽¹⁾	23.3		—		186.9		210.2
Total revenues	$	23.3	$	163.2	$	187.3	$	373.8

⁽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

12 Months Ended

Dec. 31, 2019

Equity Method Investments and Joint Ventures [Abstract]

Equity-Method Eligible Investments

White Mountains’s equity method eligible investments include certain investments in unconsolidated entities, 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 recorded within other long-term investments as of December 31, 2019 and 2018:



	December 31,
Millions	2019		2018
Equity method eligible investments, at fair value	$	761.7	$	269.7
Other ⁽¹⁾	94.6		55.9
Total other long-term investments	$	856.3	$	325.6

⁽¹⁾Consists of other long-term investments that are not equity method eligible.

The following table presents White Mountains’s significant equity method eligible investments as of December 31, 2019 and 2018:



	Basic Ownership Interest
Investee	December 31, 2019	December 31, 2018	Instrument Held
PassportCard/DavidShield	50.0%	50.0%	Common shares
MediaAlpha ⁽¹⁾	48.3%	n/a	Units
durchblicker	45.0%	45.0%	Common shares
Elementum Holdings, L.P.	30.0%	n/a	Limited partnership interest
Compare.com	18.4%	18.4%	Common shares
Tuckerman Capital Funds ⁽²⁾	17.5 - 62.4%	18.5 - 62.3%	Limited and general partnership interests
JAM Partners L.P.	11.1%	12.3%	Limited partnership interest
Enlightenment Capital Funds	10.0 - 38.4%	10.3 - 36.5%	Limited and general partnership interests
Kudu’s Participation Contracts ⁽³⁾	3.2 - 30.0%	n/a	Revenue and earnings participation contracts
Kudu ⁽³⁾	n/a	49.5%	Units

⁽¹⁾ As of December 31, 2018, MediaAlpha was a majority-owned consolidated subsidiary of White Mountains. See Note 2 — “Significant Transactions”

⁽²⁾ As of December 31, 2018, includes White Mountains’s direct investment in Galvanic Applied Sciences.

⁽³⁾ As of December 31, 2019 White Mountains consolidates Kudu. See Note 2 — “Significant Transactions”.

The following tables present aggregated summarized financial information for White Mountains’s investments in equity method eligible unconsolidated entities, excluding MediaAlpha:



	December 31,
Millions	2019		2018
Balance sheet data ⁽¹⁾:
Total assets	$	1,959.2	$	1,373.3
Total liabilities	$	653.2	$	509.2

⁽¹⁾Financial data for White Mountains’s equity method eligible investees is generally reported on a one-quarter lag.



	Year Ended December 31,
Millions	2019		2018		2017
Income statement data ⁽¹⁾:
Revenues	$	344.6	$	226.0	$	143.3
Expenses	$	88.3	$	141.4	$	80.5
Net Income	$	255.1	$	83.6	$	65.3

⁽¹⁾Financial data for White Mountains’s equity method eligible investees is generally reported on a one-quarter lag.

As a result of the MediaAlpha Transaction, White Mountains reduced its ownership interest in MediaAlpha to 48.3% of the basic units outstanding (42.0% on a fully diluted, fully converted basis). White Mountains’s remaining ownership interest in MediaAlpha no longer meets the criteria for a controlling ownership interest and, accordingly, White Mountains deconsolidated MediaAlpha as of February 26, 2019. Upon deconsolidation, White Mountains’s investment in MediaAlpha met the criteria to be accounted for under the equity method or under the fair value option. White Mountains elected the fair value option and the investment in MediaAlpha was initially measured at its estimated fair value of $114.7 million as of March 31, 2019, with the change in fair value of $114.7 million recognized as an unrealized investment gain. For the twelve months ended December 31, 2019, White Mountains recognized $180.0 million in unrealized investment gains associated with its investment in MediaAlpha including changes in the fair value of White Mountains’s investment in MediaAlpha subsequent to the MediaAlpha Transaction. White Mountains’s consolidated statement of comprehensive income and its segment disclosures include MediaAlpha’s results of operations for the period from January 1, 2019 through February 26, 2019. See Note 2 — “Significant Transactions”.

For the period from February 26, 2019 to December 31, 2019, MediaAlpha’s total revenues, total expenses, gross profit and pre-tax income were $359.2 million, $334.3 million, $59.7 million and $24.9 million.

The following tables present summarized financial information for MediaAlpha:



	December 31,
Millions	2019		2018
Balance sheet data:
Total assets	$	106.9	$	88.5
Total liabilities	$	144.6	$	46.9



	Year Ended December 31,
Millions	2019		2018		2017
Income statement data:
Total revenues	$	407.9	$	297.1	$	163.2
Total expenses	$	389.0	$	288.2	$	163.5
Net income (loss)	$	18.9	$	8.9	$	(0.3	)

Variable Interest Entities	12 Months Ended
Variable Interest Entities	Dec. 31, 2019
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Variable Interest Entities	Variable Interest Entities BAM As a mutual insurance company, BAM is owned by its members. BAM charges an insurance premium on each municipal bond insurance policy it writes. A portion of the premium is a member surplus contribution (“MSC”) and the remainder is a risk premium. In the event of a municipal bond refunding, a portion of the MSC from the original issuance can be reutilized, in effect serving as a credit against the total insurance premium on the refunding of the municipal bond. Issuers of debt insured by BAM are members of BAM so long as any of their BAM-insured debt is outstanding, and as members they have certain interests in BAM, including the right to vote for BAM’s directors and to receive dividends in the future, if declared. The equity at risk funded by BAM’s members is not sufficient to fund its operations without the additional financial support provided by the BAM Surplus Notes and accordingly, BAM is considered to be a VIE. At inception, BAM and HG Re also entered into the FLRT. 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 60% of the risk premium charged for insuring the municipal bond, net of a ceding commission. HG Re’s obligations under the FLRT are limited to the assets in the Regulation 114 Trust and the Supplemental Trust. 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. In addition, under the FLRT, HG Holdings Ltd, a subsidiary of HG Global, has the right to designate two directors for election to BAM’s board of directors. Since BAM is owned by its members, its equity and results of operations are included in non-controlling interests. 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. Elementum On May 31, 2019, White Mountains acquired a 30.0% limited partnership interest in Elementum for $55.1 million. White Mountains has determined that Elementum is a VIE but that White Mountains is not the primary beneficiary. White Mountains’s ownership interest gives White Mountains the opportunity to exert significant influence over the significant financial and operating activities of Elementum. Accordingly, Elementum meets the criteria to be accounted for under the equity method. White Mountains has taken the fair value option for its investment in Elementum. Changes in the fair value of Elementum are recorded in realized and unrealized investment gains. White Mountains’s maximum loss in Elementum is limited to the amount invested. As of December 31, 2019, Elementum is recorded within other long-term investments at a carrying amount of $55.1 million. Kudu On April 4, 2019, White Mountains completed the Kudu Transaction for cash consideration of $81.4 million. White Mountains recognized total assets acquired of $155.5 million, including $7.6 million of goodwill and $2.2 other intangible assets, total liabilities assumed of $0.8 million and non-controlling interest of $1.5 million. As a result of the Kudu Transaction, White Mountains’s basic unit ownership of Kudu increased from 49.5% to 99.1% (42.7% to 85.4% on a fully diluted, fully converted basis), and White Mountains began consolidating Kudu as a reportable segment in its financial statements during the second quarter of 2019. White Mountains’s consolidated financial statements and its segment disclosures include Kudu’s results for the period from April 4, 2019 to December 31, 2019. For periods prior to the Kudu Transaction, White Mountains determined that Kudu was a VIE but that White Mountains was not the primary beneficiary. White Mountains’s ownership interest gave White Mountains the opportunity to exert significant influence over the significant financial and operating activities of Kudu. Accordingly, for the year ended December 31, 2018, Kudu met the criteria to be accounted for under the equity method. White Mountains took the fair value option for its investment in Kudu, measuring its investment in Kudu at fair value using NAV as a practical expedient with changes therein recorded in realized and unrealized investment gains for the year ended December 31, 2018.

Fair Value of Financial Instruments

12 Months Ended

Dec. 31, 2019

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 tables presents the fair value and carrying value of these financial instruments as of December 31, 2019 and 2018:



	December 31, 2019				December 31, 2018
Millions	Fair Value		Carrying Value		Fair Value		Carrying Value
NSM Bank Facility	$	221.2	$	217.4	$	176.1	$	176.6
Other NSM debt	$	1.7	$	1.8	$	1.9	$	1.9
Kudu Bank Facility ⁽¹⁾	$	53.6	$	53.6	$	—	$	—
MediaAlpha Bank Facility	$	—	$	—	$	14.6	$	14.2
Other Operations debt	$	11.3	$	10.7	$	—	$	—

⁽¹⁾ White Mountains measured the fair value of the Kudu Bank Facility debt at the carrying value as a result of the debt being acquired on December 23, 2019. See Note 5 — “Debt”.

The fair value estimates for the NSM Bank Facility, the MediaAlpha Bank Facility and Other Operations debt have been determined based on a discounted cash flow approach and are considered to be Level 3 measurements. As a result of the MediaAlpha Transaction, White Mountains’s remaining ownership interest in MediaAlpha no longer meets the criteria for a controlling ownership interest and accordingly, White Mountains deconsolidated MediaAlpha as of February 26, 2019. See Note 2 — “Significant Transactions”.

- Definition

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

+ References + Details

Transactions with Related Persons	12 Months Ended
Transactions with Related Persons	Dec. 31, 2019
Related Party Transactions [Abstract]
Transactions with Related Persons	Transactions with Related Persons During 2017, the Company repurchased shares from Franklin Mutual Advisers, a beneficial owner of the Company. On July 13, 2017, the Company repurchased 235,000 White Mountains common shares for $850.00 per share, the market price at the time the agreement was reached.

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies White Mountains leases certain office spaces under non-cancellable operating leases that expire on various dates through 2022. Rental expense for all of White Mountains’s locations was $7.2 million, $5.5 million and $3.5 million for the years ended December 31, 2019, 2018 and 2017. White Mountains also has various other lease obligations that are immaterial in the aggregate. White Mountains’s future annual minimum rental payments required under non-cancellable leases, which are primarily for office space, are $7.1 million, $6.1 million, $5.7 million, and $18.4 million for the years ending December 31, 2020, 2021, 2022 and 2023 and thereafter. White Mountains also has future binding commitments to fund certain other long-term investments. These commitments, which totaled $183.4 million as of December 31, 2019, do not have fixed funding dates. 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 December 31, 2019: 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 A subsidiary of Sirius Group, which was sold by White Mountains in 2016, has been denied interest deductions by the Swedish Tax Authority (“STA”) for tax years 2013-2016. In October 2018, the Swedish Administrative Court ruled against Sirius Group on its appeal of the Swedish Tax Agency’s denial of certain interest deductions relating to periods prior to the sale of Sirius Group to CMI. In connection with the sale, White Mountains indemnified Sirius Group against the loss of certain tax attributes, including those related to these interest deductions. As of December 31, 2019 and December 31, 2018, White Mountains reported a liability of $16.5 million and $17.3 million, reflecting the value of these interest deductions. During 2019, the decrease in the liability of $0.8 million is related to foreign currency translation and included within net gain on sale of discontinued operations. Sirius Group has appealed the decision to the Swedish Administrative Court of Appeal. NSM Renewal Rights Liability In connection with White Mountains’s acquisition of NSM, White Mountains and NSM entered into an agreement with AIG to help facilitate a sale of NSM’s U.S. collector car renewal rights owned by AIG to a third party by December 31, 2019. Under the terms of the agreement, if the Renewal Rights were not sold by December 31, 2019, AIG had the right to require NSM to purchase the Renewal Rights for $82.5 million. On June 28, 2019, NSM acquired the Renewal Rights from AIG for $82.5 million. See Note 2 — “Significant Transactions".

Held for Sale and Discontinued Operations

12 Months Ended

Dec. 31, 2019

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Held for Sale and Discontinued Operations

OneBeacon

On September 28, 2017, Intact Financial Corporation completed its acquisition of OneBeacon in an all-cash transaction for $18.10 per share. White Mountains received total proceeds of $1.3 billion and recorded a gain of $554.6 million, net of transaction costs. For 2017 through the closing date of the transaction, net income from discontinued operations related to OneBeacon was $20.5 million.

Tranzact

On July 21, 2016, White Mountains completed the sale of Tranzact to an affiliate of Clayton, Dubilier & Rice, LLC and received net proceeds of $221.3 million at closing. During 2017, White Mountains recorded a $3.2 million increase to the gain from sale of Tranzact in discontinued operations as a result of state income tax expense.

Sirius Group

On April 18, 2016, White Mountains completed the sale of Sirius Group to CMI for approximately $2.6 billion. Of this amount, $161.8 million of this amount was used to purchase certain assets to be retained by White Mountains out of Sirius Group, including shares of OneBeacon. The amount paid at closing was based on an estimate of Sirius Group’s closing date tangible common shareholder’s equity. During 2017, White Mountains recorded a $0.7 million reduction to the gain from sale of Sirius Group as a result of a change to the valuation of the accrued incentive compensation payable to Sirius Group employees.

In October 2018, the Swedish Administrative Court ruled against Sirius Group on its appeal of the Swedish Tax Agency’s denial of certain interest deductions relating to periods prior to the sale of Sirius Group to CMI. In connection with the sale, White Mountains indemnified Sirius Group against the loss of certain tax attributes, including those related to these interest deductions. As a result, for the year ended December 31, 2018, White Mountains recorded a $17.3 million loss on sale of discontinued operations reflecting the value of these interest deductions. As of December 31, 2019 and 2018, White Mountains reported a liability of $16.5 million and $17.3 million. During 2019, the decrease in the liability of $0.8 million is related to foreign currency translation and included within net gain on sale of discontinued operations. Sirius Group has appealed the decision to the Swedish Administrative Court of Appeal. See Note 19 — “Commitments and Contingencies”.

Other

As of December 31, 2017, White Mountains has classified its Guilford, Connecticut property, which consists of an office building and adjacent land, as held for sale. The related write-down of $3.7 million was recorded within general and administrative expenses during 2017. As of December 31, 2019 and 2018, the property has been measured at its estimated fair value net of disposal costs of $3.0 million and $3.3 million.

Net Income (Loss) from Discontinued Operations

The following table present the results of operations, including related income taxes associated with the business classified as discontinued operations. For the year ended December 31, 2017, the amounts presented relate to OneBeacon, Sirius Group and Tranzact.



	Year Ended December 31, 2017
Millions	OneBeacon		Sirius Group			Tranzact		Total
Revenues
Earned insurance premiums	$	807.6	$	—		$	—	$	807.6
Net investment income	39.7		—			—		39.7
Net realized and unrealized investment gains	38.8		—			—		38.8
Other revenues	7.7		—			—		7.7
Total revenues	893.8		—			—		893.8
Expenses
Loss and loss adjustment expenses	546.0		—			—		546.0
Insurance and reinsurance acquisition expenses	145.6		—			—		145.6
Other underwriting expenses	156.2		—			—		156.2
General and administrative expenses	21.2		—			—		21.2
Interest expense	10.0		—			—		10.0
Total expenses	879.0		—			—		879.0
Pre-tax income	14.8		—			—		14.8
Income tax benefit	5.7		—			—		5.7
Net income from discontinued operations	20.5		—			—		20.5
Gain (loss) from sale of discontinued operations, net of tax	554.5		(.7		)	3.2		557.0
Total income (loss) from discontinued operations	575.0		(.7		)	3.2		577.5
Change in foreign currency translation and other comprehensive income from discontinued operations, net of tax	.3		—			—		.3
Recognition of benefit plan assets and obligations from the sale of OneBeacon, net of tax	2.9		—			—		2.9
Comprehensive income (loss) from discontinued operations	$	578.2	$	(.7	)	$	3.2	$	580.7

Net Change in Cash from Discontinued Operations

The transactions to purchase the investments in OneBeacon and other investments held by Sirius Group prior to the closing are presented in the statement of cash flows as net settlement of investment cash flows with discontinued operations. The following table presents the net change in cash associated with the businesses classified as discontinued operations:



	December 31, 2017
Millions	December 31, 2017
Net cash provided from operations	$	157.0
Net cash provided from investing activities	3.0
Net cash used for financing activities	(61.9		)
Net change in cash during the period	98.1
Cash balances at beginning of period	70.5
Net change in cash held for sale	(.9		)
Cash sold as part of sale of consolidated subsidiaries	(167.7		)
Cash balances at end of period	$	—

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 years ended December 31, 2019, 2018 and 2017:



	Year Ended December 31,
	2019			2018			2017
Basic and diluted earnings per share numerators (in millions):
Net income (loss) attributable to White Mountains’s common shareholders	$	414.5		$	(141.2	)	$	627.2
Less: total income (loss) from continuing operations, net of tax	413.7			(124.0		)	49.7
Net income (loss) from discontinued operations attributable to White Mountains’s common shareholders	.8			(17.2		)	577.5
Allocation of (earnings) losses to participating restricted common shares ⁽¹⁾	—			.2			(7.3		)
Basic and diluted earnings (loss) per share numerators	$	.8		$	(17.0	)	$	570.2
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period	3,181.6			3,382.5			4,293.8
Average unvested restricted common shares ⁽³⁾	(40.5		)	(40.1		)	(54.3		)
Basic earnings (loss) per share denominator	3,141.1			3,342.4			4,239.5
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period	3,181.6			3,382.5			4,293.8
Average unvested restricted common shares ⁽³⁾	(40.5		)	(40.1		)	(54.3		)
Diluted earnings (loss) per share denominator	3,141.1			3,342.4			4,239.5
Basic earnings (loss) per share (in dollars) - discontinued operations:	$	.25		$	(5.09	)	$	134.50
Diluted earnings (loss) per share (in dollars) - discontinued operations:	$	.25		$	(5.09	)	$	134.50


⁽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 years ended December 31, 2019, 2018 and 2017.

⁽³⁾

Restricted common shares outstanding vest either in equal annual installments or upon a stated date. See Note 10 — “Employee Share-Based Compensation Plans”.

Subsequent Event	12 Months Ended
Subsequent Event	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Event	Subsequent Event In January 2020, HG Global and BAM agreed to amend the BAM Surplus Notes to extend the end of the variable interest rate period from 2021 to 2024, to extend the initial 10-year term of the FLRT to the end of 2022 and to enter into an excess of loss reinsurance agreement (the “XOLT”). 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 million or the assets held in the Supplemental Trust at any point in time. At inception, BAM ceded exposure on one covered risk to HG Re under the XOLT. Additional cessions under the XOLT are subject to approval by HG Re. In connection with the actions described in the preceding paragraph, in January 2020, BAM made a $65.0 million special cash payment of principal and interest on the BAM Surplus Notes. 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 in the Supplemental Trust and $16.2 million was a payment of accrued interest held outside the Supplemental Trust. As of January 20, 2020, subsequent to the special cash payment, the BAM Surplus Notes had a principal balance of $409.7 million and accrued interest outstanding of $146.5 million.

Selected Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Selected Quartely Financial Data (Unaudited)

SELECTED QUARTERLY FINANCIAL DATA

(Unaudited)

The following table presents selected quarterly financial data for 2019 and 2018. The quarterly financial data includes, in the opinion of management, all recurring adjustments necessary for a fair presentation of the results of operations for the interim periods.

Prior year amounts have been reclassified to conform to the current period’s presentation. Prior year amounts have also been adjusted for the impact of White Mountains’s financial statement revisions.



	2019 Three Months Ended											2018 Three Months Ended
Millions, Except Per Share Amounts	Dec. 31			Sept. 30			June 30		Mar. 31			Dec. 31			Sept. 30			June 30			Mar. 31
Revenues	$	175.3		$	155.5		$	129.0	$	433.6		$	6.0		$	198.7		$	122.3		$	42.1
Expenses	118.8			104.4			113.2		151.9			150.1			154.4			134.7			108.1
Pre-tax income (loss)	56.5			51.1			15.8		281.7			(144.1		)	44.3			(12.4		)	(66.0		)
Tax (expense) benefit	(10.4		)	(8.8		)	.1		(10.2		)	3.6			3.6			(2.5		)	(.7		)
Income (loss) from continuing operations	46.1			42.3			15.9		271.5			(140.5		)	47.9			(14.9		)	(66.7		)
Net (loss) gain from discontinued operations, net of tax ⁽¹⁾	(.8		)	.9			—		.7			—			(17.3		)	—			.1
Non-controlling interest in consolidated subsidiaries	15.6			5.5			4.6		12.2			3.0			10.2			18.4			18.6
Income (loss) attributable to White Mountains’s common shareholders	$	60.9		$	48.7		$	20.5	$	284.4		$	(137.5	)	$	40.8		$	3.5		$	(48.0	)
Income (loss) attributable to White Mountains’s common shareholders per share:
Basic
Continuing operations	$	19.37		$	15.01		$	6.44	$	89.42		$	(43.24	)	$	18.27		$	1.02		$	(12.85	)
Discontinued operations	(.25		)	.28			—		.22			—			(5.44		)	—			.03
Total consolidated operations	$	19.12		$	15.29		$	6.44	$	89.64		$	(43.24	)	$	12.83		$	1.02		$	(12.82	)
Diluted
Continuing operations	$	19.37		$	15.01		$	6.44	$	89.42		$	(43.24	)	$	18.27		$	1.02		$	(12.85	)
Discontinued operations	(.25		)	.28			—		.22			—			(5.44		)	—			.03
Total consolidated operations	$	19.12		$	15.29		$	6.44	$	89.64		$	(43.24	)	$	12.83		$	1.02		$	(12.82	)

⁽¹⁾ During 2019 and 2018, net (loss) gain from discontinued operations arose from the tax contingency on the sale of Sirius Group. See Note 19 — “Commitments and Contingencies”.

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

12 Months Ended

Dec. 31, 2019

SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Abstract]

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

WHITE MOUNTAINS INSURANCE GROUP, LTD.

SUMMARY OF INVESTMENTS—OTHER THAN

INVESTMENTS IN RELATED PARTIES

At December 31, 2019



Millions	Cost		Carrying Value		Fair Value
Fixed maturity investments:
U.S. Government and agency obligations	$	231.7	$	232.5	$	232.5
Debt securities issued by corporations	454.9		467.2		467.2
Municipal obligations	284.7		297.1		297.1
Mortgage and asset-backed securities	206.6		209.0		209.0
Total fixed maturity investments	1,177.9		1,205.8		1,205.8
Short-term investments	201.2		201.2		201.2
Common equity securities:
Exchange traded funds	436.0		536.4		536.4
Other	117.3		147.5		147.5
Total common equity securities	553.3		683.9		683.9
Other long-term investments	667.4		856.3		856.3
Total investments	$	2,599.8	$	2,947.2	$	2,947.2

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT

12 Months Ended

Dec. 31, 2019

Condensed Financial Information Disclosure [Abstract]

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT

CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT

CONDENSED BALANCE SHEETS ⁽¹⁾



	December 31,
Millions	2019			2018
Assets:
Cash	$	.7		$	.7
Fixed maturity investments, at fair value	10.0			—
Common equity securities, at fair value	193.5			335.6
Short-term investments, at amortized cost	66.2			28.0
Other assets	1.9			1.8
Investments in consolidated subsidiaries	2,969.0			2,533.2
Total assets	$	3,241.3		$	2,899.3
Liabilities:
Payable to subsidiary	$	(69.3	)	$	15.8
Other liabilities	34.7			25.9
Total liabilities⁽²⁾	(34.6		)	41.7
White Mountains’s common shareholders’ equity	3,261.5			2,843.1
Non-controlling interests	14.4			14.5
Total liabilities and equity	$	3,241.3		$	2,899.3

⁽¹⁾ These condensed unconsolidated financial statements reflect the results of operations, financial condition and cash flows for the Company. Investments in in which White Mountains holds a controlling financial interest are accounted for using the equity method. Under the equity method, investments in subsidiaries are recorded on the condensed balance sheets at the amount of the Company’s ownership percentage of the subsidiary’s GAAP book value. The income from subsidiaries is reported on a net of tax basis as equity in earnings from consolidated and unconsolidated subsidiaries on the condensed statements of operations and comprehensive income. Capital contributions to and distributions from subsidiaries are presented within investing activities on the condensed statements of cash flows.

⁽²⁾As of December 31, 2019 and 2018, White Mountains other liabilities includes $16.5 and $17.3 related to the Sirius tax contingency. See Note 19 — “Commitments and Contingencies”.

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

SCHEDULE II (continued)

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME ⁽¹⁾



	Year Ended December 31,
Millions	2019			2018			2017
Revenues (loss) (including realized and unrealized gains and losses)	$	65.0		$	(47.7	)	$	27.3
Expenses	47.1			45.9			99.7
Pre-tax income (loss)	17.9			(93.6		)	(72.4		)
Income tax expense	(.9		)	(2.5		)	(1.4		)
Net income (loss)	17.0			(96.1		)	(73.8		)
Net gain (loss) from discontinued operations, net of tax ⁽²⁾	.8			(17.2		)	—
Equity in earnings from consolidated and unconsolidated subsidiaries, net of tax	398.5			(27.4		)	701.0			⁽³⁾
Net income attributable to non-controlling interests	(1.8		)	(.5		)	—
Net income (loss) attributable to White Mountains’s common shareholders	414.5			(141.2		)	627.2
Other comprehensive (loss) income items, net of tax	(1.4		)	(4.5		)	3.3
Comprehensive income (loss) attributable to White Mountains’s common shareholders	$	413.1		$	(145.7	)	$	630.5

⁽¹⁾ These condensed unconsolidated financial statements reflect the results of operations, financial condition and cash flows for the Company. Investments in which White Mountains holds a controlling financial interest are accounted for using the equity method. Under the equity method, investments in subsidiaries are recorded on the condensed balance sheets at the amount of the Company’s ownership percentage of the subsidiary’s GAAP book value. The income from subsidiaries is reported on a net of tax basis as equity in earnings of subsidiaries on the condensed statements of operations and comprehensive income. Capital contributions to and distributions from subsidiaries are presented within investing activities on the condensed statements of cash flows.

⁽²⁾ During 2019 and 2018, net gain (loss) from discontinued operations includes $0.8 and $(17.3) arising from the tax contingency on the sale of Sirius Group. See Note 19 — “Commitments and Contingencies”.

⁽³⁾ Equity in earnings from consolidated subsidiaries for the year ended December 31, 2017 includes $577.5 of income from discontinued operations associated primarily with the dispositions of OneBeacon, Sirius Group and Tranzact. See Note 20 — “Held for Sale and Discontinued Operations”.

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

SCHEDULE II (continued)

CONDENSED STATEMENTS OF CASH FLOWS ⁽¹⁾⁽²⁾



	Year Ended December 31,
Millions	2019			2018			2017
Net income (loss) attributable to White Mountains’s common shareholders	$	414.5		$	(141.2	)	$	627.2
Charges (credits) to reconcile net income to net cash from operations:
Net realized and unrealized investment (gains) losses on sales of investments	(61.0		)	57.8			(18.5		)
Undistributed earnings from subsidiaries	(398.5		)	27.4			(701.0		)
Net (gain) loss from sale of discontinued operations, net of tax ⁽³⁾	(.8		)	17.2			—
Other non-cash reconciling items, primarily amortization of restricted share and option awards ⁽⁴⁾	20.0			34.6			31.1
Accumulated earnings distributed from subsidiary in cash ⁽⁵⁾	—			—			1,256.7
Net change in other assets and liabilities ⁽⁶⁾	3.0			16.7			(4.9		)
Net cash (used for) provided from operations	(22.8		)	12.5			1,190.6
Cash flows from investing activities:
Net change in short-term investments⁽⁷⁾	(37.6		)	134.0			(24.7		)
Purchases of investment securities ⁽⁸⁾	(14.8		)	(321.2		)	(474.7		)
Sales and maturities of investment securities⁽⁹⁾	207.9			967.6			367.1
Issuance of debt (to) from subsidiaries ⁽¹⁰⁾	(83.5		)	(55.2		)	382.0
Repayment of debt to (from) subsidiaries⁽¹¹⁾	5.0			31.0			—
Net (contributions to) distributions from subsidiaries ^(12)(13)	(46.1		)	(258.2		)	(700.0		)
Net cash provided from (used for) investing activities	30.9			498.0			(450.3		)
Cash flows from financing activities:
Draw down of revolving line of credit ⁽¹⁴⁾	—			—			350.0
Repayment of revolving line of credit ⁽¹⁴⁾	—			—			(350.0		)
Repurchases and retirement of common shares ⁽¹⁰⁾	—			(510.9		)	(714.6		)
Dividends paid on common shares	(3.2		)	(3.8		)	(4.6		)
Payments of restricted shares withholding taxes	(4.9		)	(10.0		)	(9.3		)
Net cash used for financing activities	(8.1		)	(524.7		)	(728.5		)
Net (decrease) increase in cash during the year	—			(14.2		)	11.8
Cash balance at beginning of year	.7			14.9			3.1
Cash balance at end of year	$	.7		$	.7		$	14.9
Supplemental cash flow information: interest paid ⁽¹⁴⁾	$	—		$	—		$	(.6	)

⁽¹⁾

These condensed unconsolidated financial statements reflect the results of operations, financial condition and cash flows for the Company. Investments in which White Mountains holds a controlling financial interest are accounted for using the equity method. Under the equity method, investments in subsidiaries are recorded on the condensed balance sheets at the amount of the Company’s ownership percentage of the subsidiary’s GAAP book value. The income from subsidiaries is reported on a net of tax basis as equity in earnings of subsidiaries on the condensed statements of operations and comprehensive income. Capital contributions to and distributions from subsidiaries are presented within investing activities on the condensed statements of cash flows.

⁽²⁾

During 2017, Lone Tree Holdings, Ltd. (“LTH”), a wholly-owned subsidiary of the Company, merged into the Company. The merger was treated as a liquidation for financial statement purposes. As part of the liquidation, significant non-cash balances that were transferred from LTH to the Company included ending net equity of $2,810.4, intercompany balances of $1,863.1, investments in its subsidiaries of $964.4, short-term investments of $13.0 and other liabilities of $14.1.


⁽³⁾	During 2019 and 2018, net gain (loss) from sale of discontinued operations includes $0.8 and $(17.3) arising from the tax contingency on the sale of Sirius Group. See Note 19 — “Commitments and Contingencies”.


⁽⁴⁾	For the years ended December 31, 2019, 2018 and 2017, amortization of restricted share awards was $10.5, $13.0 and $14.8.


⁽⁵⁾	During 2017, as part of its liquidation into the Company, LTH transferred $1,256.7 of cash, which included $1,037.6 of the proceeds from the sale of OneBeacon, to the Company.


⁽⁶⁾	For 2019, 2018 and 2017, net change in other assets and liabilities also included a $(6.6), $4.0, and $11.6 net change in (receivables) payables to the Company’s subsidiaries.


⁽⁷⁾	During 2018, the Company had non-cash (purchases) and sales of short-term investments of ($284.6) and $179.2.


⁽⁸⁾	During 2018, the Company had non-cash purchases of investment securities of $603.9, which included $170.5 of fixed maturity securities, $148.8 of common equity securities and $22.7 of other long term investments.


⁽⁹⁾	During 2018, the Company had non-cash sales of investment securities of $1,065.4, which included $373.4 of fixed maturity securities, $490.1 of common equity securities and $22.7 of other long-term investments.

⁽¹⁰⁾

During 2018, the Company had non-cash issuance of debt of $349.5 to its wholly-owned subsidiary, Guilford Holding, Inc. (“Guilford”). Proceeds of the debt, which included $170.4 of fixed maturity securities and $179.2 of short-term investments, were transferred to Guilford. During 2017, the Company had non-cash issuance of debt from LTH of $94.2. During 2017, the Company used cash proceeds received from the issuance of debt from LTH, primarily to fund repurchases of its common shares.


⁽¹¹⁾	During 2018, the Company received non-cash repayments of $22.7 from its wholly-owned subsidiary, Bridge Holdings (“Bridge”) in the form of other long term investments.

⁽¹²⁾

During 2019, the Company made cash contributions of $70.5 and $2.0 to Bridge and its wholly-owned subsidiary, White Mountains Investment Bermuda, Ltd (“WMIB”). During 2018, the Company made non-cash contributions of $350.0 by transferring intercompany debt receivable from Guilford to Bridge. Also during 2018, the Company made a non-cash contribution of $1.0 by transferring intercompany debt receivable from White Mountains Investment, Ltd. (Luxembourg) (“White Mountains Investments”), a wholly-owned subsidiary of Bridge, to Bridge. During 2018, the Company made cash contributions of $255.3 and $2.9 to Bridge and White Mountains Investments. During 2017, the Company made cash contributions of $700.0 to Guilford.


⁽¹³⁾	During 2019, the Company received cash distributions of $24.4 and $1.9 from WMIB and the Company’s subsidiary, HG Global Ltd. During 2017, the Company received non-cash distributions of $1,238.9 from LTH, prior to its liquidation. The distribution was completed through the transfer of fixed maturity investments and common equity securities.


⁽¹⁴⁾	The WTM Bank Facility was a direct obligation of the Registrant as of December 31, 2017 and was terminated on May 8, 2018. See Note 5 — “Debt”.

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

SCHEDULE III SUPPLEMENTARY INSURANCE INFORMATION

12 Months Ended

Dec. 31, 2019

SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Abstract]

SCHEDULE III SUPPLEMENTARY INSURANCE INFORMATION

WHITE MOUNTAINS INSURANCE GROUP, LTD.

SUPPLEMENTARY INSURANCE INFORMATION ⁽¹⁾



	Column A	Column B		Column C		Column D		Column E		Column F		Column G		Column H		Column I		Column J		Column K
	Millions Segment	Deferred Acqui- sition Costs		Future Policy Benefits, Losses, Claims and Loss Expenses		Unearned Premiums		Other Policy Claims and Benefits Payable		Premiums Earned		Net Investment Income		Benefits, Claims, Losses and Settlement Expenses		Amortization of Deferred Policy Acquisition Costs		Other Operating Expenses		Premiums Written
Years ended:

December 31, 2019
	HG Global/ BAM	$	22.1	$	—	$	198.4	$	—	$	16.3	$	21.6	$	—	$	5.7	$	.4	$	38.7
	Other Operations ⁽²⁾	—		—		—		—		—		—		—		—		—		—
December 31, 2018
	HG Global/ BAM	19.0		—		176.0		—		13.9		16.7		—		5.3		.4		52.9
	Other Operations ⁽²⁾	—		—		—		—		—		—		—		—		—		—
December 31, 2017
	HG Global/ BAM	14.8		—		136.8		—		9.4		12.3		—		4.0		.4		63.2
	Other Operations ⁽²⁾⁽³⁾	—		—		—		—		1.0		—		1.1		.1		—		.9

⁽¹⁾Schedule excludes activity related to OneBeacon and Sirius Group for the year ended December 31, 2017. See Note 20 — “Held for Sale and Discontinued Operations”.

⁽²⁾The amounts shown exclude net investment income relating to non-insurance operations of $43.4, $42.3 and $43.7 for the twelve months ended December 31, 2019, 2018 and 2017, respectively.

⁽³⁾The Other Operations amounts shown relate to SSIE. White Mountains completed the sale of SSIE on March 7, 2017. See Note 20 — “Held for Sale and Discontinued Operations”.

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

SCHEDULE IV REINSURANCE

12 Months Ended

Dec. 31, 2019

SEC Schedule, 12-17, Insurance Companies, Reinsurance [Abstract]

SCHEDULE IV REINSURANCE

WHITE MOUNTAINS INSURANCE GROUP, LTD.

