0000776867-23-000004 | 10-K | XBRL Viewer | White Mountains Insurance Group LTD

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Cover Page - USD ($)	12 Months Ended
Cover Page - USD ($)	Dec. 31, 2022	Feb. 21, 2023	Jun. 30, 2022
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2022
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	1-8993
Entity Registrant Name	WHITE MOUNTAINS INSURANCE GROUP, LTD.
Entity Incorporation, State or Country Code	D0
Entity Tax Identification Number	94-2708455
Entity Address, Address Line One	23 South Main Street, Suite 3B
Entity Address, 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 per share
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
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 3,569,108,224
Entity Common Stock, Shares Outstanding (in shares)		2,567,527
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 25, 2023 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
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
New York Stock Exchange
Document Information [Line Items]
Trading Symbol	WTM
Security Exchange Name	NYSE

Audit Information	12 Months Ended
Audit Information	Dec. 31, 2022
Audit Information [Abstract]
Auditor Firm ID	238
Auditor Name	PricewaterhouseCoopers LLP
Auditor Location	Atlanta, Georgia

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Investments [Abstract]
Other long-term investments	$ 1,488.0	$ 1,377.8
Total investments	5,170.0	4,257.5
Total assets	7,389.3	7,000.7
Liabilities
Debt	575.2	420.9
Total liabilities	3,454.3	3,296.0
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 2,572,156 and 3,017,772 shares	2.6	3.0
Paid-in surplus	536.0	585.9
Retained earnings	3,211.8	2,957.5
Accumulated other comprehensive gain (loss), after-tax:
Net unrealized gains (losses) from foreign currency translation and interest rate swap	(3.5)	1.7
Total White Mountains’s common shareholders’ equity	3,746.9	3,548.1
Non-controlling interests	188.1	156.6
Total equity	3,935.0	3,704.7
Total liabilities and equity	7,389.3	7,000.7
HG Global-BAM
Investments [Abstract]
Fixed maturity investments, at fair value	909.9	934.1
Short-term investments, at fair value	65.9	32.4
Total investments	975.8	966.5
Cash	18.2	19.8
Insurance premiums receivable	6.6	6.9
Deferred acquisition costs	36.0	33.1
Other assets	21.9	18.5
Total assets	1,058.5	1,044.8
Liabilities
Unearned insurance premiums	298.3	266.3
Debt	146.5	0.0
Accrued incentive compensation	28.0	24.7
Other liabilities	29.0	30.9
Total liabilities	501.8	321.9
Ark
Investments [Abstract]
Fixed maturity investments, at fair value	772.8	688.6
Common equity securities, at fair value	334.6	251.1
Short-term investments, at fair value	280.9	296.2
Other long-term investments	373.6	326.2
Total investments	1,761.9	1,562.1
Cash	100.0	67.8
Reinsurance recoverables	536.1	448.4
Insurance premiums receivable	544.1	416.0
Ceded unearned premiums	59.2	67.1
Deferred acquisition costs	127.2	108.2
Goodwill and other intangible assets	292.5	292.5
Other assets	65.2	64.9
Total assets	3,486.2	3,027.0
Liabilities
Loss and loss adjustment expense reserves	1,296.5	894.7
Unearned insurance premiums	623.2	495.9
Debt	183.7	185.9
Reinsurance payable	251.1	424.1
Contingent consideration	45.3	28.0
Other liabilities	121.1	93.8
Total liabilities	2,520.9	2,122.4
Accumulated other comprehensive gain (loss), after-tax:
Non-controlling interests	247.9	230.7
Kudu
Investments [Abstract]
Other long-term investments	695.9	669.5
Cash	101.4	21.4
Accrued investment income	12.4	16.9
Goodwill and other intangible assets	8.6	8.9
Other assets	7.6	10.4
Total assets	825.9	727.1
Liabilities
Debt	208.3	218.2
Other liabilities	65.0	42.8
Total liabilities	273.3	261.0
Other Operations
Investments [Abstract]
Fixed maturity investments, at fair value	238.2	286.2
Common equity securities, at fair value	333.8	0.0
Short-term investments, at fair value	577.3	129.5
Investment in MediaAlpha, at fair value	168.6	261.6
Other long-term investments	418.5	382.1
Total investments	1,736.4	1,059.4
Cash	35.4	38.7
Goodwill and other intangible assets	91.3	39.1
Other assets	155.6	59.5
Assets held for sale - NSM Group	0.0	989.0
Assets held for sale - Other	0.0	16.1
Total assets	2,018.7	2,201.8
Liabilities
Debt	36.7	16.8
Accrued incentive compensation	86.1	48.5
Other liabilities	35.5	30.1
Liabilities held for sale - NSM Group	0.0	495.3
Total liabilities	$ 158.3	$ 590.7

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Restricted cash balance	$ 12.2	$ 4.5
Common shares, par value per share (in dollars per share)	$ 1	$ 1
Common shares, authorized shares (in shares)	50,000,000	50,000,000
Common shares, issued shares (in shares)	2,572,156	3,017,772
Common shares, outstanding shares (in shares)	2,572,156	3,017,772
Kudu
Restricted cash balance	$ 12.2	$ 4.5

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues:
Earned insurance premiums	$ 1,076.7	$ 664.2	$ 22.8
Net investment income	124.4	82.5	131.0
Net realized and unrealized investment gains (losses)	(98.5)	134.2	30.8
Net realized and unrealized investment gains (losses) from investment in MediaAlpha	(93.0)	(380.3)	686.0
Commission revenues	11.5	9.6	8.3
Other revenues	136.8	104.2	16.7
Total revenues	1,157.9	614.4	895.6
Expenses:
Loss and loss adjustment expenses	536.4	314.8
Insurance acquisition expenses	250.6	186.3	7.0
Cost of sales	98.6	69.3	11.3
General and administrative expenses	376.2	292.5	207.9
Amortization of other intangible assets	5.2	4.6	1.6
Interest expense	40.3	20.5	7.4
Total expenses	1,307.3	888.0	235.2
Pre-tax income (loss) from continuing operations	(149.4)	(273.6)	660.4
Income tax (expense) benefit	(41.4)	(44.4)	14.8
Net income (loss) from continuing operations	(190.8)	(318.0)	675.2
Net income (loss) from discontinued operations, net of tax - NSM Group	16.4	(22.6)	(9.5)
Net income (loss)	712.4	(321.9)	663.4
Net (income) loss attributable to non-controlling interests	80.4	46.5	45.3
Net income (loss) attributable to White Mountains’s common shareholders	792.8	(275.4)	708.7
Sirius Group
Expenses:
Net gain (loss) from sale of discontinued operations, net of tax	0.0	18.7	(2.3)
NSM
Expenses:
Net income (loss) from discontinued operations, net of tax - NSM Group	16.4	(22.6)	(9.5)
Net gain (loss) from sale of discontinued operations, net of tax	886.8	0.0	0.0
HG Global-BAM
Revenues:
Earned insurance premiums	33.3	26.9	22.8
Net investment income	21.5	17.5	19.5
Net realized and unrealized investment gains (losses)	(105.8)	(22.9)	23.7
Net realized and unrealized investment gains (losses) from investment in MediaAlpha	0.0	0.0	0.0
Commission revenues	0.0	0.0	0.0
Other revenues	4.6	1.5	2.5
Total revenues	(46.4)	23.0	68.5
Expenses:
Loss and loss adjustment expenses	0.0	0.0
Insurance acquisition expenses	11.2	8.3	7.0
Cost of sales	0.0	0.0	0.0
General and administrative expenses	69.1	57.1	56.8
Amortization of other intangible assets	0.0	0.0	0.0
Interest expense	8.3	0.0	0.0
Total expenses	88.6	65.4	63.8
Pre-tax income (loss) from continuing operations	(135.0)	(42.4)	4.7
Ark
Revenues:
Earned insurance premiums	1,043.4	637.3	0.0
Net investment income	16.3	2.9	0.0
Net realized and unrealized investment gains (losses)	(55.2)	16.5	0.0
Net realized and unrealized investment gains (losses) from investment in MediaAlpha	0.0	0.0
Commission revenues	0.0	0.0
Other revenues	5.0	11.8	0.0
Total revenues	1,009.5	668.5	0.0
Expenses:
Loss and loss adjustment expenses	536.4	314.8	0.0
Insurance acquisition expenses	239.4	178.0	0.0
Cost of sales	0.0	0.0
General and administrative expenses	123.5	115.5	0.0
Amortization of other intangible assets	0.0	0.0
Interest expense	15.1	7.3	0.0
Total expenses	914.4	615.6	0.0
Pre-tax income (loss) from continuing operations	95.1	52.9
Kudu
Revenues:
Earned insurance premiums	0.0	0.0	0.0
Net investment income	54.4	43.9	29.5
Net realized and unrealized investment gains (losses)	64.1	89.9	15.9
Net realized and unrealized investment gains (losses) from investment in MediaAlpha	0.0	0.0	0.0
Commission revenues	0.0	0.0	0.0
Other revenues	0.0	0.2	0.3
Total revenues	118.5	134.0	45.7
Expenses:
Loss and loss adjustment expenses	0.0
Insurance acquisition expenses	0.0	0.0	0.0
Cost of sales	0.0	0.0	0.0
General and administrative expenses	14.4	14.5	11.8
Amortization of other intangible assets	0.3	0.3	0.3
Interest expense	15.0	11.7	6.0
Total expenses	29.7	26.5	18.1
Pre-tax income (loss) from continuing operations	88.8	107.5	27.6
Other Operations
Revenues:
Earned insurance premiums	0.0	0.0	0.0
Net investment income	32.2	18.2	82.0
Net realized and unrealized investment gains (losses)	(1.6)	50.7	(8.8)
Net realized and unrealized investment gains (losses) from investment in MediaAlpha	(93.0)	(380.3)	686.0
Commission revenues	11.5	9.6	8.3
Other revenues	127.2	90.7	13.9
Total revenues	76.3	(211.1)	781.4
Expenses:
Loss and loss adjustment expenses	0.0	0.0
Insurance acquisition expenses	0.0	0.0	0.0
Cost of sales	98.6	69.3	11.3
General and administrative expenses	169.2	105.4	139.3
Amortization of other intangible assets	4.9	4.3	1.3
Interest expense	1.9	1.5	1.4
Total expenses	274.6	180.5	153.3
Pre-tax income (loss) from continuing operations	$ (198.3)	$ (391.6)	$ 628.1

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income (loss) attributable to White Mountains’s common shareholders	$ 792.8	$ (275.4)	$ 708.7
Other comprehensive income (loss), net of tax	(3.8)	1.7	1.4
Other comprehensive income (loss) from discontinued operations, net of tax - NSM Group	(5.2)	0.2	5.9
Net gain (loss) from foreign currency translation from sale of discontinued operations, net of tax - NSM Group	2.9	0.0	0.0
Comprehensive income (loss)	786.7	(273.5)	716.0
Comprehensive (income) loss attributable to non-controlling interests	0.9	0.2	(0.5)
Comprehensive income (loss) attributable to White Mountains’s common shareholders	$ 787.6	$ (273.3)	$ 715.5
Basic earnings (loss) per share
Continuing operations (usd per share)	$ (38.34)	$ (88.52)	$ 230.69
Discontinued operations (usd per share)	315.30	(0.94)	(3.72)
Total consolidated operations (usd per share)	276.96	(89.46)	226.97
Diluted earnings (loss) per share
Continuing operations (usd per share)	(38.34)	(88.52)	230.69
Discontinued operations (usd per share)	315.30	(0.94)	(3.72)
Total consolidated operations (usd per share)	276.96	(89.46)	226.97
Dividends declared and paid per White Mountains’s common share (usd per share)	$ 1.00	$ 1.00	$ 1.00

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Millions	Total	Total Equity	Common Shares and Paid-in Surplus	Retained Earnings	AOCL, After-tax	Total	Non-controlling Interests
Beginning balance at Dec. 31, 2019		$ 3,144.7	$ 596.3	$ 2,672.4	$ (7.2)	$ 3,261.5	$ (116.8)
Increase (Decrease) in Shareholders' Equity
Net income (loss)	$ 663.4	663.4		708.7		708.7	(45.3)
Other comprehensive income (loss), net of tax	1.4	7.3			6.8	6.8	0.5
Net gain (loss) from foreign currency translation from sale of discontinued operations, net of tax - NSM Group	0.0
Comprehensive income (loss)	715.5	670.7		708.7	6.8	715.5	(44.8)
Dividends declared on common shares		(3.2)		(3.2)		(3.2)
Dividends to non-controlling interests		(2.1)					(2.1)
Issuances of common shares		1.5	1.5			1.5
Repurchases and retirements of common shares	(85.1)	(85.2)	(18.5)	(66.7)		(85.2)
BAM member surplus contribution, net of tax		68.9					68.9
Amortization of restricted share awards		16.6	16.6			16.6
Recognition of equity-based compensation expense of subsidiaries		2.4	2.3			2.3	0.1
Net contributions (distributions) and dilution from other non-controlling interests		2.3	(3.0)			(3.0)	5.3
Acquisition of non-controlling interests		1.3					1.3
Ending balance at Dec. 31, 2020		3,817.9	595.2	3,311.2	(0.4)	3,906.0	(88.1)
Increase (Decrease) in Shareholders' Equity
Net income (loss)	(321.9)	(321.9)		(275.4)		(275.4)	(46.5)
Other comprehensive income (loss), net of tax	1.7	2.1			2.1	2.1
Net gain (loss) from foreign currency translation from sale of discontinued operations, net of tax - NSM Group	0.0
Comprehensive income (loss)	(273.3)	(319.8)		(275.4)	2.1	(273.3)	(46.5)
Dividends declared on common shares		(3.1)		(3.1)		(3.1)
Dividends to non-controlling interests		(2.3)					(2.3)
Issuances of common shares		1.9	1.9			1.9
Issuances of shares to non-controlling interests		6.5					6.5
Repurchases and retirements of common shares	(107.5)	(107.5)	(18.9)	(88.6)		(107.5)
BAM member surplus contribution, net of tax		62.2					62.2
Amortization of restricted share awards		14.7	14.7			14.7
Recognition of equity-based compensation expense of subsidiaries		3.5	3.0			3.0	0.5
Net contributions (distributions) and dilution from other non-controlling interests		0.4	(7.0)	13.4		6.4	(6.0)
Acquisition of non-controlling interests		230.3					230.3
Ending balance at Dec. 31, 2021	3,704.7	3,704.7	588.9	2,957.5	1.7	3,548.1	156.6
Increase (Decrease) in Shareholders' Equity
Net income (loss)	712.4	712.4		792.8		792.8	(80.4)
Other comprehensive income (loss), net of tax	(3.8)	(9.0)			(8.1)	(8.1)	(0.9)
Net gain (loss) from foreign currency translation from sale of discontinued operations, net of tax - NSM Group	(2.9)	2.9			2.9	2.9
Comprehensive income (loss)	787.6	706.3		792.8	(5.2)	787.6	(81.3)
Dividends declared on common shares		(3.0)		(3.0)		(3.0)
Dividends to non-controlling interests		(8.0)					(8.0)
Issuances of common shares		3.0	3.0			3.0
Issuances of shares to non-controlling interests		74.6					74.6
Repurchases and retirements of common shares	(615.8)	(615.8)	(90.0)	(525.8)		(615.8)
BAM member surplus contribution, net of tax		81.4					81.4
Amortization of restricted share awards		14.0	14.0			14.0
Recognition of equity-based compensation expense of subsidiaries		9.5	8.6			8.6	0.9
Net contributions (distributions) and dilution from other non-controlling interests		(14.2)	14.1	(9.7)		4.4	(18.6)
Acquisition of non-controlling interests		(17.5)					(17.5)
Ending balance at Dec. 31, 2022	$ 3,935.0	$ 3,935.0	$ 538.6	$ 3,211.8	$ (3.5)	$ 3,746.9	$ 188.1

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operations:
Net income (loss)	$ 712.4	$ (321.9)	$ 663.4
Adjustments to reconcile net income to net cash provided from (used for) operations:
Net realized and unrealized investment (gains) losses	98.5	(134.2)	(30.8)
Net realized and unrealized investment (gains) losses from investment in MediaAlpha	93.0	380.3	(686.0)
Amortization of restricted share awards	14.0	14.7	16.6
Amortization and depreciation	4.3	21.6	9.6
Deferred income tax expense (benefit)	12.9	34.7	(30.5)
Net (income) loss from discontinued operation, net of tax - NSM Group	(16.4)	22.6	9.5
Other operating items:
Net change in reinsurance recoverables	(87.7)	(15.1)	0.0
Net change in insurance premiums receivable	(127.8)	(179.3)	0.0
Net change in ceded unearned premiums	7.9	103.1	0.0
Net change in loss and loss adjustment expense reserves	401.8	198.7	0.0
Net change in unearned insurance premiums	159.3	198.6	39.1
Net change in deferred acquisition costs and value of in-force business acquired	(21.9)	(41.8)	(5.8)
Net change in reinsurance payable	(173.0)	(104.2)	0.0
Net change in restricted cash	7.7	4.5	0.0
Proceeds from Kudu Participation Contracts sold	137.5	44.4	0.0
Decrease in Debt Securities, Trading, and Equity Securities, FV-NI	(99.8)	(223.4)	(118.3)
Net change in other assets and liabilities	90.4	11.7	34.8
Net cash provided from (used for) operations - continuing operations	326.3	(3.7)	(96.1)
Net cash provided from (used for) operations - NSM Group discontinued operations (Note 21)	38.7	42.3	35.5
Net cash provided from (used for) operations	365.0	38.6	(60.6)
Cash flows from investing activities:
Net change in short-term investments	(455.1)	59.8	60.9
Sales of fixed maturity investments	188.7	286.3	390.0
Maturities, calls and paydowns of fixed maturity investments	198.5	199.0	180.4
Sales of common equity securities and investment in MediaAlpha	0.0	176.8	787.9
Distributions and redemptions of other long-term investments	115.4	106.4	69.9
Release of cash pre-funded/placed in escrow for Ark Transaction	0.0	646.3	(646.3)
Cash pre-funded for ILS funds managed by Elementum	(70.0)	0.0	0.0
Purchases of fixed maturity investments	(585.5)	(1,219.4)	(537.7)
Purchases of common equity securities	(424.5)	(203.4)	(33.8)
Purchases of other long-term investments	(178.8)	(218.0)	(76.8)
Purchases of consolidated subsidiaries, net of cash acquired	(67.9)	10.6	(9.1)
Net other investing activities	(4.4)	3.8	4.1
Net cash provided from (used for) investing activities - continuing operations	108.4	(151.8)	189.5
Net cash provided from (used for) investing activities - NSM Group discontinued operations (Note 21)	7.1	(56.5)	(124.9)
Net cash provided from (used for) investing activities	115.5	(208.3)	64.6
Cash flows from financing activities:
Draw down of debt and revolving lines of credit	213.8	401.7	32.2
Repayment of debt and revolving lines of credit	(56.7)	(120.1)	(1.9)
Cash dividends paid to common shareholders	(3.0)	(3.1)	(3.2)
Issuances of shares to non-controlling interests	74.6	6.5	0.0
Net (contributions to) distributions from discontinued operations	11.6	0.0	(85.0)
Repurchases and retirements of common shares	(615.8)	(107.5)	(85.2)
BAM member surplus contribution	81.4	62.2	68.9
Net contributions from (distributions to) other non-controlling interests	(21.6)	0.7	(2.5)
Fidus Re premium payments	(10.1)	(8.8)	(3.0)
Other financing activities, net	(1.6)	(13.0)	(0.1)
Net cash provided from (used for) financing activities - continuing operations	(327.4)	218.6	(79.8)
Net cash provided from (used for) financing activities - NSM Group discontinued operations (Note 21)	(17.5)	(1.0)	128.8
Net cash provided from (used for) financing activities – continuing operations	(344.9)	217.6	49.0
Net change in cash during the period - continuing operations	107.3	63.1	13.6
Cash balance at beginning of year	147.7	84.6	71.0
Cash balance at end of year	255.0	147.7	84.6
NSM
Adjustments to reconcile net income to net cash provided from (used for) operations:
Net (income) loss from discontinued operation, net of tax - NSM Group	(16.4)	22.6	9.5
Net (gain) loss from sale of discontined operations, net of tax	(886.8)	0.0	0.0
Cash flows from investing activities:
Proceeds from the sale of consolidated subsidiaries, net of cash sold	1,372.5	0.0	0.0
NSM \| Held for Sale
Adjustments to reconcile net income to net cash provided from (used for) operations:
Net (income) loss from discontinued operation, net of tax - NSM Group	(16.4)	22.6	9.5
Net (gain) loss from sale of discontined operations, net of tax	(886.8)	0.0	0.0
Other operating items:
Net cash provided from (used for) operations - NSM Group discontinued operations (Note 21)	38.7	42.3	35.5
Cash flows from investing activities:
Net cash provided from (used for) investing activities - NSM Group discontinued operations (Note 21)	7.1	(56.5)	(124.9)
Cash flows from financing activities:
Net cash provided from (used for) financing activities - NSM Group discontinued operations (Note 21)	(17.5)	(1.0)	128.8
Net change in cash during the period - continuing operations	32.3	(15.0)	36.6
Cash balance at beginning of year	111.6	126.6	90.0
Cash balance at end of year	0.0	111.6	126.6
Sirius Group
Adjustments to reconcile net income to net cash provided from (used for) operations:
Net (gain) loss from sale of discontined operations, net of tax	0.0	(18.7)	2.3
Sirius Group \| Held for Sale
Adjustments to reconcile net income to net cash provided from (used for) operations:
Net (gain) loss from sale of discontined operations, net of tax	0.0	(18.7)	2.3
Other Operations
Cash flows from investing activities:
Proceeds from the sale of consolidated subsidiaries, net of cash sold	19.5	0.0	0.0
MediaAlpha
Adjustments to reconcile net income to net cash provided from (used for) operations:
Net realized and unrealized investment (gains) losses from investment in MediaAlpha	$ 93.0	$ 380.3	$ (686.0)

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash acquired from acquisition	$ 0.3	$ 52.2	$ 1.5
Restricted cash balance	12.2	4.5	0.0
Discontinued operations cash balance	255.0	147.7	84.6
NSM
Cash sold in subsidiary transaction	143.9	0.0	0.0
Other Operations
Cash sold in subsidiary transaction	0.5	0.0	0.0
Held for Sale \| NSM
Cash sold in subsidiary transaction	143.9	0.0	0.0
Discontinued operations cash balance	$ 0.0	$ 111.6	$ 126.6