REINSURANCE ⁽¹⁾



Column A	Column B		Column C		Column D		Column E		Column F
$ in Millions Premiums Earned	Gross Amount		Ceded to Other Companies		Assumed from Other Companies		Net Amount		Percentage of Amount Assumed to Net
Year ended:
December 31, 2019
HG Global/BAM	$	13.6	$	—	$	2.7	$	16.3	16.6	%
Other Operations	—		—		—		—		—
December 31, 2018
HG Global/BAM	13.6		—		.3		13.9		2.2
Other Operations	—		—		—		—		—
December 31, 2017
HG Global/BAM	9.4		—		—		9.4		—
Other Operations⁽²⁾	1.0		—		—		1.0		—


⁽¹⁾	Schedule excludes activity related to OneBeacon and Sirius Group for the year ended December 31, 2017. See Note 20 — “Held for Sale and Discontinued Operations”.


⁽²⁾	The Other Operations amounts shown relate to SSIE. White Mountains completed the sale of SSIE on March 7, 2017. See Note 20 — “Held for Sale and Discontinued Operations”.

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

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2019
Accounting Policies [Abstract]
Nature of Operations and Basis of Presentation	Basis of Presentation The Company is an exempted Bermuda limited liability company whose principal businesses are conducted through its insurance 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 80 South Main Street, Hanover, New Hampshire 03755-2053 and its registered office is located at Clarendon House, 2 Church Street, Hamilton, Bermuda HM 11. 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. 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. See Note 16 — “Variable Interest Entities”. Intercompany transactions have been eliminated in consolidation. Certain amounts in the prior period financial statements have been reclassified to conform to the current presentation.
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.
Reporting 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 December 31, 2019, White Mountains’s reportable segments were HG Global/BAM, NSM, Kudu and Other Operations. As a result of the MediaAlpha Transaction, White Mountains no longer consolidated MediaAlpha, and consequently it was no longer a reportable segment. See Note 14 — “Segment Information”. 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 reinsurance 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 million of Series A Notes and $300 million of Series B Notes (the “BAM Surplus Notes”). As of December 31, 2019 and 2018, 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 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, social services and real estate. On behalf of its insurance carrier partners, NSM 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 December 31, 2019 and 2018, White Mountains owned 96.4% and 95.5% of the basic units outstanding of NSM (88.4% and 85.0% on a fully diluted, fully converted basis). NSM was acquired by White Mountains in 2018. 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. On April 4, 2019, White Mountains acquired the ownership interests in Kudu held by certain funds managed by Oaktree Capital Management, L.P. (“Oaktree”) for cash consideration of $81.4 million. In addition, White Mountains assumed all of Oaktree’s unfunded capital commitments to Kudu, increasing White Mountains’s total capital commitment to $250.0 million (the “Kudu Transaction”). As a result of the Kudu Transaction, White Mountains’s basic unit ownership of Kudu increased from 49.5% to 99.1% (42.7% to 85.4% on a fully diluted, fully converted basis), and White Mountains began consolidating Kudu as a reportable segment in its financial statements during the second quarter of 2019. See Note 2 — “Significant Transactions". During the fourth quarter of 2019, White Mountains increased its total capital commitment to Kudu by $100.0 million to $350.0 million of which $129.0 million was undrawn as of December 31, 2019. Also during the fourth quarter of 2019, Kudu obtained a committed $125.0 million credit facility, of which $68.0 million was undrawn as of December 31, 2019. The Other Operations segment consists of the Company and its wholly-owned subsidiary, White Mountains Capital, Inc., 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 (for periods after the MediaAlpha Transaction), PassportCard Limited (“PassportCard”) and DavidShield Life Insurance Agency (2000) Ltd. (“DavidShield”) (collectively, “PassportCard/ DavidShield”), Elementum Holdings LP (“Elementum”) and Kudu (for periods prior to the Kudu Transaction), and certain other consolidated and unconsolidated entities and certain other strategic investments. The MediaAlpha segment consisted of QL Holdings LLC and its wholly-owned subsidiary QuoteLab, LLC (collectively “MediaAlpha”). MediaAlpha is a marketing technology company that enables the programmatic buying and selling of vertical-specific, performance-based media between advertisers (buyers of advertising inventory) and publishers (sellers of advertising inventory). MediaAlpha operates in insurance and non-insurance verticals and uses cost-per-click, cost-per-call and cost-per-lead pricing models. MediaAlpha’s media buying platform enables advertisers to create and automate data-driven bidding strategies designed to improve the efficiency and enhance overall performance of their marketing campaigns that target high-intent consumers at the time and place they are ready to purchase. MediaAlpha’s publisher platform is used by publishers to sell their media to advertisers through transparent, programmatic, auction-based marketplaces. On February 26, 2019, MediaAlpha completed the sale of a significant minority stake to Insignia Capital Group in connection with a recapitalization and cash distribution to existing equityholders (the “MediaAlpha Transaction”). White Mountains deconsolidated MediaAlpha as a result of the MediaAlpha Transaction and it was no longer a reportable segment. White Mountains’s consolidated statement of comprehensive income and its segment disclosures include MediaAlpha’s results of operations through the date of the MediaAlpha Transaction. See Note 2 — “Significant Transactions”.
Discontinued Operations and Assets and Liabilities Held for Sale	Discontinued Operations and Assets and Liabilities Held for Sale As of December 31, 2017, White Mountains classified its Guilford, Connecticut property, which consists of an office building and adjacent land, as held for sale. The property was valued at its estimated fair value, net of disposal costs. The related write-down of $3.7 million was recorded within general and administrative expenses during 2017. As of December 31, 2019 and 2018, the property has been measured at its estimated fair value, net of disposal costs of $3.0 million and $3.3 million. See Note 20 — “Held for Sale and Discontinued Operations”.
Cash	Cash Cash includes amounts on hand and demand deposits with banks and other financial institutions. Amounts presented in the statement of cash flows are shown net of balances acquired and sold in the purchase or sale of the Company’s consolidated subsidiaries and exclude changes in amounts of restricted cash. Restricted cash consists primarily of amounts in fiduciary accounts held by NSM on behalf of insurance carriers.
Short-term Investments	Short-Term Investments Short-term investments consist of interest-bearing money market funds and other securities, which at the time of purchase, mature or become available for use within one year. Short-term investments are carried at amortized or accreted cost, which approximated fair value as of December 31, 2019 and 2018.
Investment securities	Investment Securities As of December 31, 2019 and 2018, White Mountains’s invested assets consisted of securities and other investments held for general investment purposes. White Mountains’s portfolio of fixed maturity investments, common equity securities and other long-term investments held for general investment purposes are generally classified as trading securities and are reported at fair value as of the balance sheet date. Changes in net unrealized investment gains (losses) are reported pre-tax in revenues. Realized investment gains (losses) are accounted for using the specific identification method and are reported pre-tax in revenues. Premiums and discounts on all fixed maturity investments are amortized and accreted to income over the anticipated life of the investment. White Mountains’s invested assets that are measured at fair value include fixed maturity investments, common equity securities and other long-term investments, including unconsolidated entities, non-controlling equity interests in the form of revenue and earnings participation contracts (“Kudu’s Participation Contracts”), private equity funds, hedge funds, insurance-linked securities (“ILS”) funds and private debt instruments. Whenever possible, White Mountains estimates fair value using valuation methods that maximize the use of quoted prices and other observable inputs. 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 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”). Assets and liabilities carried at fair value include substantially all of the investment portfolio and derivative instruments, both exchange traded and over the counter instruments. Valuation of assets measured at fair value require management to make estimates and apply judgment to matters that may carry a significant degree of uncertainty. In determining its estimates of fair value, White Mountains uses a variety of valuation approaches and inputs. Whenever possible, White Mountains estimates fair value using valuation methods that maximize the use of observable prices and other inputs. Where appropriate, assets and liabilities measured at fair value have been adjusted for the effect of counterparty credit risk. White Mountains uses outside pricing services and brokers to assist in determining fair values. The outside pricing services White Mountains uses have indicated that they will only provide prices where observable inputs are available. As of December 31, 2019, approximately 71% of the investment portfolio recorded at fair value was priced based upon quoted market prices or other observable inputs.
Level 1, 2 and 3 Measurements	Level 1 Measurements Investments valued using Level 1 inputs include fixed maturity investments, primarily investments in U.S. Treasuries and short-term investments, which include U.S. Treasury Bills, and common equity securities. For investments in active markets, White Mountains uses the quoted market prices provided by outside pricing services to determine fair value. Level 2 Measurements Investments valued using Level 2 inputs include fixed maturity investments which have been disaggregated into classes, including debt securities issued by corporations, municipal obligations and mortgage and asset-backed securities. Investments valued using Level 2 inputs also include certain passive exchange-traded funds (“ETFs”) that track U.S. stock indices such as the S&P 500 Index, but are traded on foreign exchanges, which White Mountains values using the fund manager’s published net asset value per share (“NAV”) to account for the difference in market close times. In circumstances where quoted market prices are unavailable or are not considered reasonable, White Mountains estimates the fair value using industry standard pricing methodologies and observable inputs such as benchmark yields, reported trades, broker-dealer quotes, issuer spreads, benchmark securities, bids, offers, credit ratings, prepayment speeds, reference data including research publications and other relevant inputs. Given that many fixed maturity investments do not trade on a daily basis, the outside pricing services evaluate a wide range of fixed maturity investments by regularly drawing parallels from recent trades and quotes of comparable securities with similar features. The characteristics used to identify comparable fixed maturity investments vary by asset type and take into account market convention. White Mountains’s process to assess the reasonableness of the market prices obtained from the outside pricing sources covers substantially all of its fixed maturity investments and includes, but is not limited to, the evaluation of pricing methodologies and a review of the pricing services’ quality control procedures on at least an annual basis, a comparison of its invested asset prices obtained from alternate independent pricing vendors on at least a semi-annual basis, monthly analytical reviews of certain prices and a review of the underlying assumptions utilized by the pricing services for select measurements on an ad hoc basis throughout the year. White Mountains also performs back-testing of selected investment sales activity to determine whether there are any significant differences between the market price used to value the security prior to sale and the actual sale price of the security on an ad-hoc basis throughout the year. Prices provided by the pricing services that vary by more than $0.5 million and 5% from the expected price based on these assessment procedures are considered outliers, as are prices that have not changed from period to period and prices that have trended unusually compared to market conditions. In circumstances where the results of White Mountains’s review process does not appear to support the market price provided by the pricing services, White Mountains challenges the vendor provided price. If White Mountains cannot gain satisfactory evidence to support the challenged price, White Mountains will rely upon its own internal pricing methodologies to estimate the fair value of the security in question. The valuation process described above is generally applicable to all of White Mountains’s fixed maturity investments. The techniques and inputs specific to asset classes within White Mountains’s fixed maturity investments for Level 2 securities that use observable inputs are as follows: Debt Securities Issued by Corporations: The fair value of debt securities issued by corporations is determined from a pricing evaluation technique that uses information from market sources and integrates relative credit information, observed market movements, and sector news. Key inputs include benchmark yields, reported trades, broker-dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, and reference data including sector, coupon, credit quality ratings, duration, credit enhancements, early redemption features and market research publications. Municipal Obligations: The fair value of municipal obligations is determined from a pricing evaluation technique that uses information from market makers, brokers-dealers, buy-side firms, and analysts along with general market information. Key inputs include benchmark yields, reported trades, issuer financial statements, material event notices and new issue data, as well as broker-dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, and reference data including type, coupon, credit quality ratings, duration, credit enhancements, geographic location and market research publications. Mortgage and Asset-Backed Securities: The fair value of mortgage and asset-backed securities is determined from a pricing evaluation technique that uses information from market sources and leveraging similar securities. Key inputs include benchmark yields, reported trades, underlying tranche cash flow data, collateral performance, plus new issue data, as well as broker-dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, and reference data including issuer, vintage, loan type, collateral attributes, prepayment speeds, default rates, recovery rates, cash flow stress testing, credit quality ratings and market research publications. Level 3 Measurements Fair value estimates for investments that trade infrequently and have few or no quoted market prices or other observable inputs are classified as Level 3 measurements. Investments valued using Level 3 fair value estimates are based upon unobservable inputs and include investments in certain fixed maturity investments, common equity securities and other long-term investments where quoted market prices or other observable inputs are unavailable or are not considered reliable or reasonable. Level 3 valuations are generated from techniques that use assumptions not observable in the market. These unobservable inputs reflect White Mountains’s assumptions of what market participants would use in valuing the investment. In certain circumstances, investment securities may start out as Level 3 when they are originally issued, but as observable inputs become available in the market, they may be reclassified to Level 2. Transfers of securities between levels are based on investments held as of the beginning of the period.
Other Long-Term Investments	Other Long-term Investments - NAV White Mountains’s portfolio of other long-term investments includes investments in private equity funds, hedge funds and ILS funds. White Mountains employs a number of procedures to assess the reasonableness of the fair value measurements for its private equity funds, hedge funds and ILS funds, including obtaining and reviewing periodic and audited annual financial statements as well as discussing each fund’s pricing with the fund manager throughout the year. However, since the fund managers do not provide sufficient information to evaluate the pricing methods and inputs for each underlying investment, White Mountains considers the inputs to be unobservable. The fair value of White Mountains’s private equity fund, hedge fund and ILS fund investments are generally determined using the fund manager’s NAV. In the event that White Mountains believes the fair value of a private equity fund, hedge fund or ILS fund differs from the NAV reported by the fund manager due to illiquidity or other factors, White Mountains will adjust the reported NAV to more appropriately represent the fair value of its investment in the private equity fund, hedge fund or ILS fund.
Derivatives	Derivatives White Mountains holds from time to time a variety of derivative financial instruments for risk management purposes. White Mountains recognizes all derivatives as either other assets or other liabilities, aside from the foreign currency forward contracts which are recognized within other long-term investments, measured at fair value, in the consolidated balance sheets. 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 December 31, 2019 and 2018, White Mountains holds an interest rate swap derivative instrument that meets the criteria for hedge accounting. In 2018, White Mountains held a foreign currency forward contract derivative instrument that did not meet the criteria for hedge accounting. The foreign currency forward contract was closed in the first quarter of 2018. From time to time, White Mountains holds warrants that it has received in the restructuring of certain of its common equity securities and fixed maturity investments. White Mountains accounts for its investments in warrants as derivatives.
Receivables	Receivables BAM’s receivables consist primarily of premiums receivable from customers for municipal bond insurance policies. NSM’s receivables consist of insurance premiums receivable from customers and commissions receivable from insurance carriers, net of a provision for amounts estimated to be uncollectible. MediaAlpha receivables consist of advertising fee receivables from publishers and advertisers.
Incentive Compensation	Incentive Compensation 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. Non-share based awards are recognized over the related service periods based on management’s best estimate of the amounts at which the awards are expected to be paid. Share-based compensation which is typically settled in cash, such as performance shares, is classified as a liability-type award. The compensation cost for liability-classified awards is measured initially at the grant date fair value and remeasured each reporting period until settlement. The compensation cost for equity-classified awards expected to be settled in shares, such as options and restricted shares, is measured at the original grant date fair value of the award. The compensation cost for all awards is recognized for the vested portion of the awards over the related service periods. See Note 10 — “Employee Share-Based Incentive Compensation Plans”.
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 trade names, URL and online names, customer relationships and contracts, information technology platforms and insurance licenses. Goodwill and other intangible assets with indefinite lives are not amortized, but rather are evaluated for impairment on an annual basis, or whenever indications of potential impairment exist. In the absence of any indications of potential impairment, the evaluation of goodwill and indefinite-lived intangible assets is performed no later than the interim period in which the anniversary of the acquisition date falls. White Mountains initially evaluates goodwill using a qualitative approach (step zero) to determine whether it is more likely than not that the implied fair value of goodwill is greater than its carrying value. If the results of the qualitative evaluation indicate that it is more likely than not that the carrying value of goodwill exceeds its implied fair value, White Mountains performs the two-step quantitative test for impairment. Other intangible assets with finite lives are measured at their acquisition date fair values, are amortized over their economic lives and presented net of accumulated amortization on the balance sheet. Other intangible assets with finite lives are
Municipal Bond Guarantee Insurance	Municipal Bond Guarantee Insurance All of the contracts issued by BAM are accounted for as insurance contracts under ASC 944-605, Financial Guarantee Insurance Contracts. Premiums are generally received upfront and an unearned premium revenue liability, equal to the amount of the premium received, is established at contract inception. Installment premiums are measured at the present value of contractual premiums, discounted at the risk-free rate, which is set at the inception of the insurance contract. Premium revenues are recognized in revenue over the period of the contracts in proportion to the amount of insurance protection provided using a constant rate. The constant rate is calculated based on the relationship between the par outstanding in a given reporting period compared with the sum of each of the par amounts outstanding for all periods. Deferred acquisition costs represent commissions, premium taxes, excise taxes and other costs which are directly attributable to and vary with the production of business. These costs are deferred and amortized to the extent they relate to successful contract acquisitions over the applicable premium recognition period as acquisition expenses. Deferred acquisition costs are limited to the amount expected to be recovered from future earned premiums and anticipated investment income. BAM’s obligation for outstanding contracts consists of the unearned premium reserve and any loss reserves. Loss reserves are recorded only to the extent that the present value of the expected amount of any losses to be paid, net of any expected recoveries, exceeds the associated unearned premium reserve. As of December 31, 2019 and 2018, BAM did not have any loss or loss adjustment expense reserves.
Revenue Recognition	Revenue Recognition NSM’s revenues consist primarily of commissions and broker revenues for placement of insurance policies and administrative fees for claims and other services provided to insurance carriers. Commission and broker revenues and service fees are measured based on the contractual rates with insurance carriers, net of any amounts expected to be uncollectible and any amounts associated with expected policy cancellations, adjustments, and are recognized when contractual performance obligations have been fulfilled. NSM’s primary contractual performance obligations are generally satisfied upon the issuance of an insurance policy by the carrier. Where NSM has significant performance obligations beyond the policy issuance date, NSM estimates the relative standalone selling price for the post-issuance services in order to allocate the transaction price using the price charged for the service when sold separately in similar circumstances to similar customers. Deferred revenues associated with unsatisfied performance obligations are recognized within other liabilities. Contingent commissions are based upon the overall profit and/or volume of the business placed with the insurance carrier during a calendar year and are determined after the contractual period has ended. NSM recognizes revenue on contingent commissions when management has determined that it is probable that the contingent commission requirements have been met. Kudu’s revenues are primarily generated from non-controlling equity interests in revenue and earnings participation contracts with asset management firms. The participation contracts are measured at fair value with the change therein recognized within unrealized investment gains and losses. Distributions from Kudu’s clients are recognized through investment income when Kudu’s right to receive payment has been established and can be reliably measured, which generally occurs on a quarterly basis in accordance with the terms of the underlying participation contracts. MediaAlpha recognized advertising and publishing fee revenues based on the contractual amount of the fees, adjusted for any amounts expected to be refunded or uncollectible, when it had satisfied its contractual performance obligations, which was generally at the time each transaction was executed. For transactions where MediaAlpha acted as the principal, such as the Open exchange, revenue amounts were reported gross. For transactions where MediaAlpha acted as an agent facilitating transactions between third parties, revenue amounts were reported at the net fee billed.
Cost of Sales and Broker Commission Expense	Cost of Sales and Broker Commission Expense NSM’s broker commission expense consists of commissions paid to sub-agents and brokers. Broker commission expense is measured in accordance with contractual terms and recognized when incurred, which is generally at the policy issuance date. MediaAlpha’s cost of sales consisted primarily of revenue sharing payments to publisher partners and traffic acquisition costs to top tier search engines. Cost of sales were measured based on contract terms and recognized when the related revenue transactions are executed. Other Operations’s cost of sales consists of salaries and related expenses, professional services and marketing and advertising expenses directly related to sales generation. These expenses are recognized as incurred.
Federal and foreign income taxes	Federal and Foreign Income Taxes A number of White Mountains’s subsidiaries file consolidated tax returns in the United States. Income earned or losses generated by companies outside the United States are generally subject to an overall effective tax rate lower than that imposed by the United States. Deferred tax assets and liabilities are recorded when a difference between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts for tax purposes exists, and for other temporary differences. The deferred tax asset or liability is recorded based on tax rates expected to be in effect when the difference reverses. The deferred tax asset is recognized when it is more likely than not that it will be realized.
Foreign currency exchange	Foreign Currency Exchange The functional currency for White Mountains’s non-U.S. based subsidiaries are measured, in most instances, using functional currencies other than the U.S. dollar. Net foreign exchange gains and losses arising from the translation of functional currencies are generally reported in shareholders’ equity, in accumulated other comprehensive income or loss. White Mountains also invests in securities denominated in foreign currencies. Assets and liabilities recorded in these foreign currencies are translated into U.S. dollars at exchange rates in effect at the balance sheet date, and revenues and expenses are converted using the weighted average exchange rates for the period.
Noncontrolling Interest	Non-controlling Interests Non-controlling interests consist of the ownership interests of non-controlling shareholders in consolidated subsidiaries, and are presented separately on the balance sheet. The portion of comprehensive income attributable to non-controlling interests is presented net of related income taxes in the statement of operations and comprehensive income. See Note 12 — “Common Shareholders’ Equity and Non-controlling Interests”.
Recent Accounting Pronouncements	Recently Adopted Changes in Accounting Principles Leases On January 1, 2019, White Mountains adopted ASU 2016-02, Leases (ASC 842), which requires lessees to recognize lease assets and liabilities on the balance sheet for both operating and financing leases, with the exception of leases with an original term of 12 months or less. White Mountains elected the optional transition method that permits prospective adoption with recognition of a cumulative effect adjustment to the opening balance of retained earnings. As a result, White Mountains has presented comparative periods prior to adoption in accordance with previous lease accounting guidance. White Mountains also elected all available practical expedients permitted under ASC 842, which allowed White Mountains to carryforward its historical lease classification and not reassess leases for the definition of a lease under the new guidance. Upon adoption on January 1, 2019, White Mountains recognized $23.2 million for both the lease right-of-use (“ROU”) assets and lease liabilities. As of December 31, 2019, White Mountains recognized $22.6 million and $22.8 million of lease ROU assets and lease liabilities. Adoption of ASU 2016-02 did not result in an adjustment to opening retained earnings. Premium Amortization on Callable Debt Securities On January 1, 2019, White Mountains adopted ASU 2017-08, Premium Amortization on Purchased Callable Debt Securities (ASC 310-20), which changes the amortization period for certain purchased callable debt securities. Under the new guidance, for investments in callable debt securities held at a premium, the premium is amortized over the period to the earliest call date. The new guidance does not change the amortization period for callable debt securities held at a discount. Adoption of ASU 2017-08 did not have any impact on White Mountains’s financial statements. Revenue Recognition On January 1, 2018, White Mountains adopted ASU 2014-09, Revenue from Contracts with Customers (ASC 606), which modifies the guidance for revenue recognition. Under ASU 2014-09, revenue is recognized at an amount that reflects the consideration to which an entity expects to be entitled once it fulfills its performance obligations under the terms of its contract with the customer. The scope of the new guidance includes agent commissions and other non-insurance revenues. Adoption of ASU 2014-09 did not have any impact on White Mountains's financial statements. Share-Based Compensation On January 1, 2018, White Mountains adopted ASU 2017-09, Stock Compensation: Scope of Modification Accounting (ASC 718), which narrows the scope of transactions subject to modification accounting to changes in the terms of an award that result in a change in the award’s fair value, vesting conditions or classification. Adoption of ASU 2017-09 did not have any impact on White Mountains’s financial statements. Business Combinations On January 1, 2018, White Mountains adopted ASU 2017-01, Business Combinations: Clarifying the Definition of a Business (ASC 805), which clarifies the definition of a business and affects the determination of whether acquisitions or disposals are accounted for as assets or as a business. Under the new guidance, when substantially all of the fair value of the assets is concentrated in a single identifiable asset or group of similar assets, it is not a business. Adoption of ASU 2017-01 did not have any impact on White Mountains’s financial statements. Cash Flow Statement On January 1, 2018, White Mountains adopted ASU 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments (ASC 230), which addresses the classification and presentation of certain items, including debt prepayment and extinguishment costs, contingent consideration payments made after a business combination and distributions received from equity method investees, for which there was diversity in practice prior to the issuance of ASU 2016-15. Also on January 1, 2018, White Mountains adopted ASU 2016-18, Statement of Cash Flows: Restricted Cash (ASC 230), which modifies the guidance for the treatment of restricted cash amounts in the cash flow statement. The new guidance requires restricted cash to be included in the reconciliation of beginning and end-of-period amounts presented on the statement of cash flows and requires a description of the nature of the changes in restricted cash during the periods presented. Adoption of ASU 2016-15 and ASU 2016-18 did not have any impact on White Mountains's statement of cash flows. Financial Instruments - Recognition and Measurement On January 1, 2018, White Mountains adopted ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities (ASC 825-10), which modifies the guidance for financial instruments, including investments in equity securities. Under the new guidance, all equity securities with readily determinable fair values are required to be measured at fair value with changes therein recognized through current period earnings. In addition, the new ASU requires a qualitative assessment for equity securities without readily determinable fair values to identify impairment, and for impaired equity securities to be measured at fair value. White Mountains measures its portfolio of investment securities at fair value with changes therein recognized through current period earnings and, accordingly, adoption of ASU 2016-01 did not have any impact on White Mountains's financial statements. Recently Issued Accounting Pronouncements Income Taxes In December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for Income Taxes (ASC 740), which eliminates exceptions related to the approach for intra-period tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. ASU 2019-12 also clarifies and simplifies other aspects of the accounting for income taxes. Adoption of ASU 2019-12 is required for fiscal years beginning after December 15, 2020, with early adoption permitted. White Mountains did not elect to adopt the new guidance in 2019 and is currently evaluating the impact of adoption. VIE In October 2018, the FASB issued ASU 2018-17, Targeted Improvements to Related party Guidance for Variable Interest Entities (ASC 810), which changes the way indirect interests held through related parties under common control are evaluated, requiring consideration of such interests on a proportional basis for purposes of determining whether fees paid to decision makers and service providers are variable interests. The new guidance is effective for fiscal years beginning after December 15, 2019. White Mountains does not currently have any variable interests where the new guidance would affect the determination of the primary beneficiary and does not expect adoption to have any impact on its financial statements. Goodwill In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment (ASC 350), which changes the guidance on goodwill impairment testing. Under the new guidance, the qualitative assessment of the recoverability of goodwill remains the same. However, the second step required under the existing guidance has been eliminated. Goodwill is considered impaired if the carrying value exceeds the estimated fair value. The new guidance is effective for fiscal years beginning after December 15, 2019. White Mountains does not expect adoption to have any impact on its periodic evaluation of goodwill. Credit Losses In June 2016, the FASB issued 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. This differs from current GAAP, which delays recognition until it is probable a loss has been incurred. The new guidance is expected to accelerate recognition of credit losses. The types of assets within the scope of the new guidance include loans and trade receivables such as premium receivables and reinsurance recoverables on paid losses. ASU 2016-13 is effective for annual periods beginning after January 1, 2020, including interim periods. White Mountains measures its portfolio of investment securities at fair value with changes therein recognized through current period earnings and does not expect adoption to have any effect on its financial statements.

Investment Securities (Tables)

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Pre-tax net investment income

The following table presents pre-tax net investment income for 2019, 2018 and 2017:



	Year Ended December 31,
Millions	2019			2018			2017
Fixed maturity investments	$	32.4		$	35.1		$	44.9
Short-term investments	5.0			8.0			1.8
Common equity securities	13.5			15.1			10.6
Other long-term investments	30.1			3.8			1.2
Total investment income	81.0			62.0			58.5
Third-party investment expenses	(1.3		)	(3.0		)	(2.5		)
Net investment income, pre-tax	$	79.7		$	59.0		$	56.0

Net Realized and Unrealized Investment Gains and Losses

The following table presents net realized and unrealized investment gains (losses) for 2019, 2018 and 2017:



	Year Ended December 31,
Millions	2019			2018			2017
Net realized investment gains (losses), pre-tax ⁽¹⁾	$	96.6		$	(12.9	)	$	24.1
Net unrealized investment gains (losses), pre-tax ⁽²⁾	336.6			(95.4		)	109.2
Net realized and unrealized investment gains (losses), pre-tax	433.2			(108.3		)	133.3
Income tax (expense) benefit attributable to net realized and unrealized investment gains (losses)	(87.0		)	18.2			(12.9		)
Net realized and unrealized investment gains (losses), after-tax	$	346.2		$	(90.1	)	$	120.4

Realized Gain (Loss) on Investments

The following tables present net realized investment gains (losses) for the years ended 2019, 2018 and 2017:



	Year Ended December 31, 2019
Millions	Net Realized Gains			Net Foreign Exchange Gains (Losses)		Total Net Realized Gains Reflected in Earnings
Fixed maturity investments	$	4.9		$	—	$	4.9
Short-term investments	.2			—		.2
Common equity securities	85.9			—		85.9
Other long-term investments ⁽¹⁾	5.6			—		5.6
Net realized investment gains, pre-tax	96.6			—		96.6
Income tax expense attributable to net realized investment gains	(10.6		)	—		(10.6		)
Net realized investment gains, after-tax	$	86.0		$	—	$	86.0



	Year Ended December 31, 2018
Millions	Net Realized (Losses) Gains			Net Foreign Exchange Gains (Losses)			Total Net Realized (Losses) Gains Reflected in Earnings
Fixed maturity investments	$	(29.8	)	$	18.2		$	(11.6	)
Short-term investments	(.8		)	—			(.8		)
Common equity securities	6.6			—			6.6
Other long-term investments	.1			(7.2		)	(7.1		)
Net realized investment (losses) gains, pre-tax	(23.9		)	11.0			(12.9		)
Income tax benefit attributable to net realized investment (losses) gains	9.1			—			9.1
Net realized investment (losses) gains, after-tax	$	(14.8	)	$	11.0		$	(3.8	)



	Year Ended December 31, 2017
Millions	Net Realized (Losses) Gains			Net Foreign Exchange Gains (Losses)			Total Net Realized Gains (Losses) Reflected in Earnings
Fixed maturity investments	$	(1.6	)	$	4.1		$	2.5
Short-term investments	(.3		)	—			(.3		)
Common equity securities	18.1			6.0			24.1
Other long-term investments	19.1			(21.3		)	(2.2		)
Net realized investment gains (losses), pre-tax	35.3			(11.2		)	24.1
Income tax expense attributable to net realized investment gains (losses)	(8.9		)	—			(8.9		)
Net realized investment gains (losses), after-tax	$	26.4		$	(11.2	)	$	15.2

Unrealized Gain (Loss) on Investments

The following tables present net unrealized investment gains (losses) and changes in the carrying value of investments measured at fair value for the years ended 2019, 2018 and 2017:



	Year Ended December 31, 2019
Millions	Net Unrealized Gains			Net Foreign Exchange Losses			Total Net Unrealized Gains Reflected in Earnings
Fixed maturity investments	$	38.6		$	—		$	38.6
Common equity securities	109.8			—			109.8
Other long-term investments ⁽¹⁾	188.5			(.3		)	188.2
Net unrealized investment gains (losses), pre-tax	336.9			(.3		)	336.6
Income tax expense attributable to net unrealized investment gains	(76.4		)	—			(76.4		)
Net unrealized investment gains (losses), after-tax	$	260.5		$	(.3	)	$	260.2



	Year Ended December 31, 2018
Millions	Net Unrealized (Losses) Gains			Net Foreign Exchange (Losses) Gains			Total Net Unrealized (Losses) Gains Reflected in Earnings
Fixed maturity investments	$	(8.3	)	$	(14.8	)	$	(23.1	)
Common equity securities	(105.5		)	—			(105.5		)
Other long-term investments	30.2			3.0			33.2
Net unrealized investment losses, pre-tax	(83.6		)	(11.8		)	(95.4		)
Income tax benefit attributable to net unrealized investment losses	9.1			—			9.1
Net unrealized investment losses, after-tax	$	(74.5	)	$	(11.8	)	$	(86.3	)



	Year Ended December 31, 2017
Millions	Net Unrealized Gains (Losses)			Net Foreign Exchange Gains (Losses)			Total Net Unrealized Gains (Losses) Reflected in Earnings
Fixed maturity investments	$	13.8		$	12.7		$	26.5
Common equity securities	99.3			—			99.3
Other long-term investments	(15.6		)	(1.0		)	(16.6		)
Net unrealized investment gains, pre-tax	97.5			11.7			109.2
Income tax expense attributable to net unrealized investment gains	(4.0		)	—			(4.0		)
Net unrealized investment gains, after-tax	$	93.5		$	11.7		$	105.2

Net unrealized investment gains (losses) for Level 3 investments



	Year Ended December 31,
Millions	2019		2018		2017
Other long-term investments	$	181.9	$	22.6	$	(15.4	)

Investment holdings, fixed maturity investments



	December 31, 2019
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Carrying Value
U.S. Government and agency obligations	$	231.7	$	1.0	$	(.2	)	$	232.5
Debt securities issued by corporations	454.9		12.5		(.2		)	467.2
Municipal obligations	284.7		12.5		(.1		)	297.1
Mortgage and asset-backed securities	206.6		2.7		(.3		)	209.0
Total fixed maturity investments	$	1,177.9	$	28.7	$	(.8	)	$	1,205.8



	December 31, 2018
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Carrying Value
U.S. Government and agency obligations	$	154.0	$	.1	$	(.9	)	$	153.2
Debt securities issued by corporations	519.0		1.0		(9.5		)	510.5
Municipal obligations	279.0		2.4		(1.1		)	280.3
Mortgage and asset-backed securities	136.1		.1		(2.7		)	133.5
Total fixed maturity investments	$	1,088.1	$	3.6	$	(14.2	)	$	1,077.5

Schedule of contractual maturities of fixed maturities



	December 31, 2019
Millions	Cost or Amortized Cost		Carrying Value
Due in one year or less	$	190.0	$	190.8
Due after one year through five years	481.6		489.3
Due after five years through ten years	165.3		173.2
Due after ten years	134.4		143.5
Mortgage and asset-backed securities	206.6		209.0
Total	$	1,177.9	$	1,205.8

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



	December 31, 2019
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Net Foreign Currency Losses			Carrying Value
Common equity securities	$	553.3	$	130.6	$	—		$	—		$	683.9
Other long-term investments	$	667.4	$	255.2	$	(64.1	)	$	(2.2	)	$	856.3



	December 31, 2018
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Net Foreign Currency Losses			Carrying Value
Common equity securities	$	904.7	$	51.0	$	(30.1	)	$	—		$	925.6
Other long-term investments	$	330.3	$	52.2	$	(54.9	)	$	(2.0	)	$	325.6

Fair value measurements by level, investment securities



	December 31, 2019
Millions	Fair Value		Level 1		Level 2		Level 3
Fixed maturity investments:
U.S. Government and agency obligations	$	232.5	$	232.5	$	—	$	—
Debt securities issued by corporations:
Financials	144.8		—		144.8		—
Industrial	59.0		—		59.0		—
Healthcare	52.6		—		52.6		—
Consumer	50.9		—		50.9		—
Energy	44.9		—		44.9		—
Technology	41.2		—		41.2		—
Communications	31.3		—		31.3		—
Utilities	25.0		—		25.0		—
Materials	17.5		—		17.5		—
Total debt securities issued by corporations	467.2		—		467.2		—

Municipal obligations	297.1		—		297.1		—
Mortgage and asset-backed securities	209.0		—		209.0		—
Total fixed maturity investments	1,205.8		232.5		973.3		—

Short-term investments ⁽¹⁾	201.2		189.4		11.8		—

Common equity securities:

Exchange traded funds ⁽²⁾	536.4		521.6		14.8		—
Other ⁽³⁾	147.5		25.9		121.5		0.1
Total common equity securities	683.9		547.5		136.3		0.1
Other long-term investments	654.0		—		—		654.0
Other long-term investments — NAV⁽⁴⁾	202.3		—		—		—
Total investments	$	2,947.2	$	969.4	$	1,121.4	$	654.1

⁽¹⁾Short-term investments are measured at amortized cost, which approximates fair value.