Basis of Presentation and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2022
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	Basis of Presentation and Significant Accounting Policies Basis of Presentation White Mountains Insurance Group, Ltd. (the “Company” or the “Registrant”) is an exempted Bermuda limited liability company whose principal businesses are conducted through its subsidiaries and other affiliates. The Company’s headquarters is located at 26 Reid Street, Hamilton, Bermuda HM 11, its principal executive office is located at 23 South Main Street, Suite 3B, Hanover, New Hampshire 03755-2053 and its registered office is located at Clarendon House, 2 Church Street, Hamilton, Bermuda HM 11. The Company’s website is located at www.whitemountains.com. The information contained on White Mountains’s website is not incorporated by reference into, and is not a part of, this report. The accompanying consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) and include the accounts of the Company, its subsidiaries (collectively with the Company, “White Mountains”) and other entities required to be consolidated under GAAP. 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. Consolidation Principles Under GAAP, the Company is required to consolidate any entity in which it holds a controlling financial interest. A controlling financial interest is usually in the form of an investment representing the majority of the subsidiary’s voting interests. However, a controlling financial interest may also arise from a financial interest in a variable interest entity (“VIE”) through arrangements that do not involve ownership of voting interests. The Company consolidates a VIE if it determines that it is the primary beneficiary. The primary beneficiary is defined as the entity who holds a variable interest that gives it both the power to direct the VIE’s activities that most significantly impact its economic performance and the obligation to absorb losses of, or the right to receive returns from, the VIE that could potentially be significant to the VIE. See Note 18 — “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 As of December 31, 2022, White Mountains conducted its operations through three reportable segments: (1) HG Global/BAM, (2) Ark, and (3) Kudu, with our remaining operating businesses, holding companies and other assets included in Other Operations. White Mountains has made its segment determination based on consideration of the following criteria: (i) the nature of the business activities of each of the Company’s subsidiaries and affiliates; (ii) the manner in which the Company’s subsidiaries and affiliates are organized; (iii) the existence of primary managers responsible for specific subsidiaries and affiliates; and (iv) the organization of information provided to the chief operating decision makers and the Board of Directors. See Note 16 — “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 purpose projects, 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. 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 (the “BAM Surplus Notes”). As of December 31, 2022 and 2021, White Mountains owned 96.9% of HG Global's preferred equity and 88.4% of its common equity. White Mountains does not have an ownership interest in BAM. However, White Mountains is required to consolidate BAM’s results in its financial statements because BAM is a VIE for which White Mountains is the primary beneficiary. BAM’s results are attributed to non-controlling interests. The Ark segment consists of Ark Insurance Holdings Limited and its subsidiaries (collectively, “Ark”). Ark is a specialty property and casualty insurance and reinsurance company that offers a wide range of niche insurance and reinsurance products, including property, specialty, marine & energy, casualty and accident & health. Ark underwrites select coverages through its two major subsidiaries in the United Kingdom and Bermuda. On January 1, 2021, White Mountains acquired a controlling ownership interest in Ark (the “Ark Transaction”). See Note 2 — “Significant Transactions”. As of December 31, 2022 and 2021, White Mountains owned 72.0% of Ark on a basic shares outstanding basis (63.0% after taking account of management’s equity incentives). The remaining shares are owned by current and former employees. In the future, management rollover shareholders could earn additional shares in Ark if and to the extent that White Mountains achieves certain multiple of invested capital return thresholds. If fully earned, these additional shares would represent 12.5% of the shares outstanding at closing. For the years of account prior to the Ark Transaction, a significant proportion of the Syndicates’ underwriting capital was provided by third-party insurance and reinsurance groups (“TPC Providers”) using whole account reinsurance contracts with Ark’s corporate member. For the years of account subsequent to the Ark Transaction, Ark is no longer using TPC Providers to provide underwriting capital for the Syndicates. Captions within results of operations and other comprehensive income are shown net of amounts relating to the TPC Providers’ share of the Syndicates’ results, including investment results. The Kudu segment consists of Kudu Investment Management, LLC and its subsidiaries (collectively, “Kudu”). Kudu provides capital solutions for boutique asset and wealth 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 generally are structured as minority preferred equity stakes with distribution rights, typically tied to gross revenues and designed to generate immediate cash yields. As of December 31, 2022 and 2021, White Mountains owned 89.3% and 99.3% of the basic units outstanding of Kudu (76.1% and 84.7% on a fully diluted, fully converted basis). White Mountains’s Other Operations consists of the Company and its wholly-owned subsidiary, White Mountains Capital, LLC (“WM Capital”), its other intermediate holding companies, its wholly-owned investment management subsidiary, White Mountains Advisors LLC (“WM Advisors”), investment assets managed by WM Advisors, its interests in MediaAlpha, Inc. (“MediaAlpha”), PassportCard Limited (“PassportCard”) and DavidShield Life Insurance Agency (2000) Ltd. (“DavidShield”) (collectively, “PassportCard/ DavidShield”), Elementum Holdings LP (“Elementum”), Outrigger Re Ltd. Segregated Account 2023-1 (“WM Outrigger Re”), certain other consolidated and unconsolidated entities (“Other Operating Businesses”) and certain other assets. Held for Sale and Discontinued Operations White Mountains recognizes assets and liabilities classified as held for sale at the lower of carrying value on the date the asset is initially classified as held for sale or fair value less costs to sell. At the time of reclassification to held for sale, White Mountains ceases recognizing depreciation and amortization on assets held for sale. The results of operations of a business that has either been disposed of or are classified as held for sale are reported in discontinued operations if the disposal of business represents a strategic shift that has (or will have) a major effect on White Mountains’s operations and financial results. See Note 21 — “Held for Sale and Discontinued Operations.” On August 1, 2022, White Mountains Holdings (Luxembourg) S.à r.l. (“WTM Holdings Seller”), an indirect wholly owned subsidiary of White Mountains, completed the previously announced sale of White Mountains Catskill Holdings, Inc. and NSM Insurance HoldCo, LLC (“NSM” and, collectively with White Mountains Catskill Holdings, Inc., the “NSM Group”) to Riser Merger Sub, Inc., an affiliate of The Carlyle Group Inc. (the “NSM Transaction”), pursuant to the terms of the securities purchase agreement, dated as of May 9, 2022. See Note 2 — “Significant Transactions.” NSM is a full-service managing general agent (“MGA”) and program administrator with delegated binding authorities for specialty property and casualty insurance. As of December 31, 2021, White Mountains owned 96.5% of the basic units outstanding of NSM (87.3% on a fully diluted, fully converted basis). As a result of the NSM Transaction, the assets and liabilities of NSM Group have been presented in the balance sheet as held for sale for periods prior to the closing of the transaction, and the results of operations for NSM Group have been classified as discontinued operations in the statements of operations and comprehensive income through the closing of the transaction. Prior period amounts have been reclassified to conform to the current period’s presentation. See Note 21 — “Held for Sale and Discontinued Operations.” Significant Accounting Policies Investment Securities As of December 31, 2022 and 2021, 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, its investment in MediaAlpha, 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. Short-term investments consist of interest-bearing money market funds, certificates of deposit and other securities, which at the time of purchase, mature or become available for use within one year. Short-term investments are carried at fair value, which approximated amortized or accreted cost as of December 31, 2022 and 2021. White Mountains’s invested assets that are measured at fair value include fixed maturity investments, common equity securities, its investment in MediaAlpha, and other long-term investments, that consists primarily of unconsolidated entities, including non-controlling equity interests in the form of revenue and earnings participation contracts (“Kudu’s Participation Contracts”), private equity funds and hedge funds, a bank loan fund, Lloyd’s of London (“Lloyd’s”) trust deposits, 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 is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants (an exit price) at a particular measurement date. 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 all of White Mountains’s investment portfolio and derivative instruments. Valuation of assets and liabilities 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 quoted market prices or other observable 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, 2022, approximately 72% 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 White Mountains’s fixed maturity investments, primarily investments in U.S. Treasuries and short-term investments, which include U.S. Treasury Bills, common equity securities, and its investment in MediaAlpha following the initial public offering of MediaAlpha on October 30, 2020 (the “MediaAlpha IPO”). 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, mortgage and asset-backed securities and collateralized loan obligations. Investments valued using Level 2 inputs also include certain international listed common equity funds, which White Mountains values using the fund manager’s published net asset value (“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 and Collateralized Loan Obligations The fair value of mortgage and asset-backed securities and collateralized loan obligations 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, 2022, $911.6 million of White Mountains’s other long-term investments, which consisted primarily of unconsolidated entities, including Kudu’s Participation Contracts and PassportCard/DavidShield were classified as Level 3 investments in the GAAP fair value hierarchy. 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. 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 its 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 other long-term investments classified as Level 3 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 As of December 31, 2022, $561.6 million of White Mountains’s other long-term investments, which consisted of private equity funds and hedge funds, a bank loan fund, Lloyd’s trust deposits and ILS funds, were valued at fair value using NAV as a practical expedient. Investments for which fair value is measured using NAV as a practical expedient are not classified within the fair value hierarchy. White Mountains employs a number of procedures to assess the reasonableness of the fair value measurements for other long-term investments measured at NAV, including obtaining and reviewing interim unaudited and annual audited financial statements as well as periodically discussing each fund’s pricing with the fund manager. 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 valuation inputs to be unobservable. The fair value of White Mountains’s other long-term investments measured at NAV are generally determined using the fund manager’s NAV. In the event that White Mountains believes the fair value 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. Cash and Restricted Cash Cash includes amounts on hand and demand deposits with banks and other financial institutions. Amounts presented in the statement of cash flows are shown net of balances acquired and sold in the purchase or sale of the Company’s consolidated subsidiaries. Cash balances that are not immediately available for general corporate purposes, including the interest reserve account that Kudu maintains under its credit facility, is classified as restricted. Derivatives From time to time, White Mountains holds derivative financial instruments for risk management purposes. White Mountains recognizes all derivatives as either assets or liabilities, measured at fair value, on its consolidated balance sheet. Changes in the fair value of derivative instruments that meet the criteria for hedge accounting are recognized in other comprehensive income (loss) and reclassified into current period pre-tax income (loss) 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 (loss). As of December 31, 2022, White Mountains holds an interest rate cap derivative instrument that does not meet the criteria for hedge accounting. See Note 9 — “Derivatives”. 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. For capital appreciation bonds, par is adjusted to the estimated equivalent par value for current interest paying bonds. See Note 10 — “Municipal Bond Guarantee Insurance”. Premiums are generally received upfront and an unearned premium revenue liability, equal to the amount of the premium received, is established at contract inception. Premium revenues are recognized in revenue over the period of the contracts in proportion to the amount of insurance protection provided using a constant rate. The constant rate is calculated based on the relationship between the par outstanding in a given reporting period compared with the sum of each of the par amounts outstanding for all periods. Insurance premiums receivable represents amounts due from customers for municipal bond insurance policies. 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. 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. A premium deficiency is recognized if the sum of expected loss and loss adjustment expenses (“LAE”), expected dividends to policyholders, unamortized acquisition costs, and maintenance costs exceeds related unearned premiums and anticipated investment income. A premium deficiency is recognized by charging any unamortized acquisition costs to expense to the extent required in order to eliminate the deficiency. If the premium deficiency exceeds unamortized acquisition costs then a liability is accrued for the excess deficiency. Loss reserves are recorded only to the extent that the present value of any payments projected to be made by BAM, net of any expected recoveries, exceeds the associated unearned premium reserve. As of December 31, 2022 and 2021, BAM did not have any loss or loss adjustment expense reserves. Property and Casualty Insurance and Reinsurance Ark writes a diversified portfolio of reinsurance and insurance, including property, specialty, marine & energy, casualty and accident & health, through its Lloyd’s Syndicates 4020 and 3902 (the “Syndicates”) and its wholly-owned subsidiary Group Ark Insurance Limited (“GAIL”). Ark accounts for insurance and reinsurance policies that it writes in accordance with ASC 944, Financial Services - Insurance. Ark’s premiums written comprise premiums on insurance contracts incepted during the year as well as premium adjustments related to prior underwriting years. Insurance premiums are recognized as revenues over the loss exposure or coverage period. In most cases, premiums are earned ratably over the term of the contract with unearned premiums calculated on a monthly pro-rata basis. Catastrophe premiums are earned in proportion to the insurance protection provided. Premiums earned are presented net of amounts ceded to reinsurers. Insurance premiums receivable, representing amounts due from insureds, are presented net of an allowance for uncollectible premiums, including expected credit losses. The allowance is based upon Ark’s ongoing review of amounts outstanding, historical loss data, including delinquencies and write-offs, current and forecasted economic conditions and other relevant factors. Credit risk is partially mitigated by Ark’s ability to cancel the policy if the policyholder does not pay the premium. Deferred acquisition costs comprise commission and brokerage fees and taxes which are directly attributable to and vary with the production of business. These costs are deferred and amortized to the extent they relate to successful contract acquisitions over the applicable premium recognition period as insurance and reinsurance acquisition expenses. Deferred acquisition costs are limited to the amount expected to be recovered from future earned premiums and anticipated investment income. A premium deficiency is recognized if the sum of expected loss and LAE, expected dividends to policyholders, unamortized acquisition costs, and maintenance costs exceeds related unearned premiums and anticipated investment income. A premium deficiency is recognized by charging any unamortized acquisition costs to expense to the extent required in order to eliminate the deficiency. If the premium deficiency exceeds unamortized acquisition costs then a liability is accrued for the excess deficiency. Losses and LAE are charged against income as incurred. Unpaid losses and LAE, including estimates for amounts incurred but not reported (“IBNR”) are based on estimates of the ultimate costs of settling claims, including the effects of inflation and other societal and economic factors. Unpaid loss and LAE reserves represent management’s best estimate of ultimate losses and LAE, net of estimated salvage and subrogation recoveries, if applicable. Such estimates are regularly reviewed and updated and any resulting adjustments are reflected in current results of operations. The process of estimating loss and LAE involves a considerable degree of judgment by management and the ultimate amount of expense to be incurred could be considerably greater than or less than the amounts currently reflected in the financial statements. See Note 5 – “Loss and Loss Adjustment Expense Reserves”. As part of its enterprise risk management function, Ark purchases reinsurance for risk mitigation purposes. Ark utilizes reinsurance and retrocession agreements to reduce earnings volatility, protect capital, limit its exposure to risk concentration and accumulation of loss and to manage within its overall internal risk tolerances or those set and agreed by regulators, ratings agencies, and Lloyd’s. Ark also enters into reinsurance and retrocession agreements to reduce its liability on individual risks and enable it to underwrite policies with higher limits where Ark believes this has a broader business benefit. Ark seeks to protect its downside risk from catastrophes and large loss events by purchasing reinsurance, including excess of loss protections, aggregate covers, and industry loss warranties. Ark also considers alternative structures such as collateralized reinsurance, retrocessional reinsurance and catastrophe bonds. The purchase of reinsurance does not discharge Ark from its primary liability for the full value of its policies, and thus the collectability of balances due from Ark’s reinsurers is critical to its financial strength. Ark monitors the financial strength and ratings of its reinsurers on an ongoing basis. See Note 6 – “Third-Party Reinsurance”. For the years of account prior to the Ark Transaction, a significant proportion of the Syndicates’ underwriting capital was provided by third-party insurance and reinsurance groups (“TPC Providers”) using whole account reinsurance contracts with Ark’s corporate member. The TPC Providers’ participation in the Syndicates for the 2020 open year of account is 42.8% of the total net result of the Syndicates. For the years of account subsequent to the Ark Transaction, Ark is no longer using TPC Providers to provide underwriting capital for the Syndicates. Captions within results of operations and other comprehensive income are shown net of amounts relating to the TPC Providers share of the Syndicates’ results, including investment results. Reinsurance recoverables represent paid losses and LAE, case reserves and IBNR reserves ceded to reinsurers under reinsurance treaties. Amounts recoverable from reinsurers are estimated in a manner consistent with the associated claim liability. Ark reports its reinsurance recoverables net of an allowance for estimated uncollectible reinsurance, including expected credit losses and coverage disputes. The allowance is based upon Ark’s ongoing review of amounts outstanding, length of collection periods, changes in reinsurer credit standing, disputes, applicable coverage defenses and other relevant factors. Reinsurance Contracts Accounted for as Deposits Reinsurance contracts that do not meet the risk transfer requirements necessary to be accounted for as reinsurance are accounted for using the deposit method. Under the deposit method, ceded premiums paid are not recognized through income but rather treated as a deposit. BAM entered into three ceded reinsurance agreements with Fidus Re Ltd. (“Fidus Re”), a Bermuda-based special purpose insurer created in 2018 solely to provide reinsurance protection to BAM. BAM also entered into an excess of loss reinsurance agreement (the “XOLT”) with HG Re. The financing expenses paid by BAM under these reinsurance agreements are recorded in general and administrative expenses. See Note 10 — “Municipal Bond Guarantee Insurance”. Ark has an aggregate excess of loss contract with SiriusPoint Ltd. (“SiriusPoint”), formerly Third Point Reinsurance Ltd., which is accounted for using the deposit method and recorded within other assets. Ark earns an annual crediting rate of 3.0%, which is recorded within other revenue. See Note 6 — “Third-Party Reinsurance”. Revenue Recognition Kudu’s revenues are primarily generated from non-controlling equity interests in revenue and earnings participation contracts with asset and wealth management firms. Kudu’s Participation Contracts are measured at fair value with the change therein recognized within net realized and unrealized investment gains (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. White Mountains’s Other Operations recognizes agent commissions and other revenues when it has satisfied its performance obligations. Deferred revenues associated with unsatisfied performance obligations are recognized within other liabilities. Cost of Sales White Mountains’s 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. 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 underwriting capacity, customer relationships and trade names. 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 White Mountains determines, based on this qualitative review, that it is more likely than not that an impairment may exist, then White Mountains performs a quantitative analysis to compare the fair value of a reporting unit with its carrying value. If the carrying value exceeds the estimated fair value, then an impairment charge is recognized through current period pre-tax income (loss). Other intangible assets with finite lives are initially measured at their acquisition date fair values and subsequently amortized over their economic lives. Other intangible assets with finite lives are 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. See Note 4 – “Goodwill and Other Intangible Assets”. 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 12 — “Employee Share-Based Incentive Compensation Plans”. Income Taxes White Mountains has subsidiaries and branches that operate in various jurisdictions around the world and are subject to tax in the jurisdictions in which they operate. As of December 31, 2022, the primary jurisdictions in which White Mountains’s subsidiaries and branches were subject to tax were Ireland, Israel, Luxembourg, the United Kingdom and 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. Deferred tax assets represent amounts available to reduce income taxes payable in future periods. 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. See Note 8 – “Income Taxes”. Leases Leases consist primarily of operating leases for office space and equipment. Lease assets and liabilities are recognized at the lease commencement date based on the present value of future minimum lease payments over the lease term. Lease assets and liabilities are not recorded for leases with a term at inception of one year or less. Lease expense is included in operating expenses. See Note 13 – “Leases”. 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 (loss) attributable to non-controlling interests is presented net of related income taxes in the statement of operations and comprehensive income (loss). See Note 14 — “Common Shareholders’ Equity and Non-controlling Interests”. 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, 2022 and 2021, White Mountains had unrealized foreign currency translation gains (losses) of $(3.5) million and $5.1 million recorded in accumulated other comprehensive income (loss) on its consolidated balance sheet. Fair Value Measurements Fair value measurements are categorized into a hierarchy that distinguishes between inputs based on market data from independent sources (observable inputs) and a reporting entity’s internal assumptions based upon the best information available when external market data is limited or unavailable (unobservable inputs). Quoted prices in active markets for identical assets or liabilities have the highest priority (Level 1), followed by observable inputs other than quoted prices, including prices for similar but not identical assets or liabilities (Level 2) and unobservable inputs, including the reporting entity’s estimates of the assumptions that market participants would use, having the lowest priority (Level 3). See Note 19 — “Fair Value of Financial Instruments”. Business Combinations White Mountains accounts for purchases of businesses using the acquisition method, which requires the measurement of assets acquired, including other intangible assets, and liabilities assumed, including contingent liabilities, at their estimated fair values as of the acquisition date. The acquisition date fair values represent management’s best estimates and are based upon established valuation techniques, reasonable assumptions and, where appropriate, valuations performed by independent third parties. In circumstances where additional information is required in order to determine the acquisition date fair value of balance sheet amounts, provisional amounts may be recorded as of the acquisition date and may be subject to subsequent adjustment throughout the measurement period, which is up to one year from the acquisition date. Measurement period adjustments are recognized in the period in which they are determined. The results of operations and cash flows of businesses acquired are included in the consolidated financial statements from the date of acquisition. White Mountains accounts for purchases of other intangible assets that do not meet the definition of a business as asset acquisitions. Asset acquisitions are recognized at the amount of consideration paid, which is deemed to equal fair value.

Significant Transactions

12 Months Ended

Dec. 31, 2022

Significant Transactions [Abstract]

Significant Transactions

NSM

On August 1, 2022, the NSM Transaction closed. White Mountains received $1.4 billion in net cash proceeds at closing and recognized a net transaction gain of $875.7 million, which was comprised of $886.8 million of net gain from sale of discontinued operations and $2.9 million of comprehensive income related to the recognition of foreign currency translation gains (losses) from the sale, partially offset by $14.0 million of compensation and other costs related to the transaction recorded in Other Operations.

Ark

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

On January 1, 2021, White Mountains completed the Ark Transaction in accordance with the terms of the Ark SPA. As of December 31, 2021, White Mountains owned 72.0% of Ark on a basic shares outstanding basis (63.0% after taking account of management’s equity incentives). The remaining shares are owned by employees. In the future, management rollover shareholders could earn additional shares in Ark if and to the extent that White Mountains achieves certain multiple of invested capital return threshold. If fully earned, these additional shares would represent 12.5% of the shares outstanding at closing.

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

In the third quarter of 2021, Ark issued $163.3 million of floating rate unsecured subordinated notes (the “Ark 2021 Subordinated Notes”) in three separate transactions. See Note 7 — “Debt”. In connection with the issuance of the Ark 2021 Subordinated Notes, White Mountains and Ark terminated White Mountains’s commitment to provide up to $200.0 million of additional equity capital to Ark in 2021.

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


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

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

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

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

The value of in-force business acquired represents the estimated profits relating to the unexpired contracts, net of related prepaid reinsurance, at the acquisition date through the expiration date of the contracts. During 2022 and 2021, Ark recognized $7.5 million and $64.2 million of amortization expense on the value of in-force business acquired. The value of the syndicate underwriting capacity intangible asset was estimated using net cash flows attributable to Ark’s rights to write business in the Lloyd’s market. The value of the in-force business acquired and the syndicate underwriting capacity were estimated using a discounted cash flow method. Significant inputs to the valuation models include estimates of growth in premium revenues, investment returns, claim costs, expenses and discount rates based on a weighted average cost of capital.

In evaluating the fair value of Ark’s loss and loss adjustment expense reserves, White Mountains determined that the risk-free rate of interest was approximately equal to the risk factor reflecting the uncertainty within the reserves and that no adjustment was necessary. For the year ended December 31, 2022 and 2021, Ark recognized pre-tax expense of $17.3 million and $5.5 million for the change in the fair value of its contingent consideration liabilities. Any future adjustments to contingent consideration liabilities will be recognized through pre-tax income (loss). As of December 31, 2022 and 2021, Ark recognized total contingent consideration liabilities of $45.3 million and $28.0 million.

Ark’s segment income and expenses for 2022 and 2021 are presented in Note 16 — “Segment Information.”

WM Outrigger Re

During the fourth quarter of 2022, Ark sponsored the formation of Outrigger Re Ltd., a Bermuda company registered as a special purpose insurer and segregated accounts company, to provide reinsurance capacity to Ark. On December 20, 2022, Outrigger Re Ltd. issued $250 million of non-voting redeemable preference shares on behalf of four segregated accounts to White Mountains and unrelated third party investors. Upon issuance of the preference shares, Outrigger Re Ltd. entered into collateralized quota share agreements with GAIL to provide reinsurance protection on Ark’s Bermuda global property catastrophe excess of loss portfolio written in calendar year 2023. The proceeds from the issuance of the preference shares were deposited into collateral trust accounts to fund any potential obligations under the reinsurance agreements with GAIL. Outrigger Re Ltd.’s obligations under the reinsurance agreements with GAIL are subject to an aggregate limit equal to the assets in the collateral trusts at any point in time. The terms of the reinsurance agreements are renewable upon the mutual agreement of Ark and the applicable preference shareholder.

White Mountains purchased 100% of the preference shares issued by its segregated account, WM Outrigger Re, for $205.0 million. White Mountains consolidates WM Outrigger Re’s results in its financial statements. WM Outrigger Re’s quota share reinsurance agreement with GAIL will eliminate in White Mountains’s consolidated financial statements. As of December 31, 2022, short-term investments of $203.7 million were held in a collateral trust, after expenses of $1.3 million.

MediaAlpha

On October 30, 2020, MediaAlpha completed the MediaAlpha IPO. In the offering, White Mountains sold 3.6 million shares at $19.00 per share ($17.67 per share net of underwriting fees) and received total proceeds of $63.8 million. White Mountains also received $55.0 million of net proceeds related to a dividend recapitalization at MediaAlpha.

Subsequent to the MediaAlpha IPO, White Mountains’s investment in MediaAlpha is accounted for at fair value based on the publicly traded share price of MediaAlpha’s common stock, and White Mountains presents its investment in MediaAlpha as a separate line item on the balance sheet.

On March 23, 2021, MediaAlpha completed a secondary offering of 8.05 million shares. In the secondary offering, White Mountains sold 3.6 million shares at $46.00 per share ($44.62 per share net of underwriting fees) for net proceeds of $160.3 million.

As of December 31, 2022, White Mountains owned 16.9 million shares, representing a 27.1% basic ownership interest (25.1% fully-diluted/fully-converted basis). At this current level of ownership, each $1.00 per share increase or decrease in the share price of MediaAlpha will result in an approximate $6.60 per share increase or decrease in White Mountains’s book value per share. At the December 31, 2022 closing price of $9.95 per share, the fair value of White Mountains’s investment in MediaAlpha was $168.6 million. See Note 17 — “Equity-Method Eligible Investments”.

Kudu On May 26, 2022, Kudu raised $114.5 million of equity capital (the “Kudu Transaction”) from Massachusetts Mutual Life Insurance Company (“Mass Mutual”), White Mountains and Kudu management. Mass Mutual, White Mountains and Kudu management contributed $64.1 million, $50.0 million and $0.4 million at a pre-money valuation of 1.3x, or $114.0 million, above the December 31, 2021 equity value of Kudu’s go-forward portfolio of participation contracts. Kudu’s go-forward portfolio of participation contracts excluded $54.3 million of enterprise value as of December 31, 2021 relating to two portfolio companies that had announced sales transactions prior to the capital raise. As a result of the Kudu Transaction, White Mountains’s basic ownership of Kudu decreased from 99.1% to 89.3%.

Investment Securities

12 Months Ended

Dec. 31, 2022

Investments, Debt and Equity Securities [Abstract]

Investment Securities

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

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

Realized investment gains (losses) resulting from sales of investment securities are accounted for using the specific identification method. Premiums and discounts on all fixed maturity investments are amortized or accreted to income over the anticipated life of the investment. Short-term investments consist of interest-bearing money market funds, certificates of deposit and other securities, which at the time of purchase, mature or become available for use within one year. Short-term investments are carried at fair value, which approximated amortized cost, as of December 31, 2022 and 2021.

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

Net Investment Income

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

The following table presents pre-tax net investment income for the years ended December 31, 2022, 2021 and 2020:


	Year Ended December 31,
Millions	2022		2021		2020
Fixed maturity investments	$	41.4	$	28.8	$	29.0
Short-term investments	16.4		.6		1.1
Common equity securities	1.6		.1		6.6
Investment in MediaAlpha	—		—		59.9

Other long-term investments	68.1		56.3		35.6
Amount attributable to TPC Providers	(1.0)		(1.0)		—
Total investment income	126.5		84.8		132.2
Third-party investment expenses	(2.1)		(2.3)		(1.2)
Net investment income, pre-tax	$	124.4	$	82.5	$	131.0

Net Realized and Unrealized Investment Gains (Losses)

The following table presents net realized and unrealized investment gains (losses) for the years ended December 31, 2022, 2021 and 2020:


	Year Ended December 31,
Millions	2022		2021		2020
Realized investment gains (losses)
Fixed maturity investments	$	(11.9)	$	3.9	$	10.9
Short-term investments	(1.4)		(.1)		.4
Common equity securities	—		.4		137.2
Investment in MediaAlpha	—		160.3		63.8
Other long-term investments	128.4		(7.7)		(25.2)
Net realized investment gains (losses)	115.1		156.8		187.1

Unrealized investment gains (losses)
Fixed maturity investments	(168.4)		(42.2)		27.5
Short-term investments	(1.1)		—		—
Common equity securities	(7.1)		14.9		(130.6)
Investment in MediaAlpha	(93.0)		(540.6)		622.2
Other long-term investments	(43.8)		172.7		10.6
Net unrealized investment gains (losses)	(313.4)		(395.2)		529.7
Net realized and unrealized investment gains (losses), before amount attributable to TPC providers (1)	(198.3)		(238.4)		716.8
Amount attributable to TPC Providers	6.8		(7.7)		—
Net realized and unrealized investment gains (losses)	$	(191.5)	$	(246.1)	$	716.8

Fixed maturity and short-term investments
Net realized and unrealized investment gains (losses)	$	(182.8)	$	(38.4)	$	38.8
Less: net realized and unrealized gains (losses) on investment securities sold during the period	(2.9)		(8.4)		(8.7)
Net unrealized investment gains (losses) recognized during the period on investment securities held at the end of the period	$	(179.9)	$	(30.0)	$	47.5

Common equity securities and investment in MediaAlpha
Net realized and unrealized investment gains (losses) on common equity securities	$	(7.1)	$	15.3	$	6.6
Net realized and unrealized investment gains (losses) from investment in MediaAlpha	(93.0)		(380.3)		686.0
Total net realized and unrealized investment gains (losses)	(100.1)		(365.0)		692.6
Less: net realized and unrealized gains (losses) on investment securities sold during the period	—		20.3		38.3
Net unrealized investment gains (losses) recognized during the period on investment securities held at the end of the period	$	(100.1)	$	(385.3)	$	654.3

(1) For 2022, 2021 and 2020, includes $(29.3), $(7.7) and $4.0 of net realized and unrealized investment gains (losses) related to foreign currency exchange.

For the years ended December 31, 2022, 2021 and 2020, 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.

White Mountains recognized gross realized investment gains of $129.9 million, $212.3 million and $214.4 million and gross realized investment losses of $14.8 million, $55.5 million and $27.3 million on sales of investment securities for the years ending December 31, 2022, 2021 and 2020.

The following table presents the total net unrealized gains (losses) attributable to Level 3 investments for the years ended December 31, 2022, 2021 and 2020 for investments held at the end of the period.


	Year Ended December 31,
Millions	2022		2021		2020

Total net unrealized investment gains on other long-term investments held at the end of period, pre-tax (1)	$	56.5	$	98.9	$	276.0

(1) For 2020, includes $278.7 of unrealized investment gains from White Mountains’s investment in MediaAlpha.

Proceeds from the sales and maturities of investments, excluding short-term investments, totaled $0.5 billion, $0.8 billion and $1.4 billion for the years ended December 31, 2022, 2021 and 2020.

Investment Holdings

The following tables present the cost or amortized cost, gross unrealized investment gains (losses), net foreign currency gains (losses) and carrying values of White Mountains’s fixed maturity investments as of December 31, 2022 and 2021.


	December 31, 2022
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains (Losses)		Carrying Value
U.S. Government and agency obligations	$	216.6	$	—	$	(10.2)	$	—	$	206.4
Debt securities issued by corporations	1,098.3		.6		(78.3)		(1.8)		1,018.8
Municipal obligations	281.6		.4		(23.4)		—		258.6
Mortgage and asset-backed securities	288.7		—		(34.5)		—		254.2
Collateralized loan obligations	190.8		.1		(6.0)		(2.0)		182.9
Total fixed maturity investments	$	2,076.0	$	1.1	$	(152.4)	$	(3.8)	$	1,920.9


	December 31, 2021
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains (Losses)		Carrying Value
U.S. Government and agency obligations	$	212.1	$	.5	$	(1.1)	$	—	$	211.5
Debt securities issued by corporations	993.3		8.7		(8.7)		(.4)		992.9
Municipal obligations	276.4		16.8		(1.3)		—		291.9
Mortgage and asset-backed securities	277.2		2.9		(2.5)		—		277.6
Collateralized loan obligations	136.5		—		(.4)		(1.1)		135.0


Total fixed maturity investments	$	1,895.5	$	28.9	$	(14.0)	$	(1.5)	$	1,908.9

The weighted average duration of White Mountains’s fixed income portfolio was 2.3 years, including short-term investments, and 3.4 years, excluding short-term investments, as of December 31, 2022.

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, 2022. 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, 2022
Millions	Cost or Amortized Cost		Carrying Value
Due in one year or less	$	204.8	$	201.2
Due after one year through five years	914.0		853.2
Due after five years through ten years	374.4		337.4
Due after ten years	103.3		92.0
Mortgage and asset-backed securities and collateralized loan obligations	479.5		437.1

Total fixed maturity investments	$	2,076.0	$	1,920.9

The following tables present the cost or amortized cost, gross unrealized investment gains (losses), net foreign currency gains (losses), and carrying values of common equity securities, White Mountains’s investment in MediaAlpha and other long-term investments as of December 31, 2022 and 2021:


	December 31, 2022
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains (Losses)		Carrying Value

Common equity securities	$	660.6	$	26.7	$	(8.4)	$	(10.5)	$	668.4
Investment in MediaAlpha	$	—	$	168.6	$	—	$	—	$	168.6


Other long-term investments	$	1,340.8	$	271.1	$	(107.1)	$	(16.8)	$	1,488.0


	December 31, 2021
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains (Losses)		Carrying Value
Common equity securities	$	236.3	$	16.1	$	—	$	(1.3)	$	251.1
Investment in MediaAlpha	$	—	$	261.6	$	—	$	—	$	261.6

Other long-term investments	$	1,186.7	$	239.0	$	(44.1)	$	(3.8)	$	1,377.8

Fair Value Measurements

As of December 31, 2022 and 2021, White Mountains used quoted market prices or other observable inputs to determine fair value for approximately 72% and 68% 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, 2022 and 2021 by level. The major security types were based on the legal form of the securities. White Mountains has disaggregated its fixed maturity investments based on the issuing entity type, which impacts credit quality, with debt securities issued by U.S. government entities carrying minimal credit risk, while the credit and other risks associated with other issuers, such as corporations, municipalities or entities issuing mortgage and asset-backed securities vary depending on the nature of the issuing entity type. White Mountains further disaggregates debt securities issued by corporations by industry sector because investors often reference commonly used benchmarks and their subsectors to monitor risk and performance. Accordingly, White Mountains has further disaggregated this asset class into subclasses based on the similar sectors and industry classifications it uses to evaluate investment risk and performance against commonly used benchmarks, such as the Bloomberg Barclays U.S. Intermediate Aggregate.