⁽²⁾ ETFs traded on foreign exchanges are priced using the fund’s published NAV to account for the difference in market close times and are therefore designated a Level 2 measurement.

⁽³⁾Primarily consists of two investments in unit trusts that predominantly invest in international equities and an open-end mutual fund that invests in domestic large-cap companies.



	December 31, 2018
Millions	Fair Value		Level 1		Level 2		Level 3
Fixed maturity investments:
U.S. Government and agency obligations	$	153.2	$	153.2	$	—	$	—

Debt securities issued by corporations:
Financials	143.4		—		143.4		—
Consumer	68.5		—		68.5		—
Technology	60.5		—		60.5		—
Energy	57.6		—		57.6		—
Healthcare	55.0		—		55.0		—
Industrial	47.6		—		47.6		—
Communications	31.8		—		31.8		—
Materials	26.3		—		26.3		—
Utilities	19.8		—		19.8		—
Total debt securities issued by corporations	510.5		—		510.5		—

Municipal obligations	280.3		—		280.3		—
Mortgage and asset-backed securities	133.5		—		133.5		—
Total fixed maturity investments	1,077.5		153.2		924.3		—

Short-term investments ⁽¹⁾	214.2		204.4		9.8		—

Common equity securities:
Exchange traded funds ⁽²⁾	675.3		617.0		58.3		—
Healthcare	14.0		14.0		—		—
Financials	13.5		13.5		—		—
Communications	12.7		12.7		—		—
Industrial	11.4		11.4		—		—
Technology	7.4		7.4		—		—
Consumer	6.2		6.2		—		—
Energy	4.1		4.1		—		—
Materials	3.1		3.1		—		—
Other ⁽³⁾	177.9		—		177.9		—
Total common equity securities	925.6		689.4		236.2		—
Other long-term investments	138.7		—		—		138.7
Other long-term investments — NAV ⁽⁴⁾	186.9		—		—		—
Total investments	$	2,542.9	$	1,047.0	$	1,170.3	$	138.7

⁽¹⁾Short-term investments are measured at amortized cost, which approximates fair value.

⁽²⁾ETFs traded on foreign exchanges are priced using the fund’s published NAV to account for the difference in market close times and are therefore designated a Level 2 measurement.

⁽³⁾Consists of two investments in unit trusts that predominantly invest in international equities.

Debt securities issued by corporations, credit ratings

The following table presents the ratings of debt securities issued by corporations held in White Mountains’s investment portfolio as of December 31, 2019 and 2018:



	Fair Value at December 31,
Millions	2019		2018
AAA	$	9.5	$	8.9
AA	73.9		88.7
A	288.5		270.5
BBB	95.3		142.4
Debt securities issued by corporations ⁽¹⁾	$	467.2	$	510.5


⁽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-backed, asset-backed securities

The following table presents the fair value of White Mountains’s mortgage and asset-backed securities as of December 31, 2019 and 2018:



	December 31, 2019						December 31, 2018
Millions	Fair Value		Level 2		Level 3		Fair Value		Level 2		Level 3
Mortgage-backed securities:
Agency:
FNMA	$	88.6	$	88.6	$	—	$	53.6	$	53.6	$	—
FHLMC	60.5		60.5		—		38.1		38.1		—
GNMA	30.8		30.8		—		23.7		23.7		—
Total agency ⁽¹⁾	179.9		179.9		—		115.4		115.4		—
Total mortgage-backed securities	179.9		179.9		—		115.4		115.4		—
Other asset-backed securities:
Vehicle receivables	15.1		15.1		—		9.2		9.2		—
Credit card receivables	14.0		14.0		—		8.9		8.9		—
Total other asset-backed securities	29.1		29.1		—		18.1		18.1		—
Total mortgage and asset-backed securities	$	209.0	$	209.0	$	—	$	133.5	$	133.5	$	—

⁽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).

Other Investments Not Readily Marketable

The following table presents the carrying values of White Mountains’s other long-term investments as of December 31, 2019 and 2018:



	Carrying Value at
Millions	December 31, 2019		December 31, 2018
Kudu’s Participation Contracts ⁽¹⁾⁽²⁾	$	266.5	$	—
MediaAlpha ⁽¹⁾⁽³⁾	180.0		—
PassportCard/DavidShield ⁽¹⁾	90.0		75.0
Elementum ⁽¹⁾	55.1		—
Other unconsolidated entities ⁽¹⁾⁽⁴⁾	31.2		60.0
Kudu ⁽⁵⁾	—		30.7
Total unconsolidated entities ⁽¹⁾	622.8		165.7
Private equity funds and hedge funds	161.1		146.1
Insurance-linked securities funds	41.2		—
Other	31.2		13.8
Total other long-term investments	$	856.3	$	325.6

⁽¹⁾See Fair Value Measurements by Level table.

⁽³⁾ The MediaAlpha Transaction was completed on February 26, 2019. See Note 2 — “Significant Transactions”.

⁽⁴⁾Includes White Mountains’s non-controlling equity interests in certain private common equity securities, limited liability companies and convertible preferred securities.

⁽⁵⁾ Includes White Mountains’s non-controlling equity interest in Kudu prior to consolidation. See Note 2 — “Significant Transactions”.

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 December 31, 2019 and 2018:



	December 31, 2019				December 31, 2018
Millions	Fair Value		Unfunded Commitments		Fair Value		Unfunded Commitments

Private equity funds
Manufacturing/Industrial	$	57.7	$	4.1	$	42.9	$	10.5
Aerospace/Defense/Government	33.8		23.3		27.6		34.9
Financial services	15.0		22.8		8.3		13.6
Direct lending	—		—		13.0		17.7
Total private equity funds	106.5		50.2		91.8		76.7

Hedge funds
Long/short banks and financial	54.6		—		54.3		—
Total hedge funds	54.6		—		54.3		—
Total private equity funds and hedge funds included in other long-term investments	$	161.1	$	50.2	$	146.1	$	76.7

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 December 31, 2019:



Millions	1 – 3 years		3 – 5 years		5 – 10 years		>10 years		Total
Private equity funds — expected lock-up period remaining	$	4.8	$	51.9	$	40.2	$	9.6	$	106.5

Rollforward of fair value investments by level

The following tables present the changes in White Mountains’s fair value measurements by level for the years ended December 31, 2019 and 2018:



							Level 3 Investments					Other Long-term Investments Measured at NAV ⁽³⁾
Millions	Level 1 Investments			Level 2 Investments			Common Equity Securities		Other Long-term Investments⁽²⁾			Other Long-term Investments Measured at NAV ⁽³⁾			Total
Balance at December 31, 2018	$	842.6		$	1,160.5		$	—	$	138.7		$	186.9		$	2,328.7		⁽¹⁾
Net realized and unrealized gains	163.0			76.1			—		181.2			12.7			433.0			⁽²⁾⁴⁾
Amortization/accretion	.2			(1.8		)	—		—			—			(1.6		)
Purchases	165.3			404.5			.1		185.4			110.8			866.1
Sales	(391.1		)	(529.7		)	—		—			(29.5		)	(950.3		)
Effect of Kudu Transaction	—			—			—		141.8			(71.7		)	70.1
Transfers in	—			—			—		10.9			4.0			14.9
Transfers out	—			—			—		(4.0		)	(10.9		)	(14.9		)
Balance at December 31, 2019	$	780.0		$	1,109.6		$	.1	$	654.0		$	202.3		$	2,746.0		⁽¹⁾

⁽¹⁾Excludes carrying value of $201.2 and $214.2 as of December 31, 2019 and 2018 classified as short-term investments.


⁽²⁾	Includes $114.7 unrealized investment gain associated with the MediaAlpha Transaction, which is recorded in a separate line item in the statement of operations titled Realized gain and unrealized investment gain from the MediaAlpha Transaction. See Note 2 — “Significant Transactions”.

⁽⁴⁾ Excludes realized and unrealized losses associated with short-term investments of $0.2 for the year ended December 31, 2019.



							Level 3 Investments		Other Long-term Investments Measured at NAV ⁽³⁾
Millions	Level 1 Investments			Level 2 Investments			Other Long- term Investments		Other Long-term Investments Measured at NAV ⁽³⁾			Total
Balance at December 31, 2017	$	890.4		$	2,105.4		$	77.2	$	135.3		$	3,208.3		⁽¹⁾⁽²⁾
Net realized and unrealized (losses) gains	(64.9		)	(64.4		)	16.2		13.3			(99.8		)	⁽⁴⁾
Amortization/accretion	.2			(2.7		)	—		—			(2.5		)
Purchases	514.7			783.8			45.3		50.5			1,394.3
Sales	(497.8		)	(1,661.6		)	—		(12.2		)	(2,171.6		)
Transfers in	—			—			—		—			—
Transfers out	—			—			—		—			—
Balance at December 31, 2018	$	842.6		$	1,160.5		$	138.7	$	186.9		$	2,328.7		⁽²⁾

⁽¹⁾Excludes carrying value of $(3.7) as of December 31, 2017 associated with foreign currency forward contracts.

⁽²⁾Excludes carrying value of $214.2 and $176.1 as of December 31, 2018 and 2017 classified as short-term investments.


⁽³⁾	Includes private equity funds, hedge funds and unconsolidated entities 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”.

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



$ in Millions	December 31, 2019
Description	Valuation Technique(s)	Fair Value ⁽¹⁾	Unobservable Inputs
			Discount Rate ⁽²⁾	Terminal Cash Flow Exit Multiple (x) or Terminal Revenue Growth Rate (%) ⁽²⁾
Kudu’s Participation Contracts	Discounted cash flow	$266.5	15% - 22%	6x - 12x
MediaAlpha	Discounted cash flow	$180.0	15%	4%
PassportCard/DavidShield	Discounted cash flow	$90.0	22%	4%
Elementum Holdings, L.P.	Discounted cash flow	$55.1	20%	4%
Private debt instruments	Discounted cash flow	$23.7	4% - 9%	N/A
All other	Discounted cash flow	$23.7	25% - 32%	4%

Compare.com	Estimated net realizable value	$2.5	Net asset value:	$2.5

⁽¹⁾Includes the net unrealized investment gains (losses) associated with foreign currency; foreign currency effects based on observable inputs.



$ in Millions	December 31, 2018
Description	Valuation Technique(s)	Fair Value ⁽¹⁾	Unobservable Inputs
			Discount Rate ⁽²⁾	Terminal Revenue Exit Multiple (x) ⁽²⁾
PassportCard/DavidShield	Discounted cash flow	$75.0	18%	1x
Compare.com	Discounted cash flow	$16.9	22%	3x
Private debt instrument	Discounted cash flow	$10.0	9%	N/A
All other	Discounted cash flow	$30.0	23%	2x - 4x

Galvanic Applied Sciences	Multiple of EBITDA	$3.1	EBITDA multiple:	6x

⁽¹⁾Includes the net unrealized investment gains (losses) associated with foreign currency; foreign currency effects based on observable inputs.

Goodwill and Other Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Recognized Identified Assets Acquired



$ in Millions	Weighted Average Economic Life (in years)	December 31, 2019									December 31, 2018
$ in Millions	Weighted Average Economic Life (in years)	Acquisition Date Fair Value		Accumulated Amortization		Impairments		Net Carrying Value			Acquisition Date Fair Value		Accumulated Amortization		Net Carrying Value
Goodwill:
NSM ⁽¹⁾⁽²⁾	N/A	$	381.6	$	—	$	—	$	381.6		$	354.3	$	—	$	354.3
Kudu	N/A	7.6		—		—		7.6			—		—		—
MediaAlpha	N/A	—		—		—		—			18.3		—		18.3
Other Operations ⁽³⁾	N/A	13.1		—		7.6		5.5			7.3		—		7.3
Total goodwill		402.3		—		7.6		394.7			379.9		—		379.9
Other intangible assets:
NSM ⁽¹⁾⁽²⁾
Customer relationships	9	121.7		19.8		1.4		100.5			85.3		6.0		79.3
Trade names	19	61.9		5.3		.4		56.2			51.2		1.8		49.4
Information technology platform	5	3.9		1.4		.6		1.9			3.7		.5		3.2
Renewal rights	12	82.5		.7		—		81.8			—		—		—
Other	3	1.7		.7		—		1.0			—		—		—
Subtotal		271.7		27.9		2.4		241.4			140.2		8.3		131.9
Kudu
Trade names	7	2.2		.2		—		2.0			—		—		—
MediaAlpha
Customer relationships	9	—		—		—		—			26.8		4.9		21.9
Information technology platform	5	—		—		—		—			33.3		30.9		2.4
Other	3	—		—		—		—			9.8		9.0		.8
Subtotal		—		—		—		—			69.9		44.8		25.1
Other Operations
Trade names	10	1.7		.5		.2		1.0			.6		.2		.4
Customer Relationships	11	7.2		.4		—		6.8			—		—		—
Information technology platform	5	.5		.3		.2		—			.5		.3		.2
Insurance licenses	N/A	8.6		—		—		8.6			—		—		—
Other	5	.2		—		—		.2			—		—		—
Subtotal		18.2		1.2		.4		16.6			1.1		.5		.6
Total other intangible assets		292.1		29.3		2.8		260.0			211.2		53.6		157.6
Total goodwill and other intangible assets		$	694.4	$	29.3	$	10.4	654.7			$	591.1	$	53.6	537.5
Goodwill and other intangible assets attributed to non-controlling interests								(23.4		)					(40.6		)
Goodwill and other intangible assets included in White Mountains’s common shareholders’ equity								$	631.3						$	496.9

⁽³⁾As of December 31, 2019 and 2018, Other Operations’ goodwill includes $0.0 and $(0.3) of the effect of foreign currency translation.

The following table presents a summary of the acquisition date fair values of goodwill and other intangible assets for acquisitions completed during 2019 and 2018:



$ in Millions
Acquisition of Subsidiary/ Asset	Goodwill and Other Intangible Assets⁽¹⁾		Acquisition Date
NSM	$	383.0	May 11, 2018
Fresh Insurance	54.6		May 18, 2018
KBK⁽³⁾	65.3		December 3, 2018
Embrace⁽²⁾	67.6		April 1, 2019
Renewal Rights ⁽³⁾	82.5		June 28, 2019
Total NSM segment	$	653.0
Kudu Transaction	$	9.8	April 4, 2019
Other Operations	$	22.6	Various

⁽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.

⁽²⁾Excludes $3.4 of software classified within other assets.

Schedule of Goodwill and Intangible Assets Rollforward

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



	December 31,
	2019									2018
Millions	Goodwill			Other Intangible Assets			Total Goodwill and Other Intangible Assets			Goodwill			Other Intangible Assets			Total Goodwill and Other Intangible Assets
Beginning balance	$	379.9		$	157.6		$	537.5		$	25.9		$	36.2		$	62.1
Acquisitions of businesses ⁽¹⁾	64.8			34.6			99.4			356.5			140.9			497.4
Acquisition of collector car renewal rights	—			82.5			82.5			—			—			—
Dispositions of businesses ⁽²⁾	(18.3		)	(23.5		)	(41.8		)	—			—			—
Attribution of acquisition date fair value estimates between goodwill and other intangible assets⁽³⁾	(26.8		)	26.8			—			—			—			—
Impairments ⁽⁴⁾	(7.6		)	(2.8		)	(10.4		)	—			—			—
Measurement period adjustments⁽⁵⁾	.9			5.9			6.8			—			—			—
Foreign currency translation	1.8			.7			2.5			(2.5		)	(.7		)	(3.2		)
Amortization	—			(21.8		)	(21.8		)	—			(18.8		)	(18.8		)
Ending balance	$	394.7		$	260.0		$	654.7		$	379.9		$	157.6		$	537.5

⁽²⁾Dispositions relate to the MediaAlpha Transaction. See Note 2 — “Significant Transactions”.


⁽³⁾	The determination of the relative fair values of goodwill and other intangible assets recognized in connection with the acquisition of KBK was completed in 2019. The attribution is net of a $5.9 measurement period adjustment for contingent consideration.

⁽⁴⁾ Impairments of $7.6 and $0.4 of goodwill and other intangible assets relate to Other Operations and $2.4 of impairments to other intangible relate to Fresh Insurance.


⁽⁵⁾	Measurement period adjustments relate to updated information about acquisition date fair values of assets acquired and liabilities assumed.

Schedule of Finite-Lived Intangible Assets, Future Amortization Expense

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



Millions	Amortization Expense
2020	$	23.9
2021	30.5
2022	29.7
2023	28.4
2024 and years after	138.9
Total ⁽¹⁾	$	251.4

Debt (Tables)

12 Months Ended

Dec. 31, 2019

Debt Disclosure [Abstract]

Schedule of debt outstanding

The following table presents White Mountains’s debt outstanding as of December 31, 2019 and 2018:



	December 31,			Effective	December 31,			Effective
$ in Millions	2019			Rate ⁽¹⁾	2018			Rate ⁽¹⁾
NSM Bank Facility	$	221.3		7.5%	$	180.4		7.4%
Unamortized issuance cost	(3.9		)		(3.8		)
NSM Bank Facility, carrying value	217.4				176.6
Other NSM debt	1.8			3.0%	1.9			2.2%
Kudu Bank Facility	57.0			8.3%	—
Unamortized issuance cost	(3.4		)		—
Kudu Bank Facility, carrying value	53.6				—
MediaAlpha Bank Facility	—				14.3			7.1%
Unamortized issuance cost	—				(.1		)
MediaAlpha Bank Facility, carrying value	—				14.2
Other Operations debt	11.1			8.3%	—
Unamortized issuance cost	(.4		)		—
Other Operations debt, carrying value	10.7				—
Total debt	$	283.5			$	192.7

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

Schedule of contractual repayments of debt

The following table presents a schedule of contractual repayments of White Mountains’s debt as of December 31, 2019:



Millions	December 31, 2019
Due in one year or less	$	2.8
Due in two to three years	7.0
Due in four to five years	226.2
Due after five years	55.2
Total	$	291.2

- 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=6877327&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=114775744&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=26873400&loc=d3e23780-122690

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
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-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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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
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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

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of total income tax benefit (expense)

The following table presents the total income tax (expense) benefit for the years ended December 31, 2019, 2018 and 2017:



	Year Ended December 31,
Millions	2019			2018			2017
Current income tax benefit (expense):
U.S. federal	$	.9		$	(.1	)	$	(.3	)
State	(3.7		)	(1.4		)	(1.3		)
Non-U.S.	(1.7		)	(2.9		)	(2.0		)
Total current income tax (expense) benefit	(4.5		)	(4.4		)	(3.6		)
Deferred income tax (expense) benefit:
U.S. federal	(14.9		)	8.3			11.4
State	(10.4		)	—			—
Non-U.S.	.5			.1			—
Total deferred income tax (expense) benefit	(24.8		)	8.4			11.4
Total income tax (expense) benefit	$	(29.3	)	$	4.0		$	7.8

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



	Year Ended December 31,
Millions	2019			2018			2017
Tax (expense) benefit at the U.S. statutory rate	$	(85.1	)	$	37.4		$	(2.7	)
Differences in taxes resulting from:
Change in valuation allowance	63.6			(31.0		)	42.6
Non-U.S. earnings, net of foreign taxes	27.1			(2.9		)	21.5
State taxes	(17.5		)	4.0			.6
Tax rate changes	(5.7		)	1.7			(44.3		)
Member’s surplus contributions	(3.6		)	(2.6		)	(3.0		)
Withholding tax	(1.6		)	(2.7		)	(2.0		)
Tax exempt interest and dividends	1.1			.6			.5
Tax reserve adjustments	(.7		)	(.8		)	(.3		)
Officer compensation	—			—			(4.1		)
Other, net	(6.9		)	.3			(1.0		)
Total income tax (expense) benefit on pre-tax income (loss)	$	(29.3	)	$	4.0		$	7.8

Schedule of components of deferred income tax assets and liabilities

The following table presents an outline of the significant components of White Mountains’s U.S. federal, state and non-U.S. deferred tax assets and liabilities:



	December 31,
Millions	2019			2018
Deferred tax assets related to:
U.S. federal and state net operating and capital loss carryforwards	$	92.3		$	95.5
Non-U.S. net operating loss carryforwards	41.7			36.6
Incentive compensation	15.0			14.1
Investment basis difference	—			11.1
Net unrealized investment losses	—			9.5
Accrued interest	5.1			—
Deferred acquisition costs	4.3			3.5
Tax credit carryforwards	4.2			4.2
Other items	3.4			5.8
Total gross deferred tax assets	166.0			180.3
Less: valuation allowances	77.9			139.9
Total net deferred tax assets	88.1			40.4
Deferred tax liabilities related to:
Net unrealized investment gains	66.3			—
Member’s surplus contributions	43.2			32.8
Investment basis difference	6.6			—
Other items	4.6			5.4
Total deferred tax liabilities	120.7			38.2
Net deferred tax (liability) asset	$	(32.6	)	$	2.2

Schedule of net operating and capital loss carryforwards by expiration dates and the deferred tax assets thereon

The following table presents net operating loss and capital loss carryforwards as of December 31, 2019, the expiration dates and the deferred tax assets thereon:



	December 31, 2019
Millions	United States			Luxembourg			United Kingdom			Israel			Total
2019-2023	$	.1		$	—		$	—		$	—		$	.1
2024-2028	—			—			—			—			—
2029-2038	302.6			58.0			—			—			360.6
No expiration date	117.4			28.5			18.7			73.6			238.2
Total	$	420.1		$	86.5		$	18.7		$	73.6		$	598.9
Gross deferred tax asset	$	88.0		$	21.6		$	3.2		$	16.9		$	129.7
Valuation allowance	(63.5		)	(21.5		)	(3.0		)	(16.9		)	(104.9		)
Net deferred tax asset	$	24.5		$	.1		$	.2		$	—		$	24.8

Reconciliation of changes in the amount of unrecognized tax benefits

The following table presents a reconciliation of the beginning and ending amount of unrecognized tax benefits from 2017 to 2019:



Millions	Permanent Differences ⁽¹⁾		Temporary Differences ⁽²⁾		Interest and Penalties ⁽³⁾		Total
Balance at December 31, 2016	$	—	$	—	$	—	$	—
Changes in prior year tax positions	.1		—		—		.1
Tax positions taken during the current year	.2		—		—		.2
Balance at December 31, 2017	.3		—		—		.3
Changes in prior year tax positions	.8		—		—		.8
Balance at December 31, 2018	1.1		—		—		1.1
Tax positions taken during the current year	1.3		—		—		1.3
Balance at December 31, 2019	$	2.4	$	—	$	—	$	2.4


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


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

⁽³⁾

Net of tax benefit.

Municipal Bond Guarantee Insurance (Tables)

12 Months Ended

Dec. 31, 2019

Insurance [Abstract]

Financial Guarantee Insurance Contracts, Premium Received over Contract Period [Table Text Block]

The following table presents a schedule of BAM’s future premium revenues as of December 31, 2019:



Millions	December 31, 2019
January 1, 2020 - March 31, 2020	$	4.8
April 1, 2020 - June 30, 2020	4.8
July 1, 2020 - September 30, 2020	4.6
October 1, 2020 - December 31, 2020	4.5
	18.7
2021	17.3
2022	16.3
2023	15.2
2024	14.2
2025 and thereafter	116.7
Total gross unearned insurance premiums	$	198.4

Schedule of Insured Obligations

The following table presents a schedule of BAM’s insured obligations as of December 31, 2019 and 2018:



	December 31, 2019		December 31, 2018
Contracts outstanding	8,987		7,525
Remaining weighted average contract period (in years)	10.7		10.7
Contractual debt service outstanding (in millions):
Principal	$	62,250.5	$	52,201.6
Interest and capital appreciation	31,799.7		26,560.3
Total debt service outstanding	$	94,050.2	$	78,761.9

Gross unearned insurance premiums	$	198.4	$	176.0

Schedule of Net Written Premiums

The following table presents a schedule of net written premiums and net earned premiums included in White Mountains’s HG Global/BAM segment for the years ended December 31, 2019, 2018 and 2017:



Millions	December 31, 2019		December 31, 2018		December 31, 2017
Written premiums:
Direct	$	28.1	$	44.8	$	63.2
Assumed	10.6		8.1		—
Gross written premiums	$	38.7	$	52.9	$	63.2
Earned premiums:
Direct	$	13.6	$	13.6	$	9.4
Assumed	2.7		.3		—
Gross earned premiums	$	16.3	$	13.9	$	9.4

Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Computation of earnings per share



	Year Ended December 31,
	2019			2018			2017
Basic and diluted earnings per share numerators (in millions):
Net income (loss) attributable to White Mountains’s common shareholders	$	414.5		$	(141.2	)	$	627.2
Less: total income (loss) from discontinued operations, net of tax	.8			(17.2		)	577.5
Net income (loss) from continuing operations attributable to White Mountains’s common shareholders	413.7			(124.0		)	49.7
Allocation of (earnings) losses to participating restricted common shares⁽¹⁾	(5.3		)	1.4			(.7		)
Basic and diluted earnings (losses) per share numerators	$	408.4		$	(122.6	)	$	49.0
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period	3,181.6			3,382.5			4,293.8
Average unvested restricted common shares⁽²⁾	(40.5		)	(40.1		)	(54.3		)
Basic earnings (losses) per share denominator	3,141.1			3,342.4			4,239.5
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period	3,181.6			3,382.5			4,293.8
Average unvested restricted common shares⁽²⁾	(40.5		)	(40.1		)	(54.3		)
Diluted earnings (losses) per share denominator	3,141.1			3,342.4			4,239.5
Basic and diluted earnings per share (in dollars) - continuing operations:
Distributed earnings - dividends declared and paid	$	1.00		$	1.00		$	1.00
Undistributed earnings (losses)	129.02			(37.67		)	10.56
Basic and diluted earnings (losses) per share	$	130.02		$	(36.67	)	$	11.56

⁽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 10 — “Employee Share-Based Incentive Compensation Plans”.

Schedule of discontinued operations balance sheet, income statement, and cash flows



	Year Ended December 31,
Millions		2019			2018			2017
Undistributed net earnings - continuing operations:
Net income (loss) attributable to White Mountains’s common shareholders, net of restricted common share amounts		$	408.4		$	(122.6	)	$	49.0
Dividends declared, net of restricted common share amounts ⁽¹⁾		(3.2		)	(3.7		)	(4.5		)
Total undistributed net earnings (losses), net of restricted common share amounts		$	405.2		$	(126.3	)	$	44.5

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

Net Income (Loss) from Discontinued Operations



	Year Ended December 31, 2017
Millions	OneBeacon		Sirius Group			Tranzact		Total
Revenues
Earned insurance premiums	$	807.6	$	—		$	—	$	807.6
Net investment income	39.7		—			—		39.7
Net realized and unrealized investment gains	38.8		—			—		38.8
Other revenues	7.7		—			—		7.7
Total revenues	893.8		—			—		893.8
Expenses
Loss and loss adjustment expenses	546.0		—			—		546.0
Insurance and reinsurance acquisition expenses	145.6		—			—		145.6
Other underwriting expenses	156.2		—			—		156.2
General and administrative expenses	21.2		—			—		21.2
Interest expense	10.0		—			—		10.0
Total expenses	879.0		—			—		879.0
Pre-tax income	14.8		—			—		14.8
Income tax benefit	5.7		—			—		5.7
Net income from discontinued operations	20.5		—			—		20.5
Gain (loss) from sale of discontinued operations, net of tax	554.5		(.7		)	3.2		557.0
Total income (loss) from discontinued operations	575.0		(.7		)	3.2		577.5
Change in foreign currency translation and other comprehensive income from discontinued operations, net of tax	.3		—			—		.3
Recognition of benefit plan assets and obligations from the sale of OneBeacon, net of tax	2.9		—			—		2.9
Comprehensive income (loss) from discontinued operations	$	578.2	$	(.7	)	$	3.2	$	580.7

Net Change in Cash from Discontinued Operations



	December 31, 2017
Millions	December 31, 2017
Net cash provided from operations	$	157.0
Net cash provided from investing activities	3.0
Net cash used for financing activities	(61.9		)
Net change in cash during the period	98.1
Cash balances at beginning of period	70.5
Net change in cash held for sale	(.9		)
Cash sold as part of sale of consolidated subsidiaries	(167.7		)
Cash balances at end of period	$	—

- 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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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+ Details

Employee Share-Based Incentive Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Summary of performance share activity

The following table presents performance share activity for the years ended December 31, 2019, 2018 and 2017 for performance shares granted under the WTM Incentive Plan:



	Year Ended December 31,
	2019					2018					2017
$ in Millions	Target Performance Shares Outstanding		Accrued Expense			Target Performance Shares Outstanding		Accrued Expense			Target Performance Shares Outstanding		Accrued Expense
Beginning of period	40,616		$	31.7		50,515		$	45.8		80,353		$	42.4
Shares paid or expired ⁽¹⁾	(13,715	)	(18.1		)	(23,186	)	(28.4		)	(30,838	)	(21.9		)
New grants	15,600		—			14,105		—			17,710		—
Forfeitures ⁽²⁾	(28	)	(.1		)	(818	)	.1			(16,710	)	(9.3		)
Expense recognized	—		30.2			—		14.2			—		34.6
End of period ⁽³⁾	42,473		$	43.7		40,616		$	31.7		50,515		$	45.8

⁽¹⁾


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

⁽³⁾

Outstanding performance share awards as of December 31, 2017 exclude 2,195 unvested performance shares awards for employees of Sirius Group, which are included in discontinued operations.

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

The following table presents performance shares outstanding and accrued expense for performance shares awarded under the WTM Incentive Plan as of December 31, 2019 for each performance cycle:



$ in Millions	Target Performance Shares Outstanding		Accrued Expense
Performance cycle:
2019 – 2021	15,600		$	6.0
2018 – 2020	13,450		10.5
2017 – 2019	14,070		27.8
Sub-total	43,120		44.3
Assumed forfeitures	(647	)	(.6		)
Total	42,473		$	43.7

Schedule of nonvested restricted stock activity

The following table presents the unrecognized compensation cost associated with the outstanding restricted share awards under the WTM Incentive Plan for the years ended December 31, 2019, 2018 and 2017:



	Year Ended December 31,
	2019					2018					2017
$ in Millions	Restricted Shares		Unamortized Issue Date Fair Value			Restricted Shares		Unamortized Issue Date Fair Value			Restricted Shares		Unamortized Issue Date Fair Value
Non-vested,
Beginning of period	41,510		$	12.5		53,755		$	14.3		70,620		$	19.7
Issued	15,600		14.5			14,105		11.4			17,985		16.3
Vested	(13,715	)	—			(25,381	)	—			(28,846	)	—
Forfeited	—		—			(969	)	(.2		)	(6,004	)	(3.5		)
Expense recognized	—		(10.3		)	—		(13.0		)	—		(18.2		)
End of period ⁽¹⁾	43,395		$	16.7		41,510		$	12.5		53,755		$	14.3

⁽¹⁾

Outstanding restricted share awards as of December 31, 2017 include 2,195 unvested restricted shares for employees of Sirius Group

Leases (Tables)

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Lease, Cost

The following table summarizes net lease expense recognized in White Mountains’s consolidated statement of operations for the year ended December 31, 2019:



Millions Lease Cost	December 31, 2019
Lease cost	$	7.2
Less: sublease income	.4
Net lease cost	$	6.8

Lessee, Operating Lease, Liability, Maturity

The following table presents the contractual maturities of the lease liabilities associated with White Mountains’s operating lease agreements as of December 31, 2019:



Millions	As of December 31, 2019
2020	$	5.9
2021	4.9
2022	4.5
2023	3.9
2024	3.1
Thereafter	3.4
Total undiscounted lease payments	25.7
Less: present value adjustment	(2.9		)
Operating lease liability	$	22.8

Schedule of Right-of-Use Assets and Lease Liabilities

The following table presents lease related assets and liabilities by reportable segment as of December 31, 2019:



	As of December 31, 2019
$ in Millions	HG/BAM		NSM		Kudu		Other Operations		Total		Weighted Average Incremental Borrowing Rate ⁽¹⁾
ROU lease asset	$	10.4	$	4.8	$	2.3	$	5.1	$	22.6	4.6%
Lease liability	$	10.4	$	4.8	$	2.3	$	5.3	$	22.8	4.6%

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

Common Shareholders’ Equity and Non-controlling Interests Common Shareholders’ Equity and Non-controlling Interests (Tables)

12 Months Ended

Dec. 31, 2019

Noncontrolling Interest [Abstract]

Noncontrolling Interest



	December 31, 2019					December 31, 2018
$ in Millions	Non-controlling Percentage		Non-controlling Equity			Non-controlling Percentage		Non-controlling Equity
Non-controlling interests, excluding BAM
HG Global	3.1	%	$	14.4		3.1	%	$	14.5
NSM	3.6		14.9			4.5		13.6
Other NSM	13.4		(.1		)	13.4		.3
Kudu	—		2.2			—		—
MediaAlpha	—		—			39.0		16.2
Other Operations	various		(1.5		)	various		1.1
Total, excluding BAM			29.9					45.7

BAM	100.0		(146.7		)	100.0		(170.6		)
Total non-controlling interests			$	(116.8	)			$	(124.9	)

Segment Information (Tables)

12 Months Ended

Dec. 31, 2019

Segment Reporting [Abstract]

Financial information for White Mountains' segments

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



Millions	HG Global/BAM ⁽¹⁾		NSM			Kudu ⁽²⁾		MediaAlpha ⁽³⁾			Other Operations		Total
Year Ended December 31, 2019
Earned insurance premiums	$	16.3	$	—		$	—	$	—		$	—	$	16.3
Net investment income	21.6		—			14.7		—			43.4		79.7
Net realized and unrealized investment gains	27.1		—			6.3		—			285.1		318.5
Gain from deconsolidation of MediaAlpha	—		—			—		—			182.2		182.2
Advertising and commission revenues ⁽⁴⁾	—		193.4			—		48.8			6.9		249.1
Other revenues	1.6		39.7			.2		—			6.1		47.6
Total revenues	66.6		233.1			21.2		48.8			523.7		893.4
Insurance acquisition expenses	5.7		—			—		—			—		5.7
Other underwriting expenses	.4		—			—		—			—		.4
Cost of sales	—		—			—		40.6			7.5		48.1
General and administrative expenses	50.5		132.2			10.1		12.5			122.5		327.8
Broker commission expense	—		64.8			—		—			—		64.8
Change in fair value of contingent consideration earnout liabilities	—		2.1			—		—			—		2.1
Amortization of other intangible assets	—		19.4			.2		1.6			.6		21.8
Interest expense	—		16.7			.1		.2			.6		17.6
Total expenses	56.6		235.2			10.4		54.9			131.2		488.3
Pre-tax income (loss)	$	10.0	$	(2.1	)	$	10.8	$	(6.1	)	$	392.5	$	405.1


⁽¹⁾	BAM manages its affairs on a statutory accounting basis. BAM’s statutory surplus includes the BAM Surplus Notes and is not reduced by accruals of interest expense on the BAM Surplus Notes. BAM’s statutory surplus is reduced only after a payment of principal or interest has been approved by the NYDFS.


⁽²⁾	Kudu’s results are from April 4, 2019, the date of the Kudu Transaction, to December 31, 2019.


⁽³⁾	MediaAlpha’s results are from January 1, 2019 to February 26, 2019, the date of the MediaAlpha Transaction.


⁽⁴⁾	Approximately 17% of NSM’s commission revenue was associated with one single carrier.