	December 31, 2022
Millions	Fair Value		Level 1		Level 2		Level 3
Fixed maturity investments:
U.S. Government and agency obligations	$	206.4	$	206.4	$	—	$	—

Debt securities issued by corporations:
Financials	291.2		—		291.2		—
Consumer	191.9		—		191.9		—
Technology	123.7		—		123.7		—
Healthcare	121.3		—		121.3		—
Industrial	115.4		—		115.4		—
Utilities	73.8		—		73.8		—
Communications	47.9		—		47.9		—
Energy	33.9		—		33.9		—
Materials	19.7		—		19.7		—

Total debt securities issued by corporations	1,018.8		—		1,018.8		—

Municipal obligations	258.6		—		258.6		—
Mortgage and asset-backed securities	254.2		—		254.2		—

Collateralized loan obligations	182.9		—		182.9		—
Total fixed maturity investments	1,920.9		206.4		1,714.5		—

Short-term investments	924.1		924.1		—		—
Common equity securities

Exchange-trade funds	333.8		333.8		—		—
Other (1)	334.6		—		334.6		—
Total common equity securities	668.4		333.8		334.6		—
Investment in MediaAlpha	168.6		168.6		—		—












Other long-term investments	926.4		—		14.8		911.6
Other long-term investments — NAV (2)	561.6		—		—		—
Total other long-term investments	1,488.0		—		14.8		911.6
Total investments	$	5,170.0	$	1,632.9	$	2,063.9	$	911.6

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

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


	December 31, 2021
Millions	Fair Value		Level 1		Level 2		Level 3
Fixed maturity investments:
U.S. Government and agency obligations	$	211.5	$	211.5	$	—	$	—

Debt securities issued by corporations:
Financials	264.2		—		264.2		—
Consumer	178.1		—		178.1		—
Technology	117.9		—		117.9		—
Industrial	112.9		—		112.9		—
Healthcare	112.8		—		112.8		—
Utilities	70.9		—		70.9		—
Communications	56.0		—		56.0		—
Energy	48.0		—		48.0		—
Materials	32.1		—		32.1		—

Total debt securities issued by corporations	992.9		—		992.9		—

Municipal obligations	291.9		—		291.9		—
Mortgage and asset-backed securities	277.6		—		277.6		—
Collateralized loan obligations	135.0		—		135.0		—


Total fixed maturity investments	1,908.9		211.5		1,697.4		—

Short-term investments	465.9		465.9		—		—
Common equity securities (1)	251.1		—		251.1		—

Investment in MediaAlpha	261.6		261.6		—		—
















Other long-term investments	895.3		—		4.7		890.6
Other long-term investments — NAV (2)	482.5		—		—		—
Total other long-term investments	1,377.8		—		4.7		890.6
Total investments	$	4,265.3	$	939.0	$	1,953.2	$	890.6

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

Investments Held on Deposit or as Collateral

As of December 31, 2022 and 2021, investments of $500.5 million and $479.5 million, were held in trusts required to be maintained in relation to HG Global’s reinsurance agreements with BAM.

HG Global is required to maintain an interest reserve account in connection with its senior notes issued in 2022. As of December 31, 2022, the interest reserve account, which is included in short-term investments, is $31.2 million. See Note 7 — “Debt”.

BAM is 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 $4.6 million and $4.8 million as of December 31, 2022 and 2021.

Lloyd’s trust deposits are generally required of Lloyd's syndicates to protect policyholders in non-U.K. markets and are pledged into Lloyd’s trust accounts to provide a portion of the capital needed to support obligations at Lloyd’s. As of December 31, 2022 and 2021, Ark held Lloyd’s trust deposits with a fair value of $137.4 million and $113.8 million.

The underwriting capacity of a member of Lloyd’s must be supported by providing a deposit (“Funds at Lloyd’s”) in the form of cash, securities or letters of credit in an amount determined by Lloyd’s. The amount of such deposit is calculated for each member through the completion of an annual capital adequacy exercise. These requirements allow Lloyd’s to evaluate that each member has sufficient assets to meet its underwriting liabilities plus a required solvency margin. As of December 31, 2022 and 2021, the fair value of Ark’s Funds at Lloyd’s investment deposits totaled $319.2 million and $342.8 million.

As at December 31, 2022 and 2021, Ark has $90.3 million and $50.0 million of short-term investments pledged as collateral under uncommitted stand by letters of credit. See Note 7 — “Debt”.

As of December 31, 2022, short-term investments of $203.7 million were held in a collateral trust account required to be maintained in relation to WM Outrigger Re’s reinsurance agreement with GAIL.

Debt Securities Issued by Corporations

The following table presents the credit ratings of debt securities issued by corporations held in White Mountains’s investment portfolio as of December 31, 2022 and 2021:


	Fair Value at December 31,
Millions	2022		2021
AAA	$	11.3	$	12.0
AA	96.0		85.0
A	567.9		490.4
BBB	337.7		396.8


Other	5.9		8.7
Debt securities issued by corporations (1)	$	1,018.8	$	992.9

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

Mortgage and Asset-backed Securities and Collateralized Loan Obligations

The following table presents the fair value of White Mountains’s mortgage and asset-backed securities and collateralized loan obligations as of December 31, 2022 and 2021:


	December 31, 2022						December 31, 2021
Millions	Fair Value		Level 2		Level 3		Fair Value		Level 2		Level 3
Mortgage-backed securities:
Agency:
FNMA	$	124.5	$	124.5	$	—	$	125.4	$	125.4	$	—
FHLMC	78.8		78.8		—		90.5		90.5		—
GNMA	28.3		28.3		—		40.1		40.1		—
Total agency (1)	231.6		231.6		—		256.0		256.0		—
Non-agency: Residential	.3		.3		—		.5		.5		—

Total non-agency	.3		.3		—		.5		.5		—
Total mortgage-backed securities	231.9		231.9		—		256.5		256.5		—
Other asset-backed securities:
Credit card receivables	11.9		11.9		—		12.3		12.3		—
Vehicle receivables	10.4		10.4		—		8.8		8.8		—

Total other asset-backed securities	22.3		22.3		—		21.1		21.1		—
Total mortgage and asset-backed securities	254.2		254.2		—		277.6		277.6		—
Collateralized loan obligations:	182.9		182.9		—		135.0		135.0		—
Total mortgage and asset-backed securities and collateralized loan obligations	$	437.1	$	437.1	$	—	$	412.6	$	412.6	$	—

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

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

As of December 31, 2022, White Mountains’s investment portfolio included $182.9 million of collateralized loan obligations that are within the senior tranches of their respective fund securitization structures. All of White Mountains’s collateral loan obligations were rated AAA or AA as of December 31, 2022.

Investment in MediaAlpha

Following the MediaAlpha IPO, White Mountains’s investment in MediaAlpha is accounted for at fair value based on the publicly traded share price of MediaAlpha’s common stock and is presented as a separate line item on the balance sheet.

At the December 31, 2022 closing price of $9.95 per share, the fair value of White Mountains’s investment in MediaAlpha was $168.6 million. See Note 2 — “Significant Transactions”.

Other Long-Term Investments

The following table presents the carrying values of White Mountains’s other long-term investments as of December 31, 2022 and 2021:


	Fair Value at December 31,
Millions	2022		2021
Kudu’s Participation Contracts	$	695.9	$	669.5
PassportCard/DavidShield	135.0		120.0
Elementum Holdings L.P.	30.0		45.0
Other unconsolidated entities (1)	37.2		34.4
Total unconsolidated entities	898.1		868.9
Private equity funds and hedge funds	197.8		153.8
Bank loan fund	174.8		163.0
Lloyd’s trust deposits	137.4		113.8
ILS funds	49.3		51.9
Private debt instruments	9.6		14.1
Other	21.0		12.3
Total other long-term investments	$	1,488.0	$	1,377.8

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

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, 2022, White Mountains held investments in 16 private equity funds and two hedge funds. The largest investment in a single private equity fund or hedge fund was $49.0 million as of December 31, 2022 and $31.3 million as of December 31, 2021.

The following table presents the fair value of investments and unfunded commitments in private equity funds and hedge funds by investment objective and sector as of December 31, 2022 and 2021:


	December 31, 2022				December 31, 2021
Millions	Fair Value		Unfunded Commitments		Fair Value		Unfunded Commitments

Private equity funds
Aerospace/Defense/Government	$	59.4	$	37.5	$	69.8	$	11.8
Financial services	77.1		54.3		67.7		29.3
Real estate	4.1		2.5		4.3		2.9



Total private equity funds	140.6		94.3		141.8		44.0

Hedge funds
Long/short equity financials and business services	49.0		—		—		—
European small/mid cap	8.2		—		12.0		—
Total hedge funds	57.2		—		12.0		—
Total private equity funds and hedge funds included in other long-term investments	$	197.8	$	94.3	$	153.8	$	44.0

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, 2022:


Millions	1 – 3 years		3 – 5 years		5 – 10 years		>10 years		Total
Private equity funds — expected lock-up period remaining	$	4.2	$	18.8	$	113.9	$	3.7	$	140.6

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, 2022 and 2021, 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. Advance notice requirements for redemptions from White Mountains’s hedge fund investments range from 45 to 90 days. One of White Mountains’s hedge fund investments also limits redemptions to every second anniversary following the date of the initial investment.

Bank Loan Fund

White Mountains’s other long-term investments include a bank loan fund with a fair value of $174.8 million as of December 31, 2022. The fair value of this investment is estimated using the NAV of the fund. The bank loan fund’s investment objective is to provide, on an unleveraged basis, high current income consistent with preservation of capital and low duration. The bank loan fund primarily invests in a broad portfolio of U.S. dollar-denominated, non-investment grade, floating-rate senior secured loans and may invest in other financial instruments, such as secured and unsecured corporate debt, credit default swaps, reverse repurchase agreements, synthetic indices and cash and cash equivalents.

The investment in the bank loan fund is subject to restrictions on redemption frequency and advance notice periods for redemptions. Amounts requested for redemptions remain subject to market fluctuations until the redemption effective date, which generally falls at the end of the defined redemption period. White Mountains may redeem all or a portion of its bank loan fund investment as of any calendar month-end upon 15 calendar days advanced written notice.

Lloyd’s Trust Deposits

White Mountains’s other long-term investments include Lloyd’s trust deposits, which consist of non-U.K. deposits and Canadian comingled pooled funds. The Lloyd’s trust deposits invest primarily in short-term government securities, agency securities and corporate bonds held in trusts that are managed by Lloyd's of London. These investments are generally required of Lloyd's syndicates to protect policyholders in non-U.K. markets and are pledged into Lloyd’s trust accounts to provide a portion of the capital needed to support obligations at Lloyd’s. The fair value of the Lloyd’s trust deposits is generally estimated using the NAV of the funds. As of December 31, 2022, White Mountains held Lloyd’s trust deposits with a fair value of $137.4 million.

Insurance-Linked Securities Funds

White Mountains’s other long-term investments include ILS fund investments. The fair value of these investments is generally estimated using the NAV of the funds. As of December 31, 2022, White Mountains held investments in ILS funds with a fair value of $49.3 million. During the fourth quarter of 2022, White Mountains agreed to invest an additional $100.0 million into ILS funds beginning in 2023. White Mountains pre-funded $70.0 million of this investment as of December 31, 2022, which has been recorded as a receivable within other assets.

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

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

Rollforward of Level 3 Investments

Level 3 measurements as of December 31, 2022 and 2021 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 table presents the changes in White Mountains’s fair value measurements for Level 3 investments for the years ended December 31, 2022 and 2021:


Level 3 Investments
Millions	Other Long-term Investments			Other Long-term Investments
Balance at December 31, 2021	$	890.6	Balance at December 31, 2020	$	614.2
Net realized and unrealized gains	60.4		Net realized and unrealized gains	117.3
Amortization/accretion	—		Amortization/accretion	—
Purchases	129.8		Purchases	225.4
Sales	(169.2)		Sales	(75.9)
Effect of Ark Transaction	—		Effect of Ark Transaction	9.6
Transfers in	—		Transfers in	—
Transfers out	—		Transfers out	—
Balance at December 31, 2022	$	911.6	Balance at December 31, 2021	$	890.6

Fair Value Measurements — Transfers Between Levels - For Years Ended December 31, 2022 and 2021

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 2022 and 2021, there were no fixed maturity investments or other long-term investments classified as Level 3 measurements in the prior period that were transferred to Level 2 measurements.

During 2022 and 2021, there were no fixed maturity investments or other long-term investments classified as Level 2 measurements in the prior period that were transferred to Level 3 measurements.

Significant Unobservable Inputs

The following tables present significant unobservable inputs used in estimating the fair value of White Mountains’s other long-term investments classified within Level 3 as of December 31, 2022 and 2021. The tables below exclude $41.1 million and $46.7 million of Level 3 other long-term investments generally valued based on recent or expected transaction prices. The fair value of investments in private equity funds and hedge funds, bank loan funds, Lloyd’s trust deposits and ILS funds are generally estimated using the NAV of the funds.

$ in Millions

December 31, 2022

Description

Valuation Technique(s) (1)

Fair Value (2)

Unobservable Inputs

Discount Rate (6)

Terminal Cash Flow Exit Multiple (x) or Terminal Revenue Growth Rate (%) (6)

Kudu’s Participation Contracts (3)(4)(5)

Discounted cash flow

$695.9

18% - 25%

7x - 16x

PassportCard/DavidShield

Discounted cash flow

$135.0

24%

Elementum Holdings, L.P.

Discounted cash flow

$30.0

21%

Private debt instruments

Discounted cash flow

$9.6

11%

N/A

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

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

(3) Since Kudu’s Participation Contracts are not subject to corporate taxes within Kudu Investment Management, LLC, pre-tax discount rates are applied to pre-tax cash flows in determining fair values. The weighted average discount rate and weighted average terminal cash flow exit multiple applied to Kudu’s Participation Contracts is 21% and 11.8x.

(4) In 2022, Kudu deployed a total of $99.8 into new and existing Kudu Participation Contracts, including Gramercy Funds Management, GenTrust, EC Management Services, Pennybacker Capital Management and TK Partners.

(5) As of December 31, 2022, two of Kudu’s Participation Contracts with a total fair value of $189.0 were valued using a probability weighted expected return method, which takes into account factors such as a discounted cash flow analysis, the expected value to be received in a pending sales transaction and the likelihood that a sales transaction will take place.

(6) 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, 2021

Description

Valuation Technique(s) (1)

Fair Value (2)

Unobservable Inputs

Discount Rate (6)

Terminal Cash Flow Exit Multiple (x) or Terminal Revenue Growth Rate (%) (6)

Kudu’s Participation Contracts (3)(4)(5)

Discounted cash flow

$669.5

18% - 23%

7x - 13x

PassportCard/DavidShield

Discounted cash flow

$120.0

23%

Elementum Holdings, L.P.

Discounted cash flow

$45.0

17%

Private debt instruments

Discounted cash flow

$9.4

N/A

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

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

(4) In 2021, Kudu deployed a total of $223.4 into new and existing Kudu Participation Contracts, including TIG Advisors, TK Partners, Third Eye Capital Management, Douglass Winthrop Advisors, Granahan Investment Management and Radcliffe Capital Management.

(5) As of December 31, 2021, one of Kudu’s Participation Contracts with a total fair value of $78.8 was valued using a probability weighted expected return method, which takes into account factors such as a discounted cash flow analysis, the expected value to be received in a pending sales transaction and the likelihood that a sales transaction will take place.

Goodwill and Other Intangible Assets

12 Months Ended

Dec. 31, 2022

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. Goodwill represents the excess of the amount paid to acquire subsidiaries over the fair value of identifiable net assets at the date of acquisition. 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, 2022 and 2021:


$ in Millions	Weighted Average Economic Life (in years)	December 31, 2022							December 31, 2021
		Acquisition Date Fair Value		Accumulated Amortization					Net Carrying Value		Acquisition Date Fair Value		Accumulated Amortization					Net Carrying Value
Goodwill:
Ark	N/A	$	116.8	$	—				$	116.8	$	116.8	$	—				$	116.8
Kudu	N/A	7.6		—					7.6		7.6		—					7.6


Other Operations	N/A	52.1		—					52.1		17.9		—					17.9
Total goodwill		176.5		—					176.5		142.3		—					142.3
Other intangible assets:
Ark
Underwriting capacity	N/A	175.7		—					175.7		175.7		—					175.7
Kudu
Trade names	7	2.2		1.2					1.0		2.2		.9					1.3





Other Operations
Trade names	15.9	17.9		3.0					14.9		8.2		1.5					6.7
Customer relationships	12.4	29.5		7.5					22.0		18.8		4.5					14.3

Other	12.1	2.8		.5					2.3		.3		.1					.2
Subtotal		50.2		11.0					39.2		27.3		6.1					21.2
Total other intangible assets		228.1		12.2					215.9		205.2		7.0					198.2
Total goodwill and other intangible assets		$	404.6	$	12.2				392.4		$	347.5	7.0					340.5
Goodwill and other intangible assets attributed to non-controlling interests						(102.7)									(91.8)
Goodwill and other intangible assets included in White Mountains’s common shareholders’ equity							$	289.7								$	248.7

Intangible Assets Valuation Methods

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

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

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 other intangible assets that provide 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.

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

Goodwill and Other Intangible Asset Rollforward

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


	December 31, 2022						December 31, 2021
Millions	Goodwill		Other Intangible Assets		Total Goodwill and Other Intangible Assets		Goodwill		Other Intangible Assets		Total Goodwill and Other Intangible Assets
Beginning balance	$	142.3	$	198.2	$	340.5	$	19.2	$	26.4	$	45.6
Acquisition of businesses (1)	59.5		—		59.5		15.8		—		15.8
Ark Transaction	—		—		—		116.8		175.7		292.5
Attribution of acquisition date fair value estimates between goodwill and other intangible assets	(22.9)		22.9		—		(9.3)		9.3		—
Measurement period adjustments (2)	(2.4)		—		(2.4)		(.2)		—		(.2)


Assets held for sale (3)	—		—		—		—		(8.6)		(8.6)


Amortization	—		(5.2)		(5.2)		—		(4.6)		(4.6)
Ending balance	$	176.5	$	215.9	$	392.4	$	142.3	$	198.2	$	340.5

(1) Relates to acquisitions within Other Operations.

(2) Measurement period adjustments relate to updated information about acquisition date fair values of assets acquired and liabilities assumed. During 2022 and 2021, adjustments relate to acquisitions within Other Operations.

(3) As of December 31, 2021, White Mountains has classified one of its Other Operating Businesses as held for sale, which includes of $8.6 of insurance licenses. See Note. 21 — “Held for Sale and Discontinued Operations.”

During the years ended December 31, 2022 and 2021, White Mountains did not recognize any impairments to goodwill and other intangible assets.

Amortization of Other Intangible Assets

Amortization expense was $5.2 million, $4.6 million and $1.6 million for the years ended December 31, 2022, 2021 and 2020.

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


Millions	Amortization Expense
2023	$	7.1
2024	6.6
2025	5.7
2026	4.8
2027 and years after	16.0
Total (1)	$	40.2

(1) Excludes Ark’s indefinite-lived intangible assets of $175.7.

Loss and Loss Adjustment Expense Reserves

12 Months Ended

Dec. 31, 2022

Insurance Loss Reserves [Abstract]

Loss and Loss Adjustment Expense Reserves

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

HG Re and BAM do not have any outstanding loss and LAE reserves related to BAM’s municipal bond guarantee business.

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

Losses and LAE are categorized by the year in which the policy is underwritten (the year of account, or underwriting year) for purposes of Ark’s claims management and estimation of the ultimate loss and LAE reserves. For purposes of Ark’s reporting under GAAP, losses and LAE are categorized by the year in which the claim is incurred (the accident year).

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

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

Uncertainties in estimating ultimate loss and LAE are magnified by the time lag between when a claim actually occurs and when it is reported and eventually settled. This time lag is sometimes referred to as the “claim-tail”. The claim-tail for reinsurance and insurance obtained through brokers, MGAs and reinsurance intermediaries (collectively the “insurance and reinsurance intermediaries”) is further extended because claims are first reported to either the original primary insurance company or the insurance and reinsurance intermediaries. The claim-tail for most property coverages is typically short (usually a few days up to a few months). Settlements for casualty/liability coverages can extend for long periods of time as claims are often reported and ultimately paid or settled years after the related loss events occur. During the long claims reporting and settlement period, additional facts regarding coverages written in prior years of account, as well as about actual claims and trends, may become known and, as a result, Ark may adjust its reserves. The inherent uncertainties of estimating reserves are increased by the diversity of loss development patterns among different types of reinsurance treaties, facultative contracts or direct insurance contracts, the necessary reliance on the ceding companies and insurance and reinsurance intermediaries for information regarding reported claims and the differing reserving practices among ceding companies and insurance and reinsurance intermediaries.

If management determines that an adjustment is appropriate, the adjustment is booked in the accounting period in which such determination is made. Accordingly, should reserves need to be increased or decreased in the future from amounts currently established, future results of operations would be negatively or positively impacted.

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

Ark performs an actuarial review of its recorded loss and LAE reserves each quarter, using several generally accepted actuarial methods to evaluate its loss reserves, each of which has its own strengths and weaknesses. Management places more or less reliance on a particular method based on the facts and circumstances at the time the reserve estimates are made. These methods generally fall into one of the following categories or are hybrids of one or more of the following categories:

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

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

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

•Bornhuetter-Ferguson methods: These methods are a blend of the expected loss ratio and loss development methods. The percent of incurred (or paid) loss to ultimate loss implied by the selected development pattern from the incurred (or paid) loss development method is used to determine the percentage of ultimate loss yet to be developed. Inception to date losses are added to losses yet to be developed, yielding an estimate of ultimate for each year of account.

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

As part of Ark’s quarterly actuarial review, Ark compares the previous quarter’s projections of incurred, paid and case reserve activity, including amounts incurred but not reported, to actual amounts experienced in the quarter. Differences between previous estimates and actual experience are evaluated to determine whether a given actuarial method for estimating loss and LAE reserves should be relied upon to a greater or lesser extent than it had been in the past. While some variance is expected each quarter due to the inherent uncertainty in estimating loss and LAE reserves, persistent or large variances would indicate that prior assumptions and/or reliance on certain actuarial methods may need to be revised going forward.

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

Ark Reserve Estimation by Line of Business

The process of establishing loss and LAE reserves, including amounts incurred but not reported, is complex and imprecise as it must consider many variables that are subject to the outcome of future events. As a result, informed subjective estimates and judgments as to the ultimate exposure to losses are an integral component of the loss and LAE reserving process. Ark categorizes and tracks insurance and reinsurance reserves by “reserving class of business” for each underwriting office, London and Bermuda, and then aggregates the reserving classes by line of business, which are summarized herein as property and accident & health, specialty, marine & energy, casualty - active and casualty - runoff.

Ark regularly reviews the appropriateness of its loss and LAE reserves at the reserving class of business level, considering a variety of trends that impact the ultimate settlement of claims for the subsets of claims in each particular reserving class.

For loss and LAE reserves as of December 31, 2022, Ark considers that the impact of the various reserving factors, as described below, on future paid losses would be similar to the impact of those factors on historical paid losses.

The major causes of material uncertainty (i.e., reserving factors) generally will vary for each line of business, as well as for each separately analyzed reserving class of business within the line of business. Also, reserving factors can have offsetting or compounding effects on estimated loss and LAE reserves. In most cases, it is not possible to measure the effect of a single reserving factor and construct a meaningful sensitivity expectation. Actual results will likely vary from expectations for each of these assumptions, resulting in an ultimate claim liability that is different from that being estimated currently.

Additional causes of material uncertainty exist in most product lines and may impact the types of claims that could occur within a particular line of business or reserving class of business. Examples where reserving factors, within a line of business or reserving class of business, are subject to change include changing types of insured (e.g., size of account, industry insured, jurisdiction), changing underwriting standards, or changing policy provisions (e.g., deductibles, policy limits, endorsements).

Following is a detailed description of the reserve factors and consideration for each of the major product lines.

Property and Accident & Health

Ark’s property and accident & health reserving line of business contains short-tailed reserving classes. As such, reserving for these classes generally involves less uncertainty given the speed of settlement.

For property reserving classes, the reserve risk is driven primarily by occasional catastrophe events, though the financial effect of these is mitigated by reinsurance and retrocessional purchases. Ark writes property business on both an insurance and reinsurance basis. The insurance business primarily consists of direct and facultative contracts. However, some business is written through lineslips and MGA binding authorities, which could have a longer tail due to the increased exposure period caused by underlying policies attaching to the binder contract. The reinsurance business can also have a longer tail due to timing delays resulting from attachment points on excess of loss contracts.

For accident & health reserving classes, the losses emanate from a wide range of personal accident, sickness, travel and medical insurance risks. The underlying business is a mix of direct and facultative contracts, as well as some MGA and reinsurance contracts, which are typically shorter tail lines. Certain smaller components of the accident & health business can be longer-tailed. The accident & health business is also exposed to occasional catastrophic events though not to the same degree as the property business.

Specialty

Ark’s specialty portfolio is comprised of a diverse portfolio of insurance and reinsurance subclasses of business including aviation, space, political and credit, cyber, terrorism and political violence, product defect and contamination, nuclear, fine art & specie, surety and mortgage. Certain subclasses of business are exposed to both catastrophe events and man-made loss events; for example, terrorism, war and war-like actions, political violence and space. Although these subclasses have different coverage and exposures, they are all short-tailed in nature and have similar reserving features.

Marine & Energy

Ark’s marine & energy reserving line of business is underwritten on both an insurance and reinsurance basis and can be broken down into physical damage on marine risks, physical damage on upstream energy platforms, and marine & energy liabilities.

The marine reserving classes consist primarily of marine hull, cargo and specie risks. These all generally have some element of transportability, which mitigates the catastrophe risk exposure. For example, having the ability to move out of the path of a hurricane if provided with sufficient notice. The marine reserving classes are generally shorter-tailed.

The energy platform reserving classes cover risks that are less transportable and therefore are exposed to catastrophe events similar to property reserving classes. Other energy reserving classes cover construction contracts, which often have considerably protracted exposure periods with the bulk of the risk towards end of the coverage period. This can have the effect of increasing the tail on an otherwise short-tail reserving class.

The marine & energy liability reserving classes, which represent a smaller portion of the marine & energy business, are typically longer-tailed compared to physical damage reserving classes.

Casualty – Active and Casualty – Runoff

Ark’s casualty reserving lines of business, which include casualty–active and casualty–runoff, are long-tailed classes of business. Consequently, the ultimate liability may not be known at the date of loss, which results in greater uncertainty when reserving for casualty lines.

The casualty–active line of business consists of U.S. reinsurance and insurance risks written on an excess of loss basis. The casualty–runoff line of business consists of international reinsurance risks and U.S. casualty insurance risks written through an MGA binding authority. The losses arising from these lines of business are primarily related to medical malpractice, professional liability and general liability coverages, which are long-tailed lines of business.

Casualty policies are generally written on either a claims made or occurrence basis. On a claims made basis, the trigger of loss is based on the date that the loss is reported. On an occurrence basis, the trigger of loss is the date that the loss occurred. Due to delays between loss occurrence and loss reporting, business written on an occurrence basis can be longer-tailed than business written on a claims made basis.

There are a number of common reserving factors for casualty lines that can affect the estimated casualty reserves, including:

•Changes in claim-handling practices, both in-house and through third-party claims administrators,

•Changes in court interpretations of policy provisions, and

•Trends in litigation or jury awards.

Cumulative Number of Reported Claims

Ark counts a claim for each unique combination of individual claimant, loss event and risk. A claim is still counted if the claim is closed with no payment. Bulk-coded losses are counted as one claim as underlying claim counts are not available.

Discounting

Ark does not discount loss and LAE reserves.

Impact of Third-Party Capital

For the years of account prior to the Ark Transaction, a significant proportion of the Syndicates’ underwriting capital was provided by TPC Providers using whole account reinsurance contracts with Ark’s corporate member. The TPC Providers’ participation in the Syndicates for the 2020 open year of account is 42.8% of the total net result of the Syndicates. For the years of account subsequent to the Ark Transaction, Ark is no longer using TPC Providers to provide underwriting capital for the Syndicates.

A Reinsurance to Close (“RITC”) agreement is generally put in place after the third year of operations for a year of account such that the outstanding loss and LAE reserves, including future development thereon, are reinsured into the next year of account. As a result, and in combination with the changing participation provided by TPC Providers, Ark’s participation on outstanding loss and LAE reserves reinsured into the next year of account may change, perhaps significantly. For example, during 2022, an RITC was executed such that the outstanding loss and LAE reserves for claims arising out of the 2019 year of account, for which the TPC Providers’ participation in the total net results of the Syndicates was 58.3%, were reinsured into the 2020 year of account, for which the TPC Providers’ participation in the total net results of the Syndicates is 42.8%.

Loss and Loss Adjustment Expense Reserve Summary

The following table summarizes the loss and LAE reserve activity of Ark’s insurance and reinsurance subsidiaries for the year ended December 31, 2022 and 2021:


	Year Ended December 31,
Millions	2022		2021
Gross beginning balance	$	894.7	$	696.0
Less: beginning reinsurance recoverable on unpaid losses (1)	(428.9)		(433.4)
Net loss and LAE reserves	465.8		262.6

Losses and LAE incurred relating to:
Current year losses	588.1		336.3
Prior year losses	(51.7)		(21.5)
Net incurred losses and LAE	536.4		314.8

Loss and LAE paid relating to:
Current year losses	(98.9)		(43.9)
Prior year losses	(158.6)		(61.6)
Net paid losses and LAE	(257.5)		(105.5)

Change in TPC Providers’ participation (2)	57.5		(2.2)
Foreign currency translation and other adjustments to loss and LAE reserves	(10.7)		(3.9)

Net ending balance	791.5		465.8
Plus: ending reinsurance recoverable on unpaid losses (3)	505.0		428.9
Gross ending balance	$	1,296.5	$	894.7

(1) The beginning reinsurance recoverable on unpaid losses includes amounts attributable to TPC Providers of $276.8 and $319.2 as of December 31, 2021 and 2020.

(2) Amount represents the impact to net loss and LAE reserves due to a change in the TPC Providers’ participation related to the annual RITC process.

(3) The ending reinsurance recoverable on unpaid losses on unpaid losses includes amounts attributable to TPC Providers of $145.4 and $276.8 as of December 31, 2022 and 2021.

During the year ended December 31, 2022, Ark experienced $51.7 million of net favorable prior year loss reserve development. Ark’s net favorable prior year loss reserve development was driven primarily by the property and accident & health ($20.8 million), marine & energy ($18.8 million) and specialty ($12.7 million) reserving lines of business. The favorable prior year loss reserve development in the property and accident & health, marine & energy and specialty reserving lines of business was driven primarily by positive claims experience within the 2021 accident year.

During the year ended December 31, 2021, Ark experienced $21.5 million of net favorable prior year loss reserve development. Ark’s net favorable prior year loss reserve development was driven primarily by the property and accident & health ($8.9 million), casualty – ongoing ($3.7 million), specialty ($3.3 million) and casualty – runoff ($3.3 million) reserving lines of business. The favorable prior year loss reserve development in the property and accident & health reserving line of business was driven primarily by positive claims experience within the 2018 and 2019 accident years.

The following table summarizes the unpaid loss and LAE reserves, net of reinsurance recoverables on unpaid losses, for each of Ark’s major reserving lines of business as of December 31, 2022 and 2021:


	Year Ended December 31,
Millions	2022		2021
Property and Accident & Health	$	258.2	$	175.0
Specialty	204.3		85.2
Marine & Energy	196.4		99.3

Casualty - Active	71.5		37.4
Casualty - Runoff	60.8		68.4
Other	.3		.5
Unpaid loss and LAE reserves, net of reinsurance recoverables on unpaid losses	791.5		465.8
Plus: Reinsurance recoverables on unpaid losses (1)
Property and Accident & Health	224.6		145.2
Specialty	97.2		68.9
Marine & Energy	79.8		70.2
Casualty - Active	49.9		41.4
Casualty - Runoff	53.5		103.2
Total Reinsurance recoverables on unpaid losses (1)	505.0		428.9
Total unpaid loss and LAE reserves	$	1,296.5	$	894.7

(1) The reinsurance recoverables on unpaid losses include amounts attributable to TPC Providers of $145.4 and $276.8 as of December 31, 2022 and 2021.

The following five tables include one table each for the property and accident & health, specialty, marine & energy, casualty-active and casualty-runoff reserving lines of business, and are presented net of reinsurance, which includes the impact of whole-account quota-share reinsurance arrangements related to TPC Providers. Through the annual RITC process, and in combination with the changing participation provided by TPC Providers, Ark’s participation on outstanding loss and LAE reserves on prior years of account can fluctuate. Depending on the change in the TPC Providers’ participation from one year of account to the next, the impact could be significant and is reflected in the tables on a retrospective basis by accident year. That is, for the RITC executed in the current year that changes Ark’s participation for claims relating to prior accident years, the prior year columns are adjusted to include the impact of the RITC. The following table summarizes the participation of Ark’s TPC Providers by year of account:


	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022
TPC Providers’ Participation	—	%	66.2	%	70.0	%	59.6	%	60.0	%	57.6	%	58.3	%	42.8	%	—	%	—	%

Each of the five tables includes three sections.

The top section of the table presents, for each of the previous 10 accident years (1) cumulative total undiscounted incurred loss and LAE as of each of the previous 10 year-end evaluations, (2) total IBNR plus expected development on reported claims as of December 31, 2022, and (3) the cumulative number of reported claims as of December 31, 2022.

The middle section of the table presents cumulative paid loss and LAE for each of the previous 10 accident years as of each of the previous 10 year-end evaluations. Also included in this section is a calculation of the loss and LAE reserves as of December 31, 2022 which is then included in the reconciliation to the consolidated balance sheet presented above. The total unpaid loss and LAE reserves as of December 31, 2022 is calculated as the cumulative incurred loss and LAE from the top section less the cumulative paid loss and LAE from the middle section, plus any outstanding liabilities from accident years prior to 2013.

The bottom section of the table is supplementary information about the average historical claims duration as of December 31, 2022. It shows the weighted average annual percentage payout of incurred loss and LAE by accident year as of each age. For example, the first column is calculated as the incremental paid loss and LAE in the first calendar year for each given accident year (e.g. calendar year 2020 for accident year 2020, calendar year 2021 for accident year 2021) divided by the cumulative incurred loss and LAE as of December 31, 2022 for that accident year. The resulting ratios are weighted together using cumulative incurred loss and LAE as of December 31, 2022.


Property and Accident & Health
$ in Millions
	Incurred Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,																				As of December 31, 2022
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022		Total IBNR plus expected development on reported claims		Cumulative number of reported claims
	Unaudited
2013	$	67.8	$	60.4	$	60.3	$	60.1	$	59.6	$	59.5	$	59.4	$	59.3	$	59.3	$	59.3	$	.1	2,530
2014			32.2		29.1		29.0		28.3		28.1		28.2		28.2		28.2		28.2		.1		2,919
2015					18.8		17.9		16.9		15.9		15.7		15.7		15.5		15.4		.1		2,826
2016							21.9		17.2		17.9		18.1		18.1		18.3		18.2		.1		3,419
2017									24.6		31.4		38.9		37.9		36.5		36.0		5.7		4,599
2018											38.1		44.5		46.4		44.1		44.2		1.3		4,254
2019													31.6		28.9		24.7		21.5		.7		3,999
2020															65.2		63.3		62.9		7.3		4,551
2021																	163.0		146.8		10.6		3,318
2022																			234.5		90.1		2,899
																	Total		$	667.0


Property and Accident & Health
Millions
	Cumulative Paid Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022
	Unaudited
2013	$	15.4	$	39.1	$	58.1	$	59.1	$	59.1	$	59.4	$	59.3	$	59.3	$	59.2	$	59.2
2014			13.6		24.9		27.1		27.5		27.6		27.8		27.9		27.8		27.9
2015					6.9		12.2		13.4		14.6		14.6		14.8		15.0		15.0
2016							8.5		13.1		16.4		16.8		16.9		17.2		17.8
2017									16.8		25.8		31.6		32.8		29.6		27.3
2018											15.6		32.2		40.1		40.0		40.8
2019													6.8		16.7		18.3		18.5
2020															11.2		34.1		47.0
2021																	30.8		86.7
2022																			70.0
																	Total		410.2
All outstanding liabilities before 2013, net of reinsurance																			1.4
Loss and LAE reserves, net of reinsurance																			$	258.2


Property and Accident & Health
	Average Annual Percentage Payout of Incurred Losses and LAE by Age, Net of Reinsurance
	Unaudited
Years	1	2	3	4	5	6	7	8	9	10
	31.4%	34.2%	19.3%	5.5%	1.2%	0.8%	0.8%	0.3%	—%	—%


Specialty
$ in Millions
	Incurred Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,																				As of December 31, 2022
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022		Total IBNR plus expected development on reported claims		Cumulative number of reported claims
	Unaudited
2013	$	47.0	$	28.5	$	17.6	$	16.2	$	15.9	$	15.8	$	15.5	$	15.7	$	15.7	$	15.8	$	.1	1,042
2014			45.5		43.8		40.8		40.4		40.8		43.3		43.4		43.3		43.1		—		1,357
2015					16.2		13.6		11.2		9.6		9.9		10.1		10.1		7.8		.1		1,840
2016							18.1		14.1		10.8		11.1		11.7		11.6		8.8		.2		1,927
2017									17.3		12.2		11.3		10.8		11.0		10.0		—		2,187
2018											13.2		14.9		15.4		14.7		13.5		.7		2,110
2019													18.5		16.3		15.4		22.4		1.1		2,347
2020															21.4		20.5		16.3		2.5		1,985
2021																	67.6		59.4		33.9		1,644
2022																			172.8		125.3		985
																	Total		$	369.9


Specialty
Millions
	Cumulative Paid Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022
	Unaudited
2013	$	17.0	$	13.2	$	14.9	$	15.4	$	15.5	$	15.7	$	15.7	$	15.7	$	15.6	$	15.6
2014			26.3		38.9		39.7		40.1		40.7		42.0		42.8		42.7		43.0
2015					4.0		7.0		7.6		8.0		8.1		8.1		8.1		6.4
2016							3.2		7.9		9.1		9.9		10.3		10.3		8.5
2017									3.1		6.6		8.4		8.5		8.5		9.2
2018											2.7		8.2		10.0		10.4		11.8
2019													4.8		6.9		7.4		18.2
2020															5.2		10.6		13.0
2021																	5.1		24.1
2022																			16.0
																	Total		165.8
All outstanding liabilities before 2013, net of reinsurance																			.2
Loss and LAE reserves, net of reinsurance																			$	204.3


Specialty
	Average Annual Percentage Payout of Incurred Losses and LAE by Age, Net of Reinsurance
	Unaudited
Years	1	2	3	4	5	6	7	8	9	10
	25.8%	33.4%	7.8%	4.8%	5.9%	5.9%	1.4%	1.9%	(3.2)%	(0.8)%


Marine & Energy
$ in Millions
	Incurred Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,																				As of December 31, 2022
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022		Total IBNR plus expected development on reported claims		Cumulative number of reported claims
	Unaudited
2013	$	55.4	$	41.7	$	32.3	$	31.0	$	30.8	$	29.6	$	29.5	$	29.3	$	29.4	$	29.3	$	(.2)	2,638
2014			34.1		19.9		17.0		16.1		14.0		13.6		13.9		13.6		13.7		(.2)		2,572
2015					21.0		16.7		15.4		12.6		12.0		12.1		12.0		12.2		—		3,238
2016							23.1		19.2		15.4		14.3		14.0		14.5		13.8		—		3,764
2017									25.3		18.6		16.8		16.2		15.9		15.0		.2		4,117
2018											24.6		19.1		16.6		17.0		16.6		.2		3,205
2019													20.7		18.6		18.6		18.3		.6		2,331
2020															24.4		21.7		23.2		1.8		1,529
2021																	83.0		66.1		24.8		1,356
2022																			148.2		99.5		1,188
																	Total		$	356.4


Marine & Energy
Millions
	Cumulative Paid Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022
	Unaudited
2013	$	7.8	$	22.2	$	27.6	$	28.6	$	29.1	$	29.3	$	29.3	$	29.1	$	29.3	$	29.3
2014			5.8		12.1		13.2		14.0		14.1		13.4		13.6		13.5		13.7
2015					4.0		7.8		9.6		10.9		10.3		10.4		10.8		11.4
2016							5.5		10.0		12.6		13.0		13.1		13.7		13.4
2017									5.1		11.1		12.8		14.0		14.1		14.1
2018											2.7		12.5		14.0		14.7		15.4
2019													3.3		10.6		12.6		14.3
2020															3.1		12.7		16.0
2021																	6.3		24.2
2022																			12.2
																	Total		164.0
All outstanding liabilities before 2013, net of reinsurance																			4.0
Loss and LAE reserves, net of reinsurance																			$	196.4


Marine & Energy
	Average Annual Percentage Payout of Incurred Losses and LAE by Age, Net of Reinsurance
	Unaudited
Years	1	2	3	4	5	6	7	8	9	10
	17.4%	35.8%	19.9%	5.9%	4.3%	6.9%	0.3%	0.3%	(0.3)%	0.1%


Casualty - Active
$ in Millions
	Incurred Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,																				As of December 31, 2022
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022		Total IBNR plus expected development on reported claims		Cumulative number of reported claims
	Unaudited
2013	$	18.2	$	13.0	$	8.5	$	8.0	$	8.0	$	8.1	$	7.7	$	7.8	$	7.8	$	7.8	$	.1	1,144
2014			12.6		8.7		7.7		7.5		7.4		7.0		7.1		6.9		7.1		.2		1,385
2015					8.8		9.0		7.4		7.3		6.6		6.4		6.3		6.5		.2		1,280
2016							7.6		7.1		7.8		7.8		7.9		8.0		8.1		.3		1,528
2017									9.5		9.6		8.7		7.3		7.0		8.4		.9		1,580
2018											11.0		11.5		9.2		9.0		6.8		1.1		1,036
2019													11.6		10.4		9.1		7.3		2.4		834
2020															9.7		8.3		7.1		4.2		524
2021																	17.4		18.4		16.3		674
2022																			32.0		28.8		832
																	Total		$	109.5


Casualty - Active
Millions
	Cumulative Paid Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022
	Unaudited
2013	$	1.5	$	3.6	$	5.3	$	5.8	$	6.3	$	6.7	$	7.0	$	7.0	$	7.3	$	7.5
2014			1.3		3.5		4.2		4.7		5.2		5.5		5.9		6.0		6.2
2015					1.8		2.4		3.2		4.4		4.7		4.9		5.1		5.5
2016							.2		1.0		2.3		4.0		4.6		5.3		6.5
2017									.8		1.7		2.8		3.4		4.2		5.7
2018											.3		1.4		3.5		4.3		4.3
2019													.3		1.4		2.3		3.0
2020															.5		1.0		2.0
2021																	.5		.9
2022																			.4
																	Total		42.0
All outstanding liabilities before 2013, net of reinsurance																			4.0
Loss and LAE reserves, net of reinsurance																			$	71.5


Casualty - Active
	Average Annual Percentage Payout of Incurred Losses and LAE by Age, Net of Reinsurance
	Unaudited
Years	1	2	3	4	5	6	7	8	9	10
	6.8%	11.7%	16.7%	12.7%	8.0%	10.8%	4.9%	3.1%	1.2%	2.9%


Casualty - Runoff
$ in Millions
	Incurred Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,																				As of December 31, 2022
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022		Total IBNR plus expected development on reported claims		Cumulative number of reported claims
	Unaudited
2013	$	47.7	$	51.4	$	47.7	$	49.0	$	47.6	$	47.3	$	47.7	$	47.5	$	47.5	$	47.5	$	1.4	1,798
2014			45.8		45.3		47.8		50.9		54.5		56.0		56.0		55.8		55.6		1.3		1,941
2015					33.8		29.4		30.6		34.0		33.8		34.8		34.1		36.6		1.6		1,995
2016							28.6		28.3		36.5		34.7		34.9		34.6		33.8		1.7		2,150
2017									27.4		30.8		28.2		28.9		28.4		26.7		2.2		1,599
2018											29.4		23.9		23.0		22.3		21.9		3.3		1,267
2019													21.1		17.8		18.0		19.4		5.0		961
2020															11.3		7.6		9.3		3.9		558
2021																	8.2		4.8		2.7		277
2022																			.6		.1		76
																	Total		$	256.2


Casualty - Runoff
Millions
	Cumulative Paid Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022
	Unaudited
2013	$	7.1	$	19.4	$	35.7	$	40.6	$	42.4	$	43.3	$	43.9	$	44.6	$	44.9	$	45.2
2014			6.4		23.1		29.5		36.4		43.1		46.9		48.5		49.3		51.8
2015					4.3		8.2		14.5		21.4		24.7		27.3		28.9		33.1
2016							3.9		10.2		17.7		22.7		25.4		27.8		28.7
2017									3.2		9.4		14.6		18.5		21.4		22.5
2018											3.4		7.4		12.6		14.9		16.3
2019													3.3		5.8		7.8		12.1
2020															.8		1.3		3.1
2021																	.5		1.7
2022																			.3
																	Total		214.8
All outstanding liabilities before 2013, net of reinsurance																			19.4
Loss and LAE reserves, net of reinsurance																			$	60.8


Casualty - Runoff
	Average Annual Percentage Payout of Incurred Losses and LAE by Age, Net of Reinsurance
	Unaudited
Years	1	2	3	4	5	6	7	8	9	10
	9.4%	15.4%	17.2%	15.7%	9.0%	7.4%	6.3%	4.3%	2.8%	1.4%

Third-Party Reinsurance

12 Months Ended

Dec. 31, 2022

Reinsurance Disclosures [Abstract]

Third-Party Reinsurance

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


	Year Ended December 31,
Millions	2022		2021
Written premiums:
Gross	$	1,452.0	$	1,058.7


Ceded	(256.8)		(199.6)
Net written premiums	$	1,195.2	$	859.1
Earned premiums:
Gross	$	1,324.2	$	886.4


Ceded	(280.8)		(249.1)
Net earned premiums	$	1,043.4	$	637.3
Losses and LAE:
Gross	$	814.9	$	442.9


Ceded	(278.5)		(128.1)
Net Losses and LAE	$	536.4	$	314.8

As of December 31, 2022, Ark had $505.0 million and $31.1 million of reinsurance recoverables on unpaid and paid losses. As of December 31, 2021, Ark had $428.9 million and $19.5 million of reinsurance recoverables on unpaid and paid losses. As reinsurance contracts do not relieve Ark of its obligation to its policyholders, Ark seeks to reduce the credit risk associated with reinsurance balances by avoiding over-reliance on specific reinsurers through the application of concentration limits and thresholds. Ark is selective with its reinsurers, placing reinsurance with only those reinsurers having a strong financial condition. Ark monitors the financial strength of its reinsurers on an ongoing basis.

As of December 31, 2022, Ark’s reinsurance recoverables of $536.1 million included $145.4 million related to TPC Providers, which are collateralized. As of December 31, 2021, Ark’s reinsurance recoverables of $448.4 million included $276.8 million related to TPC Providers, which are collateralized. The following table provides a listing of Ark’s remaining gross and net reinsurance recoverables, excluding amounts related to TPC Providers, by the reinsurer’s A.M. Best Company, Inc. (“A.M. Best”) rating and the percentage of total recoverables.


$ in Millions	As of December 31, 2022
A.M. Best Rating (1)	Gross		Collateral		Net		% of Total
A+ or better	$	190.0	$	—	$	190.0	67.4	%
A- to A	75.3		—		75.3		26.7
B++ or lower and not rated	125.4		108.9		16.5		5.9
Total	$	390.7	$	108.9	$	281.8	100.0	%

(1) A.M. Best ratings as detailed above are: “A+ or better” (Superior) “A- to A” (Excellent), “B++” (Good).

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

Reinsurance Contracts Accounted for as Deposits

Ark has an aggregate excess of loss contract with SiriusPoint, which is accounted for using the deposit method and recorded within other assets. Ark earns an annual crediting rate of 3.0%, which is recorded within other revenue. During 2021, Ark negotiated a reduction of $31.7 million, including accrued interest, to the aggregate excess of loss contract with SiriusPoint. As of December 31, 2022 and December 31, 2021, the carrying value of Ark’s deposit in SiriusPoint, including accrued interest, was $20.4 million.

See Note 10 — “Municipal Bond Guarantee Insurance” for reinsurance contracts accounted for as deposits related to White Mountains’s financial guarantee business.

Debt

12 Months Ended

Dec. 31, 2022

Debt Disclosure [Abstract]

Debt

The following table presents White Mountains’s debt outstanding as of December 31, 2022 and 2021:


	December 31,		Effective	December 31,		Effective
$ in Millions	2022		Rate (1)	2021		Rate (1)



HG Global Senior Notes	$	150.0	8.9%	$	—
Unamortized discount and issuance cost	(3.5)			—
HG Global Senior Notes, carrying value	146.5			—
Ark 2007 Subordinated Notes, carrying value	30.0			30.0
Ark 2021 Notes Tranche 1	41.3			44.2
Ark 2021 Notes Tranche 2	47.0			47.0
Ark 2021 Notes Tranche 3	70.0			70.0
Unamortized issuance cost	(4.6)			(5.3)
Ark 2021 Subordinated Notes, carrying value	153.7			155.9
Total Ark Subordinated Notes, carrying value	183.7		7.6%	185.9		6.9%




Kudu Credit Facility	215.2		6.1%	225.4		4.3%
Unamortized issuance cost	(6.9)			(7.2)
Kudu Credit Facility, carrying value	208.3			218.2






Other Operations debt	37.4		6.6%	17.1		7.5%
Unamortized issuance cost	(.7)			(.3)
Other Operations debt, carrying value	36.7			16.8
Total debt	$	575.2		$	420.9

(1) Effective rate includes the effect of the amortization of debt issuance costs and, where applicable, the original issue discount.

The following table presents a schedule of contractual repayments of White Mountains’s debt as of December 31, 2022:


Millions	December 31, 2022
Due in one year or less	$	5.4
Due in two to three years	12.6
Due in four to five years	30.7
Due after five years	542.2
Total	$	590.9

HG Global Senior Notes

On April 29, 2022, HG Global received the proceeds of its $150.0 million face value floating rate secured senior notes (the “HG Global Senior Notes”). The HG Global Senior Notes, which mature in April 2032, accrue interest at a floating rate equal to the three-month Secured Overnight Financing Rate (“SOFR”) plus 6.3% per annum. Subsequent to the five-year anniversary of the funding date, absent the occurrence of an early amortization trigger event, HG Global will make payments of principal on a quarterly basis totaling $15.0 million annually. Upon the occurrence of an early amortization trigger event, HG Global is required to use all available cash flow to repay the notes. Early amortization trigger events include scenarios in which HG Re is effectively in run off. HG Global has the option to redeem, in whole or in part, the HG Global Senior Notes after the five-year anniversary of the funding date at the outstanding principal amounts plus accrued interest.

On June 16, 2022, HG entered into an interest rate cap agreement, effective on July 25, 2022, to limit its exposure to the risk of interest rate increases on the HG Global Senior Notes. The notional amount of the interest rate cap is $150.0 million and the termination date is July 25, 2025. See Note 9 — “Derivatives.”

The HG Global Senior Notes require HG Global to maintain an interest reserve account of eight times the interest accrued for the most recent quarterly interest period. As of December 31, 2022, the interest reserve account, which is included in short-term investments, is $31.2 million.

The HG Global Senior Notes are secured by the capital stock and other equity interests of HG Global’s subsidiaries, the interest reserve account, and all cash and non-cash proceeds from the foregoing collateral. The HG Global Senior Notes contain various affirmative and negative covenants that White Mountains considers to be customary for such borrowings.

If the payments of principal and interest under the HG Global Senior Notes become subject to tax withholding on behalf of a relevant governmental authority for certain indemnified taxes, the HG Global Senior Notes require the payment of additional amounts such that the amount received by the noteholders is the same as would have been received absent the tax withholding being imposed. The HG Global Senior Notes require the payment of additional interest of 1.0% per annum if the HG Global Senior Notes receive a non-investment grade rating or are no longer rated.

As of December 31, 2022, the HG Global Senior Notes had an outstanding principal balance of $150.0 million.

Ark Subordinated Notes

In March 2007, GAIL issued $30.0 million face value of floating rate unsecured junior subordinated deferrable interest notes to Alesco Preferred Funding XII Ltd., Alesco Preferred Funding XIII Ltd. and Alesco Preferred Funding XIV Ltd (the “Ark 2007 Notes Tranche 1”) and a €12.0 million floating rate subordinated note to Dekania Europe CDO II plc (the “Ark 2007 Notes Tranche 2”) (together, the “Ark 2007 Subordinated Notes”). The Ark 2007 Notes Tranche 1, which mature in June 2037, accrue interest at a floating rate equal to the three-month U.S. LIBOR plus 4.6%. The Ark 2007 Notes Tranche 2, which matures in June 2027, accrues interest at a floating rate equal to the three-month EURIBOR plus 4.6%. During 2021, Ark repaid €12.0 million ($13.5 million based upon the foreign exchange spot rate at the date of repayment) of the outstanding principal balance on the Ark 2007 Notes Tranche 2. As of December 31, 2022, the Ark 2007 Notes Tranche 1 had an outstanding balance of $30.0 million.

In the third quarter of 2021, GAIL issued $163.3 million face value floating rate subordinated notes at par in three separate transactions for proceeds of $157.8 million, net of debt issuance costs. The Ark 2021 Subordinated Notes were issued in private placement offerings that were exempt from the registration requirements of the Securities Act of 1933. On July 13, 2021, Ark issued €39.1 million ($46.3 million based upon the foreign exchange spot rate as of the date of the transaction) face value floating rate unsecured subordinated notes (“Ark 2021 Notes Tranche 1”). The Ark 2021 Notes Tranche 1, which mature in July 2041, accrue interest at a floating rate equal to the three-month EURIBOR plus 5.75%. On August 11, 2021, Ark issued $47.0 million face value floating rate unsecured subordinated notes (“Ark 2021 Notes Tranche 2”). The Ark 2021 Notes Tranche 2, which mature in August 2041, accrue interest at a floating rate equal to the three-month U.S. LIBOR plus 5.75%. On September 8, 2021, Ark issued $70.0 million face value floating rate unsecured subordinated notes (“Ark 2021 Notes Tranche 3”). The Ark 2021 Notes Tranche 3, which mature in September 2041, accrue interest at a floating rate equal to the three-month U.S. LIBOR plus 6.1%. On the ten-year anniversary of the issue dates, the interest rate for the Ark 2021 Subordinated Notes will increase by 1.0% per annum. Ark has the option to redeem, in whole or in part, the Ark 2021 Subordinated Notes ahead of contractual maturity at the outstanding principal amounts plus accrued interest at the ten-year anniversary or any subsequent interest payment date.

All payments of principal and interest under the Ark 2021 Subordinated Notes are conditional upon GAIL’s solvency and compliance with the enhanced capital requirements of the Bermuda Monetary Authority (“BMA”). The deferral of payments of principal and interest under these conditions does not constitute a default by Ark and does not give the noteholders any rights to accelerate repayment of the Ark 2021 Subordinated Notes or take any enforcement action under the Ark 2021 Subordinated Notes.

If the payments of principal and interest under the Ark 2021 Subordinated Notes become subject to tax withholding on behalf of Bermuda or any political subdivision there, the Ark 2021 Subordinated Notes require the payment of additional amounts such that the amount received by the noteholders is the same as would have been received absent the tax withholding being imposed. The Ark 2021 Notes Tranche 3 require the payment of additional interest of 1.0% per annum upon the occurrence of a Premium Load Event until such event is remedied. Premium Load Events include the failure to meet payment obligations of the Ark 2021 Notes Tranche 3 when due, failure of GAIL to maintain an investment grade credit rating, failure to maintain 120% of GAIL’s Bermuda solvency capital requirement, failure of GAIL to maintain a debt to capital ratio below 40%, late filing of GAIL’s or Ark’s financial information, and making a restricted payment or distribution on GAIL’s common stock or other securities that rank junior or pari passu with the Ark 2021 Notes Tranche 3 when a different Premium Load Event exists or will be caused by the restricted payment.

As of December 31, 2022, the Ark 2021 Notes Tranche 1 had an outstanding balance of €39.1 million ($41.3 million based upon the foreign exchange spot rate as of December 31, 2022), the Ark 2021 Notes Tranche 2 had an outstanding balance of $47.0 million, and the Ark 2021 Notes Tranche 3 had an outstanding balance of $70.0 million.

Ark Stand By Letter of Credit Facilities

In December 2021, Ark entered into two uncommitted secured stand by letter of credit facility agreements to support the continued growth and expansion of its GAIL insurance and reinsurance operations. The stand by letter of credit facility agreements were executed with ING Bank N.V., London Branch (the “ING LOC Facility”) with capacity of $50.0 million on an uncollateralized basis and with Citibank Europe Plc (the “Citibank LOC Facility”) with capacity of $100.0 million on a collateralized basis. In September 2022, Ark entered an additional uncommitted standby letter of credit facility agreement with Lloyds Bank Corporate Markets PLC (the “Lloyds LOC Facility”) with capacity of $50.0 million on a collateralized basis.

As of December 31, 2022, the ING LOC Facility was undrawn. As of December 31, 2022, the Citibank LOC Facility and the Lloyds LOC Facility had outstanding principal balances of $53.6 million and $6.8 million and short-term investments pledged as collateral of $80.3 million and $10.0 million. Ark’s uncommitted secured stand by letter of credit facility agreements contain various representations, warranties and covenants that White Mountains considers to be customary for such borrowings.

Kudu Credit Facility and Kudu Bank Facility

During 2019, Kudu entered into a secured credit facility with Monroe Capital Management Advisors, LLC (the “Kudu Bank Facility”). On March 23, 2021, Kudu replaced the Kudu Bank Facility and entered into a secured revolving credit facility (the “Kudu Credit Facility”) with Mass Mutual to repay the Kudu Bank Facility and to fund new investments and related transaction expenses. The maximum borrowing capacity of the Kudu Credit Facility is $300.0 million. The Kudu Credit Facility matures on March 23, 2036. In connection with the replacement of the Kudu Bank Facility, Kudu recognized a total loss of $4.1 million, representing debt issuance costs and prepayment fees, which are included within interest expense for the period ended December 31, 2021.

Interest on the Kudu Credit Facility accrues at a floating interest rate equal to the greater of the three month LIBOR and 0.25%, plus in each case, the applicable spread of 4.30%. The Kudu Credit Facility requires Kudu to maintain an interest reserve account, which is included in restricted cash. As of December 31, 2022 and 2021, the interest reserve account is $12.2 million and $4.5 million. The Kudu Credit Facility requires Kudu to maintain a ratio of the outstanding balance to the sum of the fair market value of Kudu’s Participation Contracts and cash held in certain accounts (the “LTV Percentage”) of less than 50% in years 0-3, 40% in years 4-6, 25% in years 7-8, 15% in years 9-10, and 0% thereafter. As of December 31, 2022, Kudu has a 33% LTV Percentage.

Kudu may borrow undrawn balances within the initial three-year availability period, subject to customary terms and conditions, to the extent the amount borrowed under the Kudu Credit Facility does not exceed the borrowing base, which is equal to 35% of the fair value of qualifying Kudu Participation Contracts. When considering the fair value of qualifying Kudu Participation Contracts as of December 31, 2022, the available undrawn balance was $45.9 million.