Millions	HG Global/BAM ⁽¹⁾			NSM			MediaAlpha		Other Operations			Total
Year Ended December 31, 2018
Earned insurance premiums	$	13.9		$	—		$	—	$	—		$	13.9
Net investment income	16.7			—			—		42.3			59.0
Net realized and unrealized investment losses	(7.5		)	—			—		(100.8		)	(108.3		)
Advertising and commission revenues ⁽²⁾	—			89.6			295.5		4.1			389.2
Other revenues	1.2			12.0			1.6		.5			15.3
Total revenues	24.3			101.6			297.1		(53.9		)	369.1
Insurance acquisition expenses	5.3			—			—		—			5.3
Other underwriting expenses	.4			—			—		—			.4
Cost of sales	—			—			245.0		3.7			248.7
General and administrative expenses	48.0			59.4			31.7		94.4			233.5
Broker commission expense	—			28.4			—		—			28.4
Change in fair value of contingent consideration earnout liabilities	—			2.7			—		—			2.7
Amortization of other intangible assets	—			8.3			10.3		.2			18.8
Interest expense	—			8.0			1.2		.3			9.5
Total expenses	53.7			106.8			288.2		98.6			547.3
Pre-tax (loss) income	$	(29.4	)	$	(5.2	)	$	8.9	$	(152.5	)	$	(178.2	)


⁽¹⁾	BAM manages its affairs on a statutory accounting basis. BAM’s statutory surplus includes the BAM Surplus Notes and is not reduced by accruals of interest expense on the BAM Surplus Notes. BAM’s statutory surplus is reduced only after a payment of principal or interest has been approved by the NYDFS.


⁽²⁾	As of December 31, 2018, approximately 29% of MediaAlpha’s advertising revenue was associated with one customer.As of December 31, 2018, approximately 33% of NSM’s commission revenue was associated with one single carrier.



Millions	HG Global/BAM ⁽¹⁾			MediaAlpha			Other Operations		Total
Year Ended December 31, 2017
Earned insurance premiums	$	9.4		$	—		$	1.0	$	10.4
Net investment income	12.3			—			43.7		56.0
Net realized and unrealized investment gains	.6			—			132.7		133.3
Advertising and commission revenues⁽²⁾	—			163.2			3.8		167.0
Other revenues	1.0			—			6.1		7.1
Total revenues	23.3			163.2			187.3		373.8
Losses and LAE	—			—			1.1		1.1
Insurance acquisition expenses	4.0			—			.1		4.1
Other underwriting expenses	.4			—			—		.4
Cost of sales	—			135.9			3.5		139.4
General and administrative expenses	42.9			16.2			148.9		208.0
Amortization of other intangible assets	—			10.5			.2		10.7
Interest expense	—			1.0			1.3		2.3
Total expenses	47.3			163.6			155.1		366.0
Pre-tax (loss) income	$	(24.0	)	$	(.4	)	$	32.2	$	7.8


⁽¹⁾	BAM manages its affairs on a statutory accounting basis. BAM’s statutory surplus includes the BAM Surplus Notes and is not reduced by accruals of interest expense on the BAM Surplus Notes. BAM’s statutory surplus is reduced only after a payment of principal or interest has been approved by the NYDFS.


⁽²⁾	As of December 31, 2017, approximately 27% of MediaAlpha’s advertising revenue was associated with one customer.

Schedule of selected balance sheet data by segment



Millions Selected Balance Sheet Data	HG Global/BAM				NSM		Kudu		MediaAlpha		Other Operations				Held for Sale		Total
December 31, 2019:
Total investments	$	845.6			$	—	$	266.6	$	—	$	1,835.0			$	—	$	2,947.2
Total assets	$	924.0		⁽¹⁾	$	825.2	$	290.5	$	—	$	1,940.5		⁽²⁾	$	3.0	$	3,983.2
Total liabilities	$	246.8		⁽²⁾	$	401.1	$	57.0	$	—	$	133.6			$	—	$	838.5
Total White Mountains’s common shareholders’ equity	$	809.5		⁽²⁾	$	409.3	$	231.3	$	—	$	1,808.4		⁽²⁾	$	3.0	$	3,261.5
Non-controlling interest	$	(132.3	)		$	14.8	$	2.2	$	—	$	(1.5	)		$	—	$	(116.8	)
December 31, 2018:
Total investments	$	768.3			$	—	$	—	$	—	$	1,774.6			$	—	$	2,542.9
Total assets	$	816.2		⁽¹⁾	$	623.6	$	—	$	88.4	$	1,831.1		⁽²⁾	$	3.3	$	3,362.6
Total liabilities	$	212.5		⁽²⁾	$	314.8	$	—	$	46.9	$	70.2			$	—	$	644.4
Total White Mountains’s common shareholders’ equity	$	759.8		⁽²⁾	$	294.9	$	—	$	25.3	$	1,759.8		⁽²⁾	$	3.3	$	2,843.1
Non-controlling interest	$	(156.1	)		$	13.9	$	—	$	16.2	$	1.1			$	—	$	(124.9	)


⁽¹⁾	As of December 2019 and 2018, total assets in the HG Global/BAM segment reflected the elimination of $457.6 and $481.3 of BAM Surplus Notes issued to HG Global and its subsidiaries, and $162.7 and $143.7 in accrued interest related to the BAM Surplus Notes.

⁽²⁾

Reconciliation of Revenue from Segments to Consolidated

In compliance with ASC 606, Revenues from Contracts with Customers, the following tables present White Mountains’s total revenues by revenue source:



Millions	HG Global/BAM		NSM		Kudu ⁽²⁾		MediaAlpha ⁽³⁾		Other Operations		Total
Year Ended December 31, 2019
Commission and Other Revenue
Specialty Transportation	$	—	$	77.6	$	—	$	—	$	—	$	77.6
Real Estate	—		34.7		—		—		—		34.7
Social Services	—		25.9		—		—		—		25.9
Pet	—		30.0		—		—		—		30.0
United Kingdom	—		45.9		—		—		—		45.9
Other	—		19.0		—		—		6.9		25.9
Total Commission and Other Revenue	—		233.1		—		—		6.9		240.0
Advertising revenues	—		—		—		48.8		—		48.8
Products	—		—		—		—		5.5		5.5
Total revenues from contracts with customers	—		233.1		—		48.8		12.4		294.3
Other revenues⁽¹⁾	66.6		—		21.2		—		511.3		599.1
Total revenues	$	66.6	$	233.1	$	21.2	$	48.8	$	523.7	$	893.4


⁽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.


⁽²⁾	Kudu’s results are from April 4, 2019, the date of the Kudu Transaction, to December 31, 2019.


⁽³⁾	MediaAlpha’s results are from January 1, 2019 to February 26, 2019, the date of the MediaAlpha Transaction.



Millions	HG Global/BAM		NSM		MediaAlpha		Other Operations			Total
Year Ended December 31, 2018
Commission and Other Revenue
Specialty Transportation	$	—	$	28.3	$	—	$	—		$	28.3
Real Estate	—		17.8		—		—			17.8
Social Services	—		14.7		—		—			14.7
United Kingdom	—		28.0		—		—			28.0
Other	—		12.8		—		4.1			16.9
Total Commission and Other Revenue	—		101.6		—		4.1			105.7
Advertising revenues	—		—		295.5		—			295.5
Total revenues from contracts with customers	—		101.6		295.5		4.1			401.2
Other revenues⁽¹⁾	24.3		—		1.6		(58.0		)	(32.1		)
Total revenues	$	24.3	$	101.6	$	297.1	$	(53.9	)	$	369.1

⁽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		MediaAlpha		Other Operations		Total
Year Ended December 31, 2017
Commission and Other Revenue
Other	$	—	$	—	$	.4	$	.4
Total Commission and Other Revenue	—		—		.4		.4
Advertising revenues	—		163.2		—		163.2
Total revenues from contracts with customers	—		163.2		.4		163.6
Other revenues⁽¹⁾	23.3		—		186.9		210.2
Total revenues	$	23.3	$	163.2	$	187.3	$	373.8

⁽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)

12 Months Ended

Dec. 31, 2019

Schedule of Equity Method Investments [Line Items]

Schedule of changes in unconsolidated affiliates

The following table presents the carrying values of White Mountains’s equity method eligible investments recorded within other long-term investments as of December 31, 2019 and 2018:



	December 31,
Millions	2019		2018
Equity method eligible investments, at fair value	$	761.7	$	269.7
Other ⁽¹⁾	94.6		55.9
Total other long-term investments	$	856.3	$	325.6

⁽¹⁾Consists of other long-term investments that are not equity method eligible

Summarized statement of financial position

The following table presents White Mountains’s significant equity method eligible investments as of December 31, 2019 and 2018:



	Basic Ownership Interest
Investee	December 31, 2019	December 31, 2018	Instrument Held
PassportCard/DavidShield	50.0%	50.0%	Common shares
MediaAlpha ⁽¹⁾	48.3%	n/a	Units
durchblicker	45.0%	45.0%	Common shares
Elementum Holdings, L.P.	30.0%	n/a	Limited partnership interest
Compare.com	18.4%	18.4%	Common shares
Tuckerman Capital Funds ⁽²⁾	17.5 - 62.4%	18.5 - 62.3%	Limited and general partnership interests
JAM Partners L.P.	11.1%	12.3%	Limited partnership interest
Enlightenment Capital Funds	10.0 - 38.4%	10.3 - 36.5%	Limited and general partnership interests
Kudu’s Participation Contracts ⁽³⁾	3.2 - 30.0%	n/a	Revenue and earnings participation contracts
Kudu ⁽³⁾	n/a	49.5%	Units

⁽¹⁾ As of December 31, 2018, MediaAlpha was a majority-owned consolidated subsidiary of White Mountains. See Note 2 — “Significant Transactions”

⁽²⁾ As of December 31, 2018, includes White Mountains’s direct investment in Galvanic Applied Sciences.

⁽³⁾ As of December 31, 2019 White Mountains consolidates Kudu. See Note 2 — “Significant Transactions”.

Financials

Schedule of Equity Method Investments [Line Items]

Summarized statement of financial position

The following tables present aggregated summarized financial information for White Mountains’s investments in equity method eligible unconsolidated entities, excluding MediaAlpha:



	December 31,
Millions	2019		2018
Balance sheet data ⁽¹⁾:
Total assets	$	1,959.2	$	1,373.3
Total liabilities	$	653.2	$	509.2

⁽¹⁾Financial data for White Mountains’s equity method eligible investees is generally reported on a one-quarter lag.



	Year Ended December 31,
Millions	2019		2018		2017
Income statement data ⁽¹⁾:
Revenues	$	344.6	$	226.0	$	143.3
Expenses	$	88.3	$	141.4	$	80.5
Net Income	$	255.1	$	83.6	$	65.3

⁽¹⁾Financial data for White Mountains’s equity method eligible investees is generally reported on a one-quarter lag.

The following tables present summarized financial information for MediaAlpha:



	December 31,
Millions	2019		2018
Balance sheet data:
Total assets	$	106.9	$	88.5
Total liabilities	$	144.6	$	46.9



	Year Ended December 31,
Millions	2019		2018		2017
Income statement data:
Total revenues	$	407.9	$	297.1	$	163.2
Total expenses	$	389.0	$	288.2	$	163.5
Net income (loss)	$	18.9	$	8.9	$	(0.3	)

Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Summary of the fair value and carrying value of financial instruments



	December 31, 2019				December 31, 2018
Millions	Fair Value		Carrying Value		Fair Value		Carrying Value
NSM Bank Facility	$	221.2	$	217.4	$	176.1	$	176.6
Other NSM debt	$	1.7	$	1.8	$	1.9	$	1.9
Kudu Bank Facility ⁽¹⁾	$	53.6	$	53.6	$	—	$	—
MediaAlpha Bank Facility	$	—	$	—	$	14.6	$	14.2
Other Operations debt	$	11.3	$	10.7	$	—	$	—

Held for Sale and Discontinued Operations (Tables)

12 Months Ended

Dec. 31, 2019

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Schedule of discontinued operations balance sheet, income statement, and cash flows



	Year Ended December 31,
Millions		2019			2018			2017
Undistributed net earnings - continuing operations:
Net income (loss) attributable to White Mountains’s common shareholders, net of restricted common share amounts		$	408.4		$	(122.6	)	$	49.0
Dividends declared, net of restricted common share amounts ⁽¹⁾		(3.2		)	(3.7		)	(4.5		)
Total undistributed net earnings (losses), net of restricted common share amounts		$	405.2		$	(126.3	)	$	44.5

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

Net Income (Loss) from Discontinued Operations



	Year Ended December 31, 2017
Millions	OneBeacon		Sirius Group			Tranzact		Total
Revenues
Earned insurance premiums	$	807.6	$	—		$	—	$	807.6
Net investment income	39.7		—			—		39.7
Net realized and unrealized investment gains	38.8		—			—		38.8
Other revenues	7.7		—			—		7.7
Total revenues	893.8		—			—		893.8
Expenses
Loss and loss adjustment expenses	546.0		—			—		546.0
Insurance and reinsurance acquisition expenses	145.6		—			—		145.6
Other underwriting expenses	156.2		—			—		156.2
General and administrative expenses	21.2		—			—		21.2
Interest expense	10.0		—			—		10.0
Total expenses	879.0		—			—		879.0
Pre-tax income	14.8		—			—		14.8
Income tax benefit	5.7		—			—		5.7
Net income from discontinued operations	20.5		—			—		20.5
Gain (loss) from sale of discontinued operations, net of tax	554.5		(.7		)	3.2		557.0
Total income (loss) from discontinued operations	575.0		(.7		)	3.2		577.5
Change in foreign currency translation and other comprehensive income from discontinued operations, net of tax	.3		—			—		.3
Recognition of benefit plan assets and obligations from the sale of OneBeacon, net of tax	2.9		—			—		2.9
Comprehensive income (loss) from discontinued operations	$	578.2	$	(.7	)	$	3.2	$	580.7

Net Change in Cash from Discontinued Operations



	December 31, 2017
Millions	December 31, 2017
Net cash provided from operations	$	157.0
Net cash provided from investing activities	3.0
Net cash used for financing activities	(61.9		)
Net change in cash during the period	98.1
Cash balances at beginning of period	70.5
Net change in cash held for sale	(.9		)
Cash sold as part of sale of consolidated subsidiaries	(167.7		)
Cash balances at end of period	$	—

Discontinued operations, computation of earnings per share

The following table presents the Company’s computation of earnings per share for discontinued operations for the years ended December 31, 2019, 2018 and 2017:



	Year Ended December 31,
	2019			2018			2017
Basic and diluted earnings per share numerators (in millions):
Net income (loss) attributable to White Mountains’s common shareholders	$	414.5		$	(141.2	)	$	627.2
Less: total income (loss) from continuing operations, net of tax	413.7			(124.0		)	49.7
Net income (loss) from discontinued operations attributable to White Mountains’s common shareholders	.8			(17.2		)	577.5
Allocation of (earnings) losses to participating restricted common shares ⁽¹⁾	—			.2			(7.3		)
Basic and diluted earnings (loss) per share numerators	$	.8		$	(17.0	)	$	570.2
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period	3,181.6			3,382.5			4,293.8
Average unvested restricted common shares ⁽³⁾	(40.5		)	(40.1		)	(54.3		)
Basic earnings (loss) per share denominator	3,141.1			3,342.4			4,239.5
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period	3,181.6			3,382.5			4,293.8
Average unvested restricted common shares ⁽³⁾	(40.5		)	(40.1		)	(54.3		)
Diluted earnings (loss) per share denominator	3,141.1			3,342.4			4,239.5
Basic earnings (loss) per share (in dollars) - discontinued operations:	$	.25		$	(5.09	)	$	134.50
Diluted earnings (loss) per share (in dollars) - discontinued operations:	$	.25		$	(5.09	)	$	134.50


⁽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 years ended December 31, 2019, 2018 and 2017.

⁽³⁾

Restricted common shares outstanding vest either in equal annual installments or upon a stated date. See Note 10 — “Employee Share-Based Compensation Plans”.

Summary of the fair value and carrying value of financial instruments



	December 31, 2019				December 31, 2018
Millions	Fair Value		Carrying Value		Fair Value		Carrying Value
NSM Bank Facility	$	221.2	$	217.4	$	176.1	$	176.6
Other NSM debt	$	1.7	$	1.8	$	1.9	$	1.9
Kudu Bank Facility ⁽¹⁾	$	53.6	$	53.6	$	—	$	—
MediaAlpha Bank Facility	$	—	$	—	$	14.6	$	14.2
Other Operations debt	$	11.3	$	10.7	$	—	$	—

- Definition

+ References

+ Details

Selected Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information



	2019 Three Months Ended											2018 Three Months Ended
Millions, Except Per Share Amounts	Dec. 31			Sept. 30			June 30		Mar. 31			Dec. 31			Sept. 30			June 30			Mar. 31
Revenues	$	175.3		$	155.5		$	129.0	$	433.6		$	6.0		$	198.7		$	122.3		$	42.1
Expenses	118.8			104.4			113.2		151.9			150.1			154.4			134.7			108.1
Pre-tax income (loss)	56.5			51.1			15.8		281.7			(144.1		)	44.3			(12.4		)	(66.0		)
Tax (expense) benefit	(10.4		)	(8.8		)	.1		(10.2		)	3.6			3.6			(2.5		)	(.7		)
Income (loss) from continuing operations	46.1			42.3			15.9		271.5			(140.5		)	47.9			(14.9		)	(66.7		)
Net (loss) gain from discontinued operations, net of tax ⁽¹⁾	(.8		)	.9			—		.7			—			(17.3		)	—			.1
Non-controlling interest in consolidated subsidiaries	15.6			5.5			4.6		12.2			3.0			10.2			18.4			18.6
Income (loss) attributable to White Mountains’s common shareholders	$	60.9		$	48.7		$	20.5	$	284.4		$	(137.5	)	$	40.8		$	3.5		$	(48.0	)
Income (loss) attributable to White Mountains’s common shareholders per share:
Basic
Continuing operations	$	19.37		$	15.01		$	6.44	$	89.42		$	(43.24	)	$	18.27		$	1.02		$	(12.85	)
Discontinued operations	(.25		)	.28			—		.22			—			(5.44		)	—			.03
Total consolidated operations	$	19.12		$	15.29		$	6.44	$	89.64		$	(43.24	)	$	12.83		$	1.02		$	(12.82	)
Diluted
Continuing operations	$	19.37		$	15.01		$	6.44	$	89.42		$	(43.24	)	$	18.27		$	1.02		$	(12.85	)
Discontinued operations	(.25		)	.28			—		.22			—			(5.44		)	—			.03
Total consolidated operations	$	19.12		$	15.29		$	6.44	$	89.64		$	(43.24	)	$	12.83		$	1.02		$	(12.82	)

⁽¹⁾ During 2019 and 2018, net (loss) gain from discontinued operations arose from the tax contingency on the sale of Sirius Group. See Note 19 — “Commitments and Contingencies”.

Summary of Significant Accounting Policies (Reportable Segments and Discontinued Operations and Assets and Liabilities Held for Sale) (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
	Apr. 04, 2019	Dec. 31, 2019	Dec. 31, 2017	Apr. 03, 2019	Dec. 31, 2018	May 11, 2018	Feb. 05, 2018	Dec. 31, 2012
Basis of Presentation
Percentage of par value of policy reinsured		15.00%
Payments to acquire business, net	$ 81.4
HG Global
Basis of Presentation
Surplus notes								$ 503.0
Preferred stocks \| HG Global
Basis of Presentation
Ownership interest (as a percent)		96.90%			96.90%
Fully diluted ownership interest (as a percent)		88.40%			85.00%
Common Stock \| HG Global
Basis of Presentation
Ownership interest (as a percent)		88.40%			88.40%
NSM Insurance HoldCo, LLC
Basis of Presentation
Ownership interest (as a percent)		96.40%			95.50%	95.00%
Fully diluted ownership interest (as a percent)		88.40%			85.00%	83.60%
Kudu
Basis of Presentation
Ownership interest (as a percent)	99.10%			49.50%			49.50%
Fully diluted ownership interest (as a percent)	85.40%			42.70%			42.70%
Increase in capital commitment		$ 100.0
Funded capital commitment	$ 250.0	350.0
Unfunded capital commitment		129.0
Series A BAM Surplus Note \| HG Global
Basis of Presentation
Surplus notes								203.0
Series B BAM Surplus Note \| HG Global
Basis of Presentation
Surplus notes								$ 300.0
Sirius Group, Tranzact, and Star and Shield \| Discontinued Operations, Held-for-sale \| Connecticut
Basis of Presentation
Other expenses			$ 3.7
Assets held for sale		3.0			$ 3.3
Delayed Draw Term Loans \| Kudu Debt \| Kudu
Basis of Presentation
Total commitment under revolving credit facility		125.0
Undrawn amount on facility		$ 68.0

Summary of Significant Accounting Policies (Investment Securities) (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Percentage of investments recorded at fair value	71.00%	87.00%

Summary of Significant Accounting Policies - Fair Value Measurements and Other Long-Term Investments (Details)	12 Months Ended
	Dec. 31, 2019 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Variance threshold for outliers	$ 500,000
Variance threshold for outliers, percent	5.00%
Other long-term investments	$ 856,000,000
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other long-term investments	654,000,000
Fair Value Measured at Net Asset Value Per Share
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other long-term investments	$ 202,000,000

Summary of Significant Accounting Policies (Foreign Currency Exchange) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Net unrealized foreign currency translation losses and interest rate swap	$ (2.4)	$ (3.9)

- Definition

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

+ References + Details

Summary of Significant Accounting Policies (Recently Adopted Accounting Principles) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, right-of-use asset	$ 22.6
Operating lease, liability	22.8
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, right-of-use asset	22.6	$ 23.2
Operating lease, liability	$ 22.8	$ 23.2

Significant Transactions (Acquisitions) (Details)							3 Months Ended				8 Months Ended	12 Months Ended
Significant Transactions (Acquisitions) (Details)	Jun. 28, 2019 USD ($)	Apr. 04, 2019 USD ($)	Apr. 01, 2019 USD ($)	Dec. 03, 2018 USD ($)	May 11, 2018 USD ($)	Jan. 24, 2018 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) earnout_period	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	May 31, 2019 USD ($)	Apr. 03, 2019	Feb. 26, 2019	May 18, 2018 USD ($)	Feb. 05, 2018 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other Investments							$ 622,800,000				$ 165,700,000	$ 622,800,000	$ 165,700,000
Equity method investment, aggregate cost																			$ 125,000,000.0
Purchases of consolidated subsidiaries, net of cash acquired												258,000,000.0	295,200,000	$ 27,600,000
Change in fair value of contingent consideration earnout liabilities												2,100,000	2,700,000
Payments to acquire business, net		$ 81,400,000
Goodwill							394,700,000				379,900,000	394,700,000	379,900,000
NSM Holding Co LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Long-term line of credit					$ 100,000,000.0
Change in fair value of contingent consideration earnout liabilities											2,700,000	2,100,000
Contingent consideration earnout liabilities							20,600,000				20,200,000	20,600,000	20,200,000
White Mountains
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other Investments							$ 856,300,000				$ 325,600,000	$ 856,300,000	$ 325,600,000
MediaAlpha
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest (as a percent)																	48.30%
Fully diluted ownership interest (as a percent)																	42.00%
Elementum Holdings, L.P.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest (as a percent)							30.00%					30.00%			30.00%
Other Investments															$ 55,100,000
Insurance-Linked Securities Funds
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Commitment															$ 50,000,000.0
Elementum Funds
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity method investment, aggregate cost							$ 40,000,000.0					$ 40,000,000.0
NSM Insurance HoldCo, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest (as a percent)					95.00%		96.40%				95.50%	96.40%	95.50%
Purchases of consolidated subsidiaries, net of cash acquired					$ 274,200,000
Purchase price adjustment									$ 2,100,000
Assets acquired					495,200,000
Goodwill and intangible assets acquired					383,000,000.0
Liabilities acquired					204,600,000
Contingent consideration					10,200,000
Noncontrolling interest acquired					$ 14,400,000
Transaction costs										$ 6,300,000
Number of earnout periods \| earnout_period												2
Fully diluted ownership interest (as a percent)					83.60%		88.40%				85.00%	88.40%	85.00%
Fresh Insurance Services Group Limited
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest (as a percent)																		100.00%
Equity method investment, aggregate cost																		$ 49,600,000
Purchase price adjustment								$ 700,000
Assets acquired																		72,600,000
Goodwill and intangible assets acquired																		54,600,000
Liabilities acquired																		22,300,000
Contingent consideration																		7,500,000
KBK Insurance Group, Inc. & KBK Premium Services, Inc.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Purchases of consolidated subsidiaries, net of cash acquired				$ 60,000,000.0
Goodwill and intangible assets acquired				59,400,000			$ 32,600,000					$ 32,600,000
Stock issued during period, value, acquisitions				29,000,000.0
Proceeds from borrowings				$ 30,100,000
Intangible assets acquired							$ 32,700,000					$ 32,700,000
Change in fair value of contingent consideration earnout liabilities								$ 5,900,000
AIG Collector Car Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Purchases of consolidated subsidiaries, net of cash acquired	$ 82,500,000
Intangible assets acquired	82,500,000
AIG Collector Car Business \| NSM Holding Co LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from borrowings	22,500,000
AIG Collector Car Business \| White Mountains
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Stock issued during period, value, acquisitions	$ 59,100,000
DavidShield
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest (as a percent)						50.00%
PassportCard
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest (as a percent)						50.00%
DavidShield & PassportCard
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest (as a percent)							50.00%				50.00%	50.00%	50.00%
Payments to acquire businesses, gross						$ 41,800,000
Payments to acquire business, net						$ 28,300,000
Kudu
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest (as a percent)		99.10%														49.50%			49.50%
Assets acquired		$ 155,500,000																	$ 155,500,000
Liabilities acquired		800,000																	800,000
Noncontrolling interest acquired		1,500,000																	1,500,000
Goodwill		7,600,000																	7,600,000
Intangible assets acquired		$ 2,200,000																	$ 2,200,000
Fully diluted ownership interest (as a percent)		85.40%														42.70%			42.70%
Funded capital commitment		$ 250,000,000.0					$ 350,000,000.0					$ 350,000,000.0
Increase in capital commitment							100,000,000.0
Unfunded capital commitment							129,000,000.0					129,000,000.0
NSM Bank Facility \| NSM Holding Co LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total commitment under revolving credit facility					$ 234,000,000.0
NSM Bank Facility \| Term Loan \| NSM Holding Co LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Long-term line of credit							221,300,000				$ 180,400,000	221,300,000	$ 180,400,000					$ 51,000,000.0
Proceeds from borrowings												42,900,000
Total commitment under revolving credit facility					$ 224,000,000.0
Kudu Debt \| Delayed Draw Term Loans \| Kudu
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total commitment under revolving credit facility							125,000,000.0					125,000,000.0
Undrawn amount on facility							$ 68,000,000.0					68,000,000.0
Embrace Pet Insurance
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill and intangible assets acquired			$ 67,600,000
Intangible assets acquired			15,400,000
Goodwill			52,200,000
Embrace Pet Insurance \| NSM Holding Co LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Stock issued during period, value, acquisitions			58,200,000
Proceeds from borrowings			$ 20,400,000
Percentage of voting interests acquired			100.00%
Payments to acquire businesses, gross			$ 71,500,000
Embrace Pet Insurance \| NSM Bank Facility \| Term Loan \| NSM Holding Co LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from borrowings												$ 20,400,000

Significant Transactions (Dispositions) (Details) - USD ($)					3 Months Ended								9 Months Ended		12 Months Ended
	Feb. 26, 2019	Sep. 28, 2017	Jul. 21, 2016	Apr. 18, 2016	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2018	Sep. 28, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Significant Transactions
Sales of unconsolidated affiliates and consolidated subsidiaries, net of cash sold															$ 0	$ 0	$ 1,131,000,000.0
Gain (loss) on sale of other discontinued operations, net of tax															800,000	(17,200,000)	557,000,000.0
Other comprehensive (loss) income, net of tax															(1,400,000)	(4,800,000)	300,000
Net income from discontinued operations, net of tax					$ (800,000)	$ 900,000	$ 0	$ 700,000	$ 0	$ (17,300,000)	$ 0	$ 100,000			0	0	20,500,000
Tranzact
Significant Transactions
Proceeds from dividends received			$ 221,300,000
MediaAlpha
Significant Transactions
Proceeds from dividends received	$ 89,300,000
Realized gain from transaction								67,500,000							67,500,000
Ownership interest (as a percent)	48.30%
Fully diluted ownership interest (as a percent)	42.00%
Assets, fair value								114,700,000
Unrealized investment gain								$ 114,700,000							180,000,000.0
Total realized and unrealized gain on sale of minority stake															182,200,000
OneBeacon
Significant Transactions
Sale of Stock, Price Per Share		$ 18.10												$ 18.10
Sales of unconsolidated affiliates and consolidated subsidiaries, net of cash sold		$ 1,300,000,000
Gain (loss) on sale of other discontinued operations, net of tax		554,600,000
Other comprehensive (loss) income, net of tax		$ 2,900,000
Net income from discontinued operations, net of tax														$ 20,500,000
Tranzact
Significant Transactions
Sales of unconsolidated affiliates and consolidated subsidiaries, net of cash sold			$ 221,300,000
Gain (loss) on sale of other discontinued operations, net of tax																3,200,000	3,200,000
Sirius Group
Significant Transactions
Sales of unconsolidated affiliates and consolidated subsidiaries, net of cash sold				$ 2,600,000,000
Gain (loss) on sale of other discontinued operations, net of tax																(17,300,000)
Disposal group, consideration				$ 2,600,000,000
Discontinued Operations \| OneBeacon
Significant Transactions
Gain (loss) on sale of other discontinued operations, net of tax																	554,500,000
Net income from discontinued operations, net of tax																	20,500,000
Discontinued Operations \| Tranzact
Significant Transactions
Gain (loss) on sale of other discontinued operations, net of tax																	3,200,000
Net income from discontinued operations, net of tax																	0
Discontinued Operations \| Sirius Group
Significant Transactions
Gain (loss) on sale of other discontinued operations, net of tax															800,000	$ (17,200,000)	(700,000)
Net income from discontinued operations, net of tax																	$ 0
Swedish Tax Authority \| Sirius Group \| Sirius Group
Significant Transactions
Net income from discontinued operations, net of tax													$ (17,300,000)		$ 800,000
MediaAlpha
Significant Transactions
Ownership interest (as a percent)					48.30%										48.30%

Investment Securities (Net Investment Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investment income:
Total investment income	$ 81.0	$ 62.0	$ 58.5
Third-party investment expenses	(1.3)	(3.0)	(2.5)
Net investment income, pre-tax	79.7	59.0	56.0
Fixed maturity investments
Investment income:
Total investment income	32.4	35.1	44.9
Short-term investments
Investment income:
Total investment income	5.0	8.0	1.8
Common Stock
Investment income:
Total investment income	13.5	15.1	10.6
Other long-term investments
Investment income:
Total investment income	$ 30.1	$ 3.8	$ 1.2

Investment Securities (Net Realized and Unrealized Investement Gains and Losses) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Net realized investment gains (losses), pre-tax (1)		$ 96,600,000	$ (12,900,000)	$ 24,100,000
Net unrealized investment gains (losses), pre-tax (2)		336,600,000	(95,400,000)	109,200,000
Net realized and unrealized investment gains (losses), pre-tax		433,200,000	(108,300,000)	133,300,000
Income tax (expense) benefit attributable to net realized and unrealized investment gains (losses)		(87,000,000.0)	18,200,000	(12,900,000)
Net realized and unrealized investment gains (losses), after-tax		346,200,000	$ (90,100,000)	$ 120,400,000
MediaAlpha
Debt Securities, Available-for-sale [Line Items]
Realized gain from transaction	$ 67,500,000	67,500,000
Unrealized investment gain	$ 114,700,000	$ 180,000,000.0

Investment Securities (Net Realized Investment Gain (losses) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investment securities
Net realized investment gains (losses), pre-tax		$ 96.6	$ (23.9)	$ 35.3
Net realized investment gains (losses), foreign, pre-tax		0.0	11.0	(11.2)
Net realized investment gains (losses), pre-tax, total		96.6	(12.9)	24.1
Income tax expense attributable to net realized investment gains (losses)		(10.6)	9.1	8.9
Income tax expense attributable to net realized investment gains (losses), foreign		0.0	0.0	0.0
Income tax expense attributable to net realized investment gains, total		(10.6)	9.1	8.9
Net realized investment gains (losses), after-tax		86.0	(14.8)	26.4
Net realized investment gains (losses), foreign, after-tax		0.0	11.0	(11.2)
Net realized investment gains (losses), total, after-tax		86.0	(3.8)	15.2
Realized gains		104.0	49.4	61.5
Realized losses		7.4	62.3	37.4
Fixed maturity investments
Investment securities
Net realized investment gains (losses), pre-tax		4.9	(29.8)	(1.6)
Net realized investment gains (losses), foreign, pre-tax		0.0	18.2	4.1
Net realized investment gains (losses), pre-tax, total		4.9	(11.6)	2.5
Short-term investments
Investment securities
Net realized investment gains (losses), pre-tax		0.2	(0.8)	(0.3)
Net realized investment gains (losses), foreign, pre-tax		0.0	0.0	0.0
Net realized investment gains (losses), pre-tax, total		0.2	(0.8)	(0.3)
Common equity securities
Investment securities
Net realized investment gains (losses), pre-tax		85.9	6.6	18.1
Net realized investment gains (losses), foreign, pre-tax		0.0	0.0	6.0
Net realized investment gains (losses), pre-tax, total		85.9	6.6	24.1
Other long-term investments
Investment securities
Net realized investment gains (losses), pre-tax		5.6	0.1	19.1
Net realized investment gains (losses), foreign, pre-tax		0.0	(7.2)	(21.3)
Net realized investment gains (losses), pre-tax, total		5.6	$ (7.1)	$ (2.2)
MediaAlpha
Investment securities
Realized gain from transaction	$ 67.5	$ 67.5

Investment Securities (Net Unrealized Investment Gains (Losses)) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investment securities
Unrealized investment gains		$ 336,900,000	$ (83,600,000)	$ 97,500,000
Foreign Currency Transaction Gain (Loss), Unrealized		(300,000)	(11,800,000)	11,700,000
Net unrealized investment gains (losses), pre-tax		336,600,000	(95,400,000)	109,200,000
Trading Securities, Tax on Unrealized Holding Gain (Loss) on Investments		(76,400,000)	9,100,000	(4,000,000.0)
Trading Securities, Unrealized Foreign Currency Transaction Gain (Loss) Tax		0	0	0
Net Unrealized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities Tax		(76,400,000)	9,100,000	(4,000,000.0)
Unrealized investment gains after tax		260,500,000	(74,500,000)	93,500,000
Trading Securities, Unrealized Foreign Currenc Gain (Loss) Net of Tax		(300,000)	(11,800,000)	11,700,000
Net Unrealized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities Net of Tax		260,200,000	(86,300,000)	105,200,000
Fixed maturity investments
Investment securities
Unrealized investment gains		38,600,000	(8,300,000)	13,800,000
Foreign Currency Transaction Gain (Loss), Unrealized		0	(14,800,000)	12,700,000
Net unrealized investment gains (losses), pre-tax		38,600,000	(23,100,000)	26,500,000
Common equity securities
Investment securities
Unrealized investment gains		109,800,000	(105,500,000)	99,300,000
Foreign Currency Transaction Gain (Loss), Unrealized		0	0	0
Net unrealized investment gains (losses), pre-tax		109,800,000	(105,500,000)	99,300,000
Other long-term investments
Investment securities
Unrealized investment gains		188,500,000	30,200,000	(15,600,000)
Foreign Currency Transaction Gain (Loss), Unrealized		(300,000)	3,000,000.0	(1,000,000.0)
Net unrealized investment gains (losses), pre-tax		188,200,000	$ 33,200,000	$ (16,600,000)
MediaAlpha
Investment securities
Unrealized investment gain	$ 114,700,000	$ 180,000,000.0