The following table presents the change in debt under the Kudu Bank Facility and Kudu Credit Facility for the years ended December 31, 2022, 2021 and 2020:


	Year Ended December 31,
Millions	2022		2021		2020
Kudu Bank Facility
Beginning balance	$	—	$	89.2	$	57.0
Term loans
Borrowings	—		3.0		32.2
Repayments	—		(92.2)		—
Ending balance	$	—	$	—	$	89.2

Kudu Credit Facility
Beginning balance	$	225.4	$	—	$	—
Term loans
Borrowings	35.0		232.0		—
Repayments	(45.2)		(6.6)		—
Ending balance	$	215.2	$	225.4	$	—

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

Other Operations Debt

As of December 31, 2022, White Mountains’s Other Operations had debt with an outstanding principal balance of $36.7 million, which consisted of five secured credit facilities (collectively, “Other Operations debt”).

Compliance

As of December 31, 2022, White Mountains was in compliance, in all material respects, with all of the covenants under its debt facilities.

Interest

Total interest expense incurred by White Mountains for its indebtedness was $40.3 million, $20.5 million and $7.4 million for the years ended December 31, 2022, 2021 and 2020. Total interest paid by White Mountains for its indebtedness was $30.5 million, $13.9 million, and $6.1 million for the years ended December 31, 2022, 2021 and 2020.

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-URI https://asc.fasb.org/topic&trid=2208564

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (h)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1C
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (g)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1C
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1C
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1E
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495348-112611

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (i)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

+ Details

Income Taxes

12 Months Ended

Dec. 31, 2022

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 Bermuda Exempted Undertakings Tax Protection Act of 1966 states that the Company and its Bermuda-domiciled subsidiaries would be exempt from such tax until March 31, 2035. 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. As of December 31, 2022, the primary jurisdictions in which the Company’s subsidiaries and branches were subject to tax were 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, 2022, 2021 and 2020:


	Year Ended December 31,
Millions	2022		2021		2020
Current income tax (expense) benefit:
U.S. federal	$	(16.9)	$	(4.8)	$	(10.7)
State	(4.5)		(2.1)		(4.2)
Non-U.S.	(7.1)		(2.8)		(.8)
Total current income tax (expense) benefit	(28.5)		(9.7)		(15.7)
Deferred income tax (expense) benefit:
U.S. federal	(7.3)		(13.9)		21.0
State	(1.8)		(7.0)		10.1
Non-U.S.	(3.8)		(13.8)		(.6)
Total deferred income tax (expense) benefit	(12.9)		(34.7)		30.5
Total income tax (expense) benefit	$	(41.4)	$	(44.4)	$	14.8

Effective Rate Reconciliation

The following table presents a reconciliation of taxes calculated for 2022, 2021 and 2020 using the 21% 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	2022		2021		2020
Tax (expense) benefit at the U.S. statutory rate	$	31.4	$	57.5	$	(138.7)
Differences in taxes resulting from:
Non-U.S. earnings, net of foreign taxes	(41.2)		(78.2)		74.3
Change in valuation allowance	(19.6)		(2.0)		(26.6)
Member’s surplus contributions	(6.2)		(5.6)		(4.8)
Withholding tax	(3.1)		(.3)		(5.0)
State taxes	(2.8)		(7.3)		(8.9)
Officer compensation	(1.0)		(1.5)		(1.1)
Tax rate changes	(.4)		(10.9)		3.1



Tax exempt interest and dividends	.2		.2		.8
Reorganization	—		—		130.5
Tax reserve adjustments	—		—		1.9

Other, net	1.3		3.7		(10.7)


Total income tax (expense) benefit on pre-tax income (loss)	$	(41.4)	$	(44.4)	$	14.8

The non-U.S. component of pre-tax (loss) income was $(94.4) million, $(319.0) million and $327.8 million for the years ended December 31, 2022, 2021 and 2020. On June 10, 2021, the U.K. enacted an increase in its corporate tax rate from 19% to 25% for periods after April 1, 2023. During 2021, White Mountains increased its net U.K. deferred tax liability to reflect the higher tax rate. The reorganization benefit in 2020 resulted from the release of a deferred tax liability following an internal reorganization completed in connection with the MediaAlpha IPO.

Tax Payments and Receipts

Net income tax (refunds) payments totaled $10.3 million, $(0.1) million, and $15.9 million for the years ended December 31, 2022, 2021 and 2020.

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	2022		2021
Deferred tax assets related to:
U.S. federal and state net operating and capital loss carryforwards	$	85.4	$	85.7
Non-U.S. net operating loss carryforwards	36.1		46.1
Incentive compensation	21.4		14.5

Accrued interest	8.8		7.8
Deferred acquisition costs	8.0		6.4
Net unrealized investment losses	4.7		—
Tax credit carryforwards	1.8		.2







Other items	.5		.4
Total gross deferred tax assets	166.7		161.1
Less: valuation allowances	94.3		85.6
Total net deferred tax assets	72.4		75.5
Deferred tax liabilities related to:

Member’s surplus contributions	71.3		60.4
Purchase accounting	43.9		43.9
Investment basis difference	33.9		26.8


Deferred underwriting	9.7		4.1
Net unrealized investment gains (losses)	—		10.7
Other items	1.4		1.8
Total deferred tax liabilities	160.2		147.7
Net deferred tax asset (liability)	$	(87.8)	$	(72.2)

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

Valuation Allowance

White Mountains records a valuation allowance against deferred tax assets if it becomes more likely than not that all or a portion of a deferred tax asset will not be realized. Changes in valuation allowances from period to period are included in income tax expense in the period of change. In determining whether or not a valuation allowance, or change therein, is warranted, White Mountains considers factors such as prior earnings history, expected future earnings, carryback and carryforward periods and strategies that if executed would result in the realization of a deferred tax asset. 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 $94.3 million valuation allowance as of December 31, 2022, $56.6 million related to deferred tax assets on net operating losses in U.S. subsidiaries and other federal and state deferred tax benefits, $20.4 million related to net operating losses and other deferred tax benefits in Israeli subsidiaries, $16.0 million related to deferred tax assets on net operating losses and net investment unrealized gains and losses in Luxembourg subsidiaries and $1.3 million related to net operating losses in U.K. subsidiaries. Of the $85.6 million valuation allowance as of December 31, 2021, $38.2 million related to deferred tax assets on net operating losses in U.S. subsidiaries and other federal and state deferred tax benefits, $25.2 million related to deferred tax assets on net operating losses and net investment unrealized gains and losses in Luxembourg subsidiaries, $21.9 million related to net operating losses and other deferred tax benefits in Israeli subsidiaries and $0.3 million related to net operating losses in U.K. subsidiaries.

United States

During 2022, White Mountains recorded income tax expense of $7.8 million to reflect the increase in the valuation allowance on the net deferred tax assets for certain U.S. operations within Other Operations, as White Mountains management does not currently anticipate sufficient taxable income to utilize the remaining deferred tax assets. During 2021, White Mountains recorded income tax benefit of $(3.6) million to reflect the decrease in the valuation allowance on the net deferred tax assets for certain U.S. operations within Other Operations, as White Mountains management did not currently anticipate sufficient taxable income to utilize the remaining deferred tax assets.

During 2022 and 2021, White Mountains recorded income tax expense of $17.5 million and $7.8 million to reflect the increase in the valuation allowance on net deferred tax assets of BAM. White Mountains records both the tax expense related to BAM’s member surplus contributions (“MSC”) and the related changes in valuation allowance on such taxes directly through non-controlling interest equity. During 2022 and 2021, BAM had income included in equity due to MSC that was available to offset its loss from continuing operations. In 2022 and 2021, BAM recorded both the income tax benefit on MSC of $10.9 million and $7.5 million and the offsetting expense in paid-in surplus. During 2022 and 2021, BAM continued to have a full valuation allowance recorded against its net deferred tax assets, as White Mountains management is unsure it will generate sufficient taxable income to utilize the deferred tax assets.

During 2022, White Mountains recorded income tax expense of $4.0 million to reflect the establishment of a valuation allowance against the deferred tax assets relating to its investment in certain partnership portfolios, including Elementum Holdings LLC, and to reflect the change in the valuation allowance on deferred tax assets relating to net operating losses at the U.S. branches of the White Mountains U.K. holding companies. White Mountains management is unsure it will generate sufficient taxable income to utilize the deferred tax assets.

During 2021, White Mountains recorded income tax expense of $0.6 million to reflect the establishment of a valuation allowance against deferred tax assets relating to net operating losses at the U.S. branches of the White Mountains U.K. holding companies.

Non-U.S. Jurisdictions

During 2022 and 2021, White Mountains recorded income tax benefit of $9.2 million and $1.6 million to reflect the decrease of the full valuation allowance against 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 2022, White Mountains recorded income tax benefit of $1.5 million to reflect the decrease of the valuation allowance against the 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 2021, White Mountains recorded income tax expense of $1.9 million to reflect the increase of the 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 2022, White Mountains recorded income tax expense of $1.0 million to reflect the increase of the full valuation allowance against deferred tax assets at certain U.K. subsidiaries, as White Mountains management does not currently anticipate sufficient taxable income to utilize the deferred tax assets. During 2021, White Mountains recorded income tax benefit of $3.1 million to reflect the decrease of the valuation allowance against certain deferred tax assets at U.K. 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, 2022, the expiration dates and the deferred tax assets thereon:


	December 31, 2022
Millions	United States		Luxembourg		United Kingdom		Israel		Total

2022-2026	$	—	$	—	$	—	$	—	$	—
2027-2031	.2		—		—		—		.2
2032-2041	250.8		59.5		—		—		310.3
No expiration date	148.5		—		4.9		87.2		240.6
Total	$	399.5	$	59.5	$	4.9	$	87.2	$	551.1
Gross deferred tax asset	$	85.4	$	14.8	$	1.2	$	20.1	$	121.5
Valuation allowance	(85.4)		(14.8)		(1.2)		(20.1)		(121.5)
Net deferred tax asset	$	—	$	—	$	—	$	—	$	—

Included in the U.S. net operating loss carryforwards are losses of $0.6 million subject to limitation on utilization under the separate-return-limitation-year (SRLY) rules in the Internal Revenue Code. These loss carryforwards will begin to expire in 2028. As of December 31, 2022, there are U.K. foreign tax credit carryforwards available of $1.8 million, which do not have an expiration date.

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.

As of December 31, 2022 and 2021, White Mountains did not have any unrecognized tax benefits.

White Mountains classifies all interest and penalties on unrecognized tax benefits as part of income tax expense. During the years ended December 31, 2022, 2021 and 2020, White Mountains did not recognize any net interest (income) expense. There was no accrued interest as of December 31, 2022, 2021 and 2020.

Tax Examinations

With a few immaterial 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 2017.

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI https://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Derivatives	12 Months Ended
Derivatives	Dec. 31, 2022
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives	Derivatives HG Global Interest Rate Cap On June 16, 2022, HG entered into an interest rate cap agreement, effective on July 25, 2022, to limit its exposure to the risk of interest rate increases on the HG Global Senior Notes. The notional amount of the interest rate cap is $150.0 million and the termination date is July 25, 2025. HG paid initial premiums of $3.3 million for the interest rate cap. Under the terms of the interest rate cap agreement, if the current three-month SOFR rate at the measurement date exceeds 3.5%, HG will receive payments from the counterparty equal to the difference between the three-month SOFR rate on the determination date and 3.5%, multiplied by the notional amount of the cap based on the number of days in the quarter and a year equal to 360 days. As of December 31, 2022, the three-month SOFR rate was 4.6%. HG accounts for the interest rate cap as a derivative at fair value, with changes in fair value recognized in current period earnings within interest expense. For the year ended December 31, 2022, White Mountains recognized a gain of $0.8 million related to the change in fair value on the interest rate cap within interest expense. As of December 31, 2022, the estimated fair value of the interest rate cap recorded in other assets was $4.1 million. White Mountains classifies the interest rate cap as a Level 2 measurement.

Municipal Bond Guarantee Insurance

12 Months Ended

Dec. 31, 2022

Insurance [Abstract]

Municipal Bond Guarantee Insurance

HG Global was established to fund the startup of BAM, a mutual municipal bond insurer. HG Global, together with its subsidiaries, provided the initial capitalization of BAM through the purchase of $503.0 million of BAM Surplus Notes.

Reinsurance Treaties

FLRT

BAM is a party to a first loss reinsurance treaty (“FLRT”) with HG Re under which HG Re provides first loss protection up to 15%-of-par outstanding on each municipal bond insured by BAM. For capital appreciation bonds, par is adjusted to the estimated equivalent par value for current interest paying bonds. In return, BAM cedes approximately 60% of the risk premium charged for insuring the municipal bond, which is net of a ceding commission. The FLRT is a perpetual agreement with terms that can be renegotiated after a specified period of time. During 2021, BAM and HG Re agreed that the terms may be renegotiated at the end of 2024, and each subsequent five-year period thereafter.

Fidus Re

BAM is party to a collateralized financial guarantee excess of loss reinsurance agreement that serves to increase BAM’s claims paying resources and is provided by Fidus Re.

In 2018, Fidus Re was initially capitalized by the issuance of $100.0 million of insurance-linked securities (the “Fidus Re 2018 Agreement”). The proceeds from issuance were placed in a collateral trust supporting Fidus Re’s obligations to BAM. The insurance-linked securities were issued by Fidus Re with an initial term of 12 years and are callable five years after the date of issuance. Under the Fidus Re 2018 Agreement, Fidus Re reinsures 90% of aggregate losses exceeding $165.0 million on a portion of BAM’s financial guarantee portfolio (the “2018 Covered Portfolio”) up to a total reimbursement of $100.0 million. The Fidus Re 2018 Agreement does not provide coverage for losses in excess of $276.1 million. The 2018 Covered Portfolio consists of approximately 27% of BAM’s gross par outstanding as of December 31, 2022.

In 2021, Fidus Re issued an additional $150.0 million of insurance linked securities (the “Fidus Re 2021 Agreement”) which have an initial term of 12 years and are callable five years after the date of issuance. The proceeds from issuance were placed in a collateral trust supporting Fidus Re’s obligations to BAM. Under the Fidus Re 2021 Agreement, Fidus Re reinsures 90% of aggregate losses exceeding $135.0 million on a portion of BAM’s financial guarantee portfolio (the “2021 Covered Portfolio”) up to a total reimbursement of $150.0 million. The Fidus Re 2021 Agreement does not provide coverage for losses in excess of $301.7 million. The 2021 Covered Portfolio consists of approximately 32% of BAM’s gross par outstanding as of December 31, 2022.

In the fourth quarter of 2022, Fidus Re issued an additional $150.0 million of insurance linked securities (the “Fidus Re 2022 Agreement”) which have an initial term of 12 years and are callable seven years after the date of issuance. The proceeds from issuance were placed in a collateral trust supporting Fidus Re’s obligations to BAM. Under the Fidus Re 2022 Agreement, Fidus Re reinsures 90% of aggregate losses exceeding $110.0 million on a portion of BAM’s financial guarantee portfolio (the “2022 Covered Portfolio”) up to a total reimbursement of $150.0 million. The Fidus Re 2022 Agreement does not provide coverage for losses in excess of $276.7 million. The 2022 Covered Portfolio consists of approximately 33% of BAM’s gross par outstanding as of December 31, 2022.

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

XOLT

In January 2020, BAM entered into the XOLT with HG Re. Under the XOLT, HG Re provides last dollar protection for exposures on municipal bonds insured by BAM in excess of the New York State Department of Financial Services (“NYDFS”) single issuer limits. As of December 31, 2022, the XOLT is subject to an aggregate limit equal to the lesser of $125.0 million or the assets held in the supplemental collateral trust (the “Supplemental Trust”) at any point in time. The agreement is accounted for using deposit accounting and any related financing expenses are recorded in general and administrative expenses as the agreement does not meet the risk transfer requirements necessary to be accounted for as reinsurance.

Collateral Trusts

HG Re’s obligations under the FLRT are subject to an aggregate limit equal to the assets in two collateral trusts: the Supplemental Trust and the Regulation 114 Trust (together, the “Collateral Trusts”) at any point in time.

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 HG Re’s unearned premiums and unpaid loss and LAE reserves, if any. If, at the end of any quarter, the Regulation 114 Trust balance is below the target balance, funds will be withdrawn from the Supplemental Trust and deposited into the Regulation 114 Trust in an amount equal to the shortfall. If, at the end of any quarter, the Regulation 114 Trust balance is above 102% of the target balance, funds will be withdrawn from the Regulation 114 Trust and deposited into the Supplemental Trust. The Regulation 114 Trust balance as of December 31, 2022 and 2021 was $288.6 million and $250.2 million.

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

As the BAM Surplus Notes are repaid over time, the BAM Surplus Notes will be replaced in the Supplemental Trust by cash and fixed income securities. The Supplemental Trust balance as of December 31, 2022 and 2021 was $568.3 million and $601.8 million.

As of December 31, 2022 and 2021, the Collateral Trusts held assets of $856.9 million and $852.0 million, which included $503.3 million and $481.7 million of cash and investments, $340.0 million and $364.6 million of BAM Surplus Notes and $13.6 million and $5.7 million of interest receivable on the BAM Surplus Notes.

BAM Surplus Notes

Through 2024, the interest rate on the BAM Surplus Notes is a variable rate equal to the one-year U.S. Treasury rate plus 300 basis points, set annually. During 2023, the interest rate on the BAM Surplus Notes will be 7.7%. Beginning in 2025, the interest rate will be fixed at the higher of the then current variable rate or 8.0%. Under its agreements with HG Global, BAM is required to seek regulatory approval to pay principal and interest 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.

In December 2022, BAM made a $36.0 million cash payment of principal and interest on the BAM Surplus Notes held by HG Global. Of this payment, $24.6 million was a repayment of principal held in the Supplemental Trust, $1.0 million was a payment of accrued interest held in the Supplemental Trust and $10.4 million was a payment of accrued interest held outside the Supplemental Trust.

In December 2021, BAM made a $33.8 million cash payment of principal and interest on the BAM Surplus Notes held by HG Global. Of this payment, $23.6 million was a repayment of principal held in the Supplemental Trust, $0.4 million was a payment of accrued interest held inside the Supplemental Trust and $9.8 million was a payment of accrued interest held outside the Supplemental Trust.

As of December 31, 2022 and 2021, the principal balance on the BAM Surplus Notes was $340.0 million and $364.6 million, and total interest receivable on the BAM Surplus Notes was $157.9 million and $157.6 million.

Insured Obligations and Premiums

The following table presents a schedule of BAM’s insured obligations as of December 31, 2022 and 2021:


	December 31,
	2022		2021
Contracts outstanding	13,382		12,350
Remaining weighted average contract period (in years)	10.8		10.8
Contractual debt service outstanding (in millions):
Principal	$	99,996.9	$	89,196.5
Interest	48,880.6		41,486.5
Total debt service outstanding	$	148,877.5	$	130,683.0

Gross unearned insurance premiums (in millions)	$	298.3	$	266.3

The following table presents a schedule of BAM’s future premium revenues as of December 31, 2022:


Millions	December 31, 2022
January 1, 2023 - March 31, 2023	$	7.0
April 1, 2023 - June 30, 2023	7.0
July 1, 2023 - September 30, 2023	6.8
October 1, 2023 - December 31, 2023	6.7
	27.5
2024	25.9
2025	24.2
2026	22.6
2027	21.0
2028 and thereafter	177.1
Total gross unearned insurance premiums	$	298.3

The following table presents a schedule of written premiums and earned premiums included in White Mountains’s HG Global/BAM segment for the years ended December 31, 2022, 2021 and 2020:


	December 31,
Millions	2022		2021		2020
Written premiums:
Direct	$	63.8	$	51.0	$	61.5
Assumed	1.3		4.6		.2
Gross written premiums (1)	$	65.1	$	55.6	$	61.7
Earned premiums:
Direct	$	28.6	$	23.2	$	19.4
Assumed	4.7		3.7		3.4
Gross earned premiums (1)	$	33.3	$	26.9	$	22.8

(1) There are no ceded premium amounts in the periods presented and Gross earned premium are equivalent to net written premiums and net earned premiums.

In September 2022, BAM entered into a 100% facultative quota share reinsurance agreement under which it assumed a portfolio of municipal bond guarantee contracts with a par value of $42.5 million.

In January 2021, BAM entered into a 100% facultative quota share reinsurance agreement under which it assumed a portfolio of municipal bond guarantee contracts with a par value of $805.5 million.

In the second quarter of 2020, BAM assumed a municipal bond guarantee contract with a par value of $36.9 million through an endorsement to the facultative quota share reinsurance agreement.

None of the contracts assumed under these reinsurance agreements 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, 2022. The agreements, which cover future claims exposure only, meet the risk transfer criteria under ASC 944-20, Insurance Activities and accordingly have been accounted for as reinsurance.

Earnings Per Share

12 Months Ended

Dec. 31, 2022

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, 2022, 2021 and 2020. See Note 21 — “Held for Sale and Discontinued Operations”.


	Year Ended December 31,
	2022		2021		2020
Basic and diluted earnings per share numerators (in millions):
Net income (loss) attributable to White Mountains’s common shareholders	$	792.8	$	(275.4)	$	708.7
Less: total income (loss) from discontinued operations, net of tax (1)	903.2		(3.9)		(11.8)
Less: net (income) loss from discontinued operations attributable to non-controlling interests	(.7)		1.0		.2
Net income (loss) from continuing operations attributable to White Mountains’s common shareholders	(109.7)		(272.5)		720.3
Allocation of (earnings) losses to participating restricted common shares (2)	1.3		3.2		(9.5)


Basic and diluted earnings (losses) per share numerators	$	(108.4)	$	(269.3)	$	710.8




Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period	2,862.4		3,079.0		3,122.2
Average unvested restricted common shares (3)	(36.2)		(36.5)		(40.8)
Basic earnings (losses) per share denominator	2,826.2		3,042.5		3,081.4
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period	2,862.4		3,079.0		3,122.2
Average unvested restricted common shares (3)	(36.2)		(36.5)		(40.8)

Diluted earnings (losses) per share denominator	2,826.2		3,042.5		3,081.4
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)	(39.34)		(89.52)		229.69
Basic and diluted earnings (losses) per share	$	(38.34)	$	(88.52)	$	230.69

(1) Includes net income (loss) from discontinued operations, net of tax - NSM Group, net gain (loss) from sale of discontinued operations, net of tax - NSM Group and net gain (loss) from sale of discontinued operations, net of tax - Sirius Group. See Note 21 — “Held for Sale and Discontinued Operations.”

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

(3) Restricted shares outstanding vest upon a stated date. See Note 12 — “Employee Share-Based Incentive Compensation Plans”.

The following table presents the undistributed net earnings (losses) from continuing operations for the years ended December 31, 2022, 2021 and 2020. See Note 21 — “Held for Sale and Discontinued Operations”.


	Year Ended December 31,
Millions		2022		2021		2020
Undistributed net earnings - continuing operations:
Net income (loss) attributable to White Mountains’s common shareholders, net of restricted common share amounts		$	(108.4)	$	(269.3)	$	710.8
Dividends declared, net of restricted common share amounts (1)		(3.0)		(3.1)		(3.1)
Total undistributed net earnings (losses), net of restricted common share amounts		$	(111.4)	$	(272.4)	$	707.7

(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, 2022

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

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.

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, 2022, 2021 and 2020 for performance shares granted under the WTM Incentive Plan:


	Year Ended December 31,
	2022			2021			2020
$ in Millions	Target Performance Shares Outstanding	Accrued Expense		Target Performance Shares Outstanding	Accrued Expense		Target Performance Shares Outstanding	Accrued Expense
Beginning of period	40,828	$	42.2	42,458	$	56.3	42,473	$	43.7
Shares paid or expired (1)	(14,625)	(26.4)		(14,336)	(35.2)		(14,070)	(27.7)
New grants	13,225	—		13,475	—		14,055	—
Forfeitures and cancellations (2)	21	(.4)		(769)	.4		—	(.4)

Expense recognized	—	52.1		—	20.7		—	40.7
End of period	39,449	$	67.5	40,828	$	42.2	42,458	$	56.3

(1)WTM performance share payments in 2022 for the 2019-2021 performance cycle, which were paid in March 2022 at 172% of target. WTM performance share payments in 2021 for the 2018-2020 performance cycle, which were paid in March 2021 at 200% of target. WTM performance share payments in 2020 for the 2017-2019 performance cycle, which were paid in March 2020, ranged from 174% to 180% of target.

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

During 2022, White Mountains granted 13,225 performance shares for the 2023-2025 performance cycle. During 2021, White Mountains granted 13,475 performance shares for the 2022-2024 performance cycle. During 2020, White Mountains granted 14,055 performance shares for the 2020-2022 performance cycle.

For the 2019-2021 performance cycle, the Company issued common shares for 750 performance shares earned and all other performance shares earned were settled in cash. For the 2018-2020 and 2017-2019 performance cycles, all performance shares earned were settled in cash. If the outstanding performance shares had vested on December 31, 2022, the total additional compensation cost to be recognized would have been $36.7 million, based on accrual factors as of December 31, 2022 (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, 2022 for each performance cycle:


	December 31, 2022
$ in Millions	Target Performance Shares Outstanding	Accrued Expense
Performance cycle:
2022 – 2024	13,225	$	11.0
2021 – 2023	13,475	19.7
2020 – 2022	13,350	37.8
Sub-total	40,050	68.5
Assumed forfeitures	(601)	(1.0)
Total	39,449	$	67.5

For the 2022-2024 performance cycle, the targeted performance goal for full payment of outstanding performance shares granted under the WTM Incentive Plan is 9% average annual growth in adjusted book value per share and intrinsic value per share. Average annual growth of 4% or less would result in no payout and average annual growth of 14% or more would result in a payout of 200%.

For the 2021-2023 performance cycle, the targeted performance goal for full payment of outstanding performance shares granted under the WTM Incentive Plan is 8% average annual growth in adjusted book value per share and intrinsic value per share. Average annual growth of 3% or less would result in no payout and average annual growth of 13% or more would result in a payout of 200%.

For the 2020-2022 performance cycle, the targeted performance goal for full payment of outstanding performance shares granted under the WTM Incentive Plan is 7% average annual growth in adjusted book value per share and intrinsic value per share. Average annual growth of 2% or less would result in no payout and average annual growth of 12% or more would result in a payout of 200%.

Restricted Shares

Restricted shares are grants of a specified number of common shares that generally vest at the end of a 34-month service period. The following table presents the unrecognized compensation cost associated with the outstanding restricted share awards under the WTM Incentive Plan for the years ended December 31, 2022, 2021 and 2020:


	Year Ended December 31,
	2022			2021			2020
$ 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	37,850	$	15.9	43,105	$	15.2	43,395	$	16.7
Issued	13,225	13.8		13,475	16.1		14,055	15.1
Vested	(12,725)	—		(17,936)	—		(14,345)	—
Forfeited	—	—		(794)	(.8)		—	—

Expense recognized	—	(14.2)		—	(14.6)		—	(16.6)
End of period	38,350	$	15.5	37,850	$	15.9	43,105	$	15.2

During 2022, White Mountains issued 13,225 restricted shares that vest on January 1, 2025. During 2021, White Mountains issued 13,475 restricted shares that vest on January 1, 2024. During 2020, White Mountains issued 14,055 restricted shares that vest on January 1, 2023. The unamortized issue date fair value as of December 31, 2022 is expected to be recognized ratably over the remaining vesting periods.

Leases

12 Months Ended

Dec. 31, 2022

Leases [Abstract]

Leases

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

As of December 31, 2022 and 2021, the right-of-use (“ROU”) asset was $25.2 million and $28.1 million and lease liabilities were $27.1 million and $30.0 million.

The following table summarizes net lease expense recognized in White Mountains’s consolidated statement of operations for the years ended December 31, 2022 and 2021:


	December 31,
Millions	2022		2021
Lease cost	$	8.0	$	6.7
Less: sublease income	.7		.4
Net lease cost	$	7.3	$	6.3

The following table presents the contractual maturities of the lease liabilities associated with White Mountains’s operating lease agreements as of December 31, 2022:


Millions	December 31, 2022
2023	$	8.7
2024	7.6
2025	5.1
2026	2.8
2027	1.6
Thereafter	3.9
Total undiscounted lease payments	29.7
Less: present value adjustment	(2.6)
Operating lease liability	$	27.1

The following table presents lease related assets and liabilities by reportable segment as of December 31, 2022 and 2021:


	As of December 31, 2022
$ in Millions	HG/BAM		Ark		Kudu		Other Operations		Total		Weighted Average Incremental Borrowing Rate (1)
ROU lease asset	$	5.7	$	6.6	$	5.8	$	7.1	$	25.2	4.1%
Lease liability	$	6.2	$	6.6	$	6.5	$	7.8	$	27.1

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


	As of December 31, 2021
$ in Millions	HG/BAM		Ark		Kudu		Other Operations		Total		Weighted Average Incremental Borrowing Rate (1)
ROU lease asset	$	7.6	$	7.0	$	6.4	$	7.1	28.1		4.0%
Lease liability	$	8.1	$	7.0	$	7.1	$	7.8	$	30.0

(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, 2022

Stockholders' Equity Note [Abstract]

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, 2022, White Mountains may repurchase an additional 320,550 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 2022, the Company repurchased 461,256 common shares for $615.8 million at an average share price of $1,335.11, which included 129,450 common shares repurchased under the board authorizations for $150.9 million at an average share price of $1,165.84 and 4,011 to satisfy employee income tax withholding pursuant to employee benefit plans. In addition, on September 26, 2022, the Company completed a self-tender offer, through which it repurchased 327,795 of its common shares at a purchase price of $1,400.00 per share for a total cost of approximately $460.8 million, including expenses.