Investment Securities (Investment Gains (Losses) For Level 3) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investment securities
Unrealized investment gains	$ 336.9	$ (83.6)	$ 97.5
Other long-term investments
Investment securities
Unrealized investment gains	188.5	30.2	(15.6)
Other long-term investments \| Level 3 Inputs
Investment securities
Unrealized investment gains	$ 181.9	$ 22.6	$ (15.4)

Investment Securities (Investment Holdings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
U.S. Government and agency obligations
Investment securities
Cost or Amortized Cost	$ 231.7	$ 154.0
Gross Unrealized Gains	1.0	0.1
Gross Unrealized Losses	(0.2)	(0.9)
Fixed maturity investments, at fair value	232.5	153.2
Debt securities issued by corporations
Investment securities
Cost or Amortized Cost	454.9	519.0
Gross Unrealized Gains	12.5	1.0
Gross Unrealized Losses	(0.2)	(9.5)
Fixed maturity investments, at fair value	467.2	510.5
Mortgage and asset-backed securities
Investment securities
Cost or Amortized Cost	206.6	279.0
Gross Unrealized Gains	2.7	2.4
Gross Unrealized Losses	(0.3)	(1.1)
Fixed maturity investments, at fair value	209.0	280.3
Municipal obligations
Investment securities
Cost or Amortized Cost	284.7	136.1
Gross Unrealized Gains	12.5	0.1
Gross Unrealized Losses	(0.1)	(2.7)
Fixed maturity investments, at fair value	297.1	133.5
Total fixed maturity investments
Investment securities
Cost or Amortized Cost	1,177.9	1,088.1
Gross Unrealized Gains	28.7	3.6
Gross Unrealized Losses	(0.8)	(14.2)
Total fixed maturity investments	$ 1,205.8	$ 1,077.5
Including Short Term Fixed
Investment securities
Duration of fixed maturities (years)	2 years 9 months 18 days
Excluding Short Term Investments
Investment securities
Duration of fixed maturities (years)	3 years 3 months 18 days

Investment Securities (Cost and Amortized Cost Maturity Schedule) (Details) $ in Millions	Dec. 31, 2019 USD ($)
Trading Securities by Maturity Cost or Amortized Cost
Cost of Amortized Cost	$ 1,177.9
Trading Securities by Maturity, Fair Value
Carrying Value of Fixed Maturities	1,205.8
Fixed Maturities and Convertible Fixed Maturities Excluding A B S M B S and Preferred Stock
Trading Securities by Maturity Cost or Amortized Cost
Due in one year or less	190.0
Due after one year through five years	481.6
Due after five years through ten years	165.3
Due after ten years	134.4
Trading Securities by Maturity, Fair Value
Due in one year or less	190.8
Due after one year through five years	489.3
Due after five years through ten years	173.2
Due after ten years	143.5
Mortgage and asset-backed securities
Trading Securities by Maturity Cost or Amortized Cost
Mortgage and asset-backed securities	206.6
Trading Securities by Maturity, Fair Value
Mortgage and asset-backed securities	$ 209.0

Investment Securities (Cost or Amortized Cost, Gross Unrealized Investment Gains and Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investment securities
Sales and maturities of investment securities	$ 1,000.0	$ 2,200.0	$ 2,800.0
Common Stock
Investment securities
Cost or Amortized Cost	553.3	904.7
Gross Unrealized Gains	130.6	51.0
Gross Unrealized Losses	0.0	(30.1)
Net Foreign Currency Gains	0.0	0.0
Fixed maturity investments, at fair value	683.9	925.6
Other long-term investments
Investment securities
Cost or Amortized Cost	667.4	330.3
Gross Unrealized Gains	255.2	52.2
Gross Unrealized Losses	(64.1)	(54.9)
Net Foreign Currency Gains	(2.2)	(2.0)
Fixed maturity investments, at fair value	$ 856.3	$ 325.6

Investment Securities (Investments Held on Deposit or as Collateral) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Investments held in trusts	$ 319.9	$ 254.3
Assets held by insurance regulators	$ 9.9	$ 6.1
Percentage of investments recorded at fair value	71.00%	87.00%

Investment Securities (Debt Securities Issued By Corporation) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investment securities
Fair value investments	$ 2,746.0	$ 2,328.7	$ 3,208.3
Debt securities issued by corporations
Investment securities
Fair value investments	467.2	510.5
AAA \| Debt securities issued by corporations
Investment securities
Fair value investments	9.5	8.9
AA \| Debt securities issued by corporations
Investment securities
Fair value investments	73.9	88.7
A \| Debt securities issued by corporations
Investment securities
Fair value investments	288.5	270.5
BBB \| Debt securities issued by corporations
Investment securities
Fair value investments	$ 95.3	$ 142.4

Investment Securities (Mortgage-backed Asset Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Investment securities
Fair value investments	$ 2,746.0	$ 2,328.7		$ 3,208.3
FNMA
Investment securities
Fair value investments	88.6	53.6
FHLMC
Investment securities
Fair value investments	60.5	38.1
GNMA
Investment securities
Fair value investments	30.8	23.7
Total Agency
Investment securities
Fair value investments	179.9	115.4
Total mortgage-backed securities
Investment securities
Fair value investments	179.9	115.4
Vehicle receivables
Investment securities
Fair value investments	15.1	9.2
Credit card receivables
Investment securities
Fair value investments	14.0	8.9
Total other asset-backed securities
Investment securities
Fair value investments	29.1	18.1
Total mortgage and asset- backed securities
Investment securities
Fair value investments	209.0	133.5
Level 2 Inputs
Investment securities
Fair value investments	1,109.6	1,160.5	$ 1,160.5	$ 2,105.4
Level 2 Inputs \| FNMA
Investment securities
Fair value investments	88.6	53.6
Level 2 Inputs \| FHLMC
Investment securities
Fair value investments	60.5	38.1
Level 2 Inputs \| GNMA
Investment securities
Fair value investments	30.8	23.7
Level 2 Inputs \| Total Agency
Investment securities
Fair value investments	179.9	115.4
Level 2 Inputs \| Total mortgage-backed securities
Investment securities
Fair value investments	179.9	115.4
Level 2 Inputs \| Vehicle receivables
Investment securities
Fair value investments	15.1	9.2
Level 2 Inputs \| Credit card receivables
Investment securities
Fair value investments	14.0	8.9
Level 2 Inputs \| Total other asset-backed securities
Investment securities
Fair value investments	29.1	18.1
Level 2 Inputs \| Total mortgage and asset- backed securities
Investment securities
Fair value investments	209.0	133.5
Level 3 Inputs \| FNMA
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| FHLMC
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| GNMA
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| Total Agency
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| Total mortgage-backed securities
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| Vehicle receivables
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| Credit card receivables
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| Total other asset-backed securities
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| Total mortgage and asset- backed securities
Investment securities
Fair value investments	$ 0.0	$ 0.0

Investment Securities (Other Long-Term Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Investment securities
Other Investments	$ 622.8	$ 165.7
Kudu investments
Investment securities
Other Investments	266.5	0.0
MediaAlpha
Investment securities
Other Investments	180.0	0.0
DavidShield & PassportCard
Investment securities
Other Investments	90.0	75.0
Elementum Holdings, L.P.
Investment securities
Other Investments	55.1	0.0
Other unconsolidated private equity investments, at fair value
Investment securities
Other Investments	31.2	60.0
Kudu
Investment securities
Other Investments	0.0	30.7
Hedge Funds and Private Equity Funds
Investment securities
Other Investments	161.1	146.1
Insurance-linked securities funds
Investment securities
Other Investments	41.2	0.0
Other long-term investments
Investment securities
Other Investments	31.2	13.8
White Mountains
Investment securities
Other Investments	$ 856.3	$ 325.6

Investment Securities (Fair Value of Hedge Funds Subject to Restrictions on Redemption Frequency) (Details) $ in Millions	Dec. 31, 2019 USD ($) fund	Dec. 31, 2018 USD ($)
Private equity funds
Investment securities
Number of Investments Held \| fund	12
Trading security, fair value	$ 106.5
Hedge funds
Investment securities
Number of Investments Held \| fund	1
Total private equity funds and hedge funds included in other long-term investments
Investment securities
Other long-term investments largest single investment	$ 54.6	$ 54.3
Trading security, fair value	161.1	146.1
Fair value unfunded commitments	50.2	76.7
Private equity funds \| Private equity funds
Investment securities
Trading security, fair value	106.5	91.8
Fair value unfunded commitments	50.2	76.7
Private equity funds \| Manufacturing/Industrial
Investment securities
Trading security, fair value	57.7	42.9
Fair value unfunded commitments	4.1	10.5
Private equity funds \| Aerospace/Defense/Government
Investment securities
Trading security, fair value	33.8	27.6
Fair value unfunded commitments	23.3	34.9
Private equity funds \| Financial services
Investment securities
Trading security, fair value	15.0	8.3
Fair value unfunded commitments	22.8	13.6
Private equity funds \| Direct lending
Investment securities
Trading security, fair value	0.0	13.0
Fair value unfunded commitments	0.0	17.7
Hedge funds \| Hedge funds
Investment securities
Trading security, fair value	54.6	54.3
Fair value unfunded commitments	0.0	0.0
Hedge funds \| Hedge Fund, Long/ Short Equity Banks and Financial
Investment securities
Trading security, fair value	54.6	54.3
Fair value unfunded commitments	$ 0.0	$ 0.0

Investment Securities (Investments In Private Equity Funds Subject to Lock-Up Periods) (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) fund	Dec. 31, 2018 USD ($)
Hedge funds
Investment securities
Number of Investments Held \| fund	1
Private equity funds
Investment securities
Trading security, fair value	$ 106,500,000
Number of Investments Held \| fund	12
Insurance-Linked Securities Funds
Investment securities
Other long-term investments largest single investment	$ 41,200,000
Number of Investments Held	3
Cash in transit	$ 4,800,000
Unfunded Capital Commitment	10,000,000.0
1 – 3 years \| Private equity funds
Investment securities
Trading security, fair value	4,800,000
3 – 5 years \| Private equity funds
Investment securities
Trading security, fair value	51,900,000
5 – 10 years \| Private equity funds
Investment securities
Trading security, fair value	40,200,000
10 years \| Private equity funds
Investment securities
Trading security, fair value	9,600,000
Hedge funds \| Hedge funds
Investment securities
Trading security, fair value	54,600,000	$ 54,300,000
Elementum Funds \| Insurance-Linked Securities Funds
Investment securities
Commitment	$ 50,000,000.0
Minimum
Investment securities
Redemptions and Advanced Redemption Notice Period	30 days
Maximum
Investment securities
Redemptions and Advanced Redemption Notice Period	90 days

Investment Securities (Rollforward of Fair Value Measurements by Level) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	$ 2,328,700,000	$ 2,328,700,000	$ 3,208,300,000
Total realized and unrealized gains (losses)		433,000,000.0	(99,800,000)
Amortization/Accretion		(1,600,000)	(2,500,000)
Purchases		866,100,000	1,394,300,000
Sales		(950,300,000)	(2,171,600,000)
Transfers in		14,900,000	0
Transfers out		(14,900,000)	0
Fair value investments		2,746,000,000.0	2,328,700,000
Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	2,542,900,000	2,542,900,000
Fair value investments		2,947,200,000	2,542,900,000
Other long-term investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	138,700,000	138,700,000
Fair value investments		654,000,000.0	138,700,000
Short-term investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Securities, realized and unrealized gain (loss)		200,000	800,000
Short-term investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value disclosure, investments				$ 176,100,000
Short-term investments, at amortized cost (which approximates fair value)		201,200,000	214,200,000
Foreign Currency on Cash and Open Trades
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Securities, realized and unrealized gain (loss)			4,200,000
Foreign Exchange Forward
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Securities, realized and unrealized gain (loss)			3,500,000
Level 1 Inputs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	842,600,000	842,600,000	890,400,000
Total realized and unrealized gains (losses)		163,000,000.0	(64,900,000)
Amortization/Accretion		200,000	200,000
Purchases		165,300,000	514,700,000
Sales		(391,100,000)	(497,800,000)
Transfers in		0	0
Transfers out		0	0
Fair value investments		780,000,000.0	842,600,000
Level 1 Inputs \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	1,047,000,000.0	1,047,000,000.0
Fair value investments		969,400,000	1,047,000,000.0
Level 1 Inputs \| Common equity securities \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		547,500,000
Level 1 Inputs \| Other long-term investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		0
Level 1 Inputs \| Short-term investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Short-term investments, at amortized cost (which approximates fair value)		189,400,000	204,400,000
Level 2 Inputs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	1,160,500,000	1,160,500,000	2,105,400,000
Total realized and unrealized gains (losses)		76,100,000	(64,400,000)
Amortization/Accretion		(1,800,000)	(2,700,000)
Purchases		404,500,000	783,800,000
Sales		(529,700,000)	(1,661,600,000)
Transfers in		0	0
Transfers out		0	0
Fair value investments		1,109,600,000	1,160,500,000
Level 2 Inputs \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	1,170,300,000	1,170,300,000
Fair value investments		1,121,400,000	1,170,300,000
Level 2 Inputs \| Common equity securities \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments		136,300,000
Level 2 Inputs \| Other long-term investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	0	0
Fair value investments		0	0
Level 2 Inputs \| Short-term investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Short-term investments, at amortized cost (which approximates fair value)		11,800,000	9,800,000
Level 3 Inputs \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	138,700,000	138,700,000
Fair value investments		654,100,000	138,700,000
Level 3 Inputs \| Common equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	0	0
Total realized and unrealized gains (losses)		0
Amortization/Accretion		0
Purchases		100,000
Sales		0
Transfers in		0
Transfers out		0
Fair value investments		100,000	0
Level 3 Inputs \| Other long-term investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	138,700,000	138,700,000	77,200,000
Total realized and unrealized gains (losses)		181,200,000	16,200,000
Amortization/Accretion		0	0
Purchases		185,400,000	45,300,000
Sales		0
Transfers in		10,900,000	0
Transfers out		(4,000,000.0)	0
Fair value investments		654,000,000.0	138,700,000
Level 3 Inputs \| Other long-term investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	138,700,000	138,700,000
Fair value investments		654,000,000.0	138,700,000
Level 3 Inputs \| Hedge Funds and Private Equity Funds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Amortization/Accretion			0
Transfers in			0
Transfers out			0
Level 3 Inputs \| Short-term investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Short-term investments, at amortized cost (which approximates fair value)		0	0
Level 3 Inputs \| Foreign Exchange Forward \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value disclosure, investments			(3,700,000)
Fair Value Measured at Net Asset Value Per Share \| Other long-term investments \| Fair value measured on a recurring basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	186,900,000	186,900,000
Fair value investments			186,900,000
Fair Value Measured at Net Asset Value Per Share \| Hedge Funds and Private Equity Funds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value investments	186,900,000	186,900,000	135,300,000
Total realized and unrealized gains (losses)		12,700,000	13,300,000
Amortization/Accretion		0
Purchases		110,800,000	50,500,000
Sales		(29,500,000)	(12,200,000)
Transfers in		4,000,000.0
Transfers out		(10,900,000)
Fair value investments		202,300,000	$ 186,900,000
MediaAlpha
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Unrealized investment gain	$ 114,700,000	180,000,000.0
Kudu
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Effect of Kudu Transaction		70,100,000
Kudu \| Level 1 Inputs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Effect of Kudu Transaction		0
Kudu \| Level 2 Inputs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Effect of Kudu Transaction		0
Kudu \| Level 3 Inputs \| Common equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Effect of Kudu Transaction		0
Kudu \| Level 3 Inputs \| Other long-term investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Effect of Kudu Transaction		141,800,000
Kudu \| Fair Value Measured at Net Asset Value Per Share \| Hedge Funds and Private Equity Funds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Effect of Kudu Transaction		$ (71,700,000)

Investment Securities (Significant Unobservable Inputs) (Details) - Standard Poors NR Rating $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Measurement Input, Discount Rate \| MediaAlpha
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	15.00%
Measurement Input, Discount Rate \| DavidShield & PassportCard
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	22.00%	18.00%
Measurement Input, Discount Rate \| Elementum Holdings, L.P.
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	20.00%
Terminal Revenue Growth Rate	4.00%
Measurement Input, Discount Rate \| Private debt instrument
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate		9.00%
Measurement Input, Discount Rate \| Other
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate		23.00%
Terminal Revenue Growth Rate	4.00%
Measurement Input, Discount Rate \| Compare.com
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate		22.00%
Measurement Input, Revenue Multiple \| DavidShield & PassportCard
Quantitative information for Level 3 Fair Value Measurements Assets
Terminal Revenue Growth Rate	4.00%
Equity Securities, FV-NI, Measurement Input		1
Measurement Input, Revenue Multiple \| Compare.com
Quantitative information for Level 3 Fair Value Measurements Assets
Equity Securities, FV-NI, Measurement Input		3
Measurement Input, Long-term Revenue Growth Rate \| MediaAlpha
Quantitative information for Level 3 Fair Value Measurements Assets
Terminal Revenue Growth Rate	4.00%
Estimated Net Realizable Value \| Compare.com
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	$ 2.5
Minimum \| Measurement Input, Discount Rate \| Kudu Investments
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	15.00%
Minimum \| Measurement Input, Discount Rate \| Private debt instrument
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	4.00%
Minimum \| Measurement Input, Discount Rate \| Other
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	25.00%
Minimum \| Measurement Input, Revenue Multiple \| Other
Quantitative information for Level 3 Fair Value Measurements Assets
Equity Securities, FV-NI, Measurement Input		2
Maximum \| Measurement Input, Discount Rate \| Kudu Investments
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	22.00%
Maximum \| Measurement Input, Discount Rate \| Private debt instrument
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	9.00%
Maximum \| Measurement Input, Discount Rate \| Other
Quantitative information for Level 3 Fair Value Measurements Assets
Fair Value, Discount Rate	32.00%
Maximum \| Measurement Input, Revenue Multiple \| Other
Quantitative information for Level 3 Fair Value Measurements Assets
Equity Securities, FV-NI, Measurement Input		4
Estimated Net Realizable Value \| Compare.com
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	$ 2.5
Discounted Cash Flow Valuation Technique \| Kudu Investments
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	266.5
Discounted Cash Flow Valuation Technique \| MediaAlpha
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	180.0
Discounted Cash Flow Valuation Technique \| DavidShield & PassportCard
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	90.0	$ 75.0
Discounted Cash Flow Valuation Technique \| Elementum Holdings, L.P.
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	55.1
Discounted Cash Flow Valuation Technique \| Private debt instrument
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	23.7	10.0
Discounted Cash Flow Valuation Technique \| Other
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	$ 23.7	30.0
Discounted Cash Flow Valuation Technique \| Compare.com
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value		16.9
Multiple of EBITDA \| Galvanic
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value		$ 3.1
Equity Securities, FV-NI, Measurement Input		6

Goodwill and Other Intangible Assets (Summary of Goodwill and Intangible Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Goodwill, fair value	$ 402.3	$ 379.9
Goodwill, impairment loss	7.6
Goodwill	394.7	379.9
Other intangible assets, fair value	694.4	591.1
Other intangible assets, accumulated amortization	29.3	53.6
Other intangible assets, net	251.4
Goodwill and Intangible Asset Impairment	10.4
Goodwill and other intangible assets	654.7	537.5
NSM Holding Co LLC
Goodwill [Line Items]
Goodwill, fair value	381.6	354.3
Goodwill	381.6	354.3
Other intangible assets, fair value	271.7	140.2
Other intangible assets, accumulated amortization	27.9	8.3
Impairments	2.4
Other intangible assets, net	241.4	131.9
Kudu
Goodwill [Line Items]
Goodwill, fair value	7.6	0.0
Goodwill	7.6	0.0
MediaAlpha
Goodwill [Line Items]
Goodwill, fair value	0.0	18.3
Goodwill	0.0	18.3
Other intangible assets, fair value	0.0	69.9
Other intangible assets, accumulated amortization	0.0	44.8
Impairments	0.0
Other intangible assets, net	0.0	25.1
Other
Goodwill [Line Items]
Goodwill, fair value	13.1	7.3
Goodwill, impairment loss	7.6
Goodwill	5.5	7.3
Other intangible assets, fair value	18.2	1.1
Other intangible assets, accumulated amortization	1.2	0.5
Impairments	0.4
Other intangible assets, net	$ 16.6	0.6
Customer Relationships \| NSM Holding Co LLC
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life	9 years
Other intangible assets, fair value	$ 121.7	85.3
Other intangible assets, accumulated amortization	19.8	6.0
Impairments	1.4
Other intangible assets, net	$ 100.5	79.3
Customer Relationships \| MediaAlpha
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life	9 years
Other intangible assets, fair value	$ 0.0	26.8
Other intangible assets, accumulated amortization	0.0	4.9
Impairments	0.0
Other intangible assets, net	$ 0.0	21.9
Customer Relationships \| Other
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life	11 years
Other intangible assets, fair value	$ 7.2	0.0
Other intangible assets, accumulated amortization	0.4	0.0
Other intangible assets, net	$ 6.8	0.0
Trade Names \| NSM Holding Co LLC
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life	19 years
Other intangible assets, fair value	$ 61.9	51.2
Other intangible assets, accumulated amortization	5.3	1.8
Impairments	0.4
Other intangible assets, net	$ 56.2	49.4
Trade Names \| Kudu
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life	7 years
Other intangible assets, fair value	$ 2.2	0.0
Other intangible assets, accumulated amortization	0.2	0.0
Impairments	0.0
Other intangible assets, net	$ 2.0	0.0
Trade Names \| Other
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life	10 years
Other intangible assets, fair value	$ 1.7	0.6
Other intangible assets, accumulated amortization	0.5	0.2
Impairments	0.2
Other intangible assets, net	$ 1.0	0.4
Information Technology \| NSM Holding Co LLC
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life	5 years
Other intangible assets, fair value	$ 3.9	3.7
Other intangible assets, accumulated amortization	1.4	0.5
Impairments	0.6
Other intangible assets, net	$ 1.9	3.2
Information Technology \| MediaAlpha
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life	5 years
Other intangible assets, fair value	$ 0.0	33.3
Other intangible assets, accumulated amortization	0.0	30.9
Impairments	0.0
Other intangible assets, net	$ 0.0	2.4
Information Technology \| Other
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life	5 years
Other intangible assets, fair value	$ 0.5	0.5
Other intangible assets, accumulated amortization	0.3	0.3
Impairments	0.2
Other intangible assets, net		0.2
Insurance licenses \| Other
Goodwill [Line Items]
Other intangible assets, fair value	8.6	0.0
Other intangible assets, accumulated amortization	0.0	0.0
Other intangible assets, net	$ 8.6	0.0
Renewal Rights \| NSM Holding Co LLC
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life	12 years
Other intangible assets, fair value	$ 82.5
Other intangible assets, accumulated amortization	0.7
Impairments	0.0
Other intangible assets, net	$ 81.8
Other \| NSM Holding Co LLC
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life	3 years
Other intangible assets, fair value	$ 1.7
Other intangible assets, accumulated amortization	0.7
Impairments	0.0
Other intangible assets, net	$ 1.0
Other \| MediaAlpha
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life	3 years
Other intangible assets, fair value	$ 0.0	9.8
Other intangible assets, accumulated amortization	0.0	9.0
Impairments	0.0
Other intangible assets, net	$ 0.0	0.8
Other \| Other
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life	5 years
Other intangible assets, fair value	$ 0.2	0.0
Other intangible assets, accumulated amortization	0.0	0.0
Other intangible assets, net	0.2	0.0
Other Intangible Assets
Goodwill [Line Items]
Other intangible assets, fair value	292.1	211.2
Other intangible assets, accumulated amortization	29.3	53.6
Impairments	2.8
Other intangible assets, net	260.0	157.6
Non-controlling Interests
Goodwill [Line Items]
Goodwill and other intangible assets	(23.4)	(40.6)
Parent
Goodwill [Line Items]
Goodwill and other intangible assets	631.3	496.9
Goodwill
Goodwill [Line Items]
Goodwill	394.7	379.9	$ 25.9
Goodwill, foreign currency translation gain	1.8	(2.5)
Goodwill \| NSM Holding Co LLC
Goodwill [Line Items]
Goodwill, foreign currency translation gain	1.4	(2.2)
Goodwill \| Other
Goodwill [Line Items]
Goodwill, foreign currency translation gain	0.0	(0.3)
Other Intangible Assets \| NSM Holding Co LLC
Goodwill [Line Items]
Goodwill, foreign currency translation gain	$ 0.7	$ (0.7)

Goodwill and Other Intangible Assets - Fair Value of Goodwill and Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2019	Jun. 28, 2019	Apr. 04, 2019	Apr. 01, 2019	Mar. 12, 2019	Dec. 03, 2018	May 18, 2018	May 11, 2018
NSM Holding Co LLC
Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired	$ 653.0
Renewal Rights
Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired		$ 82.5
NSM Holding Co LLC
Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired								$ 383.0
Fresh Insurance Services Group Limited
Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired							$ 54.6
KBK Insurance Group, Inc. & KBK Premium Services, Inc.
Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired						$ 65.3
Embrace Pet Insurance
Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired				$ 67.6
Kudu
Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired			$ 9.8
Other Operations
Finite-Lived Intangible Assets [Line Items]
Goodwill and intangible assets acquired					$ 22.6
Other Assets \| Embrace Pet Insurance
Finite-Lived Intangible Assets [Line Items]
Software				$ 3.4

Goodwill and Other Intangible Assets - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Finite-Lived Intangible Assets [Line Items]
Goodwill, impairment loss	$ 7.6
Other Operations
Finite-Lived Intangible Assets [Line Items]
Goodwill, impairment loss	7.6
Impairments	0.4
Fresh Insurance Services Group Limited
Finite-Lived Intangible Assets [Line Items]
Impairments	2.4
Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Impairments	$ 2.8

Goodwill and Other Intangible Assets (Goodwill and Intangible Assets Rollforward) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Beginning balance	$ 379.9
Ending balance	394.7	$ 379.9
Finite-lived Intangible Assets [Roll Forward]
Amortization	(21.8)	(18.8)	$ (10.7)
Goodwill and Intangible Assets [Roll Forward]
Purchases of consolidated subsidiaries, net of cash acquired	258.0	295.2	27.6
Goodwill, impairment loss	7.6
Other Intangible Assets
Goodwill [Roll Forward]
Measurement period adjustments(5)	26.8
Measurement period adjustments	5.9
Finite-lived Intangible Assets [Roll Forward]
Beginning balance	157.6	36.2
Acquisitions of businesses	34.6	140.9
Foreign currency translation	0.7	(0.7)
Amortization	(21.8)	(18.8)
Ending balance	260.0	157.6	36.2
Goodwill and Intangible Assets [Roll Forward]
Impairments	2.8
Renewal Rights
Finite-lived Intangible Assets [Roll Forward]
Acquisitions of businesses	82.5
Goodwill
Goodwill [Roll Forward]
Beginning balance	379.9	25.9
Acquisitions of businesses	64.8	356.5
Dispositions of businesses (2)	(18.3)
Measurement period adjustments(5)	(26.8)
Write-off	(7.6)
Measurement period adjustments	0.9
Foreign currency translation	1.8	(2.5)
Ending balance	394.7	379.9	25.9
Intangible Asset and Goodwill
Goodwill [Roll Forward]
Dispositions of businesses (2)	(41.8)
Measurement period adjustments	6.8
Finite-lived Intangible Assets [Roll Forward]
Acquisitions of businesses	99.4	497.4
Foreign currency translation	2.5	(3.2)
Amortization	(21.8)	(18.8)
Goodwill and Intangible Assets [Roll Forward]
Beginning balance	537.5	62.1
Write-off	(10.4)
Ending balance	654.7	537.5	62.1
Intangible Asset and Goodwill \| Renewal Rights
Finite-lived Intangible Assets [Roll Forward]
Acquisitions of businesses	82.5
MediaAlpha \| Other Intangible Assets
Goodwill [Roll Forward]
Dispositions of businesses (2)	(23.5)
Finite-lived Intangible Assets [Roll Forward]
Write-off	(2.8)
Other Operations
Goodwill and Intangible Assets [Roll Forward]
Goodwill, impairment loss	7.6
Impairments	0.4
NSM Holding Co LLC
Goodwill [Roll Forward]
Beginning balance	354.3
Ending balance	381.6	354.3
Finite-lived Intangible Assets [Roll Forward]
Amortization	(19.4)	(8.3)	$ 0.0
Goodwill and Intangible Assets [Roll Forward]
Impairments	2.4
NSM Holding Co LLC \| Renewal Rights
Goodwill and Intangible Assets [Roll Forward]
Impairments	0.0
NSM Holding Co LLC \| Goodwill
Goodwill [Roll Forward]
Foreign currency translation	1.4	$ (2.2)
Fresh Insurance Services Group Limited
Goodwill and Intangible Assets [Roll Forward]
Impairments	2.4
KBK Insurance Group, Inc. & KBK Premium Services, Inc. \| Goodwill
Goodwill [Roll Forward]
Measurement period adjustments(5)	$ 5.9

Goodwill and Other Intangible Assets (Amortization Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of other intangible assets	$ 21.8	$ 18.8	$ 10.7
Finite-lived intangible assets, next twelve months	23.9
Finite-lived intangible assets, year two	30.5
Finite-lived intangible assets, year three	29.7
Finite-lived intangible assets, year four	28.4
Finite-lived intangible assets, year five and thereafter	138.9
Total (1)	251.4
Indefinite-lived intangible assets	$ 8.6

Debt (Debt Outstanding) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	May 18, 2018	May 11, 2018
Debt Instrument
Debt	$ 283.5	$ 192.7
Other Debt
Debt Instrument
Debt instrument at face value	11.1	0.0
NSM Holding Co LLC
Debt Instrument
Debt instrument at face value				$ 100.0
Debt	219.2	178.5
Kudu \| Kudu Debt
Debt Instrument
Debt	53.6
MediaAlpha
Debt Instrument
Debt	0.0	14.2
MediaAlpha \| MediaAlpha Bank Facility
Debt Instrument
Debt instrument at face value	0.0	14.3
Unamortized Debt Issuance Expense	0.0	(0.1)
Debt	$ 0.0	$ 14.2
Effective yield (as a percent)		7.10%
Other Operations \| Other Debt
Debt Instrument
Debt	$ 10.7
Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Debt Instrument
Debt instrument at face value	221.3	$ 180.4	$ 51.0
Unamortized Debt Issuance Expense	(3.9)	(3.8)
Debt	$ 217.4	$ 176.6
Effective yield (as a percent)	7.50%	7.40%
Term Loan \| NSM Holding Co LLC \| Other NSM
Debt Instrument
Debt instrument at face value	$ 1.8
Debt	$ 1.8	$ 1.9
Effective yield (as a percent)	3.00%	2.20%
Term Loan \| Kudu \| Kudu Debt
Debt Instrument
Unamortized Debt Issuance Expense	$ (3.4)
Effective yield (as a percent)	8.30%
Term Loan \| MediaAlpha \| MediaAlpha Bank Facility
Debt Instrument
Debt instrument at face value		$ 14.3
Term Loan \| Other Operations \| Other Debt
Debt Instrument
Unamortized Debt Issuance Expense	$ (0.4)
Effective yield (as a percent)	8.30%

Debt (Schedule of Contractual Repayments) (Details) $ in Millions	Dec. 31, 2019 USD ($)
Debt Disclosure [Abstract]
Due in one year or less	$ 2.8
Due in two to three years	7.0
Due in four to five years	226.2
Due after five years	55.2
Total	$ 291.2

Debt (Narrative) (Details) - USD ($) $ in Millions		3 Months Ended	8 Months Ended	12 Months Ended
Debt (Narrative) (Details) - USD ($) $ in Millions	Apr. 01, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 23, 2019	Jun. 15, 2018	May 18, 2018	May 11, 2018	May 12, 2017	Aug. 14, 2013
Debt Instrument
Interest expense on debt				$ 17.6	$ 9.5	$ 2.3
Repayments of debt, principal				22.9	15.4	365.0
Debt		$ 283.5	$ 192.7	283.5	192.7
Draw down of debt and revolving line of credit				206.4	84.1	376.0
Interest paid				16.3	8.8	1.4
WTM Bank Facility
Debt Instrument
Total commitment under revolving credit facility												$ 425.0
Interest expense on debt				0.3	0.6
NSM Holding Co LLC
Debt Instrument
Debt instrument at face value										$ 100.0
Debt		219.2	178.5	219.2	178.5
NSM Holding Co LLC \| NSM Bank Facility
Debt Instrument
Total commitment under revolving credit facility										234.0
Kudu \| Kudu Debt
Debt Instrument
Total commitment under revolving credit facility							$ 125.0
MediaAlpha
Debt Instrument
Debt		0.0	14.2	0.0	14.2
MediaAlpha \| MediaAlpha Bank Facility
Debt Instrument
Total commitment under revolving credit facility											$ 20.0
Interest expense on debt					1.2	1.0
Debt instrument at face value		0.0	14.3	0.0	14.3
Debt		$ 0.0	$ 14.2	$ 0.0	$ 14.2
Effective yield (as a percent)			7.10%		7.10%
Draw down of debt and revolving line of credit					$ 3.0	20.0
MediaAlpha \| Previous MediaAlpha Bank Facility
Debt Instrument
Total commitment under revolving credit facility			$ 20.0		20.0
Repayments of debt, principal						12.9
Term Loan \| Other Operations
Debt Instrument
Debt instrument at face value			11.3		11.3
Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Debt Instrument
Total commitment under revolving credit facility										224.0
Debt instrument at face value		$ 221.3	180.4	$ 221.3	180.4				$ 51.0
Repayments of debt, principal			0.8	2.0
Proceeds from borrowings				42.9
Debt		$ 217.4	$ 176.6	$ 217.4	$ 176.6
Effective yield (as a percent)		7.50%	7.40%	7.50%	7.40%
Term Loan \| NSM Holding Co LLC \| Other NSM
Debt Instrument
Debt instrument at face value		$ 1.8		$ 1.8
Debt		$ 1.8	$ 1.9	$ 1.8	$ 1.9
Effective yield (as a percent)		3.00%	2.20%	3.00%	2.20%
Term Loan \| Kudu \| Kudu Debt
Debt Instrument
Total commitment under revolving credit facility							57.0
Debt instrument at face value		$ 57.0		$ 57.0
Term Loan \| MediaAlpha \| MediaAlpha Bank Facility
Debt Instrument
Total commitment under revolving credit facility			$ 18.4		$ 18.4
Debt instrument at face value			14.3		14.3
Repayments of debt, principal					3.6	2.1
Delayed Draw Term Loans \| Other Operations
Debt Instrument
Debt instrument at face value			3.0		3.0
Delayed Draw Term Loans \| Kudu \| Kudu Debt
Debt Instrument
Total commitment under revolving credit facility							63.0
Revolving Credit Facility \| Other Operations
Debt Instrument
Debt instrument at face value			2.0		2.0
Revolving Credit Facility \| NSM Holding Co LLC \| NSM Bank Facility
Debt Instrument
Total commitment under revolving credit facility										$ 10.0
Repayments of debt, principal			2.0	6.5
Proceeds from borrowings				$ 6.5
Revolving Credit Facility \| Kudu \| Kudu Debt
Debt Instrument
Total commitment under revolving credit facility							5.0
Current borrowing capacity							$ 57.0
Revolving Credit Facility \| MediaAlpha \| MediaAlpha Bank Facility
Debt Instrument
Amount outstanding			$ 10.0		10.0
Repayments of debt, principal					9.0
Draw down of debt and revolving line of credit						6.0
London Interbank Offered Rate (LIBOR) \| Term Loan \| Minimum \| NSM Holding Co LLC \| NSM Bank Facility
Debt Instrument
Basis spread on variable rate		4.25%	4.25%
London Interbank Offered Rate (LIBOR) \| Term Loan \| Maximum \| NSM Holding Co LLC \| NSM Bank Facility
Debt Instrument
Basis spread on variable rate		4.75%	4.75%
London Interbank Offered Rate (LIBOR) \| Line of Credit \| Kudu \| Kudu Debt
Debt Instrument
Basis spread on variable rate				1.00%
London Interbank Offered Rate (LIBOR) \| Line of Credit \| Minimum \| Kudu \| Kudu Debt
Debt Instrument
Basis spread on variable rate		5.50%
London Interbank Offered Rate (LIBOR) \| Line of Credit \| Maximum \| Kudu \| Kudu Debt
Debt Instrument
Basis spread on variable rate		6.25%
Prime Rate \| Term Loan \| Minimum \| NSM Holding Co LLC \| NSM Bank Facility
Debt Instrument
Basis spread on variable rate		3.25%	3.25%
Prime Rate \| Term Loan \| Maximum \| NSM Holding Co LLC \| NSM Bank Facility
Debt Instrument
Basis spread on variable rate		3.75%	3.75%
Prime Rate \| Line of Credit \| Minimum \| Kudu \| Kudu Debt
Debt Instrument
Basis spread on variable rate		4.50%
Prime Rate \| Line of Credit \| Maximum \| Kudu \| Kudu Debt
Debt Instrument
Basis spread on variable rate		5.25%
Interest Rate Swap \| NSM Holding Co LLC
Debt Instrument
Fixed interest rate		2.97%		2.97%
Variable interest rate		1.71%		1.71%
Interest Rate Swap \| Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Debt Instrument
Total commitment under revolving credit facility								$ 151.0
Hedged liability, fair value hedge								$ 151.0
Fixed interest rate		2.97%		2.97%
Debt		$ 148.7		$ 148.7
Debt, weighted average interest rate		7.06%		7.06%
Embrace Pet Insurance \| NSM Holding Co LLC
Debt Instrument
Proceeds from borrowings	$ 20.4
Embrace Pet Insurance \| Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Debt Instrument
Proceeds from borrowings				$ 20.4
NSM Holding Co LLC
Debt Instrument
Interest expense on debt				16.7	$ 8.0	$ 0.0
Designated as Hedging Instrument \| Interest Rate Swap \| Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Debt Instrument
Debt		$ 148.7		$ 148.7
Debt, weighted average interest rate		7.47%		7.47%
Not Designated as Hedging Instrument \| Interest Rate Swap \| Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Debt Instrument
Debt		$ 72.6		$ 72.6
Effective yield (as a percent)		6.21%		6.21%
Renewal Rights \| Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Debt Instrument
Proceeds from borrowings				$ 22.5

Income Taxes (Income Tax (Benefit) Expense (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current income tax benefit (expense):
U.S. federal									$ 0.9	$ (0.1)	$ (0.3)
State									(3.7)	(1.4)	(1.3)
Non-U.S.									(1.7)	(2.9)	(2.0)
Total current tax expense									(4.5)	(4.4)	(3.6)
Deferred income tax (expense) benefit:
U.S. federal									(14.9)	8.3	11.4
State									(10.4)	0.0	0.0
Non-U.S.									0.5	0.1	0.0
Total deferred income tax (expense) benefit									(24.8)	8.4	11.4
Total income tax (expense) benefit	$ (10.4)	$ (8.8)	$ 0.1	$ (10.2)	$ 3.6	$ 3.6	$ (2.5)	$ (0.7)	$ (29.3)	$ 4.0	$ 7.8

Income Taxes (Effective Rate Reconciliation) (Details) - USD ($) $ in Millions			3 Months Ended								12 Months Ended
	Dec. 22, 2017	Dec. 21, 2017	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
U.S. statutory rate (as a percent)	21.00%	35.00%									21.00%	35.00%
Tax (expense) benefit at the U.S. statutory rate											$ (85.1)	$ 37.4	$ (2.7)
Differences in taxes resulting from:
Change in valuation allowance											63.6	(31.0)	42.6
Non-U.S. earnings, net of foreign taxes											27.1	(2.9)	21.5
State taxes											(17.5)	4.0	0.6
Tax rate changes											(5.7)	1.7	(44.3)
Member’s surplus contributions											(3.6)	(2.6)	(3.0)
Withholding tax											(1.6)	(2.7)	(2.0)
Tax exempt interest and dividends											1.1	0.6	0.5
Tax reserve adjustments											(0.7)	(0.8)	(0.3)
Officer compensation											0.0	0.0	(4.1)
Other, net											(6.9)	0.3	(1.0)
Total income tax (expense) benefit			$ (10.4)	$ (8.8)	$ 0.1	$ (10.2)	$ 3.6	$ 3.6	$ (2.5)	$ (0.7)	(29.3)	4.0	7.8
Pre-tax income (loss)			$ 56.5	$ 51.1	$ 15.8	$ 281.7	$ (144.1)	$ 44.3	$ (12.4)	$ (66.0)	405.1	(178.2)	7.8
Tax Payments and Receipts
Net income tax payments to (receipts from) national governments, total											3.7	3.5	2.0
Non-US
Differences in taxes resulting from:
Pre-tax income (loss)											$ 100.4	$ (30.1)	$ 71.3

Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions			12 Months Ended
	Dec. 22, 2017	Dec. 21, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets related to:
U.S. federal and state net operating and capital loss carryforwards			$ 92.3	$ 95.5
Non-U.S. net operating loss carryforwards			41.7	36.6
Incentive compensation			15.0	14.1
Investment basis difference			0.0	11.1
Net unrealized investment losses			0.0	9.5
Accrued interest			5.1	0.0
Deferred acquisition costs			4.3	3.5
Tax credit carryforwards			4.2	4.2
Other items			3.4	5.8
Total gross deferred tax assets			166.0	180.3
Less: valuation allowances			77.9	139.9
Total net deferred tax assets			88.1	40.4
Deferred tax liabilities related to:
Net unrealized investment gains			66.3	0.0
Member’s surplus contributions			43.2	32.8
Investment basis difference			6.6	0.0
Other items			4.6	5.4
Total deferred tax liabilities			120.7	38.2
Net deferred tax (liability) asset				$ 2.2
Net deferred tax (liability) asset			$ 32.6
U.S. statutory rate (as a percent)	21.00%	35.00%	21.00%	35.00%
Percentage of utilization of net operating losses				80.00%
Change in valuation allowance			$ (63.6)	$ 31.0	$ (42.6)
United States
Deferred tax liabilities related to:
Provisional income tax expense			$ 43.1

Income Taxes (Valuation Allowance) (Details) - USD ($) $ in Millions			3 Months Ended								12 Months Ended
	Dec. 22, 2017	Dec. 21, 2017	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Valuation Allowance [Line Items]
U.S. statutory rate (as a percent)	21.00%	35.00%									21.00%	35.00%
Valuation allowance			$ 77.9				$ 139.9				$ 77.9	$ 139.9
Change in valuation allowance											(63.6)	31.0	$ (42.6)
Income tax (expense) benefit			(10.4)	$ (8.8)	$ 0.1	$ (10.2)	3.6	$ 3.6	$ (2.5)	$ (0.7)	(29.3)	4.0	$ 7.8
U.S. losses and other federal deferred tax benefits
Valuation Allowance [Line Items]
Valuation allowance			34.9				102.6				34.9	102.6
Net operating losses in Luxembourg subsidiaries
Valuation Allowance [Line Items]
Valuation allowance			22.6								22.6
Net Operating Losses in Israel Subsidiaries
Valuation Allowance [Line Items]
Valuation allowance			17.3				14.5				17.3	14.5
Net Operating Losses in Netherlands Subsidiaries
Valuation Allowance [Line Items]
Valuation allowance			3.1								3.1
Luxembourg \| U.S. losses and other federal deferred tax benefits
Valuation Allowance [Line Items]
Change in valuation allowance											1.1	1.2
United States
Valuation Allowance [Line Items]
Provisional income tax expense											43.1
Israel \| Net Operating Losses in Israel Subsidiaries
Valuation Allowance [Line Items]
Change in valuation allowance											1.6	2.1
United Kingdom \| Net Operating Losses in United Kingdom Subsidiaries
Valuation Allowance [Line Items]
Change in valuation allowance											1.3	0.7
Subsidiaries \| Luxembourg \| Net operating losses in Luxembourg subsidiaries
Valuation Allowance [Line Items]
Valuation allowance							21.1					21.1
Subsidiaries \| United Kingdom \| Net operating losses in Luxembourg subsidiaries
Valuation Allowance [Line Items]
Valuation allowance							1.7					1.7
Guilford Holdings, Inc. \| United States
Valuation Allowance [Line Items]
Change in valuation allowance											(63.2)	22.7
BAM
Valuation Allowance [Line Items]
Change in valuation allowance											(4.5)	1.5
Income tax (expense) benefit											10.5	8.7
White Mountains Catskill Holdings, Inc.
Valuation Allowance [Line Items]
Valuation allowance			$ 0.1				$ 2.8				$ 0.1	$ 2.8

Income Taxes (Net Operating and Capital Loss Carryforwards) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Net deferred tax assets
Total net deferred tax assets	$ 88.1	$ 40.4
Tax credit carryforwards, foreign	3.8
Alternative minimum tax credit carryforwards, not subject to expiration	0.4
Operating and Capital Loss Carryforward
Net deferred tax assets
Operating loss carryforwards	598.9
Gross deferred tax asset	129.7
Valuation allowance	(104.9)
Total net deferred tax assets	24.8
Operating and Capital Loss Carryforward \| United States
Net deferred tax assets
Operating loss carryforwards	420.1
Gross deferred tax asset	88.0
Valuation allowance	(63.5)
Total net deferred tax assets	24.5
Operating and Capital Loss Carryforward \| Luxembourg
Net deferred tax assets
Operating loss carryforwards	86.5
Gross deferred tax asset	21.6
Valuation allowance	(21.5)
Total net deferred tax assets	0.1
Operating and Capital Loss Carryforward \| United Kingdom
Net deferred tax assets
Operating loss carryforwards	18.7
Gross deferred tax asset	3.2
Valuation allowance	(3.0)
Total net deferred tax assets	0.2
Operating and Capital Loss Carryforward \| Israel
Net deferred tax assets
Operating loss carryforwards	73.6
Gross deferred tax asset	16.9
Valuation allowance	(16.9)
Total net deferred tax assets	0.0
2019-2023 \| Operating and Capital Loss Carryforward
Net deferred tax assets
Operating loss carryforwards	0.1
2019-2023 \| Operating and Capital Loss Carryforward \| United States
Net deferred tax assets
Operating loss carryforwards	0.1
2019-2023 \| Operating and Capital Loss Carryforward \| Luxembourg
Net deferred tax assets
Operating loss carryforwards	0.0
2019-2023 \| Operating and Capital Loss Carryforward \| United Kingdom
Net deferred tax assets
Operating loss carryforwards	0.0
2019-2023 \| Operating and Capital Loss Carryforward \| Israel
Net deferred tax assets
Operating loss carryforwards	0.0
2024-2028 \| Operating and Capital Loss Carryforward
Net deferred tax assets
Operating loss carryforwards	0.0
2024-2028 \| Operating and Capital Loss Carryforward \| United States
Net deferred tax assets
Operating loss carryforwards	0.0
2024-2028 \| Operating and Capital Loss Carryforward \| Luxembourg
Net deferred tax assets
Operating loss carryforwards	0.0
2024-2028 \| Operating and Capital Loss Carryforward \| United Kingdom
Net deferred tax assets
Operating loss carryforwards	0.0
2024-2028 \| Operating and Capital Loss Carryforward \| Israel
Net deferred tax assets
Operating loss carryforwards	0.0
2029-2038 \| Operating and Capital Loss Carryforward
Net deferred tax assets
Operating loss carryforwards	360.6
2029-2038 \| Operating and Capital Loss Carryforward \| United States
Net deferred tax assets
Operating loss carryforwards	302.6
2029-2038 \| Operating and Capital Loss Carryforward \| Luxembourg
Net deferred tax assets
Operating loss carryforwards	58.0
2029-2038 \| Operating and Capital Loss Carryforward \| United Kingdom
Net deferred tax assets
Operating loss carryforwards	0.0
2029-2038 \| Operating and Capital Loss Carryforward \| Israel
Net deferred tax assets
Operating loss carryforwards	0.0
No expiration date \| Operating and Capital Loss Carryforward
Net deferred tax assets
Operating loss carryforwards	238.2
No expiration date \| Operating and Capital Loss Carryforward \| United States
Net deferred tax assets
Operating loss carryforwards	117.4
No expiration date \| Operating and Capital Loss Carryforward \| Luxembourg
Net deferred tax assets
Operating loss carryforwards	28.5
No expiration date \| Operating and Capital Loss Carryforward \| United Kingdom
Net deferred tax assets
Operating loss carryforwards	18.7
No expiration date \| Operating and Capital Loss Carryforward \| Israel
Net deferred tax assets
Operating loss carryforwards	$ 73.6

Income Taxes (ASC 740-10) (Details) - USD ($) $ in Millions	12 Months Ended
Income Taxes (ASC 740-10) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Percentage of likelihood for realization of benefit upon ultimate settlement			50.00%
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns
Balance at beginning	$ 1.1	$ 0.3	$ 0.0
Changes in prior year tax positions	1.3	0.8	0.1
Tax positions taken during the current year			0.2
Balance at year end	2.4	1.1	0.3
Permanent Differences
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns
Balance at beginning	1.1	0.3	0.0
Changes in prior year tax positions	1.3	0.8	0.1
Tax positions taken during the current year			0.2
Balance at year end	2.4	1.1	0.3
Temporary Differences
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns
Balance at beginning	0.0	0.0	0.0
Changes in prior year tax positions		0.0	0.0
Tax positions taken during the current year			0.0
Balance at year end	0.0	0.0	0.0
Interest and Penalties Net of Tax Benefit
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns
Balance at beginning	0.0	0.0	0.0
Changes in prior year tax positions		0.0	0.0
Tax positions taken during the current year			0.0
Balance at year end	$ 0.0	$ 0.0	$ 0.0

Municipal Bond Guarantee Insurance (Details) $ in Millions	1 Months Ended	12 Months Ended
Municipal Bond Guarantee Insurance (Details) $ in Millions	Apr. 30, 2018 USD ($)	Dec. 31, 2019 USD ($) Contract	Dec. 31, 2018 USD ($) Contract	Dec. 31, 2017 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2020	Sep. 30, 2019 USD ($)	Jul. 31, 2012 USD ($)
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Percentage of par value of policy reinsured		15.00%
Percentage of risk premium ceded			60.00%
Assets Held-in-trust		$ 786.7	$ 757.4
Interest receivable		$ 162.7	$ 143.7
HG Re
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Percentage of par value of policy reinsured			15.00%
White Mountains
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Capital contributions					$ 594.5
HG Global
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Surplus notes					503.0
Percent over a target trust balance		102.00%
Cash and fixed income securities								$ 100.0
Supplement Trust target		$ 603.0
BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Contracts outstanding \| Contract		8,987	7,525
Remaining weighted average contract period (in years)		10 years 8 months 12 days
Municipal bond outstanding principal		$ 62,250.5	$ 52,201.6				$ 1,100.0
Municipal bond outstanding interest		31,799.7	26,560.3
Municipal bond debt service outstanding		94,050.2	78,761.9
Unearned premium revenue		198.4	$ 176.0
January 1, 2020 - March 31, 2020		4.8
April 1, 2020 - June 30, 2020		4.8
July 1, 2020 - September 30, 2020		4.6
October 1, 2020 - December 31, 2020		4.5
2020		18.7
2021		17.3
2022		16.3
2023		15.2
2024		14.2
2025 and thereafter		$ 116.7
BAM Management
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Capital contributions					$ 14.5
Preferred stocks \| HG Global
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Ownership interest (as a percent)		96.90%	96.90%
Common Stock \| HG Global
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Ownership interest (as a percent)		88.40%	88.40%
BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Surplus notes		$ 457.6	$ 481.3
Accrued interest on surplus notes		162.7	143.7
Supplemental Trust [Member] \| BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Special cash payment		23.7	17.7	$ 4.0
Accrued interest on surplus notes		0.3	0.7	0.1
Surplus Note
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Assets Held-in-trust		457.6	481.3
Surplus Note \| BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Special cash payment		32.0	23.0	5.0
Accrued interest on surplus notes		$ 8.0	$ 4.6	0.9
BAM \| Fidus Re Ltd.
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Losses above retention, percentage of liability	90.00%
Fidus Re Ltd. \| BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Insurance linked securities	$ 100.0
Collateralized financial guarantee, term	12 years
Collateral Financial Guarantee, Callable Term		5 years
Liabilities for guarantees on long-duration contracts, guaranteed benefit liability, gross	$ 165.0
Financial guarantee insurance contracts, reimbusement	$ 100.0
Percentage of Quota Share Reinsurance Agreement			100.00%
Direct written premiums			$ 2,200.0
Maximum \| Fidus Re Ltd. \| BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Liabilities for guarantees on long-duration contracts, guaranteed benefit liability, gross		$ 276.1
Series B BAM Surplus Note \| HG Global
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Surplus notes								$ 300.0
Series A BAM Surplus Note \| HG Global
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Surplus notes				$ 203.0
Surplus Note \| BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Special cash payment		32.0	23.0
Accrued interest on surplus notes		$ 8.0	$ 4.6
Fixed interest rate \| Surplus Note \| BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Interest rate (as a percent)		8.00%
Forecast \| Surplus Note \| BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Interest rate (as a percent)						4.60%

Municipal Bond Guarantee Insurance Schedule of Net Written Premiums (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earned premiums:
Net earned premiums	$ 16.3	$ 13.9	$ 10.4
HG/BAM
Written premiums:
Direct	28.1	44.8	63.2
Assumed	10.6	8.1	0.0
Gross written premiums	38.7	52.9	63.2
Earned premiums:
Net earned premiums	13.6	13.6	9.4
Assumed	2.7	0.3	0.0
Net earned premiums	$ 16.3	$ 13.9	$ 9.4

Derivatives (Forward Contracts) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Forward Contracts
Derivative [Line Items]
Realized and unrealized gains (losses)	$ (3.5)	$ (23.8)

Derivatives - Interest Rate Swap (Details) - USD ($)	3 Months Ended	8 Months Ended	12 Months Ended
Derivatives - Interest Rate Swap (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Jun. 15, 2018	May 11, 2018
Derivative [Line Items]
Debt	$ 283,500,000	$ 192,700,000	$ 283,500,000
NSM Holding Co LLC
Derivative [Line Items]
Debt	219,200,000	178,500,000	219,200,000
NSM Bank Facility \| NSM Holding Co LLC
Derivative [Line Items]
Total commitment under revolving credit facility					$ 234,000,000.0
NSM Bank Facility \| NSM Holding Co LLC \| Term Loan
Derivative [Line Items]
Total commitment under revolving credit facility					$ 224,000,000.0
Debt	$ 217,400,000	$ 176,600,000	$ 217,400,000
NSM Bank Facility \| NSM Holding Co LLC \| Term Loan \| London Interbank Offered Rate (LIBOR) \| Minimum
Derivative [Line Items]
Basis spread on variable rate	4.25%	4.25%
NSM Bank Facility \| NSM Holding Co LLC \| Term Loan \| London Interbank Offered Rate (LIBOR) \| Maximum
Derivative [Line Items]
Basis spread on variable rate	4.75%	4.75%
NSM Bank Facility \| NSM Holding Co LLC \| Term Loan \| Prime Rate \| Minimum
Derivative [Line Items]
Basis spread on variable rate	3.25%	3.25%
NSM Bank Facility \| NSM Holding Co LLC \| Term Loan \| Prime Rate \| Maximum
Derivative [Line Items]
Basis spread on variable rate	3.75%	3.75%
Interest Rate Swap \| NSM Holding Co LLC
Derivative [Line Items]
Fixed interest rate	2.97%		2.97%
Variable interest rate	1.71%		1.71%
Net interest expense		$ 700,000	$ 1,100,000
Derivative, fair value, net	$ 6,600,000	2,700,000	6,600,000
Change in the fair value of the swap		$ (2,700,000)	$ (3,900,000)
Interest Rate Swap \| NSM Bank Facility \| NSM Holding Co LLC \| Term Loan
Derivative [Line Items]
Total commitment under revolving credit facility				$ 151,000,000.0
Fixed interest rate	2.97%		2.97%
Debt	$ 148,700,000		$ 148,700,000
Debt, weighted average interest rate	7.06%		7.06%
Designated as Hedging Instrument \| Interest Rate Swap \| NSM Bank Facility \| NSM Holding Co LLC \| Term Loan
Derivative [Line Items]
Debt	$ 148,700,000		$ 148,700,000
Debt, weighted average interest rate	7.47%		7.47%

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Basic and diluted earnings per share numerators (in millions):
Net income (loss) attributable to White Mountains’s common shareholders	$ 60.9	$ 48.7	$ 20.5	$ 284.4	$ (137.5)	$ 40.8	$ 3.5	$ (48.0)	$ 414.5	$ (141.2)	$ 627.2
Less: total income (loss) from discontinued operations, net of tax									0.8	(17.2)	577.5
Net income (loss) attributable to White Mountains’ common shareholders									413.7	(124.0)	49.7
Allocation of (earnings) losses to participating restricted common shares									(5.3)	1.4	(0.7)
Basic and diluted earnings per share numerators									$ 408.4	$ (122.6)	$ 49.0
Basic earnings per share denominators (in thousands):
Weighted Average Number of Shares Issued, Basic									3,181,600	3,382,500	4,293,800
Average unvested restricted common shares									(40,500)	(40,100)	(54,300)
Basic earnings (losses) per share denominator									3,141,100	3,342,400	4,239,500
Diluted earnings per share denominator (in thousands):
Average outstanding dilutive options to acquire common shares									3,181,600	3,382,500	4,293,800
Average unvested restricted common shares									(40,500)	(40,100)	(54,300)
Diluted earnings (loss) per share denominator									3,141,100	3,342,400	4,239,500
Diluted earnings per share (in dollars) - continuing operations:
Dividends declared and paid									$ 1.00	$ 1.00	$ 1.00
Undistributed earnings (losses)									129.02	(37.67)	10.56
Basic and diluted earnings (losses) per share									$ 130.02	$ (36.67)	$ 11.56

Earnings Per Share (Schedule of Undistributed Net Earnings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net income (loss) attributable to White Mountains’s common shareholders, net of restricted common share amounts	$ 408.4	$ (122.6)	$ 49.0
Dividends declared, net of restricted common share amounts	(3.2)	(3.7)	(4.5)
Total undistributed net earnings (losses), net of restricted common share amounts	$ 405.2	$ (126.3)	$ 44.5

Employee Share-Based Incentive Compensation Plans (WTM Performance Shares) (Details) - Performance Shares $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) multiplier shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($) shares
White Mountains
Share-based compensation arrangement by share-based payment award
Multiplier for determining payout, low end of range \| multiplier	0
Multiplier for determining payout, high end of range \| multiplier	2
Performance cycle period	3 years
W T M Incentive Plan \| White Mountains
Target Performance Share activity
Beginning of period	40,616	50,515	80,353
Shares paid or expired	(13,715)	(23,186)	(30,838)
New grants	15,600	14,105	17,710
Forfeitures	(28)	(818)	(16,710)
End of period	42,473	40,616	50,515
Unamortized grant date fair value
Beginning of period \| $	$ 31.7	$ 45.8	$ 42.4
Shares paid or expired \| $	(18.1)	(28.4)	(21.9)
Forfeitures \| $	(0.1)	0.1	(9.3)
Expense recognized \| $	30.2	14.2	34.6
End of period \| $	43.7	$ 31.7	$ 45.8
Unamortized grant date fair value \| $	$ 17.2
W T M Incentive Plan \| Sirius Group
Target Performance Share activity
Beginning of period		2,195
End of period			2,195
W T M Incentive and Phantom Plan \| Range Of Performance Cycle From 2016-2018
Unamortized grant date fair value
Performance goal percentage for minimum payout	139.00%
Payout for maximum growth target percentage	166.00%
W T M Incentive and Phantom Plan \| Range Of Performance Cycle From 2015 to 2017
Unamortized grant date fair value
Performance goal percentage for minimum payout		145.00%
Payout for maximum growth target percentage		147.00%
W T M Incentive and Phantom Plan \| Range Of Performance Cycle From 2014 to 2016
Unamortized grant date fair value
Performance goal percentage for minimum payout			34.00%
Payout for maximum growth target percentage			76.00%

Employee Share-Based Incentive Compensation Plans (WTM Performance Shares Granted Under the WTM Incentive Plan) (Details) - W T M Incentive Plan - Performance Shares - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Range Of Performance Cycle 2019 to 2021
Share-based compensation arrangement by share-based payment award
Targeted performance goal for personnel expressed as percentage of growth in intrinsic business value per share	7.00%
Payout for maximum growth target percentage	200.00%
Range Of Performance Cycle 2018 to 2020
Share-based compensation arrangement by share-based payment award
Targeted performance goal for personnel expressed as percentage of growth in intrinsic business value per share	6.00%
Payout for maximum growth target percentage	200.00%
Range Of Performance Cycle From 2017 to 2019
Share-based compensation arrangement by share-based payment award
Targeted performance goal for personnel expressed as percentage of growth in intrinsic business value per share	5.00%
Payout for maximum growth target percentage	200.00%
White Mountains
Share-based compensation arrangement by share-based payment award
Options nonvested, number before forfeitures (in shares)	43,120
Incentive compensation payable before forfeitures	$ 44.3
Assumed forfeitures (shares)	(647)
Assumed forfeitures in period amount	(0.6)
Shares outstanding (in shares)	42,473	40,616	50,515	80,353
Accrued incentive compensation	$ 43.7	$ 31.7	$ 45.8	$ 42.4
White Mountains \| Range Of Performance Cycle 2019 to 2021
Share-based compensation arrangement by share-based payment award
Options nonvested, number before forfeitures (in shares)	15,600
Incentive compensation payable before forfeitures	$ 6.0
White Mountains \| Range Of Performance Cycle 2018 to 2020
Share-based compensation arrangement by share-based payment award
Options nonvested, number before forfeitures (in shares)	13,450
Incentive compensation payable before forfeitures	$ 10.5
White Mountains \| Range Of Performance Cycle From 2017 to 2019
Share-based compensation arrangement by share-based payment award
Options nonvested, number before forfeitures (in shares)	14,070
Incentive compensation payable before forfeitures	$ 27.8
Minimum \| Range Of Performance Cycle 2019 to 2021
Share-based compensation arrangement by share-based payment award
Performance goal percentage for minimum payout	2.00%
Minimum \| Range Of Performance Cycle 2018 to 2020
Share-based compensation arrangement by share-based payment award
Performance goal percentage for minimum payout	2.00%
Minimum \| Range Of Performance Cycle From 2017 to 2019
Share-based compensation arrangement by share-based payment award
Performance goal percentage for minimum payout	1.00%
Maximum \| Range Of Performance Cycle 2019 to 2021
Share-based compensation arrangement by share-based payment award
Performance goal percentage for minimum payout	12.00%
Maximum \| Range Of Performance Cycle 2018 to 2020
Share-based compensation arrangement by share-based payment award
Performance goal percentage for minimum payout	10.00%
Maximum \| Range Of Performance Cycle From 2017 to 2019
Share-based compensation arrangement by share-based payment award
Performance goal percentage for minimum payout	9.00%

Employee Share-Based Incentive Compensation Plans (WTM Restricted Shares) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
W T M Incentive and Phantom Plan \| Restricted Share Cliff Vesting in January 2022
Target Performance Share activity
Issued (in shares)	15,600
W T M Incentive and Phantom Plan \| Restricted Share Cliff Vesting in January 2021
Target Performance Share activity
Issued (in shares)		13,450
W T M Incentive and Phantom Plan \| Restricted Share Cliff Vesting in January 2020
Target Performance Share activity
Issued (in shares)			17,485
W T M Incentive and Phantom Plan \| Restricted Share Cliff Vesting in January 2019
Target Performance Share activity
Issued (in shares)		290	250
W T M Incentive and Phantom Plan \| Restricted Share Cliff Vesting in January 2018
Target Performance Share activity
Issued (in shares)		365	250
White Mountains \| W T M Incentive Plan \| Restricted Stock
Target Performance Share activity
Beginning of period	41,510	53,755	70,620
Issued (in shares)	15,600	14,105	17,985
Vested (in shares)	(13,715)	(25,381)	(28,846)
Assumed forfeitures and cancellations (in shares)	0	(969)	(6,004)
End of period	43,395	41,510	53,755
Unamortized grant date fair value
Beginning balance	$ 12.5	$ 14.3	$ 19.7
Issued	14.5	11.4	16.3
Assumed forfeitures and cancellations	0.0	(0.2)	(3.5)
Expense recognized	(10.3)	(13.0)	(18.2)
Ending balance	$ 16.7	$ 12.5	$ 14.3
Sirius Group \| W T M Incentive Plan \| Restricted Stock
Target Performance Share activity
Beginning of period		2,195
End of period			2,195

Employee Share-Based Incentive Compensation Plans (WTM Non-Qualified Options) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
	Jan. 20, 2017	Mar. 31, 2017	Dec. 31, 2017
Share-based compensation arrangement by share-based payment award
Shares issued, price per share			$ 742
Employee Stock Option \| Chief Executive Officer
Share-based compensation arrangement by share-based payment award
Non-option equity instruments, exercised	125,000	40,000
Exercises in period, intrinsic value		$ 4.4
Common Stock
Share-based compensation arrangement by share-based payment award
Conversion of stock, shares converted		5,142

Leases - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
ROU lease asset	$ 22.6
Operating lease, liability	22.8
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
ROU lease asset	22.6	$ 23.2
Operating lease, liability	$ 22.8	$ 23.2

Leases - Schedule of Lease Cost (Details) $ in Millions	12 Months Ended
Leases - Schedule of Lease Cost (Details) $ in Millions	Dec. 31, 2019 USD ($)
Leases [Abstract]
Lease cost	$ 7.2
Less: sublease income	0.4
Net lease cost	$ 6.8

Leases - Schedule of Future Minimum Payments on Operating Leases (Details) $ in Millions	Dec. 31, 2019 USD ($)
Leases [Abstract]
2020	$ 5.9
2021	4.9
2022	4.5
2023	3.9
2024	3.1
Thereafter	3.4
Total undiscounted lease payments	25.7
Less: present value adjustment	(2.9)
Operating lease, liability	$ 22.8

Leases - Schedule of Right-of-Use Assets and Lease Liabilities (Details) $ in Millions	Dec. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
ROU lease asset	$ 22.6
Lease liability	$ 22.8
Operating lease, weighted average incremental borrowing rate, percent	4.60%
HG/BAM
Lessee, Lease, Description [Line Items]
ROU lease asset	$ 10.4
Lease liability	10.4
NSM Holding Co LLC
Lessee, Lease, Description [Line Items]
ROU lease asset	4.8
Lease liability	4.8
Kudu investments
Lessee, Lease, Description [Line Items]
ROU lease asset	2.3
Lease liability	2.3
Other
Lessee, Lease, Description [Line Items]
ROU lease asset	5.1
Lease liability	$ 5.3

Common Shareholders’ Equity and Non-controlling Interests (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Common Shares Repurchased and Retired [Abstract]
Value of common shares repurchased and retired during the period	$ 4.9	$ 519.1	$ 723.9
Value of each common share repurchased and retired during the period (in dollars per share)	$ 858	$ 877	$ 869
Common Shares Issued [Abstract]
Stock issued during period, shares, new issues	17,917	16,377	25,086
Shares issued to directors (in shares)	2,317	2,272
Dividends, Common Stock [Abstract]
Cash dividends declared and paid	$ 3.2	$ 3.8	$ 4.6
Dividends delared and paid (in dollars per share)	$ 1.00
Noncontrolling interest, ownership percentage by noncontrolling owners
Non-controlling interests	$ (116.8)	$ (124.9)
Common Stock
Common Shares Repurchased and Retired [Abstract]
Common shares repurchased and retired during the period	5,679	592,458	832,725
Restricted Stock
Common Shares Issued [Abstract]
Stock issued during period, shares, new issues	15,600	14,105	17,985
General Board Authorization
Common Shares Repurchased and Retired [Abstract]
Additional authorized repurchase of common shares	635,705
Common shares repurchased and retired during the period		582,493	821,732
Value of common shares repurchased and retired during the period		$ 511.0	$ 713.1
Value of each common share repurchased and retired during the period (in dollars per share)		$ 877	$ 870
Chief Executive Officer \| Restricted Stock
Common Shares Issued [Abstract]
Stock issued during period, shares, new issues			5,142
Directors \| Restricted Stock
Common Shares Issued [Abstract]
Stock issued during period, shares, new issues			1,959
Repurchased for Employee Benefit Plans
Common Shares Repurchased and Retired [Abstract]
Common shares repurchased and retired during the period		9,965	10,993
HG Global
Dividends, Common Stock [Abstract]
Noncontrolling interest, ownership percentage by noncontrolling owners	3.10%	3.10%
Non-controlling interests	$ 14.4	$ 14.5
NSM Insurance HoldCo, LLC
Dividends, Common Stock [Abstract]
Noncontrolling interest, ownership percentage by noncontrolling owners	3.60%	4.50%
Non-controlling interests	$ 14.9	$ 13.6
Other NSM
Dividends, Common Stock [Abstract]
Noncontrolling interest, ownership percentage by noncontrolling owners	13.40%	13.40%
Non-controlling interests	$ (0.1)	$ 0.3
Kudu
Dividends, Common Stock [Abstract]
Noncontrolling interest, ownership percentage by noncontrolling owners	0.00%	0.00%
Non-controlling interests	$ 2.2	$ 0.0
MediaAlpha
Dividends, Common Stock [Abstract]
Noncontrolling interest, ownership percentage by noncontrolling owners	0.00%	39.00%
Non-controlling interests	$ 0.0	$ 16.2
Other
Dividends, Common Stock [Abstract]
Non-controlling interests	$ (1.5)	$ 1.1
BAM
Dividends, Common Stock [Abstract]
Noncontrolling interest, ownership percentage by noncontrolling owners	100.00%	100.00%
Non-controlling interests	$ (146.7)	$ (170.6)
Total Non-Controlling Excluding Reciprocals
Dividends, Common Stock [Abstract]
Non-controlling interests	$ 29.9	$ 45.7