During 2021, the Company repurchased 98,511 common shares for $107.5 million at an average share price of $1,091.29, which was comprised of 91,293 common shares repurchased under the board authorizations for $100.0 million at an average share price of $1,095.37 and 7,218 common shares repurchased to satisfy employee income tax withholding pursuant to employee benefit plans.

During 2020, the Company repurchased 99,087 common shares for $85.1 million at an average share price of $858.81, which was comprised of 93,188 common shares repurchased under the board authorizations for $78.5 million at an average share price of $1,115.51 and 5,899 common shares repurchased to satisfy employee income tax withholding pursuant to employee benefit plans.

Common Shares Issued

During 2022, the Company issued a total of 15,640 common shares, which consisted of 13,225 restricted shares issued to key personnel and 2,415 shares issued to directors of the Company.

During 2021, the Company issued a total of 15,066 common shares, which consisted of 13,475 restricted shares issued to key personnel and 1,591 shares issued to directors of the Company.

During 2020, the Company issued a total of 15,745 common shares, which consisted of 14,055 restricted shares issued to key personnel, 1,440 shares issued to directors of the Company and 250 shares issued to MediaAlpha’s management.

Dividends on Common Shares

For the years ended December 31, 2022, 2021 and 2020, the Company declared and paid cash dividends totaling $3.0 million, $3.1 million and $3.2 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, 2022 and 2021:


	December 31, 2022				December 31, 2021
$ in Millions	Non-controlling Percentage (1)		Non-controlling Equity		Non-controlling Percentage (1)		Non-controlling Equity
Non-controlling interests, excluding BAM
HG Global	3.1	%	$	(.6)	3.1	%	$	8.9
Ark	28.0	%	247.9		28.0	%	230.7
Kudu	10.8	%	75.1		2.5	%	12.4
NSM (2)	—	%	—		3.5	%	16.7


Other	various		20.4		various		11.9
Total, excluding BAM			342.8				280.6

BAM	100.0	%	(154.7)		100.0	%	(124.0)
Total non-controlling interests			$	188.1			$	156.6

(1) The non-controlling percentage represents the basic ownership interests held by non-controlling shareholders with the exception of HG Global, for which the non-controlling percentage represents the preferred share ownership held by non-controlling shareholders.

(2) As a result of the NSM Transaction, NSM has been classified as discontinued operations through the closing of the transaction. See Note 21 — “Held for Sale and Discontinued Operations.”

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Statutory Capital and Surplus	12 Months Ended
Statutory Capital and Surplus	Dec. 31, 2022
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 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, 2022, HG Re had statutory capital and surplus of $730.8 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, 2022, 2021 and 2020 was $55.0 million, $49.3 million and $59.3 million. BAM’s statutory surplus, as reported to regulatory authorities as of December 31, 2022, was $283.4 million, which exceeds the minimum statutory surplus necessary for BAM to maintain its New York State financial guarantee insurance license of $66.0 million. Ark Syndicates 4020 and 3902 are subject to oversight by the Council of Lloyd’s. Ark Syndicate Management Limited (“ASML”) is authorized by the U.K.’s Prudential Regulation Authority and regulated by the Financial Conduct Authority under the Financial Services and Markets Act 2000. The underwriting capacity of a Member of Lloyd’s must be supported by providing a deposit in the form of cash, securities or letters of credit in an amount determined under the capital adequacy regime of the U.K.’s Prudential Regulation Authority (the “PRA”). This amount is determined by Lloyd’s and is based on each syndicate’s solvency and capital requirement as calculated through its internal model. In addition, if the Funds at Lloyd’s are not sufficient to cover all losses, the Lloyd’s Central Fund provides an additional discretionary level of security for policyholders. As of December 31, 2022, Ark had provided Funds at Lloyd’s of $325.4 million. GAIL is subject to regulation and supervision by the BMA. As of December 31, 2022, GAIL had statutory capital and surplus of $877.6 million. GAIL’s minimum statutory capital and surplus requirement established by the BMA was $419.7 million as of December 31, 2022. WM Outrigger Re WM Outrigger Re is a special purpose insurer under Bermuda insurance regulations and is subject to regulation and supervision by the BMA. As of December 31, 2022, WM Outrigger Re had statutory capital and surplus of $204.0 million. As a special purpose insurer, WM Outrigger Re has a nominal minimum regulatory capital requirement of $1. 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 insurance and reinsurance subsidiaries: HG Global/BAM 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, 2022, HG Re had $9.3 million of cash and investments and $111.7 million of accrued interest on the BAM Surplus Notes held outside the Collateral Trusts. As of December 31, 2022, HG Re had $730.8 million of statutory capital and surplus and $856.9 million of assets held in the Collateral Trusts. Under its agreements with HG Global, BAM is required to seek regulatory approval to pay principal and interest 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. In December 2022, BAM made a $36.0 million cash payment of principal and interest on the BAM Surplus Notes held by HG Global. Of this payment, $24.6 million was a repayment of principal held in the Supplemental Trust, $1.0 million was a payment of accrued interest held in the Supplemental Trust and $10.4 million was a payment of accrued interest held outside the Supplemental Trust. In December 2021, BAM made a $33.8 million cash payment of principal and interest on the BAM Surplus Notes held by HG Global. Of this payment, $23.6 million was a repayment of principal held in the Supplemental Trust, $0.4 million was a payment of accrued interest held in the Supplemental Trust and $9.8 million was a payment of accrued interest held outside the Supplemental Trust. Ark During any 12-month period, GAIL, a class 4 licensed Bermuda insurer, has the ability to (i) make capital distributions of up to 15% of its total statutory capital per the previous year’s statutory financial statements, or (ii) make dividend payments of up to 25% of its total statutory capital and surplus per the previous year’s statutory financial statements, without prior approval of Bermuda regulatory authorities. Accordingly, GAIL will have the ability to make capital distributions of up to $113.2 million during 2023, which is equal to 15% of its December 31, 2022 statutory capital of $754.7 million, subject to meeting all appropriate liquidity and solvency requirements and the filing of its December 31, 2022 statutory financial statements. During 2022, GAIL did not pay any dividends to its immediate parent.

Segment Information

12 Months Ended

Dec. 31, 2022

Segment Reporting [Abstract]

Segment Information

As of December 31, 2022, White Mountains conducted its operations through three reportable segments: (1) HG Global/BAM, (2) Ark, and (3) Kudu, with our remaining operating businesses, holding companies and other assets included in Other Operations. White Mountains has made its segment determination based on consideration of the following criteria: (i) the nature of the business activities of each of the Company’s subsidiaries and affiliates; (ii) the manner in which the Company’s subsidiaries and affiliates are organized; (iii) the existence of primary managers responsible for specific subsidiaries and affiliates; and (iv) the organization of information provided to the chief operating decision makers and the Board of Directors. Significant intercompany transactions among White Mountains’s segments have been eliminated herein.

As a result of the NSM Transaction, the results of operations for NSM, previously reported as a segment, have been classified as discontinued operations in the statements of operations and comprehensive income through the closing of the transaction. Prior period amounts have been reclassified to conform to the current period’s presentation. See Note 21 — “Held for Sale and Discontinued Operations.”

As a result of the Ark Transaction, White Mountains began consolidating Ark in its financial statements as of January 1, 2021. See Note 2 — “Significant Transactions”.

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


Millions	HG Global/BAM (1)		Ark		Kudu		Other Operations		Total
Year Ended December 31, 2022
Earned insurance premiums (2)	$	33.3	$	1,043.4	$	—	$	—	$	1,076.7
Net investment income	21.5		16.3		54.4		32.2		124.4

Net realized and unrealized investment gains (losses)	(105.8)		(55.2)		64.1		(1.6)		(98.5)
Net realized and unrealized investment gains (losses) from investment in MediaAlpha	—		—		—		(93.0)		(93.0)
Commission revenues	—		—		—		11.5		11.5
Other revenues	4.6		5.0		—		127.2		136.8
Total revenues	(46.4)		1,009.5		118.5		76.3		1,157.9

Loss and loss adjustment expenses	—		536.4		—		—		536.4
Insurance acquisition expenses	11.2		239.4		—		—		250.6

Cost of sales	—		—		—		98.6		98.6
General and administrative expenses	69.1		123.5		14.4		169.2		376.2


Amortization of other intangible assets	—		—		.3		4.9		5.2

Interest expense	8.3		15.1		15.0		1.9		40.3
Total expenses	88.6		914.4		29.7		274.6		1,307.3
Pre-tax income (loss)	$	(135.0)	$	95.1	$	88.8	$	(198.3)	$	(149.4)

(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) Ark’s earned insurance premiums based on the location of Ark’s underwriting offices in the United Kingdom and Bermuda are $638.5 and $404.9.


Millions	HG Global/BAM (1)		Ark		Kudu		Other Operations		Total
Year Ended December 31, 2021
Earned insurance premiums (2)	$	26.9	$	637.3	$	—	$	—	$	664.2
Net investment income	17.5		2.9		43.9		18.2		82.5

Net realized and unrealized investment gains (losses)	(22.9)		16.5		89.9		50.7		134.2
Net realized and unrealized investment gains (losses) from investment in MediaAlpha	—		—		—		(380.3)		(380.3)

Commission revenues	—		—		—		9.6		9.6
Other revenues	1.5		11.8		.2		90.7		104.2
Total revenues	23.0		668.5		134.0		(211.1)		614.4
Losses and loss adjustment expenses	—		314.8				—		314.8
Insurance acquisition expenses	8.3		178.0		—		—		186.3

Cost of sales	—		—		—		69.3		69.3
General and administrative expenses	57.1		115.5		14.5		105.4		292.5


Amortization of other intangible assets	—		—		.3		4.3		4.6
Interest expense	—		7.3		11.7		1.5		20.5
Total expenses	65.4		615.6		26.5		180.5		888.0
Pre-tax income (loss)	$	(42.4)	$	52.9	$	107.5	$	(391.6)	$	(273.6)

(2) Ark’s earned insurance premiums based on the location of Ark’s underwriting offices in the United Kingdom and Bermuda are $459.3 and $178.0.


Millions	HG Global/BAM (1)		Kudu		Other Operations		Total
Year Ended December 31, 2020
Earned insurance premiums	$	22.8	$	—	$	—	$	22.8
Net investment income	19.5		29.5		82.0		131.0
Net realized and unrealized investment gains (losses)	23.7		15.9		(8.8)		30.8
Net realized and unrealized investment gains from investment in MediaAlpha	—		—		686.0		686.0

Commission revenues	—		—		8.3		8.3
Other revenues	2.5		.3		13.9		16.7
Total revenues	68.5		45.7		781.4		895.6

Insurance acquisition expenses	7.0		—		—		7.0

Cost of sales	—		—		11.3		11.3
General and administrative expenses	56.8		11.8		139.3		207.9


Amortization of other intangible assets	—		.3		1.3		1.6
Interest expense	—		6.0		1.4		7.4
Total expenses	63.8		18.1		153.3		235.2
Pre-tax income (loss)	$	4.7	$	27.6	$	628.1	$	660.4


Millions Selected Balance Sheet Data	HG Global/BAM			Ark		Kudu		Other Operations			Held for Sale		Total
December 31, 2022:
Total investments	$	975.8		$	1,761.9	$	695.9	$	1,736.4		$	—	$	5,170.0


Total assets	$	1,058.5	(1)	$	3,486.2	$	825.9	$	2,018.7	(2)	$	—	$	7,389.3


Total liabilities	$	501.8	(2)	$	2,520.9	$	273.3	$	158.3		$	—	$	3,454.3
Total White Mountains’s common shareholders’ equity	$	712.0	(2)	$	717.4	$	477.5	$	1,840.0	(2)	$	—	$	3,746.9
Non-controlling interest	$	(155.3)		$	247.9	$	75.1	$	20.4		$	—	$	188.1
December 31, 2021:
Total investments	$	966.5		$	1,562.1	$	669.5	$	1,059.4		$	—	$	4,257.5


Total assets	$	1,044.8	(1)	$	3,027.0	$	727.1	$	1,196.7	(2)	$	1,005.1	$	7,000.7


Total liabilities	$	321.9	(2)	$	2,122.4	$	261.0	$	95.4		$	495.3	$	3,296.0
Total White Mountains’s common shareholders’ equity	$	838.0	(2)	$	673.9	$	453.7	$	1,089.4	(2)	$	493.1	$	3,548.1
Non-controlling interest	$	(115.1)		$	230.7	$	12.4	$	11.9		$	16.7	$	156.6

(1) As of December 2022 and 2021, total assets in the HG Global/BAM segment reflected the elimination of $340.0 and $364.6 of BAM Surplus Notes issued to HG Global and its subsidiaries, and $157.9 and $157.6 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 Other Operations and therefore added back to White Mountains’s common shareholders’ equity within the HG Global/BAM segment. As of December 31, 2022 and 2021, the HG Global preferred dividends payable to White Mountains’s subsidiaries was $341.4 and $400.5.

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8924-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8981-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Section 50
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-Subparagraph (f)
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Subparagraph (e)
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8844-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 32
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org/topic&trid=2134510

+ Details

Equity Method Eligible Investments

12 Months Ended

Dec. 31, 2022

Equity Method Investments and Joint Ventures [Abstract]

Equity Method Eligible Investments

White Mountains’s equity method eligible investments include Kudu’s Participation Contracts, White Mountains’s investment in MediaAlpha, PassportCard/DavidShield, Elementum Holdings, L.P. and certain other unconsolidated entities, 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 ownership interests and carrying values of equity method eligible investments as of December 31, 2022 and 2021:


	December 31, 2022				December 31, 2021
$ in Millions	Ownership Interest		Carrying Value		Ownership Interest		Carrying Value
Kudu Participation Contracts (1)	4.1 - 30.0%		$	695.9	3.2 - 32.0%		$	669.5
Investment in MediaAlpha	27.1	%	168.6		28.0	%	261.6
PassportCard/DavidShield	53.8	%	135.0		53.8	%	120.0
Elementum Holdings, L.P.	29.7	%	30.0		29.7	%	45.0
Other equity method eligible investments, at fair value	Under 50.0%		84.4		Under 50.0%		109.3
Other equity method eligible investments, at fair value	50.0% and over		—		50.0% and over		17.8

(1) Ownership interest generally references basic ownership interest with the exception of Kudu’s Participation Contracts, which are non-controlling equity interests in the form of revenue and earnings participation contracts.

For the years ended December 31, 2022, 2021 and 2020, White Mountains received dividend and income distributions from equity method eligible investments of $68.9 million, $56.2 million and $95.0 million, which were recorded within net investment income in the consolidated statement of operations.

Subsequent to the MediaAlpha IPO, White Mountains’s investment in MediaAlpha is accounted for at fair value based on the publicly traded share price of MediaAlpha’s common stock and White Mountains presents its investment in MediaAlpha as a separate line item on the balance sheet. See Note 2 — “Significant Transactions.

For the years ended December 31, 2021 and 2020, MediaAlpha was considered a significant subsidiary. The following tables present summarized financial information for MediaAlpha as of December 31, 2022 and 2021 for the years ended December 31, 2022, 2021, and 2020:


	December 31,
Millions	2022		2021
Balance sheet data:
Total assets	$	170.1	$	289.8
Total liabilities	$	256.2	$	351.4


	Year Ended December 31,
Millions	2022		2021		2020
Income statement data:
Total revenues	$	459.1	$	645.3	$	584.8
Total expenses	$	531.5	$	653.8	$	574.2
Net income (loss)	$	(72.4)	$	(8.5)	$	10.6

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


	December 31,
Millions	2022		2021
Balance sheet data(1):
Total assets	$	2,252.5	$	1,845.7
Total liabilities	$	526.9	$	373.4

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


	Year Ended December 31,
Millions	2022		2021		2020
Income statement data(1):
Total revenues	$	735.3	$	987.4	$	526.5
Total expenses	$	515.9	$	418.7	$	325.9
Net income (loss)	$	219.4	$	568.7	$	200.6

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

Variable Interest Entities	12 Months Ended
Variable Interest Entities	Dec. 31, 2022
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 an 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. 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 approximately 60% of the risk premium charged for insuring the municipal bond, net of a ceding commission. HG Re’s obligations under the FLRT are subject to an aggregate limit equal to the assets in the Regulation 114 Trust and the Supplemental Trust 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 and therefore does not consolidate Elementum. White Mountains’s ownership interest gives White Mountains the ability 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 net realized and unrealized investment gains (losses). As of December 31, 2022, White Mountains’s maximum exposure to loss on its limited partnership interest in Elementum is the carrying value of $30.0 million. PassportCard/DavidShield On January 24, 2018, White Mountains acquired a 50.0% ownership interest in DavidShield, its joint venture partner in 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 50.0% 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/DavidShield. The gross purchase price for the 50.0% interest in DavidShield was $41.8 million, or $28.3 million net of the financing provided for the restructuring. On May 7, 2020, White Mountains made an additional $15.0 million investment in PassportCard/DavidShield to support operations through the ongoing COVID-19 pandemic. The transaction increased White Mountains’s ownership interest from 50.0% to 53.8%, but had no impact on the governance structure of the companies, including White Mountains’s board representation or other investor rights. The governance structures for both PassportCard and DavidShield were designed to give White Mountains and its co-investor equal power to make the decisions that most significantly impact operations. As a result of the transaction, White Mountains’s re-evaluated its accounting treatment for its investment in PassportCard/DavidShield. Because White Mountains does not have the unilateral power to direct the operations of PassportCard or DavidShield, White Mountains does not hold a controlling financial interest and does not consolidate either entity. White Mountains’s ownership interest gives White Mountains the ability to exert significant influence over the significant financial and operating activities of PassportCard/DavidShield. Accordingly, White Mountains’s investment in PassportCard/DavidShield meets the criteria to be accounted for under the equity method. White Mountains has taken the fair value option for its investment in PassportCard/DavidShield. Changes in the fair value of PassportCard/DavidShield are recorded in net realized and unrealized investment gains (losses). As of December 31, 2022, White Mountains’s maximum exposure to loss on its equity investment in PassportCard/DavidShield and the non-interest-bearing loan to its partner is the total carrying value of $144.6 million. WM Outrigger Re During the fourth quarter of 2022, Ark sponsored the formation of Outrigger Re Ltd., a Bermuda company registered as a special purpose insurer and segregated accounts company, to provide collateralized reinsurance protection on Ark’s Bermuda global property catastrophe excess of loss portfolio written in calendar year 2023. Within Outrigger Re Ltd., distinct segregated accounts are formed and capitalized in order to enter into reinsurance agreements with GAIL. On December 20, 2022, Outrigger Re Ltd. issued non-voting redeemable preference shares on behalf of four segregated accounts to White Mountains and unrelated third party investors. White Mountains purchased 100% of the preference shares issued by its segregated account, WM Outrigger Re, for $205.0 million. Outrigger Re Ltd. and WM Outrigger Re were determined to be VIEs. White Mountains is the primary beneficiary of WM Outrigger Re, as it has both the power to direct the activities that most significantly impact WM Outrigger Re’s economic performance and the obligation to absorb losses, or the right to receive returns, that could potentially be significant to WM Outrigger Re. As a result, White Mountains consolidates WM Outrigger Re’s results in its financial statements. The assets of WM Outrigger Re can only be used to settle the liabilities of WM Outrigger Re, and there is no recourse to the Company for any creditors of WM Outrigger Re. White Mountains is not the primary beneficiary of Outrigger Re Ltd. or the other segregated accounts. Limited Partnerships White Mountains investments in limited partnerships are generally considered VIEs because the limited partnership interests do not have substantive kick-out rights or participating rights. White Mountains does not have the unilateral power to direct the operations of these limited partnerships, and therefore White Mountains is not the primary beneficiary and does not consolidate the limited partnerships. White Mountains has taken the fair value option for its investments in limited partnerships, which are generally measured at NAV as the practical expedient. As of December 31, 2022, White Mountains’s maximum exposure to loss on its investments in limited partnerships is the carrying value of $140.6 million.

Fair Value of Financial Instruments

12 Months Ended

Dec. 31, 2022

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. See Note 7 — “Debt”.

The following table presents the fair value and carrying value of these financial instruments as of December 31, 2022 and 2021:


	December 31, 2022				December 31, 2021
Millions	Fair Value		Carrying Value		Fair Value		Carrying Value
HG Global Senior Notes	$	155.7	$	146.5	$	—	$	—
Ark 2007 Subordinated Notes	$	28.4	$	30.0	$	27.6	$	30.0
Ark 2021 Subordinated Notes	$	163.1	$	153.7	$	162.8	$	155.9
Kudu Credit Facility	$	223.9	$	208.3	$	246.8	$	218.2
Other Operations debt	$	38.2	$	36.7	$	17.7	$	16.8

The fair value estimates for the HG Global Senior Notes, Ark 2007 Subordinated Notes, Ark 2021 Subordinated Notes, Kudu Credit Facility and Other Operations debt have been determined based on a discounted cash flow approach and are considered to be Level 3 measurements.

For the fair value level measurements associated with White Mountains’s investment securities. See Note 3 — “Investment Securities.” For the fair value level measurements associated with White Mountains’s derivative instruments. See Note 9 — “Derivatives.”

- Definition

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

+ References + Details

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Contingencies White Mountains, and the insurance industry in general, is routinely subject to claims related litigation and arbitration in the normal course of business, as well as litigation and arbitration that do not arise from, nor are directly related to, claims activity. White Mountains’s estimates of the costs of settling matters routinely encountered in claims activity are reflected in the reserves for unpaid loss and LAE. See Note 5 — “Losses and Loss Adjustment Expense Reserves.” White Mountains considers the requirements of ASC 450 when evaluating its exposure to non-claims related litigation and arbitration. ASC 450 requires that accruals be established for litigation and arbitration if it is probable that a loss has been incurred and it can be reasonably estimated. ASC 450 also requires that litigation and arbitration be disclosed if it is probable that a loss has been incurred or if there is a reasonable possibility that a loss may have been incurred. White Mountains does not have any current non-claims related litigation that may have a material adverse effect on White Mountains’s financial condition, results of operations or cash flows.

Held for Sale and Discontinued Operations

12 Months Ended

Dec. 31, 2022

Discontinued Operations and Disposal Groups [Abstract]

Held for Sale and Discontinued Operations

NSM

On August 1, 2022, White Mountains closed the NSM Transaction. See Note 2 — “Significant Transactions.” As a result of the NSM Transaction, the assets and liabilities of NSM Group have been presented in the balance sheet as held for sale for periods prior to the closing of the transaction, and the results of operations for NSM Group have been classified as discontinued operations in the statements of operations and comprehensive income through the closing of the transaction. Prior period amounts have been reclassified to conform to the current period’s presentation.

Sirius Group

On April 18, 2016, White Mountains completed the sale of Sirius International Insurance Group, Ltd. (“Sirius Group”) to CM International Pte. Ltd. and CM Bermuda Limited (collectively “CMI”). In connection with the sale, White Mountains indemnified Sirius Group against the loss of certain interest deductions claimed by Sirius Group related to periods prior to the sale of Sirius Group to CMI that had been disputed by the Swedish Tax Agency (STA). In late October 2018, the Swedish Administrative Court ruled against Sirius Group on its appeal of the STA’s denial of these interest deductions. As a result, in 2018 White Mountains recorded a loss of $17.3 million within net (loss) gain on sale of discontinued operations reflecting the value of these interest deductions.

As of December 31, 2020, White Mountains’s liability related to the tax indemnification provided in connection with the sale of Sirius Group in 2016 was $18.7 million. In April 2021, the Swedish Tax Agency informed the Swedish Administrative Court of Appeal that Sirius Group should prevail in its appeal and that the interest deductions should not be disallowed. In June 2021, the Swedish Administrative Court of Appeal ruled in Sirius Group’s favor. For the year ended December 31, 2021, White Mountains recorded a gain of $17.6 million in discontinued operations to reverse the liability accrued as of December 31, 2020 and $1.1 million gain related to foreign currency translation.

Other

As of December 31, 2021, White Mountains classified one of the Other Operating Businesses, which included $16.1 million of insurance licenses, investments and cash, as assets held for sale. On May 12, 2022, the Other Operating Business was sold for $19.5 million and White Mountains recorded a $3.7 million realized gain in other revenues within Other Operations.

Summary of Reclassified Balances and Related Items

Net Assets Held for Sale

The following summarizes the assets and liabilities associated with NSM Group classified as held for sale. As of December 31, 2021, the amounts presented exclude $16.1 million of insurance licenses, investments and cash classified as assets held for sale related to one of the Other Operating Businesses.


Millions	December 31, 2021
Assets held for sale
Short-term investments, at fair value	$	7.8
Cash (restricted $89.2)	111.6
Premiums and commissions receivable	85.0
Goodwill and other intangible assets	725.4
Other assets	59.2

Total assets held for sale	$	989.0
Liabilities held for sale
Debt	$	272.1
Premiums payable	135.9
Contingent consideration	6.8
Other liabilities	80.5
Total liabilities held for sale	495.3
Net assets held for sale	$	493.7

Net Income (Loss) from Discontinued Operations

The following summarizes the results of operations, including related income taxes associated with the businesses classified as discontinued operations for the year ended December 31, 2022, 2021 and 2020:


	December 31,
Millions	2022 (1)		2021		2020
Revenues
Commission revenues	$	176.9	$	258.0	$	232.5
Other revenues	48.1		72.4		52.6
Total revenues - NSM Group	225.0		330.4		285.1
Expenses
General and administrative expenses	126.8		190.4		179.5
Broker commission expenses	52.9		80.2		75.3
Change in fair value of contingent consideration	.1		1.0		(3.3)
Amortization of other intangible assets	9.1		35.2		26.7
Loss on assets held for sale	—		28.7		—
Interest expense	12.1		23.3		22.1
Total expenses - NSM Group	201.0		358.8		300.3
Pre-tax income (loss) from discontinued operations - NSM Group	24.0		(28.4)		(15.2)
Income tax (expense) benefit	(7.6)		5.8		5.7
Net income (loss) from discontinued operations, net tax - NSM Group	16.4		(22.6)		(9.5)
Net gain (loss) from sale of discontinued operations, net of tax - NSM Group	886.8		—		—
Net gain (loss) from sale of discontinued operations, net of tax - Sirius Group	—		18.7		(2.3)
Total income (loss) from discontinued operations, net of tax	903.2		(3.9)		(11.8)
Net (income) loss from discontinued operations attributable to non-controlling interests	(.7)		1.0		$	.2
Total income (loss) from discontinued operations attributable to White Mountains’s common shareholders	902.5		(2.9)		(11.6)
Other comprehensive income (loss) from discontinued operations, net of tax - NSM Group	(5.2)		.2		5.9
Net gain (loss) from foreign currency translation from sale of discontinued operations, net of tax - NSM Group	2.9		—		—
Comprehensive income (loss) from discontinued operations	900.2		(2.7)		(5.7)
Other comprehensive (income) loss from discontinued operations attributable to non-controlling interests	.2		(.1)		(.3)
Comprehensive income (loss) from discontinued operations attributable to White Mountains’s common shareholders	$	900.4	$	(2.8)	$	(6.0)

(1) As a result of the NSM Transaction, the results of operations for NSM Group are presented for the period from January 1, 2022 to August 1, 2022.

Net Change in Cash from Discontinued Operations

The following summarizes the net change in cash associated with the businesses classified as discontinued operations for the year ended December 31, 2022, 2021 and 2020:


	Year Ended December 31,
Millions	2022		2021		2020
Net cash provided from (used for) operations	$	38.7	$	42.3	$	35.5
Net cash provided from (used for) investing activities	7.1		(56.5)		(124.9)
Net cash used from (used for) financing activities	(17.5)		(1.0)		128.8
Effect of exchange rate changes on cash	4.0		.2		(2.8)
Net change in cash during the period	32.3		(15.0)		36.6
Cash balances at beginning of period (includes restricted cash of $89.2, $78.4 and $56.3)	111.6		126.6		90.0
Cash sold as part of the sale of NSM Group (includes restricted cash of $105.1, $0.0 and $0.0)	(143.9)		—		—
Cash balances at end of period (includes restricted cash of $0.0, $89.2 and $78.4)	—		111.6		126.6
Supplemental cash flows information:
Interest paid	$	(12.0)	$	(16.6)	$	(20.9)
Net income tax payments	$	—	$	—	$	—

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, 2022, 2021 and 2020:


	Year Ended December 31,
	2022		2021		2020
Basic and diluted earnings per share numerators (in millions):
Net income (loss) attributable to White Mountains’s common shareholders	$	792.8	$	(275.4)	$	708.7
Less: net income (loss) from continuing operations	(190.8)		(318.0)		675.2
Less: net (income) loss from continuing operations attributable to non-controlling interest	81.1		45.5		45.1
Total income (loss) from discontinued operations attributable to White Mountains’s common shareholders (1)	902.5		(2.9)		(11.6)
Allocation of (earnings) losses to participating restricted common shares (2)	(11.4)		—		.2
Basic and diluted (loss) earnings per share numerators	$	891.1	$	(2.9)	$	(11.4)
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period	2,862.4		3,079.0		3,122.2
Average unvested restricted common shares (3)	(36.2)		(36.5)		(40.8)
Basic earnings (loss) per share denominator	2,826.2		3,042.5		3,081.4
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period	2,862.4		3,079.0		3,122.2
Average unvested restricted common shares (3)	(36.2)		(36.5)		(40.8)

Diluted earnings (loss) per share denominator	2,826.2		3,042.5		3,081.4
Basic (loss) earnings per share (in dollars) - discontinued operations:	$	315.30	$	(.94)	$	(3.72)
Diluted (loss) earnings per share (in dollars) - discontinued operations:	$	315.30	$	(.94)	$	(3.72)

(1) Includes net income (loss) from discontinued operations, net of tax - NSM Group, net gain (loss) from sale of discontinued operations, net of tax - NSM Group, net gain (loss) from sale of discontinued operations, net of tax - Sirius Group and net (income) loss from discontinued operations attributable to non-controlling interests.