Statutory Capital and Surplus (Details) - USD ($)	1 Months Ended		12 Months Ended
Statutory Capital and Surplus (Details) - USD ($)	Jan. 31, 2020	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statutory Accounting Practices [Line Items]
Repayments of debt, principal			$ 22,900,000	$ 15,400,000	$ 365,000,000.0
Other long-term investments		$ 856,000,000	856,000,000
Kudu
Statutory Accounting Practices [Line Items]
Proceeds from borrowings		57,000,000.0
Distributions made		53,700,000
BAM
Statutory Accounting Practices [Line Items]
Accrued interest on surplus notes		162,700,000	162,700,000	143,700,000
Other Operations
Statutory Accounting Practices [Line Items]
Unrestricted cash		602,600,000	602,600,000
Other long-term investments		202,300,000	202,300,000
HG Re \| HG Global-BAM
Statutory Accounting Practices [Line Items]
Statutory capital and surplus		745,400,000	745,400,000
Surplus required		1	1
Cash outside of collateral trusts		3,000,000.0	3,000,000.0
Collateral held in supplement trust		786,700,000	786,700,000
Cash and investments outside of collateral trusts		6,300,000	6,300,000
Accrued interest held in Supplemental Trust		111,200,000	111,200,000
BAM \| HG Global-BAM
Statutory Accounting Practices [Line Items]
Statutory capital and surplus		402,400,000	402,400,000
Statutory net income (loss)			(38,300,000)	(34,600,000)	(25,400,000)
Surplus required		66,000,000.0	$ 66,000,000.0
HG Global
Statutory Accounting Practices [Line Items]
Percent over a target trust balance			102.00%
Supplement Trust target		603,000,000.0	$ 603,000,000.0
HG Global \| HG Global-BAM
Statutory Accounting Practices [Line Items]
Preferred stock, value		$ 619,000,000.0	$ 619,000,000.0
Ownership interest (as a percent)		96.90%	96.90%
Preferred stock dividend rate			6.00%
White Mountains \| Kudu
Statutory Accounting Practices [Line Items]
Distributions made		$ 53,300,000
NSM Insurance HoldCo, LLC \| NSM Insurance HoldCo, LLC
Statutory Accounting Practices [Line Items]
Cash		33,400,000	$ 33,400,000
Kudu
Statutory Accounting Practices [Line Items]
Cash and short-term investments		5,900,000	5,900,000
Surplus Note \| BAM
Statutory Accounting Practices [Line Items]
Special cash payment			32,000,000.0	23,000,000.0	5,000,000.0
Accrued interest on surplus notes		8,000,000.0	8,000,000.0	4,600,000	$ 900,000
Preferred stocks \| HG Global
Statutory Accounting Practices [Line Items]
Dividends payable		2,000,000.0	2,000,000.0
Preferred stocks \| HG Global \| HG Global-BAM
Statutory Accounting Practices [Line Items]
Dividends payable		341,700,000	341,700,000
Preferred stocks \| White Mountains \| HG Global \| HG Global-BAM
Statutory Accounting Practices [Line Items]
Dividends payable		330,200,000	330,200,000
Common Equities \| Other Operations
Statutory Accounting Practices [Line Items]
Distributions made				3,200,000
Common equity securities		683,900,000	683,900,000
Surplus Note \| BAM
Statutory Accounting Practices [Line Items]
Accrued interest held in Supplemental Trust		300,000	300,000	700,000
Special cash payment			32,000,000.0	23,000,000.0
Accrued interest on surplus notes		$ 8,000,000.0	8,000,000.0	4,600,000
Repayments of debt, principal			$ 23,700,000	$ 17,700,000
Subsequent Event \| BAM
Statutory Accounting Practices [Line Items]
Accrued interest on surplus notes	$ 146,500,000
Subsequent Event \| Surplus Note \| BAM
Statutory Accounting Practices [Line Items]
Accrued interest held in Supplemental Trust	900,000
Special cash payment	65,000,000.0
Accrued interest on surplus notes	16,200,000
Repayments of debt, principal	$ 47,900,000

Segment Information (Details) - USD ($)	3 Months Ended								10 Months Ended	12 Months Ended
Segment Information (Details) - USD ($)	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment reporting information
Earned insurance premiums										$ 16,300,000	$ 13,900,000	$ 10,400,000
Net investment income										79,700,000	59,000,000.0	56,000,000.0
Net realized and unrealized investment gains										433,200,000	(108,300,000)	133,300,000
Net realized and unrealized investment gains										318,500,000
Commission revenues										249,100,000	389,200,000	167,000,000.0
Other revenue										47,600,000	15,300,000	7,100,000
Total revenues	$ 175,300,000	$ 155,500,000	$ 129,000,000.0	$ 433,600,000	$ 6,000,000.0	$ 198,700,000	$ 122,300,000	$ 42,100,000		893,400,000	369,100,000	373,800,000
Loss and loss adjustment expenses												1,100,000
Insurance acquisition expense										5,700,000	5,300,000	4,100,000
Other underwriting expenses										400,000	400,000	400,000
Change in fair value of contingent consideration earnout liabilities										2,100,000	2,700,000
Cost of sales										48,100,000	248,700,000	139,400,000
General and administrative expenses										327,800,000	233,500,000	208,000,000.0
Broker commission expense										64,800,000	28,400,000
Amortization of other intangible assets										21,800,000	18,800,000	10,700,000
Interest expense										17,600,000	9,500,000	2,300,000
Total expenses	118,800,000	104,400,000	113,200,000	151,900,000	150,100,000	154,400,000	134,700,000	108,100,000		488,300,000	547,300,000	366,000,000.0
Pre-tax income (loss)	$ 56,500,000	$ 51,100,000	$ 15,800,000	$ 281,700,000	$ (144,100,000)	$ 44,300,000	$ (12,400,000)	$ (66,000,000.0)		405,100,000	(178,200,000)	7,800,000
HG Global-BAM
Segment reporting information
Net investment income										21,600,000	16,700,000	12,300,000
Net realized and unrealized investment gains											(7,500,000)	600,000
Net realized and unrealized investment gains										27,100,000
Commission revenues										0
Other revenue										1,600,000	1,200,000	1,000,000.0
Total revenues										66,600,000	24,300,000	23,300,000
Insurance acquisition expense										5,700,000	5,300,000	4,000,000.0
Other underwriting expenses										400,000	400,000	400,000
Cost of sales										0
General and administrative expenses										50,500,000	48,000,000.0	42,900,000
Broker commission expense										0
Amortization of other intangible assets										0
Interest expense										0
Total expenses										56,600,000	53,700,000	47,300,000
Pre-tax income (loss)										10,000,000.0	(29,400,000)	(24,000,000.0)
NSM Holding Co LLC
Segment reporting information
Earned insurance premiums										0
Net investment income										0
Net realized and unrealized investment gains										0
Commission revenues										193,400,000	89,600,000	0
Other revenue										39,700,000	12,000,000.0	0
Total revenues										233,100,000	101,600,000	0
Insurance acquisition expense										0
Other underwriting expenses										0
Change in fair value of contingent consideration earnout liabilities										2,100,000	2,700,000	0
Cost of sales										0
General and administrative expenses										132,200,000	59,400,000	0
Broker commission expense										64,800,000	28,400,000	0
Amortization of other intangible assets										19,400,000	8,300,000	0
Interest expense										16,700,000	8,000,000.0	0
Total expenses										235,200,000	106,800,000	0
Pre-tax income (loss)										$ (2,100,000)	$ (5,200,000)
Percentage of commission revenue										17.00%	33.00%
Kudu
Segment reporting information
Earned insurance premiums										$ 0
Net investment income										14,700,000	$ 0	0
Net realized and unrealized investment gains											0	0
Net realized and unrealized investment gains										6,300,000
Commission revenues										0
Other revenue										200,000	0	0
Total revenues										21,200,000	0	0
Insurance acquisition expense										0
Other underwriting expenses										0
Cost of sales										0
General and administrative expenses										10,100,000	0	0
Broker commission expense										0
Amortization of other intangible assets										200,000	0	0
Interest expense										100,000	0	0
Total expenses										10,400,000	0	0
Pre-tax income (loss)										10,800,000
MediaAlpha
Segment reporting information
Commission revenues										48,800,000	295,500,000	163,200,000
Other revenue										0	1,600,000	0
Total revenues										48,800,000	297,100,000	163,200,000
Cost of sales										40,600,000	245,000,000.0	135,900,000
General and administrative expenses										12,500,000	31,700,000	16,200,000
Amortization of other intangible assets										1,600,000	10,300,000	10,500,000
Interest expense										200,000	1,200,000	1,000,000.0
Total expenses										54,900,000	288,200,000	163,600,000
Pre-tax income (loss)										(6,100,000)	$ 8,900,000	$ (400,000)
Percentage of advertising revenue											29.00%	27.00%
Other
Segment reporting information
Earned insurance premiums										0	$ 0	$ 1,000,000.0
Net investment income										43,400,000	42,300,000	43,700,000
Net realized and unrealized investment gains											(100,800,000)	132,700,000
Net realized and unrealized investment gains										285,100,000
Realized gain and unrealized investment gain from the MediaAlpha Transaction											0	0
Commission revenues										6,900,000	4,100,000	3,800,000
Other revenue										6,100,000	500,000	6,100,000
Total revenues										523,700,000	(53,900,000)	187,300,000
Loss and loss adjustment expenses										0	0	1,100,000
Insurance acquisition expense										0	0	100,000
Other underwriting expenses										0
Cost of sales										7,500,000	3,700,000	3,500,000
General and administrative expenses										122,500,000	94,400,000	148,900,000
Broker commission expense										0
Amortization of other intangible assets										600,000	200,000	200,000
Interest expense										600,000	300,000	1,300,000
Total expenses										131,200,000	98,600,000	155,100,000
Pre-tax income (loss)										392,500,000	$ (152,500,000)	$ 32,200,000
MediaAlpha
Segment reporting information
Gain from deconsolidation of MediaAlpha										182,200,000
MediaAlpha \| MediaAlpha
Segment reporting information
Total revenues									$ 359,200,000
MediaAlpha \| Other
Segment reporting information
Realized gain and unrealized investment gain from the MediaAlpha Transaction										$ 182,200,000

Segment Information (Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2012
Segment reporting information
Total investments	$ 2,947.2	$ 2,542.9
Assets	3,983.2	3,362.6
Liabilities	838.5	644.4
White Mountains’ common shareholders’ equity	3,261.5	2,843.1
Non-controlling interests	(116.8)	(124.9)
HG Global-BAM
Segment reporting information
Total investments	845.6	768.3
Assets	924.0	816.2
Liabilities	246.8	212.5
White Mountains’ common shareholders’ equity	809.5	759.8
Non-controlling interests	(132.3)	(156.1)
NSM Holding Co LLC
Segment reporting information
Total investments	0.0	0.0
Assets	825.2	623.6
Liabilities	401.1	314.8
White Mountains’ common shareholders’ equity	409.3	294.9
Non-controlling interests	14.8	13.9
Kudu
Segment reporting information
Total investments	266.6	0.0
Assets	290.5	0.0
Liabilities	57.0	0.0
White Mountains’ common shareholders’ equity	231.3	0.0
Non-controlling interests	2.2	0.0
MediaAlpha
Segment reporting information
Total investments	0.0	0.0
Assets	0.0	88.4
Liabilities	0.0	46.9
White Mountains’ common shareholders’ equity	0.0	25.3
Non-controlling interests	0.0	16.2
Other Operations
Segment reporting information
Total investments	1,835.0	1,774.6
Assets	1,940.5	1,831.1
Liabilities	133.6	70.2
White Mountains’ common shareholders’ equity	1,808.4	1,759.8
Non-controlling interests	(1.5)	1.1
Discontinued Operations, Held-for-sale
Segment reporting information
Total investments	0.0	0.0
Assets	3.0	3.3
Liabilities	0.0	0.0
White Mountains’ common shareholders’ equity	3.0	3.3
Non-controlling interests	0.0	0.0
BAM
Segment reporting information
Surplus notes	457.6	481.3
Accrued interest on surplus notes	162.7	143.7
HG Global
Segment reporting information
Non-controlling interests	14.4	14.5
Surplus notes			$ 503.0
Preferred Dividends Payable \| HG Global
Segment reporting information
Liabilities	$ 330.3	$ 278.5

Segment Information (Revenue) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment reporting information
Total revenues from contracts with customers									$ 294.3	$ 401.2	$ 163.6
Other revenues									599.1	(32.1)	210.2
Revenues	$ 175.3	$ 155.5	$ 129.0	$ 433.6	$ 6.0	$ 198.7	$ 122.3	$ 42.1	893.4	369.1	373.8
HG Global-BAM
Segment reporting information
Total revenues from contracts with customers									0.0	0.0	0.0
Other revenues									66.6	24.3	23.3
Revenues									66.6	24.3	23.3
NSM Holding Co LLC
Segment reporting information
Total revenues from contracts with customers									233.1	101.6
Other revenues									0.0	0.0
Revenues									233.1	101.6	0.0
Kudu
Segment reporting information
Total revenues from contracts with customers									0.0
Other revenues									21.2
Revenues									21.2
MediaAlpha
Segment reporting information
Total revenues from contracts with customers									48.8	295.5	163.2
Other revenues									0.0	1.6	0.0
Revenues									48.8	297.1	163.2
Other Operations
Segment reporting information
Total revenues from contracts with customers									12.4	4.1	0.4
Other revenues									511.3	(58.0)	186.9
Revenues									523.7	(53.9)	187.3
Specialty Transportation
Segment reporting information
Total revenues from contracts with customers									77.6	28.3
Specialty Transportation \| HG Global-BAM
Segment reporting information
Total revenues from contracts with customers										0.0
Specialty Transportation \| NSM Holding Co LLC
Segment reporting information
Total revenues from contracts with customers									77.6	28.3
Specialty Transportation \| Kudu
Segment reporting information
Total revenues from contracts with customers									0.0
Specialty Transportation \| MediaAlpha
Segment reporting information
Total revenues from contracts with customers									0.0	0.0
Specialty Transportation \| Other Operations
Segment reporting information
Total revenues from contracts with customers									0.0	0.0
Real Estate
Segment reporting information
Total revenues from contracts with customers									34.7	17.8
Real Estate \| HG Global-BAM
Segment reporting information
Total revenues from contracts with customers										0.0
Real Estate \| NSM Holding Co LLC
Segment reporting information
Total revenues from contracts with customers									34.7	17.8
Real Estate \| Kudu
Segment reporting information
Total revenues from contracts with customers									0.0
Real Estate \| MediaAlpha
Segment reporting information
Total revenues from contracts with customers									0.0	0.0
Real Estate \| Other Operations
Segment reporting information
Total revenues from contracts with customers									0.0	0.0
Social Services
Segment reporting information
Total revenues from contracts with customers									25.9	14.7
Social Services \| HG Global-BAM
Segment reporting information
Total revenues from contracts with customers										0.0
Social Services \| NSM Holding Co LLC
Segment reporting information
Total revenues from contracts with customers									25.9	14.7
Social Services \| Kudu
Segment reporting information
Total revenues from contracts with customers									0.0
Social Services \| MediaAlpha
Segment reporting information
Total revenues from contracts with customers									0.0	0.0
Social Services \| Other Operations
Segment reporting information
Total revenues from contracts with customers									0.0	0.0
Pet
Segment reporting information
Total revenues from contracts with customers									30.0
Pet \| NSM Holding Co LLC
Segment reporting information
Total revenues from contracts with customers									30.0
Pet \| Kudu
Segment reporting information
Total revenues from contracts with customers									0.0
Pet \| MediaAlpha
Segment reporting information
Total revenues from contracts with customers									0.0
Pet \| Other Operations
Segment reporting information
Total revenues from contracts with customers									0.0
Other
Segment reporting information
Total revenues from contracts with customers									25.9	16.9	0.4
Other \| HG Global-BAM
Segment reporting information
Total revenues from contracts with customers										0.0	0.0
Other \| NSM Holding Co LLC
Segment reporting information
Total revenues from contracts with customers									19.0	12.8
Other \| Kudu
Segment reporting information
Total revenues from contracts with customers									0.0
Other \| MediaAlpha
Segment reporting information
Total revenues from contracts with customers									0.0	0.0	0.0
Other \| Other Operations
Segment reporting information
Total revenues from contracts with customers									6.9	4.1	0.4
Total Commission and Other Revenue
Segment reporting information
Total revenues from contracts with customers									240.0	105.7	0.4
Total Commission and Other Revenue \| HG Global-BAM
Segment reporting information
Total revenues from contracts with customers										0.0	0.0
Total Commission and Other Revenue \| NSM Holding Co LLC
Segment reporting information
Total revenues from contracts with customers									233.1	101.6
Total Commission and Other Revenue \| Kudu
Segment reporting information
Total revenues from contracts with customers									0.0
Total Commission and Other Revenue \| MediaAlpha
Segment reporting information
Total revenues from contracts with customers									0.0	0.0	0.0
Total Commission and Other Revenue \| Other Operations
Segment reporting information
Total revenues from contracts with customers									6.9	4.1	0.4
Advertising revenues
Segment reporting information
Total revenues from contracts with customers									48.8	295.5	163.2
Advertising revenues \| HG Global-BAM
Segment reporting information
Total revenues from contracts with customers									0.0	0.0	0.0
Advertising revenues \| NSM Holding Co LLC
Segment reporting information
Total revenues from contracts with customers									0.0	0.0
Advertising revenues \| Kudu
Segment reporting information
Total revenues from contracts with customers									0.0
Advertising revenues \| MediaAlpha
Segment reporting information
Total revenues from contracts with customers									48.8	295.5	163.2
Advertising revenues \| Other Operations
Segment reporting information
Total revenues from contracts with customers									0.0	0.0	$ 0.0
Products
Segment reporting information
Total revenues from contracts with customers									5.5
Products \| HG Global-BAM
Segment reporting information
Total revenues from contracts with customers									0.0
Products \| NSM Holding Co LLC
Segment reporting information
Total revenues from contracts with customers									0.0
Products \| Kudu
Segment reporting information
Total revenues from contracts with customers									0.0
Products \| MediaAlpha
Segment reporting information
Total revenues from contracts with customers									0.0
Products \| Other Operations
Segment reporting information
Total revenues from contracts with customers									5.5
United Kingdom
Segment reporting information
Total revenues from contracts with customers									45.9	28.0
United Kingdom \| HG Global-BAM
Segment reporting information
Total revenues from contracts with customers									0.0	0.0
United Kingdom \| NSM Holding Co LLC
Segment reporting information
Total revenues from contracts with customers									45.9	28.0
United Kingdom \| Kudu
Segment reporting information
Total revenues from contracts with customers									0.0
United Kingdom \| MediaAlpha
Segment reporting information
Total revenues from contracts with customers									0.0	0.0
United Kingdom \| Other Operations
Segment reporting information
Total revenues from contracts with customers									$ 0.0	$ 0.0

Equity-Method Eligible Investments (Carrying Values of Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Other Investments	$ 622.8	$ 165.7
White Mountains
Schedule of Equity Method Investments [Line Items]
Other Investments	856.3	325.6
White Mountains \| Limited liability companies and private equity securities
Schedule of Equity Method Investments [Line Items]
Other Investments	761.7	269.7
White Mountains \| Other unconsolidated investments
Schedule of Equity Method Investments [Line Items]
Other Investments	$ 94.6	$ 55.9

Equity-Method Eligible Investments (Details)	Dec. 31, 2019	May 31, 2019	Dec. 31, 2018
DavidShield & PassportCard
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	50.00%		50.00%
MediaAlpha
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	48.30%
durchblicker
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	45.00%		45.00%
Elementum Holdings, L.P.
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	30.00%	30.00%
Compare.com
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	18.40%		18.40%
JAM Partners L.P.
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	11.10%		12.30%
Kudu
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)			49.50%
Minimum \| Tuckerman Capital Fund III, L.P.
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	17.50%		18.50%
Minimum \| Enlightenment Capital Funds
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	10.00%		10.30%
Minimum \| Kudu Investments
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	3.20%
Maximum \| Tuckerman Capital Fund III, L.P.
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	62.40%		62.30%
Maximum \| Enlightenment Capital Funds
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	38.40%		36.50%
Maximum \| Kudu Investments
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	30.00%

Equity-Method Eligible Investments (Balance Sheet and Income Statement Tables) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investments in unconsolidated affiliates
Assets	$ 3,983.2				$ 3,362.6				$ 3,983.2	$ 3,362.6
Liabilities	838.5				644.4				838.5	644.4
Revenues	175.3	$ 155.5	$ 129.0	$ 433.6	6.0	$ 198.7	$ 122.3	$ 42.1	893.4	369.1	$ 373.8
White Mountains
Investments in unconsolidated affiliates
Assets	1,959.2				1,373.3				1,959.2	1,373.3
Liabilities	653.2				509.2				653.2	509.2
Revenues									344.6	226.0	143.3
Expenses									88.3	141.4	80.5
Net Income									255.1	83.6	65.3
MediaAlpha
Investments in unconsolidated affiliates
Assets	106.9				88.5				106.9	88.5
Liabilities	$ 144.6				$ 46.9				144.6	46.9
Revenues									407.9	297.1	163.2
Expenses									389.0	288.2	163.5
Net Income									$ 18.9	$ 8.9	$ (0.3)

- Definition

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

+ References + Details

Equity-Method Eligible Investments - Narrative (Details) - USD ($)	3 Months Ended								10 Months Ended	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Feb. 26, 2019
Schedule of Equity Method Investments [Line Items]
Revenues	$ 175,300,000	$ 155,500,000	$ 129,000,000.0	$ 433,600,000	$ 6,000,000.0	$ 198,700,000	$ 122,300,000	$ 42,100,000		$ 893,400,000	$ 369,100,000	$ 373,800,000
MediaAlpha
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)													48.30%
Fully diluted ownership interest (as a percent)													42.00%
Assets, fair value				114,700,000
Unrealized investment gain				$ 114,700,000						180,000,000.0
MediaAlpha
Schedule of Equity Method Investments [Line Items]
Revenues										$ 48,800,000	$ 297,100,000	$ 163,200,000
MediaAlpha \| MediaAlpha
Schedule of Equity Method Investments [Line Items]
Revenues									$ 359,200,000
Expenses									334,300,000
Gross profit									59,700,000
Pre-tax income									$ 24,900,000

Variable Interest Entities (Details) $ in Millions		12 Months Ended
Variable Interest Entities (Details) $ in Millions	Apr. 04, 2019 USD ($)	Dec. 31, 2019 USD ($) director	May 31, 2019 USD ($)	Apr. 03, 2019	Dec. 31, 2018 USD ($)	Feb. 05, 2018 USD ($)
Variable Interest Entity [Line Items]
Percentage of par value of policy reinsured		15.00%
Other Investments		$ 622.8			$ 165.7
Payments to acquire business, net	$ 81.4
Goodwill		$ 394.7			379.9
BAM
Variable Interest Entity [Line Items]
Right to elect directors on board number \| director		2
First Loss Reinsurance Treaty \| HG Global
Variable Interest Entity [Line Items]
Percentage of par value of policy reinsured		15.00%
First Loss Reinsurance Treaty \| BAM
Variable Interest Entity [Line Items]
Percentage of premiums		60.00%
Elementum Holdings, L.P.
Variable Interest Entity [Line Items]
Ownership interest (as a percent)		30.00%	30.00%
Other Investments			$ 55.1
Kudu
Variable Interest Entity [Line Items]
Ownership interest (as a percent)	99.10%			49.50%		49.50%
Assets acquired	$ 155.5					$ 155.5
Fully diluted ownership interest (as a percent)	85.40%			42.70%		42.70%
Goodwill	$ 7.6					$ 7.6
Intangible assets acquired	2.2					2.2
Liabilities acquired	0.8					0.8
Noncontrolling interest acquired	$ 1.5					$ 1.5
Elementum Holdings, L.P.
Variable Interest Entity [Line Items]
Other Investments		$ 55.1			$ 0.0

Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	$ 283.5	$ 192.7
NSM Holding Co LLC
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	219.2	178.5
NSM Holding Co LLC \| Fair value \| NSM Bank Facility
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	221.2	176.1
NSM Holding Co LLC \| Fair value \| Other NSM
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	1.7	1.9
Kudu \| Kudu Debt
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	53.6
MediaAlpha
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	0.0	14.2
MediaAlpha \| MediaAlpha Bank Facility
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	0.0	14.2
MediaAlpha \| Fair value \| MediaAlpha Bank Facility
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	0.0	14.6
MediaAlpha \| Carrying Value \| MediaAlpha Bank Facility
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	0.0	14.2
Other Operations \| Fair value
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	11.3	0.0
Other Operations \| Carrying Value
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt		0.0
Term Loan \| NSM Holding Co LLC \| NSM Bank Facility
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	217.4	176.6
Term Loan \| NSM Holding Co LLC \| Other NSM
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	1.8	1.9
Term Loan \| NSM Holding Co LLC \| Carrying Value \| NSM Bank Facility
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	$ 217.4	$ 176.6

Transactions with Related Persons (Details) - $ / shares		12 Months Ended
	Jul. 13, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Value of each common share repurchased and retired during the period (in dollars per share)		$ 858	$ 877	$ 869
Franklin Mutual Advisers
Related Party Transaction [Line Items]
Value of each common share repurchased and retired during the period (in dollars per share)	$ 850.00
Common Stock
Related Party Transaction [Line Items]
Common shares repurchased and retired during the period		5,679	592,458	832,725
Common Stock \| Franklin Mutual Advisers
Related Party Transaction [Line Items]
Common shares repurchased and retired during the period	235,000

Commitments and Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jun. 28, 2019
Loss Contingencies [Line Items]
Rent expense	$ 7.2	$ 5.5	$ 3.5
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Capital lease payments due next year	7.1
Capital lease payments due in two years	6.1
Capital lease payments due in three years	5.7
Capital Lease payments due in four years and thereafter	18.4
Commitments to fund other-long term investments	183.4
Sirius Group \| Sirius Group \| Swedish Tax Authority
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Loss contingency accrual	16.5	17.3
Loss contingency accrual, period increase (decrease)	(0.8)	$ 17.3
American International Group \| NSM Insurance HoldCo, LLC
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Purchase obligation	$ 82.5
Intangible assets acquired				$ 82.5

Held for Sale and Discontinued Operations (Details) - USD ($) $ / shares in Units, $ in Millions				3 Months Ended								9 Months Ended		12 Months Ended
	Sep. 28, 2017	Jul. 21, 2016	Apr. 18, 2016	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2018	Sep. 28, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Discontinued Operations
Sales of unconsolidated affiliates and consolidated subsidiaries, net of cash sold														$ 0.0	$ 0.0	$ 1,131.0
Gain (loss) on sale of other discontinued operations, net of tax														0.8	(17.2)	557.0
Net income from discontinued operations, net of tax				$ (0.8)	$ 0.9	$ 0.0	$ 0.7	$ 0.0	$ (17.3)	$ 0.0	$ 0.1			0.0	0.0	20.5
Payments to acquire other investments														177.7	95.9	84.1
OneBeacon
Discontinued Operations
Sale of Stock, Price Per Share	$ 18.10												$ 18.10
Sales of unconsolidated affiliates and consolidated subsidiaries, net of cash sold	$ 1,300.0
Gain (loss) on sale of other discontinued operations, net of tax	$ 554.6
Net income from discontinued operations, net of tax													$ 20.5
OneBeacon \| Discontinued Operations
Discontinued Operations
Gain (loss) on sale of other discontinued operations, net of tax																554.5
Net income from discontinued operations, net of tax																20.5
Tranzact
Discontinued Operations
Sales of unconsolidated affiliates and consolidated subsidiaries, net of cash sold		$ 221.3
Gain (loss) on sale of other discontinued operations, net of tax															3.2	3.2
Tranzact \| Discontinued Operations
Discontinued Operations
Gain (loss) on sale of other discontinued operations, net of tax																3.2
Net income from discontinued operations, net of tax																0.0
Sirius Group
Discontinued Operations
Sales of unconsolidated affiliates and consolidated subsidiaries, net of cash sold			$ 2,600.0
Gain (loss) on sale of other discontinued operations, net of tax															(17.3)
Payments to acquire other investments			$ 161.8
Discontinued operations, liability				16.5				17.3						16.5	17.3
Sirius Group \| Discontinued Operations
Discontinued Operations
Gain (loss) on sale of other discontinued operations, net of tax														0.8	(17.2)	(0.7)
Net income from discontinued operations, net of tax																0.0
Connecticut \| Sirius Group, Tranzact, and Star and Shield \| Discontinued Operations, Held-for-sale
Discontinued Operations
Other expenses																$ 3.7
Assets held for sale				$ 3.0				$ 3.3						3.0	3.3
OneBeacon \| Intact Financial Corporation
Discontinued Operations
Sale of Stock, Price Per Share	$ 18.10												$ 18.10
Swedish Tax Authority \| Sirius Group \| Sirius Group
Discontinued Operations
Net income from discontinued operations, net of tax												$ (17.3)		0.8
Loss contingency accrual, period increase (decrease)														$ (0.8)	$ 17.3

Held for Sale and Discontinued Operations (Loss from Discontinued Operations) (Details) - USD ($) $ in Millions		3 Months Ended								9 Months Ended	12 Months Ended
	Sep. 28, 2017	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 28, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues
Earned insurance premiums											$ 16.3	$ 13.9	$ 10.4
Net investment income											79.7	59.0	56.0
Other revenue											47.6	15.3	7.1
Net realized and unrealized investment gains (losses)											433.2	(108.3)	133.3
Revenues		$ 175.3	$ 155.5	$ 129.0	$ 433.6	$ 6.0	$ 198.7	$ 122.3	$ 42.1		893.4	369.1	373.8
Expenses
Loss and loss adjustment expenses													1.1
Other underwriting expenses											0.4	0.4	0.4
General and administrative expenses											327.8	233.5	208.0
Interest expense on debt											17.6	9.5	2.3
Total expenses		118.8	104.4	113.2	151.9	150.1	154.4	134.7	108.1		488.3	547.3	366.0
Net income from discontinued operations, net of tax		$ (0.8)	$ 0.9	$ 0.0	$ 0.7	$ 0.0	$ (17.3)	$ 0.0	$ 0.1		0.0	0.0	20.5
Gain (loss) on sale of other discontinued operations, net of tax											0.8	(17.2)	557.0
Total income (loss) from discontinued operations											0.8	(17.2)	577.5
Comprehensive income from discontinued operations											413.1	(146.0)	630.7
Discontinued Operations
Expenses
Total income (loss) from discontinued operations											0.8	(17.2)	577.5
Recognition of foreign currency translation from sale of OneBeacon, net of tax													0.0
OneBeacon
Expenses
Net income from discontinued operations, net of tax										$ 20.5
Gain (loss) on sale of other discontinued operations, net of tax	$ 554.6
OneBeacon \| Discontinued Operations
Revenues
Earned insurance premiums													807.6
Net investment income													39.7
Other revenue													7.7
Net realized and unrealized investment gains (losses)													38.8
Revenues													893.8
Expenses
Loss and loss adjustment expenses													546.0
Insurance and reinsurance acquisition expenses													145.6
Other underwriting expenses													156.2
General and administrative expenses													21.2
Interest expense on debt													10.0
Total expenses													879.0
Net income from discontinued operations													14.8
Income tax benefit													5.7
Net income from discontinued operations, net of tax													20.5
Gain (loss) on sale of other discontinued operations, net of tax													554.5
Total income (loss) from discontinued operations													575.0
Change in foreign currency translation and other comprehensive income from discontinued operations, net of tax													0.3
Recognition of foreign currency translation from sale of OneBeacon, net of tax													2.9
Comprehensive income from discontinued operations													578.2
Sirius Group
Expenses
Gain (loss) on sale of other discontinued operations, net of tax												(17.3)
Sirius Group \| Discontinued Operations
Revenues
Earned insurance premiums													0.0
Net investment income													0.0
Other revenue													0.0
Net realized and unrealized investment gains (losses)													0.0
Revenues													0.0
Expenses
Loss and loss adjustment expenses													0.0
Insurance and reinsurance acquisition expenses													0.0
Other underwriting expenses													0.0
General and administrative expenses													0.0
Interest expense on debt													0.0
Total expenses													0.0
Net income from discontinued operations													0.0
Income tax benefit													0.0
Net income from discontinued operations, net of tax													0.0
Gain (loss) on sale of other discontinued operations, net of tax											$ 0.8	(17.2)	(0.7)
Total income (loss) from discontinued operations													(0.7)
Change in foreign currency translation and other comprehensive income from discontinued operations, net of tax													0.0
Comprehensive income from discontinued operations													(0.7)
Tranzact
Expenses
Gain (loss) on sale of other discontinued operations, net of tax												$ 3.2	3.2
Tranzact \| Discontinued Operations
Revenues
Earned insurance premiums													0.0
Net investment income													0.0
Other revenue													0.0
Net realized and unrealized investment gains (losses)													0.0
Revenues													0.0
Expenses
Loss and loss adjustment expenses													0.0
Insurance and reinsurance acquisition expenses													0.0
Other underwriting expenses													0.0
General and administrative expenses													0.0
Interest expense on debt													0.0
Total expenses													0.0
Net income from discontinued operations													0.0
Income tax benefit													0.0
Net income from discontinued operations, net of tax													0.0
Gain (loss) on sale of other discontinued operations, net of tax													3.2
Total income (loss) from discontinued operations													3.2
Change in foreign currency translation and other comprehensive income from discontinued operations, net of tax													0.0
Comprehensive income from discontinued operations													3.2
Total \| Discontinued Operations
Revenues
Earned insurance premiums													807.6
Net investment income													39.7
Other revenue													7.7
Net realized and unrealized investment gains (losses)													38.8
Revenues													893.8
Expenses
Loss and loss adjustment expenses													546.0
Insurance and reinsurance acquisition expenses													145.6
Other underwriting expenses													156.2
General and administrative expenses													21.2
Interest expense on debt													10.0
Total expenses													879.0
Net income from discontinued operations													14.8
Income tax benefit													5.7
Net income from discontinued operations, net of tax													20.5
Gain (loss) on sale of other discontinued operations, net of tax													557.0
Change in foreign currency translation and other comprehensive income from discontinued operations, net of tax													0.3
Recognition of foreign currency translation from sale of OneBeacon, net of tax													2.9
Comprehensive income from discontinued operations													$ 580.7

Held for Sale and Discontinued Operations (Cash Flows Table) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net cash provided from discontinued operations (See Note 20)	$ 0.0	$ 0.0	$ 157.0
Net cash provided from investing activities — discontinued operations (See Note 20)	0.0	0.0	3.0
Net cash used for financing activities — discontinued operations (See Note 20)	0.0	0.0	(61.9)
Net change in cash during the period			98.1
Cash balance at beginning of year	110.3	97.1	80.2
Net change in cash during the period - continuing operations			(0.9)
Cash sold as part of sale of consolidated subsidiaries			(167.7)
Cash balance at end of year	$ 161.0	110.3	97.1
Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash balance at beginning of year		$ 0.0	70.5
Cash balance at end of year			$ 0.0

Held for Sale and Discontinued Operations (Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Basic and diluted earnings per share numerators (in millions):
Net income (loss) attributable to White Mountains’s common shareholders	$ 60.9	$ 48.7	$ 20.5	$ 284.4	$ (137.5)	$ 40.8	$ 3.5	$ (48.0)	$ 414.5	$ (141.2)	$ 627.2
Net income (loss) attributable to White Mountains’ common shareholders									413.7	(124.0)	49.7
Total income (loss) from discontinued operations									0.8	(17.2)	577.5
Allocation of (earnings) losses to participating restricted common shares									(5.3)	1.4	(0.7)
Basic and diluted earnings (loss) per share numerators									$ 408.4	$ (122.6)	$ 49.0
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period									3,181,600	3,382,500	4,293,800
Average unvested restricted common shares									(40,500)	(40,100)	(54,300)
Basic earnings (loss) per share denominator									3,141,100	3,342,400	4,239,500
Diluted earnings per share denominator (in thousands):
Average outstanding dilutive options to acquire common shares									3,181,600	3,382,500	4,293,800
Average unvested restricted common shares									(40,500)	(40,100)	(54,300)
Diluted earnings (loss) per share denominator									3,141,100	3,342,400	4,239,500
Basic (losses) earnings per share (in usd per share)	$ 19.12	$ 15.29	$ 6.44	$ 89.64	$ (43.24)	$ 12.83	$ 1.02	$ (12.82)	$ 130.27	$ (41.76)	$ 146.06
Diluted (losses) earnings per share (in usd per share)	$ 19.12	$ 15.29	$ 6.44	$ 89.64	$ (43.24)	$ 12.83	$ 1.02	$ (12.82)	$ 130.27	$ (41.76)	$ 146.06
Discontinued Operations
Basic and diluted earnings per share numerators (in millions):
Net income (loss) attributable to White Mountains’s common shareholders									$ 414.5	$ (141.2)	$ 627.2
Net income (loss) attributable to White Mountains’ common shareholders									413.7	(124.0)	49.7
Total income (loss) from discontinued operations									0.8	(17.2)	577.5
Allocation of (earnings) losses to participating restricted common shares									0.0	0.2	(7.3)
Basic and diluted earnings (loss) per share numerators									$ 0.8	$ (17.0)	$ 570.2
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period									3,181,600	3,382,500	4,293,800
Average unvested restricted common shares									(40,500)	(40,100)	(54,300)
Basic earnings (loss) per share denominator									3,141,100	3,342,400	4,239,500
Diluted earnings per share denominator (in thousands):
Average outstanding dilutive options to acquire common shares									3,181,600	3,382,500	4,293,800
Average unvested restricted common shares									(40,500)	(40,100)	(54,300)
Diluted earnings (loss) per share denominator									3,141,100	3,342,400	4,239,500
Basic (losses) earnings per share (in usd per share)									$ 0.25	$ (5.09)	$ 134.50
Diluted (losses) earnings per share (in usd per share)									$ 0.25	$ (5.09)	$ 134.50

Subsequent Event (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
Subsequent Event (Details) - USD ($) $ in Millions	Jan. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Subsequent Event [Line Items]
Repayments of debt, principal		$ 22.9	$ 15.4	$ 365.0
Subsequent Event
Subsequent Event [Line Items]
Maximum exposure to any single issuer	$ 75.0
BAM \| Subsequent Event
Subsequent Event [Line Items]
Accrued interest on surplus notes	146.5
Surplus notes	409.7
Surplus Note \| BAM
Subsequent Event [Line Items]
Special cash payment		32.0	23.0
Repayments of debt, principal		23.7	17.7
Accrued interest held in Supplemental Trust		0.3	0.7
Accrued interest on surplus notes		$ 8.0	$ 4.6
Surplus Note \| BAM \| Subsequent Event
Subsequent Event [Line Items]
Special cash payment	65.0
Repayments of debt, principal	47.9
Accrued interest held in Supplemental Trust	0.9
Accrued interest on surplus notes	$ 16.2

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 175.3	$ 155.5	$ 129.0	$ 433.6	$ 6.0	$ 198.7	$ 122.3	$ 42.1	$ 893.4	$ 369.1	$ 373.8
Expenses	118.8	104.4	113.2	151.9	150.1	154.4	134.7	108.1	488.3	547.3	366.0
Pre-tax income (loss)	56.5	51.1	15.8	281.7	(144.1)	44.3	(12.4)	(66.0)	405.1	(178.2)	7.8
Tax (expense) benefit	(10.4)	(8.8)	0.1	(10.2)	3.6	3.6	(2.5)	(0.7)	(29.3)	4.0	7.8
Net income (loss) from continuing operations	46.1	42.3	15.9	271.5	(140.5)	47.9	(14.9)	(66.7)	375.8	(174.2)	15.6
Net income from discontinued operations, net of tax	(0.8)	0.9	0.0	0.7	0.0	(17.3)	0.0	0.1	0.0	0.0	20.5
Non-controlling interest in consolidated subsidiaries	15.6	5.5	4.6	12.2	3.0	10.2	18.4	18.6	37.9	50.2	34.1
Net income attributable to White Mountains’s common shareholders	$ 60.9	$ 48.7	$ 20.5	$ 284.4	$ (137.5)	$ 40.8	$ 3.5	$ (48.0)	$ 414.5	$ (141.2)	$ 627.2
Basic earnings (loss) per share
Continuing operations	$ 19.37	$ 15.01	$ 6.44	$ 89.42	$ (43.24)	$ 18.27	$ 1.02	$ (12.85)	$ 130.02	$ (36.67)	$ 11.56
Discontinued operations	(0.25)	0.28	0	0.22	0	(5.44)	0	0.03	0.25	(5.09)	134.50
Total consolidated operations	19.12	15.29	6.44	89.64	(43.24)	12.83	1.02	(12.82)	130.27	(41.76)	146.06
Diluted earnings (loss) per share
Continuing operations	19.37	15.01	6.44	89.42	(43.24)	18.27	1.02	(12.85)	130.02	(36.67)	11.56
Discontinued operations	(0.25)	0.28	0	0.22	0	(5.44)	0	0.03	0.25	(5.09)	134.50
Total consolidated operations	$ 19.12	$ 15.29	$ 6.44	$ 89.64	$ (43.24)	$ 12.83	$ 1.02	$ (12.82)	$ 130.27	$ (41.76)	$ 146.06

SCHEDULE I SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES (Details) $ in Millions	Dec. 31, 2019 USD ($)
Summary of investments other than investments in related parties
Cost	$ 2,599.8
Carrying Value	2,947.2
Fair Value	2,947.2
Fixed maturity investments
Summary of investments other than investments in related parties
Cost	1,177.9
Carrying Value	1,205.8
Fair Value	1,205.8
U.S. Government and agency obligations
Summary of investments other than investments in related parties
Cost	231.7
Carrying Value	232.5
Fair Value	232.5
Debt securities issued by corporations
Summary of investments other than investments in related parties
Cost	454.9
Carrying Value	467.2
Fair Value	467.2
Municipal obligations
Summary of investments other than investments in related parties
Cost	284.7
Carrying Value	297.1
Fair Value	297.1
Mortgage and asset-backed securities
Summary of investments other than investments in related parties
Cost	206.6
Carrying Value	209.0
Fair Value	209.0
Short-term investments
Summary of investments other than investments in related parties
Cost	201.2
Carrying Value	201.2
Fair Value	201.2
Exchange traded funds
Summary of investments other than investments in related parties
Cost	436.0
Carrying Value	536.4
Fair Value	536.4
Common equity securities
Summary of investments other than investments in related parties
Cost	553.3
Carrying Value	683.9
Fair Value	683.9
Other
Summary of investments other than investments in related parties
Cost	117.3
Carrying Value	147.5
Fair Value	147.5
Other long-term investments
Summary of investments other than investments in related parties
Cost	667.4
Carrying Value	856.3
Fair Value	$ 856.3

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT - Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets
Total assets	$ 3,983.2	$ 3,362.6
Liabilities
Payable to subsidiary	6.6	4.0	$ 11.6
Total liabilities	838.5	644.4
White Mountains’s common shareholders’ equity	3,144.7	2,718.2
Non-controlling interests	(116.8)	(124.9)
Total liabilities and equity	3,983.2	3,362.6
Fair value investments	2,746.0	2,328.7	3,208.3
White Mountains Insurance Group Ltd.
Assets
Cash	0.7	0.7
Fixed maturity investments, at fair value	10.0	0.0
Common equity securities, at fair value	193.5	335.6
Short-term investments, at amortized cost	66.2	28.0
Other assets	1.9	1.8
Investments in consolidated subsidiaries	2,969.0	2,533.2
Total assets	3,241.3	2,899.3
Liabilities
Payable to subsidiary	(69.3)	15.8
Other liabilities	34.7	25.9
Total liabilities	(34.6)	41.7
White Mountains’s common shareholders’ equity	3,261.5	2,843.1
Non-controlling interests	14.4	14.5
Total liabilities and equity	3,241.3	2,899.3
Sirius Group
Assets
Cash	0.0	0.0	$ 0.0	$ 70.5
Sirius Group \| Swedish Tax Authority \| Sirius Group
Liabilities
Loss contingency accrual	$ 16.5	$ 17.3

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT - Statement of Operations and Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended								9 Months Ended	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Revenues (loss) (including realized and unrealized gains and losses)	$ 175.3	$ 155.5	$ 129.0	$ 433.6	$ 6.0	$ 198.7	$ 122.3	$ 42.1		$ 893.4	$ 369.1	$ 373.8
Expenses	118.8	104.4	113.2	151.9	150.1	154.4	134.7	108.1		488.3	547.3	366.0
Pre-tax income (loss)	56.5	51.1	15.8	281.7	(144.1)	44.3	(12.4)	(66.0)		405.1	(178.2)	7.8
Income tax (expense) benefit	(10.4)	(8.8)	0.1	(10.2)	3.6	3.6	(2.5)	(0.7)		(29.3)	4.0	7.8
Net income (loss) from continuing operations	46.1	42.3	15.9	271.5	(140.5)	47.9	(14.9)	(66.7)		375.8	(174.2)	15.6
Net income from discontinued operations, net of tax	(0.8)	0.9	0.0	0.7	0.0	(17.3)	0.0	0.1		0.0	0.0	20.5
Net loss attributable to non-controlling interests	15.6	5.5	4.6	12.2	3.0	10.2	18.4	18.6		37.9	50.2	34.1
Net income (loss) attributable to White Mountains’s common shareholders	$ 60.9	$ 48.7	$ 20.5	$ 284.4	$ (137.5)	$ 40.8	$ 3.5	$ (48.0)		414.5	(141.2)	627.2
Other comprehensive (loss) income, net of tax										(1.4)	(4.8)	0.3
Comprehensive income (loss) attributable to White Mountains’s common shareholders										413.1	(145.7)	630.5
Total income (loss) from discontinued operations										0.8	(17.2)	577.5
White Mountains Insurance Group Ltd.
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Revenues (loss) (including realized and unrealized gains and losses)										65.0	(47.7)	27.3
Expenses										47.1	45.9	99.7
Pre-tax income (loss)										17.9	(93.6)	(72.4)
Income tax (expense) benefit										0.9	2.5	1.4
Net income (loss) from continuing operations										17.0	(96.1)	(73.8)
Net income from discontinued operations, net of tax										0.8	(17.2)	0.0
Equity in earnings of unconsolidated affiliates										398.5	(27.4)	701.0
Net loss attributable to non-controlling interests										(1.8)	(0.5)	0.0
Net income (loss) attributable to White Mountains’s common shareholders										414.5	(141.2)	627.2
Other comprehensive (loss) income, net of tax										(1.4)	(4.5)	3.3
Comprehensive income (loss) attributable to White Mountains’s common shareholders										413.1	(145.7)	630.5
Discontinued Operations
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Net income (loss) attributable to White Mountains’s common shareholders										414.5	(141.2)	627.2
Total income (loss) from discontinued operations										0.8	(17.2)	577.5
Discontinued Operations \| Sirius Group
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Revenues (loss) (including realized and unrealized gains and losses)												0.0
Expenses												0.0
Net income from discontinued operations, net of tax												0.0
Total income (loss) from discontinued operations												(0.7)
Discontinued Operations \| OneBeacon, Sirius Group, and Tranzact
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Total income (loss) from discontinued operations												$ 577.5
Swedish Tax Authority \| Sirius Group \| Sirius Group
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Net income from discontinued operations, net of tax									$ (17.3)	0.8
Loss contingency accrual, period increase (decrease)										$ (0.8)	$ 17.3

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT - Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended								9 Months Ended	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Net income (loss) attributable to White Mountains’s common shareholders	$ 60.9	$ 48.7	$ 20.5	$ 284.4	$ (137.5)	$ 40.8	$ 3.5	$ (48.0)		$ 414.5	$ (141.2)	$ 627.2
Charges (credits) to reconcile net income to net cash provided from (used for) operations:
Net realized and unrealized investment (gains) losses										(433.2)	108.3	(133.3)
Net income from discontinued operations, net of tax	0.8	$ (0.9)	$ 0.0	(0.7)	0.0	$ 17.3	$ 0.0	(0.1)		0.0	0.0	(20.5)
Net change in other assets and liabilities, net										18.7	(27.1)	(20.8)
Net cash (used for) provided from operations										(120.5)	(31.1)	94.6
Cash flows from investing activities:
Net decrease in short-term investments										21.9	(39.0)	(1.7)
Net cash (used for) provided from investing activities										(59.9)	459.2	718.5
Cash flows from financing activities:
Draw down of debt and revolving line of credit										206.4	84.1	376.0
Repayment of debt and revolving line of credit										(22.9)	(15.4)	(365.0)
Repurchases and retirement of common shares										0.0	(511.9)	(714.6)
Dividends paid on common shares										(3.2)	(3.8)	(4.6)
Net cash provided from (used for) financing activities										230.5	(414.3)	(699.0)
Net change in cash during the period - continuing operations												(0.9)
Cash balance at beginning of year				110.3				97.1	$ 97.1	110.3	97.1	80.2
Cash balance at end of year	161.0				110.3					161.0	110.3	97.1
Interest paid										(16.3)	(8.8)	(1.4)
White Mountains’s common shareholders’ equity	3,144.7				2,718.2					3,144.7	2,718.2
Amortization of restricted share and option awards										10.5	13.0	14.8
Payable to subsidiary	(6.6)				(4.0)					(6.6)	(4.0)	(11.6)
Lone Tree Holdings Ltd.
Cash flows from financing activities:
White Mountains’s common shareholders’ equity												2,810.4
Other liabilities												14.1
Investments in consolidated subsidiaries												964.4
Short-term investments, at amortized cost												13.0
White Mountains Insurance Group Ltd.
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Net income (loss) attributable to White Mountains’s common shareholders										414.5	(141.2)	627.2
Charges (credits) to reconcile net income to net cash provided from (used for) operations:
Net realized and unrealized investment (gains) losses										(61.0)	57.8	(18.5)
Undistributed earnings from subsidiaries										(398.5)	27.4	(701.0)
Net income from discontinued operations, net of tax										(0.8)	17.2	0.0
Other non-cash reconciling items, primarily amortization of restricted share and option awards (4)										20.0	34.6	31.1
Accumulated earnings distributed from subsidiary in cash										0.0	0.0	1,256.7
Net change in other assets and liabilities, net										3.0	16.7	(4.9)
Net cash (used for) provided from operations										(22.8)	12.5	1,190.6
Cash flows from investing activities:
Net decrease in short-term investments										(37.6)	134.0	(24.7)
Payments to Acquire Investments										(14.8)	(321.2)	(474.7)
Proceeds from Sale and Maturity of Debt and Equity Securities, FV-NI, Held-for-investment										207.9	967.6	367.1
Issuance of debt (to) from subsidiaries										(83.5)	(55.2)	382.0
Repayment of debt (to) from subsidiaries										5.0	31.0	0.0
Payments to acquire interest in subsidiary										46.1	258.2	700.0
Net cash (used for) provided from investing activities										30.9	498.0	(450.3)
Cash flows from financing activities:
Draw down of debt and revolving line of credit										0.0	0.0	350.0
Repayment of debt and revolving line of credit										0.0	0.0	(350.0)
Repurchases and retirement of common shares										0.0	(510.9)	(714.6)
Dividends paid on common shares										(3.2)	(3.8)	(4.6)
Payments of restricted shares withholding taxes										(4.9)	(10.0)	(9.3)
Net cash provided from (used for) financing activities										(8.1)	(524.7)	(728.5)
Net change in cash during the period - continuing operations										0.0	(14.2)	11.8
Cash balance at beginning of year				$ 0.7				$ 14.9	14.9	0.7	14.9	3.1
Cash balance at end of year	0.7				0.7					0.7	0.7	14.9
Interest paid										0.0	0.0	(0.6)
White Mountains’s common shareholders’ equity	3,261.5				2,843.1					3,261.5	2,843.1
Other liabilities	34.7				25.9					34.7	25.9
Investments in consolidated subsidiaries	2,969.0				2,533.2					2,969.0	2,533.2
Short-term investments, at amortized cost	66.2				28.0					66.2	28.0
Payable to subsidiary	$ 69.3				$ (15.8)					69.3	(15.8)
Transfer from investments												1,238.9
Lone Tree Holdings Ltd. \| White Mountains Insurance Group Ltd.
Cash flows from financing activities:
Net change in due to affiliates												1,256.7
Proceeds from divestiture of businesses												1,037.6
Bridge Holdings, Ltd. \| White Mountains Insurance Group Ltd.
Cash flows from investing activities:
Payments to acquire interest in subsidiary											(255.3)
Cash flows from financing activities:
Transfer to investments										70.5	(22.7)
White Mountains Investment, Ltd. \| White Mountains Insurance Group Ltd.
Cash flows from investing activities:
Payments to acquire interest in subsidiary											(2.9)
Cash flows from financing activities:
Transfer to investments										2.0
Transfer from investments										24.4
HG Global \| White Mountains Insurance Group Ltd.
Cash flows from financing activities:
Transfer from investments										1.9
Intercompany balances \| Lone Tree Holdings Ltd.
Cash flows from financing activities:
Other liabilities												1,863.1
Non-cash reconciling item \| White Mountains Insurance Group Ltd.
Cash flows from financing activities:
Transfer to investments												$ (94.2)
Non-cash reconciling item \| Guilford Holdings, Inc.
Cash flows from financing activities:
Transfer to investments											(349.5)
Noncash Total \| White Mountains Insurance Group Ltd.
Cash flows from financing activities:
Transfer to investments											603.9
Transfer from investments											1,065.4
Fixed maturity investments \| White Mountains Insurance Group Ltd.
Cash flows from financing activities:
Transfer to investments											170.5
Transfer from investments											373.4
Fixed maturity investments \| Guilford Holdings, Inc.
Cash flows from financing activities:
Transfer from investments											170.4
Common equity securities \| White Mountains Insurance Group Ltd.
Cash flows from financing activities:
Transfer to investments											148.8
Transfer from investments											490.1
Other long-term investments \| White Mountains Insurance Group Ltd.
Cash flows from financing activities:
Transfer to investments											22.7
Transfer from investments											22.7
Short-term investments \| White Mountains Insurance Group Ltd.
Cash flows from financing activities:
Transfer to investments											(284.6)
Transfer from investments											179.2
Short-term investments \| Guilford Holdings, Inc.
Cash flows from financing activities:
Transfer from investments											179.2
Bridge Holdings, Ltd. \| Guilford Holdings, Inc.
Cash flows from financing activities:
Transfer to investments											(350.0)
Bridge Holdings, Ltd. \| White Mountains Investment, Ltd.
Cash flows from financing activities:
Transfer to investments											$ (1.0)
Swedish Tax Authority \| Sirius Group \| Sirius Group
Charges (credits) to reconcile net income to net cash provided from (used for) operations:
Net income from discontinued operations, net of tax									$ 17.3	$ (0.8)

SCHEDULE III SUPPLEMENTARY INSURANCE INFORMATION (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SUPPLEMENTARY INSURANCE INFORMATION
Net investment income	$ 79.7	$ 59.0	$ 56.0
HG Global-BAM
SUPPLEMENTARY INSURANCE INFORMATION
Deferred acquisition costs	22.1	19.0	14.8
Future policy benefits, losses, claims and loss expenses	0.0	0.0	0.0
Unearned premiums	198.4	176.0	136.8
Other policy claims and benefits payable	0.0	0.0	0.0
Premiums earned	16.3	13.9	9.4
Net investment income	21.6	16.7	12.3
Benefits, claims, losses, and settlement expenses	0.0	0.0	0.0
Amortization of deferred policy acquisition costs	5.7	5.3	4.0
Other operating expenses	0.4	0.4	0.4
Premiums written	38.7	52.9	63.2
Net investment income	21.6	16.7	12.3
Other Operations
SUPPLEMENTARY INSURANCE INFORMATION
Deferred acquisition costs	0.0	0.0	0.0
Future policy benefits, losses, claims and loss expenses	0.0	0.0	0.0
Unearned premiums	0.0	0.0	0.0
Other policy claims and benefits payable	0.0	0.0	0.0
Premiums earned	0.0	0.0	1.0
Net investment income	0.0	0.0	0.0
Benefits, claims, losses, and settlement expenses	0.0	0.0	1.1
Amortization of deferred policy acquisition costs	0.0	0.0	0.1
Other operating expenses	0.0	0.0	0.0
Premiums written	0.0	0.0	0.9
Non-insurance \| Operating Segments
SUPPLEMENTARY INSURANCE INFORMATION
Net investment income	$ 43.4	$ 42.3	$ 43.7

SCHEDULE IV REINSURANCE (Details) - USD ($) $ in Millions	12 Months Ended
SCHEDULE IV REINSURANCE (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Premiums earned
Net earned premiums	$ 16.3	$ 13.9	$ 10.4
HG Global/BAM
Premiums earned
Gross Amount	13.6	13.6	9.4
Ceded to Other Companies	0.0	0.0	0.0
Assumed from Other Companies	2.7	0.3	0.0
Net earned premiums	$ 16.3	$ 13.9	$ 9.4
Percentage of Amount Assumed to Net	16.60%	2.20%	0.00%
Other Segments
Premiums earned
Gross Amount	$ 0.0	$ 0.0	$ 1.0
Ceded to Other Companies	0.0	0.0	0.0
Assumed from Other Companies	0.0	0.0	0.0
Net earned premiums	$ 0.0	$ 0.0	$ 1.0
Percentage of Amount Assumed to Net	0.00%	0.00%	0.00%

Label	Element	Value
Common Stock Including Additional Paid in Capital [Member]
Noncontrolling Interest, Decrease from Deconsolidation	us-gaap_NoncontrollingInterestDecreaseFromDeconsolidation	$ 0

Investment Securities (Fair Value Measurement by Level) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) Investment	Dec. 31, 2018 USD ($) Investment	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Investment securities
Percentage of investments recorded at fair value	71.00%	87.00%
Fair value investments	$ 2,746.0	$ 2,328.7		$ 3,208.3
Debt securities issued by corporations
Investment securities
Fair value investments	467.2	510.5
Mortgage and asset-backed securities
Investment securities
Fair value investments	$ 209.0	$ 133.5
Common Stock
Investment securities
Number of investments \| Investment	2	2
Level 1
Investment securities
Fair value investments	$ 780.0	$ 842.6	$ 842.6	890.4
Level 2
Investment securities
Fair value investments	1,109.6	1,160.5	1,160.5	2,105.4
Level 2 \| Mortgage and asset-backed securities
Investment securities
Fair value investments	209.0	133.5
Level 3 Inputs \| Mortgage and asset-backed securities
Investment securities
Fair value investments	0.0	0.0
Level 3 Inputs \| Common equity securities
Investment securities
Fair value investments	0.1	0.0
Level 3 Inputs \| Other long-term investments
Investment securities
Fair value investments	654.0	138.7	138.7	77.2
Fair Value Measured at Net Asset Value Per Share \| Hedge Funds and Private Equity Funds
Investment securities
Fair value investments	202.3	186.9		$ 135.3
Fair value measured on a recurring basis
Investment securities
Fair value investments	2,947.2	2,542.9
Fair value measured on a recurring basis \| U.S. Government and agency obligations
Investment securities
Fair value investments	232.5	153.2
Fair value measured on a recurring basis \| Debt securities issued by corporations
Investment securities
Fair value investments	467.2	510.5
Fair value measured on a recurring basis \| Mortgage and asset-backed securities
Investment securities
Fair value investments	209.0	133.5
Fair value measured on a recurring basis \| Municipal obligations
Investment securities
Fair value investments	297.1	280.3
Fair value measured on a recurring basis \| Fixed maturity investments
Investment securities
Fair value investments	1,205.8	1,077.5
Fair value measured on a recurring basis \| Short-term investments
Investment securities
Short-term investments, at fair value	201.2	214.2
Fair value measured on a recurring basis \| Other long-term investments
Investment securities
Fair value investments	654.0	138.7
Fair value measured on a recurring basis \| Level 1
Investment securities
Fair value investments	969.4	1,047.0
Fair value measured on a recurring basis \| Level 1 \| U.S. Government and agency obligations
Investment securities
Fair value investments	232.5	153.2
Fair value measured on a recurring basis \| Level 1 \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Fair value measured on a recurring basis \| Level 1 \| Mortgage and asset-backed securities
Investment securities
Fair value investments	0.0	0.0
Fair value measured on a recurring basis \| Level 1 \| Municipal obligations
Investment securities
Fair value investments	0.0	0.0
Fair value measured on a recurring basis \| Level 1 \| Fixed maturity investments
Investment securities
Fair value investments	232.5	153.2
Fair value measured on a recurring basis \| Level 1 \| Short-term investments
Investment securities
Short-term investments, at fair value	189.4	204.4
Fair value measured on a recurring basis \| Level 1 \| Common equity securities
Investment securities
Fair value investments	547.5
Fair value measured on a recurring basis \| Level 1 \| Other long-term investments
Investment securities
Fair value investments	0.0		$ 2,328.7
Fair value measured on a recurring basis \| Level 2
Investment securities
Fair value investments	1,121.4	1,170.3
Fair value measured on a recurring basis \| Level 2 \| U.S. Government and agency obligations
Investment securities
Fair value investments	0.0	0.0
Fair value measured on a recurring basis \| Level 2 \| Debt securities issued by corporations
Investment securities
Fair value investments	467.2	510.5
Fair value measured on a recurring basis \| Level 2 \| Mortgage and asset-backed securities
Investment securities
Fair value investments	209.0	133.5
Fair value measured on a recurring basis \| Level 2 \| Municipal obligations
Investment securities
Fair value investments	297.1	280.3
Fair value measured on a recurring basis \| Level 2 \| Fixed maturity investments
Investment securities
Fair value investments	973.3	924.3
Fair value measured on a recurring basis \| Level 2 \| Short-term investments
Investment securities
Short-term investments, at fair value	11.8	9.8
Fair value measured on a recurring basis \| Level 2 \| Common equity securities
Investment securities
Fair value investments	136.3
Fair value measured on a recurring basis \| Level 2 \| Other long-term investments
Investment securities
Fair value investments	0.0	0.0
Fair value measured on a recurring basis \| Level 3 Inputs
Investment securities
Fair value investments	654.1	138.7
Fair value measured on a recurring basis \| Level 3 Inputs \| U.S. Government and agency obligations
Investment securities
Fair value investments	0.0	0.0
Fair value measured on a recurring basis \| Level 3 Inputs \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Fair value measured on a recurring basis \| Level 3 Inputs \| Mortgage and asset-backed securities
Investment securities
Fair value investments	0.0	0.0
Fair value measured on a recurring basis \| Level 3 Inputs \| Municipal obligations
Investment securities
Fair value investments	0.0	0.0
Fair value measured on a recurring basis \| Level 3 Inputs \| Fixed maturity investments
Investment securities
Fair value investments	0.0	0.0
Fair value measured on a recurring basis \| Level 3 Inputs \| Short-term investments
Investment securities
Short-term investments, at fair value	0.0	0.0
Fair value measured on a recurring basis \| Level 3 Inputs \| Other long-term investments
Investment securities
Fair value investments	654.0	138.7
Fair value measured on a recurring basis \| Fair Value Measured at Net Asset Value Per Share \| Other long-term investments
Investment securities
Fair value investments		186.9
Financials \| Fair value measured on a recurring basis \| Debt securities issued by corporations
Investment securities
Fair value investments	144.8	143.4
Financials \| Fair value measured on a recurring basis \| Common equity securities
Investment securities
Fair value investments		13.5
Financials \| Fair value measured on a recurring basis \| Level 1 \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Financials \| Fair value measured on a recurring basis \| Level 1 \| Common equity securities
Investment securities
Fair value investments		13.5
Financials \| Fair value measured on a recurring basis \| Level 2 \| Debt securities issued by corporations
Investment securities
Fair value investments	144.8	143.4
Financials \| Fair value measured on a recurring basis \| Level 2 \| Common equity securities
Investment securities
Fair value investments		0.0
Financials \| Fair value measured on a recurring basis \| Level 3 Inputs \| Debt securities issued by corporations
Investment securities
Fair value investments		0.0
Financials \| Fair value measured on a recurring basis \| Level 3 Inputs \| Common equity securities
Investment securities
Fair value investments		0.0
Industrial \| Fair value measured on a recurring basis \| Debt securities issued by corporations
Investment securities
Fair value investments	59.0	47.6
Industrial \| Fair value measured on a recurring basis \| Common equity securities
Investment securities
Fair value investments		11.4
Industrial \| Fair value measured on a recurring basis \| Level 1 \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Industrial \| Fair value measured on a recurring basis \| Level 1 \| Common equity securities
Investment securities
Fair value investments		11.4
Industrial \| Fair value measured on a recurring basis \| Level 2 \| Debt securities issued by corporations
Investment securities
Fair value investments	59.0	47.6
Industrial \| Fair value measured on a recurring basis \| Level 2 \| Common equity securities
Investment securities
Fair value investments		0.0
Industrial \| Fair value measured on a recurring basis \| Level 3 Inputs \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Industrial \| Fair value measured on a recurring basis \| Level 3 Inputs \| Common equity securities
Investment securities
Fair value investments		0.0
Healthcare \| Fair value measured on a recurring basis \| Debt securities issued by corporations
Investment securities
Fair value investments	52.6	55.0
Healthcare \| Fair value measured on a recurring basis \| Common equity securities
Investment securities
Fair value investments		14.0
Healthcare \| Fair value measured on a recurring basis \| Level 1 \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Healthcare \| Fair value measured on a recurring basis \| Level 1 \| Common equity securities
Investment securities
Fair value investments		14.0
Healthcare \| Fair value measured on a recurring basis \| Level 2 \| Debt securities issued by corporations
Investment securities
Fair value investments	52.6	55.0
Healthcare \| Fair value measured on a recurring basis \| Level 2 \| Common equity securities
Investment securities
Fair value investments		0.0
Healthcare \| Fair value measured on a recurring basis \| Level 3 Inputs \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Healthcare \| Fair value measured on a recurring basis \| Level 3 Inputs \| Common equity securities
Investment securities
Fair value investments		0.0
Consumer \| Fair value measured on a recurring basis \| Debt securities issued by corporations
Investment securities
Fair value investments	50.9	68.5
Consumer \| Fair value measured on a recurring basis \| Common equity securities
Investment securities
Fair value investments		6.2
Consumer \| Fair value measured on a recurring basis \| Level 1 \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Consumer \| Fair value measured on a recurring basis \| Level 1 \| Common equity securities
Investment securities
Fair value investments		6.2
Consumer \| Fair value measured on a recurring basis \| Level 2 \| Debt securities issued by corporations
Investment securities
Fair value investments	50.9	68.5
Consumer \| Fair value measured on a recurring basis \| Level 2 \| Common equity securities
Investment securities
Fair value investments		0.0
Consumer \| Fair value measured on a recurring basis \| Level 3 Inputs \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Consumer \| Fair value measured on a recurring basis \| Level 3 Inputs \| Common equity securities
Investment securities
Fair value investments		0.0
Energy \| Fair value measured on a recurring basis \| Debt securities issued by corporations
Investment securities
Fair value investments	44.9	57.6
Energy \| Fair value measured on a recurring basis \| Common equity securities
Investment securities
Fair value investments		4.1
Energy \| Fair value measured on a recurring basis \| Level 1 \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Energy \| Fair value measured on a recurring basis \| Level 1 \| Common equity securities
Investment securities
Fair value investments		4.1
Energy \| Fair value measured on a recurring basis \| Level 2 \| Debt securities issued by corporations
Investment securities
Fair value investments	44.9	57.6
Energy \| Fair value measured on a recurring basis \| Level 2 \| Common equity securities
Investment securities
Fair value investments		0.0
Energy \| Fair value measured on a recurring basis \| Level 3 Inputs \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Energy \| Fair value measured on a recurring basis \| Level 3 Inputs \| Common equity securities
Investment securities
Fair value investments		0.0
Technology \| Fair value measured on a recurring basis \| Debt securities issued by corporations
Investment securities
Fair value investments	41.2	60.5
Technology \| Fair value measured on a recurring basis \| Common equity securities
Investment securities
Fair value investments		7.4
Technology \| Fair value measured on a recurring basis \| Level 1 \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Technology \| Fair value measured on a recurring basis \| Level 1 \| Common equity securities
Investment securities
Fair value investments		7.4
Technology \| Fair value measured on a recurring basis \| Level 2 \| Debt securities issued by corporations
Investment securities
Fair value investments	41.2	60.5
Technology \| Fair value measured on a recurring basis \| Level 2 \| Common equity securities
Investment securities
Fair value investments		0.0
Technology \| Fair value measured on a recurring basis \| Level 3 Inputs \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Technology \| Fair value measured on a recurring basis \| Level 3 Inputs \| Common equity securities
Investment securities
Fair value investments		0.0
Communications \| Fair value measured on a recurring basis \| Debt securities issued by corporations
Investment securities
Fair value investments	31.3	31.8
Communications \| Fair value measured on a recurring basis \| Common equity securities
Investment securities
Fair value investments		12.7
Communications \| Fair value measured on a recurring basis \| Level 1 \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Communications \| Fair value measured on a recurring basis \| Level 1 \| Common equity securities
Investment securities
Fair value investments		12.7
Communications \| Fair value measured on a recurring basis \| Level 2 \| Debt securities issued by corporations
Investment securities
Fair value investments	31.3	31.8
Communications \| Fair value measured on a recurring basis \| Level 2 \| Common equity securities
Investment securities
Fair value investments		0.0
Communications \| Fair value measured on a recurring basis \| Level 3 Inputs \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Communications \| Fair value measured on a recurring basis \| Level 3 Inputs \| Common equity securities
Investment securities
Fair value investments		0.0
Utilities \| Fair value measured on a recurring basis \| Debt securities issued by corporations
Investment securities
Fair value investments	25.0	19.8
Utilities \| Fair value measured on a recurring basis \| Level 1 \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Utilities \| Fair value measured on a recurring basis \| Level 2 \| Debt securities issued by corporations
Investment securities
Fair value investments	25.0	19.8
Utilities \| Fair value measured on a recurring basis \| Level 3 Inputs \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Materials \| Fair value measured on a recurring basis \| Debt securities issued by corporations
Investment securities
Fair value investments	17.5	26.3
Materials \| Fair value measured on a recurring basis \| Common equity securities
Investment securities
Fair value investments		3.1
Materials \| Fair value measured on a recurring basis \| Level 1 \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Materials \| Fair value measured on a recurring basis \| Level 1 \| Common equity securities
Investment securities
Fair value investments		3.1
Materials \| Fair value measured on a recurring basis \| Level 2 \| Debt securities issued by corporations
Investment securities
Fair value investments	17.5	26.3
Materials \| Fair value measured on a recurring basis \| Level 2 \| Common equity securities
Investment securities
Fair value investments		0.0
Materials \| Fair value measured on a recurring basis \| Level 3 Inputs \| Debt securities issued by corporations
Investment securities
Fair value investments	0.0	0.0
Materials \| Fair value measured on a recurring basis \| Level 3 Inputs \| Common equity securities
Investment securities
Fair value investments		0.0
Exchange traded funds \| Fair value measured on a recurring basis \| Common equity securities
Investment securities
Fair value investments	536.4	675.3
Exchange traded funds \| Fair value measured on a recurring basis \| Level 1 \| Common equity securities
Investment securities
Fair value investments	521.6	617.0
Exchange traded funds \| Fair value measured on a recurring basis \| Level 2 \| Common equity securities
Investment securities
Fair value investments	14.8	58.3
Exchange traded funds \| Fair value measured on a recurring basis \| Level 3 Inputs \| Common equity securities
Investment securities
Fair value investments	0.0	0.0
Other \| Fair value measured on a recurring basis \| Common equity securities
Investment securities
Fair value investments	147.5	177.9
Other \| Fair value measured on a recurring basis \| Level 1 \| Common equity securities
Investment securities
Fair value investments	25.9	0.0
Other \| Fair value measured on a recurring basis \| Level 2 \| Common equity securities
Investment securities
Fair value investments	121.5	177.9
Other \| Fair value measured on a recurring basis \| Level 3 Inputs \| Common equity securities
Investment securities
Fair value investments	0.1	0.0
Common equity securities \| Fair value measured on a recurring basis \| Common equity securities
Investment securities
Fair value investments	683.9	925.6
Common equity securities \| Fair value measured on a recurring basis \| Level 1 \| Common equity securities
Investment securities
Fair value investments		689.4
Common equity securities \| Fair value measured on a recurring basis \| Level 2 \| Common equity securities
Investment securities
Fair value investments		236.2
Common equity securities \| Fair value measured on a recurring basis \| Level 3 Inputs \| Common equity securities
Investment securities
Fair value investments	$ 0.1	$ 0.0