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

(3) Restricted shares outstanding vest upon a stated date. See Note 12 — “Employee Share-Based Incentive Compensation Plans.”

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

12 Months Ended

Dec. 31, 2022

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, 2022


Millions	Cost		Carrying Value		Fair Value
Fixed maturity investments:
U.S. Government and agency obligations	$	216.6	$	206.4	$	206.4
Debt securities issued by corporations	1,098.3		1,018.8		1,018.8
Municipal obligations	281.6		258.6		258.6
Mortgage and asset-backed securities	288.7		254.2		254.2
Collateralized loan obligations	190.8		182.9		182.9

Total fixed maturity investments	2,076.0		1,920.9		1,920.9
Short-term investments	925.2		924.1		924.1



Investment in MediaAlpha	—		168.6		168.6
Common equity securities:
Common equity securities - Industrial, Miscellaneous, and Other	324.3		334.6		334.6
Common equity securities - Exchange traded funds	336.3		333.8		333.8
Total common equity securities	660.6		668.4		668.4
Other long-term investments	1,340.8		1,488.0		1,488.0
Total investments	$	5,002.6	$	5,170.0	$	5,170.0

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT

12 Months Ended

Dec. 31, 2022

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	2022		2021
Assets:
Cash	$	.1	$	.6
Fixed maturity investments, at fair value	49.2		—
Common equity securities, at fair value	342.8		—
Other long-term investments	49.3		—
Short-term investments, at fair value	105.2		6.7

Other assets	75.3		3.0
Investments in consolidated subsidiaries	3,026.6		3,661.3
Total assets	$	3,648.5	$	3,671.6
Liabilities:
Net Payable to subsidiary	$	(125.2)	$	104.9
Other liabilities	27.4		9.6
Total liabilities	(97.8)		114.5
White Mountains’s common shareholders’ equity	3,746.9		3,548.1
Non-controlling interests	(.6)		9.0
Total liabilities and equity	$	3,648.5	$	3,671.6

(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 from consolidated and unconsolidated subsidiaries on the condensed statements of operations and comprehensive income (loss). Capital contributions to and distributions from consolidated subsidiaries are presented within investing activities on the condensed statements of cash flows.

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 (LOSS) (1)


	Year Ended December 31,
Millions	2022		2021		2020
Revenues (loss) (including realized and unrealized gains and losses)	$	(.4)	$	(.2)	$	(8.7)
Expenses	67.1		39.0		61.0
Pre-tax income (loss) from continuing operations	(67.5)		(39.2)		(69.7)
Income tax (expense) benefit	(.9)		—		(.3)
Net income (loss) from continuing operations	(68.4)		(39.2)		(70.0)
Equity in earnings from consolidated subsidiaries, net of tax	853.8		(257.4)		782.0


Net gain (loss) from sale of discontinued operations, net of tax - Sirius Group (2)	—		18.7		(2.3)
Net (income) loss attributable to non-controlling interests	7.4		2.5		(1.0)
Net income (loss) attributable to White Mountains’s common shareholders	792.8		(275.4)		708.7
Other comprehensive income (loss), net of tax	(3.8)		1.7		1.4
Other comprehensive income (loss) from discontinued operations, net of tax - NSM Group	(5.2)		.2		5.9
Net gain (loss) from foreign currency translation from sale of discontinued operations, net of tax - NSM Group	2.9		—		—
Comprehensive income (loss)	786.7		$	(273.5)	$	716.0
Comprehensive (income) loss attributable to non-controlling interests	.9		$	.2	$	(.5)
Comprehensive income (loss) attributable to White Mountains’s common shareholders	787.6		$	(273.3)	$	715.5

(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 (loss). Capital contributions to and distributions from subsidiaries are presented within investing activities on the condensed statements of cash flows.

(2) During 2021 and 2020, net gain (loss) from sale of discontinued operations, net of tax includes $18.7 and $(2.3) arising from the tax contingency on the sale of Sirius Group. See Note 21 — “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	2022		2021		2020
Net income (loss) attributable to White Mountains’s common shareholders	$	792.8	$	(275.4)	$	708.7
Charges (credits) to reconcile net income to net cash from operations:
Net realized and unrealized investment (gains) losses	5.6		.1		10.1
Undistributed earnings from consolidated subsidiaries	(853.8)		257.4		(782.0)


Net (gain) loss from sale of discontinued operations, net of tax - Sirius Group (3)	—		(18.7)		2.3
Other non-cash reconciling items (4)	(.4)		14.1		19.0
Accumulated earnings distributed from subsidiary in cash (5)	7.0		—		—
Net change in other assets and liabilities (2)(6)	17.2		(5.7)		(2.5)


Net cash (used for) provided from operations	(31.6)		(28.2)		(44.4)
Cash flows from investing activities:
Net change in short-term investments (2)(7)(8)(9)	1,165.6		17.7		(127.4)
Purchases of investment securities	(359.2)		—		(6.7)
Sales and maturities of investment securities	15.7		—		189.7
Purchases of investment securities from subsidiaries	(14.0)		(26.4)		—
Sales of investment securities to subsidiaries	—		36.4		—

Cash pre-funded for ILS funds managed by Elementum	(70.0)		—		—
Net issuance of debt (to) from subsidiaries (10)	(142.0)		94.0		(44.5)
Net repayment of debt (to) from subsidiaries (7)(11)	(15.0)		—		92.6

Net distributions from (contributions to) subsidiaries (7)(9)	49.3		17.0		29.1
Proceeds from the sale of Other Operating Businesses, net of cash sold of $0.5 $0.0 and $0.0	19.5		—		—


Net cash provided from (used for) investing activities	649.9		138.7		132.8
Cash flows from financing activities:



Repurchases and retirement of common shares	(615.8)		(107.5)		(85.2)
Dividends paid on common shares	(3.0)		(3.1)		(3.2)



Net cash used for financing activities	(618.8)		(110.6)		(88.4)
Net decrease in cash during the year	(.5)		(.1)		—
Cash balance at beginning of year	.6		.7		.7
Cash balance at end of year	$	.1	$	.6	$	.7

(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 consolidated 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 consolidated subsidiaries is reported on a net of tax basis as equity in earnings of subsidiaries on the condensed statements of operations and comprehensive income (loss). Capital contributions to and distributions from consolidated subsidiaries are presented within investing activities on the condensed statements of cash flows.

(2) During 2022, Bridge Holdings, Ltd. (“Bridge”), 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 were transferred from Bridge to the Company including ending net equity of $3,540.6, intercompany note receivable of $76.4, investments in its subsidiaries of $2,003.6, fixed maturity investments of $28.6, common equity securities of $8.1, other long-term investments of $52.2, short-term investments of $1,358.7 and other assets of $6.0.

(3) During 2021 and 2020, amounts represent $18.7 and $(2.3) arising from the tax contingency on the sale of Sirius Group. See Note 21 — “Held for Sale and Discontinued Operations”.

(4) For the years ended December 31, 2022, 2021 and 2020, amortization of restricted share awards was $14.0, $14.7 and $16.6 and net income (loss) attributable to non-controlling interests was $(7.4), $(2.5) and $1.0.

(5) During 2022, as part of the merger of Bridge into the Company, Bridge transferred $7.0 of cash.

(6) For 2022, 2021 and 2020, net change in other assets and liabilities also included $3.3, $6.5, and $(4.8) of net changes in (receivables) payables to the Company’s subsidiaries.

(7) During 2021, Bridge repaid $200.0 of outstanding intercompany debt to the Company by transferring shares of its wholly-owned subsidiary, White Mountains Lincoln Holdings, Inc., (“WM Lincoln”), which had carrying value of $212.6. The $12.6 in excess of the intercompany debt was a non-cash distribution to the Company. Also, as part of the transaction, the Company received a distribution of $18.0 from Bridge, including $17.9 of short-term investments and $0.1 of cash. Subsequent to that transaction, the Company contributed the shares of WM Lincoln, which had a carrying value of $212.6, to its wholly-owned subsidiary White Mountains Adams, Inc. (“WM Adams”). The Company also contributed an additional $42.7 to WM Adams, including $37.1 of short-term investments and $5.6 of cash.

(8) During 2020, the Company had non-cash purchases of short-term investments of $169.6.

(9) During 2022, the Company made cash contributions to its wholly-owned subsidiaries White Mountains Investments (Bermuda), Ltd. (“WMIB”) of $51.0 and WM Adams of $25.0. Also, during 2022, the Company made non-cash contributions of $100.0 in short term investments to WM Adams. During 2022, the Company received cash distributions of $116.3 from HG Global, $7.7 from Ark and $1.3 from its wholly-owned subsidiary, PSC Holdings, Ltd (“PSC Holdings”). During 2021, the Company received a distribution of $19.7, including $19.1 of short-term investments and $0.6 of cash, from WMIB. During 2020, the Company received distributions of $6.8 and $22.3 from PSC Holdings, Ltd. and HG Global.

(10) During 2022, prior to the merger of Bridge into the Company, Bridge had an issuance of debt of $69.0 to the Company. Also, during 2022, the Company had issuances of debt of $205.0 to WM Hinson (Bermuda) Ltd, a wholly-owned subsidiaries of the Company, and $6.0 to HG Global. During 2020, the Company had a non-cash issuance of debt of $169.6 to Bridge. Proceeds of the debt, which were short-term investments, were transferred to Bridge.

(11) During 2022, prior to the merger of Bridge into the Company, the Company had a repayment of debt to Bridge of $15.0.

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, 2022

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

Schedule III - Supplementary Insurance Information

WHITE MOUNTAINS INSURANCE GROUP, LTD.

SUPPLEMENTARY INSURANCE INFORMATION


	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 Acquisition 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 Acquisition Costs		Other Operating Expenses		Premiums Written
Years ended:

December 31, 2022


	HG Global/BAM	$	36.0	$	—	$	298.3	$	—	$	33.3	$	21.5	$	—	$	11.2	$	.4	$	65.1

	Ark	127.2		1,296.5		623.2		—		1,043.4		16.3		536.4		238.3		78.7		1,195.2
December 31, 2021


	HG Global/BAM	33.1		—		266.3		—		26.9		17.5		—		8.3		.4		55.8
	Ark	100.8		894.7		495.9		—		637.3		2.9		314.8		111.3		64.6		859.1

December 31, 2020

	HG Global/BAM	27.8		—		237.5		—		22.8		19.5		—		7.0		.4		61.7

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

SCHEDULE IV REINSURANCE

12 Months Ended

Dec. 31, 2022

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

Schedule IV - Reinsurance

WHITE MOUNTAINS INSURANCE GROUP, LTD.

REINSURANCE


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, 2022


HG Global/BAM	$	28.6	$	—	$	4.7	$	33.3	14.1	%

Ark	655.5		(280.8)		668.7		1,043.4		64.1
December 31, 2021
HG Global/BAM	23.2		—		3.7		26.9		13.8
Ark	556.0		(249.1)		330.4		637.3		51.8


December 31, 2020

HG Global/BAM	19.4		—		3.4		22.8		14.9

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

SCHEDULE V VALUATION AND QUALIFYING ACCOUNTS

12 Months Ended

Dec. 31, 2022

SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]

SCHEDULE V VALUATION AND QUALIFYING ACCOUNTS

WHITE MOUNTAINS INSURANCE GROUP, LTD.

VALUATION AND QUALIFYING ACCOUNTS


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

December 31, 2022
Reinsurance recoverables:
Allowance for uncollectible balances	$	3.6	$	4.6	$	—	$	(0.4)	$	7.8




December 31, 2021
Reinsurance recoverables:
Allowance for uncollectible balances	2.3		1.3		—		—		3.6

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

SCHEDULE VI SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS

12 Months Ended

Dec. 31, 2022

SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Abstract]

SCHEDULE VI SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS

WHITE MOUNTAINS INSURANCE GROUP, LTD.

SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS

(Millions)


Column A	Column B		Column C		Column D	Column E		Column F		Column G		Column H				Column I		Column J		Column K
	Deferred acquisition costs		Reserves for Unpaid Claims and Claims Adjustment Expenses		Discount, if any, deducted in Column C	Unearned Premiums		Earned Premiums		Net investment income		Claims and Claims Adjustment Expenses Incurred Related to				Amortization of deferred policy acquisition costs		Paid Claims and Claims Adjustment Expenses		Premiums written
Affiliation with registrant												Current Year		Prior Year
Ark:
2022	$	127.2	$	1,296.5	—	$	623.2	$	1,043.4	$	16.3	$	588.1	$	(51.7)	$	238.3	$	257.5	$	1,195.2
2021	100.8		894.7		—	495.9		637.3		2.9		336.3		(21.5)		111.3		—		859.1

Basis of Presentation and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation White Mountains Insurance Group, Ltd. (the “Company” or the “Registrant”) is an exempted Bermuda limited liability company whose principal businesses are conducted through its subsidiaries and other affiliates. The Company’s headquarters is located at 26 Reid Street, Hamilton, Bermuda HM 11, its principal executive office is located at 23 South Main Street, Suite 3B, Hanover, New Hampshire 03755-2053 and its registered office is located at Clarendon House, 2 Church Street, Hamilton, Bermuda HM 11. The Company’s website is located at www.whitemountains.com. The information contained on White Mountains’s website is not incorporated by reference into, and is not a part of, this report. The accompanying consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) and include the accounts of the Company, its subsidiaries (collectively with the Company, “White Mountains”) and other entities required to be consolidated under GAAP. 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.
Consolidation Principles	Consolidation Principles Under GAAP, the Company is required to consolidate any entity in which it holds a controlling financial interest. A controlling financial interest is usually in the form of an investment representing the majority of the subsidiary’s voting interests. However, a controlling financial interest may also arise from a financial interest in a variable interest entity (“VIE”) through arrangements that do not involve ownership of voting interests. The Company consolidates a VIE if it determines that it is the primary beneficiary. The primary beneficiary is defined as the entity who holds a variable interest that gives it both the power to direct the VIE’s activities that most significantly impact its economic performance and the obligation to absorb losses of, or the right to receive returns from, the VIE that could potentially be significant to the VIE. See Note 18 — “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 As of December 31, 2022, White Mountains conducted its operations through three reportable segments: (1) HG Global/BAM, (2) Ark, and (3) Kudu, with our remaining operating businesses, holding companies and other assets included in Other Operations. White Mountains has made its segment determination based on consideration of the following criteria: (i) the nature of the business activities of each of the Company’s subsidiaries and affiliates; (ii) the manner in which the Company’s subsidiaries and affiliates are organized; (iii) the existence of primary managers responsible for specific subsidiaries and affiliates; and (iv) the organization of information provided to the chief operating decision makers and the Board of Directors. See Note 16 — “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 purpose projects, 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. 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 (the “BAM Surplus Notes”). As of December 31, 2022 and 2021, White Mountains owned 96.9% of HG Global's preferred equity and 88.4% of its common equity. White Mountains does not have an ownership interest in BAM. However, White Mountains is required to consolidate BAM’s results in its financial statements because BAM is a VIE for which White Mountains is the primary beneficiary. BAM’s results are attributed to non-controlling interests. The Ark segment consists of Ark Insurance Holdings Limited and its subsidiaries (collectively, “Ark”). Ark is a specialty property and casualty insurance and reinsurance company that offers a wide range of niche insurance and reinsurance products, including property, specialty, marine & energy, casualty and accident & health. Ark underwrites select coverages through its two major subsidiaries in the United Kingdom and Bermuda. On January 1, 2021, White Mountains acquired a controlling ownership interest in Ark (the “Ark Transaction”). See Note 2 — “Significant Transactions”. As of December 31, 2022 and 2021, White Mountains owned 72.0% of Ark on a basic shares outstanding basis (63.0% after taking account of management’s equity incentives). The remaining shares are owned by current and former employees. In the future, management rollover shareholders could earn additional shares in Ark if and to the extent that White Mountains achieves certain multiple of invested capital return thresholds. If fully earned, these additional shares would represent 12.5% of the shares outstanding at closing. For the years of account prior to the Ark Transaction, a significant proportion of the Syndicates’ underwriting capital was provided by third-party insurance and reinsurance groups (“TPC Providers”) using whole account reinsurance contracts with Ark’s corporate member. For the years of account subsequent to the Ark Transaction, Ark is no longer using TPC Providers to provide underwriting capital for the Syndicates. Captions within results of operations and other comprehensive income are shown net of amounts relating to the TPC Providers’ share of the Syndicates’ results, including investment results. The Kudu segment consists of Kudu Investment Management, LLC and its subsidiaries (collectively, “Kudu”). Kudu provides capital solutions for boutique asset and wealth 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 generally are structured as minority preferred equity stakes with distribution rights, typically tied to gross revenues and designed to generate immediate cash yields. As of December 31, 2022 and 2021, White Mountains owned 89.3% and 99.3% of the basic units outstanding of Kudu (76.1% and 84.7% on a fully diluted, fully converted basis). White Mountains’s Other Operations consists of the Company and its wholly-owned subsidiary, White Mountains Capital, LLC (“WM Capital”), its other intermediate holding companies, its wholly-owned investment management subsidiary, White Mountains Advisors LLC (“WM Advisors”), investment assets managed by WM Advisors, its interests in MediaAlpha, Inc. (“MediaAlpha”), PassportCard Limited (“PassportCard”) and DavidShield Life Insurance Agency (2000) Ltd. (“DavidShield”) (collectively, “PassportCard/ DavidShield”), Elementum Holdings LP (“Elementum”), Outrigger Re Ltd. Segregated Account 2023-1 (“WM Outrigger Re”), certain other consolidated and unconsolidated entities (“Other Operating Businesses”) and certain other assets.
Held for Sale and Discontinued Operations	Held for Sale and Discontinued Operations White Mountains recognizes assets and liabilities classified as held for sale at the lower of carrying value on the date the asset is initially classified as held for sale or fair value less costs to sell. At the time of reclassification to held for sale, White Mountains ceases recognizing depreciation and amortization on assets held for sale. The results of operations of a business that has either been disposed of or are classified as held for sale are reported in discontinued operations if the disposal of business represents a strategic shift that has (or will have) a major effect on White Mountains’s operations and financial results. See Note 21 — “Held for Sale and Discontinued Operations.” On August 1, 2022, White Mountains Holdings (Luxembourg) S.à r.l. (“WTM Holdings Seller”), an indirect wholly owned subsidiary of White Mountains, completed the previously announced sale of White Mountains Catskill Holdings, Inc. and NSM Insurance HoldCo, LLC (“NSM” and, collectively with White Mountains Catskill Holdings, Inc., the “NSM Group”) to Riser Merger Sub, Inc., an affiliate of The Carlyle Group Inc. (the “NSM Transaction”), pursuant to the terms of the securities purchase agreement, dated as of May 9, 2022. See Note 2 — “Significant Transactions.” NSM is a full-service managing general agent (“MGA”) and program administrator with delegated binding authorities for specialty property and casualty insurance. As of December 31, 2021, White Mountains owned 96.5% of the basic units outstanding of NSM (87.3% on a fully diluted, fully converted basis). As a result of the NSM Transaction, the assets and liabilities of NSM Group have been presented in the balance sheet as held for sale for periods prior to the closing of the transaction, and the results of operations for NSM Group have been classified as discontinued operations in the statements of operations and comprehensive income through the closing of the transaction. Prior period amounts have been reclassified to conform to the current period’s presentation. See Note 21 — “Held for Sale and Discontinued Operations.”
Investment Securities	Investment Securities As of December 31, 2022 and 2021, 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, its investment in MediaAlpha, 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. Short-term investments consist of interest-bearing money market funds, certificates of deposit and other securities, which at the time of purchase, mature or become available for use within one year. Short-term investments are carried at fair value, which approximated amortized or accreted cost as of December 31, 2022 and 2021. White Mountains’s invested assets that are measured at fair value include fixed maturity investments, common equity securities, its investment in MediaAlpha, and other long-term investments, that consists primarily of unconsolidated entities, including non-controlling equity interests in the form of revenue and earnings participation contracts (“Kudu’s Participation Contracts”), private equity funds and hedge funds, a bank loan fund, Lloyd’s of London (“Lloyd’s”) trust deposits, 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 is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants (an exit price) at a particular measurement date. 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 all of White Mountains’s investment portfolio and derivative instruments. Valuation of assets and liabilities 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 quoted market prices or other observable 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, 2022, approximately 72% 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 White Mountains’s fixed maturity investments, primarily investments in U.S. Treasuries and short-term investments, which include U.S. Treasury Bills, common equity securities, and its investment in MediaAlpha following the initial public offering of MediaAlpha on October 30, 2020 (the “MediaAlpha IPO”). 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, mortgage and asset-backed securities and collateralized loan obligations. Investments valued using Level 2 inputs also include certain international listed common equity funds, which White Mountains values using the fund manager’s published net asset value (“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 and Collateralized Loan Obligations The fair value of mortgage and asset-backed securities and collateralized loan obligations 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 As of December 31, 2022, $911.6 million of White Mountains’s other long-term investments, which consisted primarily of unconsolidated entities, including Kudu’s Participation Contracts and PassportCard/DavidShield were classified as Level 3 investments in the GAAP fair value hierarchy. 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. 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 its 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 other long-term investments classified as Level 3 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 As of December 31, 2022, $561.6 million of White Mountains’s other long-term investments, which consisted of private equity funds and hedge funds, a bank loan fund, Lloyd’s trust deposits and ILS funds, were valued at fair value using NAV as a practical expedient. Investments for which fair value is measured using NAV as a practical expedient are not classified within the fair value hierarchy. White Mountains employs a number of procedures to assess the reasonableness of the fair value measurements for other long-term investments measured at NAV, including obtaining and reviewing interim unaudited and annual audited financial statements as well as periodically discussing each fund’s pricing with the fund manager. 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 valuation inputs to be unobservable. The fair value of White Mountains’s other long-term investments measured at NAV are generally determined using the fund manager’s NAV. In the event that White Mountains believes the fair value 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.
Cash and Restricted Cash	Cash and Restricted Cash Cash includes amounts on hand and demand deposits with banks and other financial institutions. Amounts presented in the statement of cash flows are shown net of balances acquired and sold in the purchase or sale of the Company’s consolidated subsidiaries. Cash balances that are not immediately available for general corporate purposes, including the interest reserve account that Kudu maintains under its credit facility, is classified as restricted.
Derivatives	Derivatives From time to time, White Mountains holds derivative financial instruments for risk management purposes. White Mountains recognizes all derivatives as either assets or liabilities, measured at fair value, on its consolidated balance sheet. Changes in the fair value of derivative instruments that meet the criteria for hedge accounting are recognized in other comprehensive income (loss) and reclassified into current period pre-tax income (loss) 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 (loss). As of December 31, 2022, White Mountains holds an interest rate cap derivative instrument that does not meet the criteria for hedge accounting. See Note 9 — “Derivatives”.
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. For capital appreciation bonds, par is adjusted to the estimated equivalent par value for current interest paying bonds. See Note 10 — “Municipal Bond Guarantee Insurance”. Premiums are generally received upfront and an unearned premium revenue liability, equal to the amount of the premium received, is established at contract inception. Premium revenues are recognized in revenue over the period of the contracts in proportion to the amount of insurance protection provided using a constant rate. The constant rate is calculated based on the relationship between the par outstanding in a given reporting period compared with the sum of each of the par amounts outstanding for all periods. Insurance premiums receivable represents amounts due from customers for municipal bond insurance policies. 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. 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. A premium deficiency is recognized if the sum of expected loss and loss adjustment expenses (“LAE”), expected dividends to policyholders, unamortized acquisition costs, and maintenance costs exceeds related unearned premiums and anticipated investment income. A premium deficiency is recognized by charging any unamortized acquisition costs to expense to the extent required in order to eliminate the deficiency. If the premium deficiency exceeds unamortized acquisition costs then a liability is accrued for the excess deficiency. Loss reserves are recorded only to the extent that the present value of any payments projected to be made by BAM, net of any expected recoveries, exceeds the associated unearned premium reserve. As of December 31, 2022 and 2021, BAM did not have any loss or loss adjustment expense reserves.
Property and Casualty Insurance and Reinsurance	Property and Casualty Insurance and Reinsurance Ark writes a diversified portfolio of reinsurance and insurance, including property, specialty, marine & energy, casualty and accident & health, through its Lloyd’s Syndicates 4020 and 3902 (the “Syndicates”) and its wholly-owned subsidiary Group Ark Insurance Limited (“GAIL”). Ark accounts for insurance and reinsurance policies that it writes in accordance with ASC 944, Financial Services - Insurance. Ark’s premiums written comprise premiums on insurance contracts incepted during the year as well as premium adjustments related to prior underwriting years. Insurance premiums are recognized as revenues over the loss exposure or coverage period. In most cases, premiums are earned ratably over the term of the contract with unearned premiums calculated on a monthly pro-rata basis. Catastrophe premiums are earned in proportion to the insurance protection provided. Premiums earned are presented net of amounts ceded to reinsurers. Insurance premiums receivable, representing amounts due from insureds, are presented net of an allowance for uncollectible premiums, including expected credit losses. The allowance is based upon Ark’s ongoing review of amounts outstanding, historical loss data, including delinquencies and write-offs, current and forecasted economic conditions and other relevant factors. Credit risk is partially mitigated by Ark’s ability to cancel the policy if the policyholder does not pay the premium. Deferred acquisition costs comprise commission and brokerage fees and taxes which are directly attributable to and vary with the production of business. These costs are deferred and amortized to the extent they relate to successful contract acquisitions over the applicable premium recognition period as insurance and reinsurance acquisition expenses. Deferred acquisition costs are limited to the amount expected to be recovered from future earned premiums and anticipated investment income. A premium deficiency is recognized if the sum of expected loss and LAE, expected dividends to policyholders, unamortized acquisition costs, and maintenance costs exceeds related unearned premiums and anticipated investment income. A premium deficiency is recognized by charging any unamortized acquisition costs to expense to the extent required in order to eliminate the deficiency. If the premium deficiency exceeds unamortized acquisition costs then a liability is accrued for the excess deficiency. Losses and LAE are charged against income as incurred. Unpaid losses and LAE, including estimates for amounts incurred but not reported (“IBNR”) are based on estimates of the ultimate costs of settling claims, including the effects of inflation and other societal and economic factors. Unpaid loss and LAE reserves represent management’s best estimate of ultimate losses and LAE, net of estimated salvage and subrogation recoveries, if applicable. Such estimates are regularly reviewed and updated and any resulting adjustments are reflected in current results of operations. The process of estimating loss and LAE involves a considerable degree of judgment by management and the ultimate amount of expense to be incurred could be considerably greater than or less than the amounts currently reflected in the financial statements. See Note 5 – “Loss and Loss Adjustment Expense Reserves”. As part of its enterprise risk management function, Ark purchases reinsurance for risk mitigation purposes. Ark utilizes reinsurance and retrocession agreements to reduce earnings volatility, protect capital, limit its exposure to risk concentration and accumulation of loss and to manage within its overall internal risk tolerances or those set and agreed by regulators, ratings agencies, and Lloyd’s. Ark also enters into reinsurance and retrocession agreements to reduce its liability on individual risks and enable it to underwrite policies with higher limits where Ark believes this has a broader business benefit. Ark seeks to protect its downside risk from catastrophes and large loss events by purchasing reinsurance, including excess of loss protections, aggregate covers, and industry loss warranties. Ark also considers alternative structures such as collateralized reinsurance, retrocessional reinsurance and catastrophe bonds. The purchase of reinsurance does not discharge Ark from its primary liability for the full value of its policies, and thus the collectability of balances due from Ark’s reinsurers is critical to its financial strength. Ark monitors the financial strength and ratings of its reinsurers on an ongoing basis. See Note 6 – “Third-Party Reinsurance”. For the years of account prior to the Ark Transaction, a significant proportion of the Syndicates’ underwriting capital was provided by third-party insurance and reinsurance groups (“TPC Providers”) using whole account reinsurance contracts with Ark’s corporate member. The TPC Providers’ participation in the Syndicates for the 2020 open year of account is 42.8% of the total net result of the Syndicates. For the years of account subsequent to the Ark Transaction, Ark is no longer using TPC Providers to provide underwriting capital for the Syndicates. Captions within results of operations and other comprehensive income are shown net of amounts relating to the TPC Providers share of the Syndicates’ results, including investment results. Reinsurance recoverables represent paid losses and LAE, case reserves and IBNR reserves ceded to reinsurers under reinsurance treaties. Amounts recoverable from reinsurers are estimated in a manner consistent with the associated claim liability. Ark reports its reinsurance recoverables net of an allowance for estimated uncollectible reinsurance, including expected credit losses and coverage disputes. The allowance is based upon Ark’s ongoing review of amounts outstanding, length of collection periods, changes in reinsurer credit standing, disputes, applicable coverage defenses and other relevant factors.
Reinsurance Contracts Accounted for as Deposits	Reinsurance Contracts Accounted for as Deposits Reinsurance contracts that do not meet the risk transfer requirements necessary to be accounted for as reinsurance are accounted for using the deposit method. Under the deposit method, ceded premiums paid are not recognized through income but rather treated as a deposit. BAM entered into three ceded reinsurance agreements with Fidus Re Ltd. (“Fidus Re”), a Bermuda-based special purpose insurer created in 2018 solely to provide reinsurance protection to BAM. BAM also entered into an excess of loss reinsurance agreement (the “XOLT”) with HG Re. The financing expenses paid by BAM under these reinsurance agreements are recorded in general and administrative expenses. See Note 10 — “Municipal Bond Guarantee Insurance”. Ark has an aggregate excess of loss contract with SiriusPoint Ltd. (“SiriusPoint”), formerly Third Point Reinsurance Ltd., which is accounted for using the deposit method and recorded within other assets. Ark earns an annual crediting rate of 3.0%, which is recorded within other revenue. See Note 6 — “Third-Party Reinsurance”.
Revenue Recognition	Revenue Recognition Kudu’s revenues are primarily generated from non-controlling equity interests in revenue and earnings participation contracts with asset and wealth management firms. Kudu’s Participation Contracts are measured at fair value with the change therein recognized within net realized and unrealized investment gains (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. White Mountains’s Other Operations recognizes agent commissions and other revenues when it has satisfied its performance obligations. Deferred revenues associated with unsatisfied performance obligations are recognized within other liabilities.
Cost of Sales	Cost of Sales White Mountains’s 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.
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 underwriting capacity, customer relationships and trade names. 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 White Mountains determines, based on this qualitative review, that it is more likely than not that an impairment may exist, then White Mountains performs a quantitative analysis to compare the fair value of a reporting unit with its carrying value. If the carrying value exceeds the estimated fair value, then an impairment charge is recognized through current period pre-tax income (loss). Other intangible assets with finite lives are initially measured at their acquisition date fair values and subsequently amortized over their economic lives. Other intangible assets with finite lives are 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. See Note 4 – “Goodwill and Other Intangible Assets”.
Incentive Compensation	Incentive CompensationWhite 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 12 — “Employee Share-Based Incentive Compensation Plans”.
Income Taxes	Income Taxes White Mountains has subsidiaries and branches that operate in various jurisdictions around the world and are subject to tax in the jurisdictions in which they operate. As of December 31, 2022, the primary jurisdictions in which White Mountains’s subsidiaries and branches were subject to tax were Ireland, Israel, Luxembourg, the United Kingdom and 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. Deferred tax assets represent amounts available to reduce income taxes payable in future periods. 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. See Note 8 – “Income Taxes”.
Leases	Leases Leases consist primarily of operating leases for office space and equipment. Lease assets and liabilities are recognized at the lease commencement date based on the present value of future minimum lease payments over the lease term. Lease assets and liabilities are not recorded for leases with a term at inception of one year or less. Lease expense is included in operating expenses. See Note 13 – “Leases”.
Non-controlling Interests	Non-controlling InterestsNon-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 (loss) attributable to non-controlling interests is presented net of related income taxes in the statement of operations and comprehensive income (loss). See Note 14 — “Common Shareholders’ Equity and Non-controlling Interests”.
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. As of December 31, 2022 and 2021, White Mountains had unrealized foreign currency translation gains (losses) of $(3.5) million and $5.1 million recorded in accumulated other comprehensive income (loss) on its consolidated balance sheet.
Fair Value Measurements	Fair Value MeasurementsFair 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). See Note 19 — “Fair Value of Financial Instruments”.
Business Combinations	Business Combinations White Mountains accounts for purchases of businesses using the acquisition method, which requires the measurement of assets acquired, including other intangible assets, and liabilities assumed, including contingent liabilities, at their estimated fair values as of the acquisition date. The acquisition date fair values represent management’s best estimates and are based upon established valuation techniques, reasonable assumptions and, where appropriate, valuations performed by independent third parties. In circumstances where additional information is required in order to determine the acquisition date fair value of balance sheet amounts, provisional amounts may be recorded as of the acquisition date and may be subject to subsequent adjustment throughout the measurement period, which is up to one year from the acquisition date. Measurement period adjustments are recognized in the period in which they are determined. The results of operations and cash flows of businesses acquired are included in the consolidated financial statements from the date of acquisition. White Mountains accounts for purchases of other intangible assets that do not meet the definition of a business as asset acquisitions. Asset acquisitions are recognized at the amount of consideration paid, which is deemed to equal fair value.

Significant Transactions (Tables)

12 Months Ended

Dec. 31, 2022

Significant Transactions [Abstract]

Schedule of Recognized Identified Assets Acquired

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


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

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

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


$ in Millions	Weighted Average Economic Life (in years)	December 31, 2022							December 31, 2021
		Acquisition Date Fair Value		Accumulated Amortization					Net Carrying Value		Acquisition Date Fair Value		Accumulated Amortization					Net Carrying Value
Goodwill:
Ark	N/A	$	116.8	$	—				$	116.8	$	116.8	$	—				$	116.8
Kudu	N/A	7.6		—					7.6		7.6		—					7.6


Other Operations	N/A	52.1		—					52.1		17.9		—					17.9
Total goodwill		176.5		—					176.5		142.3		—					142.3
Other intangible assets:
Ark
Underwriting capacity	N/A	175.7		—					175.7		175.7		—					175.7
Kudu
Trade names	7	2.2		1.2					1.0		2.2		.9					1.3





Other Operations
Trade names	15.9	17.9		3.0					14.9		8.2		1.5					6.7
Customer relationships	12.4	29.5		7.5					22.0		18.8		4.5					14.3

Other	12.1	2.8		.5					2.3		.3		.1					.2
Subtotal		50.2		11.0					39.2		27.3		6.1					21.2
Total other intangible assets		228.1		12.2					215.9		205.2		7.0					198.2
Total goodwill and other intangible assets		$	404.6	$	12.2				392.4		$	347.5	7.0					340.5
Goodwill and other intangible assets attributed to non-controlling interests						(102.7)									(91.8)
Goodwill and other intangible assets included in White Mountains’s common shareholders’ equity							$	289.7								$	248.7

Investment Securities (Tables)

12 Months Ended

Dec. 31, 2022

Investments, Debt and Equity Securities [Abstract]

Schedule of pre-tax net investment income

The following table presents pre-tax net investment income for the years ended December 31, 2022, 2021 and 2020:


	Year Ended December 31,
Millions	2022		2021		2020
Fixed maturity investments	$	41.4	$	28.8	$	29.0
Short-term investments	16.4		.6		1.1
Common equity securities	1.6		.1		6.6
Investment in MediaAlpha	—		—		59.9

Other long-term investments	68.1		56.3		35.6
Amount attributable to TPC Providers	(1.0)		(1.0)		—
Total investment income	126.5		84.8		132.2
Third-party investment expenses	(2.1)		(2.3)		(1.2)
Net investment income, pre-tax	$	124.4	$	82.5	$	131.0

Schedule of net realized and unrealized investment gains and losses

The following table presents net realized and unrealized investment gains (losses) for the years ended December 31, 2022, 2021 and 2020:


	Year Ended December 31,
Millions	2022		2021		2020
Realized investment gains (losses)
Fixed maturity investments	$	(11.9)	$	3.9	$	10.9
Short-term investments	(1.4)		(.1)		.4
Common equity securities	—		.4		137.2
Investment in MediaAlpha	—		160.3		63.8
Other long-term investments	128.4		(7.7)		(25.2)
Net realized investment gains (losses)	115.1		156.8		187.1

Unrealized investment gains (losses)
Fixed maturity investments	(168.4)		(42.2)		27.5
Short-term investments	(1.1)		—		—
Common equity securities	(7.1)		14.9		(130.6)
Investment in MediaAlpha	(93.0)		(540.6)		622.2
Other long-term investments	(43.8)		172.7		10.6
Net unrealized investment gains (losses)	(313.4)		(395.2)		529.7
Net realized and unrealized investment gains (losses), before amount attributable to TPC providers (1)	(198.3)		(238.4)		716.8
Amount attributable to TPC Providers	6.8		(7.7)		—
Net realized and unrealized investment gains (losses)	$	(191.5)	$	(246.1)	$	716.8

Fixed maturity and short-term investments
Net realized and unrealized investment gains (losses)	$	(182.8)	$	(38.4)	$	38.8
Less: net realized and unrealized gains (losses) on investment securities sold during the period	(2.9)		(8.4)		(8.7)
Net unrealized investment gains (losses) recognized during the period on investment securities held at the end of the period	$	(179.9)	$	(30.0)	$	47.5

Common equity securities and investment in MediaAlpha
Net realized and unrealized investment gains (losses) on common equity securities	$	(7.1)	$	15.3	$	6.6
Net realized and unrealized investment gains (losses) from investment in MediaAlpha	(93.0)		(380.3)		686.0
Total net realized and unrealized investment gains (losses)	(100.1)		(365.0)		692.6
Less: net realized and unrealized gains (losses) on investment securities sold during the period	—		20.3		38.3
Net unrealized investment gains (losses) recognized during the period on investment securities held at the end of the period	$	(100.1)	$	(385.3)	$	654.3

(1) For 2022, 2021 and 2020, includes $(29.3), $(7.7) and $4.0 of net realized and unrealized investment gains (losses) related to foreign currency exchange.

Schedule of net unrealized investment gains (losses) for Level 3 investments


	Year Ended December 31,
Millions	2022		2021		2020

Total net unrealized investment gains on other long-term investments held at the end of period, pre-tax (1)	$	56.5	$	98.9	$	276.0

(1) For 2020, includes $278.7 of unrealized investment gains from White Mountains’s investment in MediaAlpha.

Schedule of fixed maturity investment holdings


	December 31, 2022
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains (Losses)		Carrying Value
U.S. Government and agency obligations	$	216.6	$	—	$	(10.2)	$	—	$	206.4
Debt securities issued by corporations	1,098.3		.6		(78.3)		(1.8)		1,018.8
Municipal obligations	281.6		.4		(23.4)		—		258.6
Mortgage and asset-backed securities	288.7		—		(34.5)		—		254.2
Collateralized loan obligations	190.8		.1		(6.0)		(2.0)		182.9
Total fixed maturity investments	$	2,076.0	$	1.1	$	(152.4)	$	(3.8)	$	1,920.9


	December 31, 2021
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains (Losses)		Carrying Value
U.S. Government and agency obligations	$	212.1	$	.5	$	(1.1)	$	—	$	211.5
Debt securities issued by corporations	993.3		8.7		(8.7)		(.4)		992.9
Municipal obligations	276.4		16.8		(1.3)		—		291.9
Mortgage and asset-backed securities	277.2		2.9		(2.5)		—		277.6
Collateralized loan obligations	136.5		—		(.4)		(1.1)		135.0


Total fixed maturity investments	$	1,895.5	$	28.9	$	(14.0)	$	(1.5)	$	1,908.9


	December 31, 2022
Millions	Cost or Amortized Cost		Carrying Value
Due in one year or less	$	204.8	$	201.2
Due after one year through five years	914.0		853.2
Due after five years through ten years	374.4		337.4
Due after ten years	103.3		92.0
Mortgage and asset-backed securities and collateralized loan obligations	479.5		437.1

Total fixed maturity investments	$	2,076.0	$	1,920.9

Schedule of equity securities and other long-term investments


	December 31, 2022
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains (Losses)		Carrying Value

Common equity securities	$	660.6	$	26.7	$	(8.4)	$	(10.5)	$	668.4
Investment in MediaAlpha	$	—	$	168.6	$	—	$	—	$	168.6


Other long-term investments	$	1,340.8	$	271.1	$	(107.1)	$	(16.8)	$	1,488.0


	December 31, 2021
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains (Losses)		Carrying Value
Common equity securities	$	236.3	$	16.1	$	—	$	(1.3)	$	251.1
Investment in MediaAlpha	$	—	$	261.6	$	—	$	—	$	261.6

Other long-term investments	$	1,186.7	$	239.0	$	(44.1)	$	(3.8)	$	1,377.8

Schedule of fair value measurements for investment securities by level


	December 31, 2022
Millions	Fair Value		Level 1		Level 2		Level 3
Fixed maturity investments:
U.S. Government and agency obligations	$	206.4	$	206.4	$	—	$	—

Debt securities issued by corporations:
Financials	291.2		—		291.2		—
Consumer	191.9		—		191.9		—
Technology	123.7		—		123.7		—
Healthcare	121.3		—		121.3		—
Industrial	115.4		—		115.4		—
Utilities	73.8		—		73.8		—
Communications	47.9		—		47.9		—
Energy	33.9		—		33.9		—
Materials	19.7		—		19.7		—

Total debt securities issued by corporations	1,018.8		—		1,018.8		—

Municipal obligations	258.6		—		258.6		—
Mortgage and asset-backed securities	254.2		—		254.2		—

Collateralized loan obligations	182.9		—		182.9		—
Total fixed maturity investments	1,920.9		206.4		1,714.5		—

Short-term investments	924.1		924.1		—		—
Common equity securities

Exchange-trade funds	333.8		333.8		—		—
Other (1)	334.6		—		334.6		—
Total common equity securities	668.4		333.8		334.6		—
Investment in MediaAlpha	168.6		168.6		—		—












Other long-term investments	926.4		—		14.8		911.6
Other long-term investments — NAV (2)	561.6		—		—		—
Total other long-term investments	1,488.0		—		14.8		911.6
Total investments	$	5,170.0	$	1,632.9	$	2,063.9	$	911.6

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


	December 31, 2021
Millions	Fair Value		Level 1		Level 2		Level 3
Fixed maturity investments:
U.S. Government and agency obligations	$	211.5	$	211.5	$	—	$	—

Debt securities issued by corporations:
Financials	264.2		—		264.2		—
Consumer	178.1		—		178.1		—
Technology	117.9		—		117.9		—
Industrial	112.9		—		112.9		—
Healthcare	112.8		—		112.8		—
Utilities	70.9		—		70.9		—
Communications	56.0		—		56.0		—
Energy	48.0		—		48.0		—
Materials	32.1		—		32.1		—

Total debt securities issued by corporations	992.9		—		992.9		—

Municipal obligations	291.9		—		291.9		—
Mortgage and asset-backed securities	277.6		—		277.6		—
Collateralized loan obligations	135.0		—		135.0		—


Total fixed maturity investments	1,908.9		211.5		1,697.4		—

Short-term investments	465.9		465.9		—		—
Common equity securities (1)	251.1		—		251.1		—

Investment in MediaAlpha	261.6		261.6		—		—
















Other long-term investments	895.3		—		4.7		890.6
Other long-term investments — NAV (2)	482.5		—		—		—
Total other long-term investments	1,377.8		—		4.7		890.6
Total investments	$	4,265.3	$	939.0	$	1,953.2	$	890.6

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

Schedule of credit ratings of debt securities issued

The following table presents the credit ratings of debt securities issued by corporations held in White Mountains’s investment portfolio as of December 31, 2022 and 2021:


	Fair Value at December 31,
Millions	2022		2021
AAA	$	11.3	$	12.0
AA	96.0		85.0
A	567.9		490.4
BBB	337.7		396.8


Other	5.9		8.7
Debt securities issued by corporations (1)	$	1,018.8	$	992.9

Schedule of mortgage and asset-backed securities

The following table presents the fair value of White Mountains’s mortgage and asset-backed securities and collateralized loan obligations as of December 31, 2022 and 2021:


	December 31, 2022						December 31, 2021
Millions	Fair Value		Level 2		Level 3		Fair Value		Level 2		Level 3
Mortgage-backed securities:
Agency:
FNMA	$	124.5	$	124.5	$	—	$	125.4	$	125.4	$	—
FHLMC	78.8		78.8		—		90.5		90.5		—
GNMA	28.3		28.3		—		40.1		40.1		—
Total agency (1)	231.6		231.6		—		256.0		256.0		—
Non-agency: Residential	.3		.3		—		.5		.5		—

Total non-agency	.3		.3		—		.5		.5		—
Total mortgage-backed securities	231.9		231.9		—		256.5		256.5		—
Other asset-backed securities:
Credit card receivables	11.9		11.9		—		12.3		12.3		—
Vehicle receivables	10.4		10.4		—		8.8		8.8		—

Total other asset-backed securities	22.3		22.3		—		21.1		21.1		—
Total mortgage and asset-backed securities	254.2		254.2		—		277.6		277.6		—
Collateralized loan obligations:	182.9		182.9		—		135.0		135.0		—
Total mortgage and asset-backed securities and collateralized loan obligations	$	437.1	$	437.1	$	—	$	412.6	$	412.6	$	—

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

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

Schedule of carrying values for other long-term investments

The following table presents the carrying values of White Mountains’s other long-term investments as of December 31, 2022 and 2021:


	Fair Value at December 31,
Millions	2022		2021
Kudu’s Participation Contracts	$	695.9	$	669.5
PassportCard/DavidShield	135.0		120.0
Elementum Holdings L.P.	30.0		45.0
Other unconsolidated entities (1)	37.2		34.4
Total unconsolidated entities	898.1		868.9
Private equity funds and hedge funds	197.8		153.8
Bank loan fund	174.8		163.0
Lloyd’s trust deposits	137.4		113.8
ILS funds	49.3		51.9
Private debt instruments	9.6		14.1
Other	21.0		12.3
Total other long-term investments	$	1,488.0	$	1,377.8

Schedule of investments and unfunded commitments by investment objective and sector

The following table presents the fair value of investments and unfunded commitments in private equity funds and hedge funds by investment objective and sector as of December 31, 2022 and 2021:


	December 31, 2022				December 31, 2021
Millions	Fair Value		Unfunded Commitments		Fair Value		Unfunded Commitments

Private equity funds
Aerospace/Defense/Government	$	59.4	$	37.5	$	69.8	$	11.8
Financial services	77.1		54.3		67.7		29.3
Real estate	4.1		2.5		4.3		2.9



Total private equity funds	140.6		94.3		141.8		44.0

Hedge funds
Long/short equity financials and business services	49.0		—		—		—
European small/mid cap	8.2		—		12.0		—
Total hedge funds	57.2		—		12.0		—
Total private equity funds and hedge funds included in other long-term investments	$	197.8	$	94.3	$	153.8	$	44.0

Schedule investments in 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, 2022:


Millions	1 – 3 years		3 – 5 years		5 – 10 years		>10 years		Total
Private equity funds — expected lock-up period remaining	$	4.2	$	18.8	$	113.9	$	3.7	$	140.6

Schedule of fair value investments by level

The following table presents the changes in White Mountains’s fair value measurements for Level 3 investments for the years ended December 31, 2022 and 2021:


Level 3 Investments
Millions	Other Long-term Investments			Other Long-term Investments
Balance at December 31, 2021	$	890.6	Balance at December 31, 2020	$	614.2
Net realized and unrealized gains	60.4		Net realized and unrealized gains	117.3
Amortization/accretion	—		Amortization/accretion	—
Purchases	129.8		Purchases	225.4
Sales	(169.2)		Sales	(75.9)
Effect of Ark Transaction	—		Effect of Ark Transaction	9.6
Transfers in	—		Transfers in	—
Transfers out	—		Transfers out	—
Balance at December 31, 2022	$	911.6	Balance at December 31, 2021	$	890.6

Schedule of significant unobservable inputs used in estimating the fair value of other long-term investments

$ in Millions

December 31, 2022

Description

Valuation Technique(s) (1)

Fair Value (2)

Unobservable Inputs

Discount Rate (6)

Terminal Cash Flow Exit Multiple (x) or Terminal Revenue Growth Rate (%) (6)

Kudu’s Participation Contracts (3)(4)(5)

Discounted cash flow

$695.9

18% - 25%

7x - 16x

PassportCard/DavidShield

Discounted cash flow

$135.0

24%

Elementum Holdings, L.P.

Discounted cash flow

$30.0

21%

Private debt instruments

Discounted cash flow

$9.6

11%

N/A

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

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

$ in Millions

December 31, 2021

Description

Valuation Technique(s) (1)

Fair Value (2)

Unobservable Inputs

Discount Rate (6)

Terminal Cash Flow Exit Multiple (x) or Terminal Revenue Growth Rate (%) (6)

Kudu’s Participation Contracts (3)(4)(5)

Discounted cash flow

$669.5

18% - 23%

7x - 13x

PassportCard/DavidShield

Discounted cash flow

$120.0

23%

Elementum Holdings, L.P.

Discounted cash flow

$45.0

17%

Private debt instruments

Discounted cash flow

$9.4

N/A

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

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

Goodwill and Other Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2022

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Recognized Identified Assets Acquired

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


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

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

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


$ in Millions	Weighted Average Economic Life (in years)	December 31, 2022							December 31, 2021
		Acquisition Date Fair Value		Accumulated Amortization					Net Carrying Value		Acquisition Date Fair Value		Accumulated Amortization					Net Carrying Value
Goodwill:
Ark	N/A	$	116.8	$	—				$	116.8	$	116.8	$	—				$	116.8
Kudu	N/A	7.6		—					7.6		7.6		—					7.6


Other Operations	N/A	52.1		—					52.1		17.9		—					17.9
Total goodwill		176.5		—					176.5		142.3		—					142.3
Other intangible assets:
Ark
Underwriting capacity	N/A	175.7		—					175.7		175.7		—					175.7
Kudu
Trade names	7	2.2		1.2					1.0		2.2		.9					1.3





Other Operations
Trade names	15.9	17.9		3.0					14.9		8.2		1.5					6.7
Customer relationships	12.4	29.5		7.5					22.0		18.8		4.5					14.3

Other	12.1	2.8		.5					2.3		.3		.1					.2
Subtotal		50.2		11.0					39.2		27.3		6.1					21.2
Total other intangible assets		228.1		12.2					215.9		205.2		7.0					198.2
Total goodwill and other intangible assets		$	404.6	$	12.2				392.4		$	347.5	7.0					340.5
Goodwill and other intangible assets attributed to non-controlling interests						(102.7)									(91.8)
Goodwill and other intangible assets included in White Mountains’s common shareholders’ equity							$	289.7								$	248.7

Schedule of Goodwill and Intangible Assets Rollforward

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


	December 31, 2022						December 31, 2021
Millions	Goodwill		Other Intangible Assets		Total Goodwill and Other Intangible Assets		Goodwill		Other Intangible Assets		Total Goodwill and Other Intangible Assets
Beginning balance	$	142.3	$	198.2	$	340.5	$	19.2	$	26.4	$	45.6
Acquisition of businesses (1)	59.5		—		59.5		15.8		—		15.8
Ark Transaction	—		—		—		116.8		175.7		292.5
Attribution of acquisition date fair value estimates between goodwill and other intangible assets	(22.9)		22.9		—		(9.3)		9.3		—
Measurement period adjustments (2)	(2.4)		—		(2.4)		(.2)		—		(.2)


Assets held for sale (3)	—		—		—		—		(8.6)		(8.6)


Amortization	—		(5.2)		(5.2)		—		(4.6)		(4.6)
Ending balance	$	176.5	$	215.9	$	392.4	$	142.3	$	198.2	$	340.5

(1) Relates to acquisitions within Other Operations.

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
2023	$	7.1
2024	6.6
2025	5.7
2026	4.8
2027 and years after	16.0
Total (1)	$	40.2

(1) Excludes Ark’s indefinite-lived intangible assets of $175.7.

Loss and Loss Adjustment Expense Reserves (Tables)

12 Months Ended

Dec. 31, 2022

Insurance Loss Reserves [Abstract]

Schedule of Liability for Unpaid Claims and Claims Adjustment Expense

The following table summarizes the loss and LAE reserve activity of Ark’s insurance and reinsurance subsidiaries for the year ended December 31, 2022 and 2021:


	Year Ended December 31,
Millions	2022		2021
Gross beginning balance	$	894.7	$	696.0
Less: beginning reinsurance recoverable on unpaid losses (1)	(428.9)		(433.4)
Net loss and LAE reserves	465.8		262.6

Losses and LAE incurred relating to:
Current year losses	588.1		336.3
Prior year losses	(51.7)		(21.5)
Net incurred losses and LAE	536.4		314.8

Loss and LAE paid relating to:
Current year losses	(98.9)		(43.9)
Prior year losses	(158.6)		(61.6)
Net paid losses and LAE	(257.5)		(105.5)

Change in TPC Providers’ participation (2)	57.5		(2.2)
Foreign currency translation and other adjustments to loss and LAE reserves	(10.7)		(3.9)

Net ending balance	791.5		465.8
Plus: ending reinsurance recoverable on unpaid losses (3)	505.0		428.9
Gross ending balance	$	1,296.5	$	894.7

(1) The beginning reinsurance recoverable on unpaid losses includes amounts attributable to TPC Providers of $276.8 and $319.2 as of December 31, 2021 and 2020.

(2) Amount represents the impact to net loss and LAE reserves due to a change in the TPC Providers’ participation related to the annual RITC process.

(3) The ending reinsurance recoverable on unpaid losses on unpaid losses includes amounts attributable to TPC Providers of $145.4 and $276.8 as of December 31, 2022 and 2021.


	Year Ended December 31,
Millions	2022		2021
Property and Accident & Health	$	258.2	$	175.0
Specialty	204.3		85.2
Marine & Energy	196.4		99.3

Casualty - Active	71.5		37.4
Casualty - Runoff	60.8		68.4
Other	.3		.5
Unpaid loss and LAE reserves, net of reinsurance recoverables on unpaid losses	791.5		465.8
Plus: Reinsurance recoverables on unpaid losses (1)
Property and Accident & Health	224.6		145.2
Specialty	97.2		68.9
Marine & Energy	79.8		70.2
Casualty - Active	49.9		41.4
Casualty - Runoff	53.5		103.2
Total Reinsurance recoverables on unpaid losses (1)	505.0		428.9
Total unpaid loss and LAE reserves	$	1,296.5	$	894.7

(1) The reinsurance recoverables on unpaid losses include amounts attributable to TPC Providers of $145.4 and $276.8 as of December 31, 2022 and 2021.

Schedule of Third Party Participation of LAE Reserves by Year of Account


	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022
TPC Providers’ Participation	—	%	66.2	%	70.0	%	59.6	%	60.0	%	57.6	%	58.3	%	42.8	%	—	%	—	%

Short-duration Insurance Contracts, Claims Development


Property and Accident & Health
$ in Millions
	Incurred Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,																				As of December 31, 2022
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022		Total IBNR plus expected development on reported claims		Cumulative number of reported claims
	Unaudited
2013	$	67.8	$	60.4	$	60.3	$	60.1	$	59.6	$	59.5	$	59.4	$	59.3	$	59.3	$	59.3	$	.1	2,530
2014			32.2		29.1		29.0		28.3		28.1		28.2		28.2		28.2		28.2		.1		2,919
2015					18.8		17.9		16.9		15.9		15.7		15.7		15.5		15.4		.1		2,826
2016							21.9		17.2		17.9		18.1		18.1		18.3		18.2		.1		3,419
2017									24.6		31.4		38.9		37.9		36.5		36.0		5.7		4,599
2018											38.1		44.5		46.4		44.1		44.2		1.3		4,254
2019													31.6		28.9		24.7		21.5		.7		3,999
2020															65.2		63.3		62.9		7.3		4,551
2021																	163.0		146.8		10.6		3,318
2022																			234.5		90.1		2,899
																	Total		$	667.0


Property and Accident & Health
Millions
	Cumulative Paid Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022
	Unaudited
2013	$	15.4	$	39.1	$	58.1	$	59.1	$	59.1	$	59.4	$	59.3	$	59.3	$	59.2	$	59.2
2014			13.6		24.9		27.1		27.5		27.6		27.8		27.9		27.8		27.9
2015					6.9		12.2		13.4		14.6		14.6		14.8		15.0		15.0
2016							8.5		13.1		16.4		16.8		16.9		17.2		17.8
2017									16.8		25.8		31.6		32.8		29.6		27.3
2018											15.6		32.2		40.1		40.0		40.8
2019													6.8		16.7		18.3		18.5
2020															11.2		34.1		47.0
2021																	30.8		86.7
2022																			70.0
																	Total		410.2
All outstanding liabilities before 2013, net of reinsurance																			1.4
Loss and LAE reserves, net of reinsurance																			$	258.2


Specialty
$ in Millions
	Incurred Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,																				As of December 31, 2022
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022		Total IBNR plus expected development on reported claims		Cumulative number of reported claims
	Unaudited
2013	$	47.0	$	28.5	$	17.6	$	16.2	$	15.9	$	15.8	$	15.5	$	15.7	$	15.7	$	15.8	$	.1	1,042
2014			45.5		43.8		40.8		40.4		40.8		43.3		43.4		43.3		43.1		—		1,357
2015					16.2		13.6		11.2		9.6		9.9		10.1		10.1		7.8		.1		1,840
2016							18.1		14.1		10.8		11.1		11.7		11.6		8.8		.2		1,927
2017									17.3		12.2		11.3		10.8		11.0		10.0		—		2,187
2018											13.2		14.9		15.4		14.7		13.5		.7		2,110
2019													18.5		16.3		15.4		22.4		1.1		2,347
2020															21.4		20.5		16.3		2.5		1,985
2021																	67.6		59.4		33.9		1,644
2022																			172.8		125.3		985
																	Total		$	369.9


Specialty
Millions
	Cumulative Paid Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022
	Unaudited
2013	$	17.0	$	13.2	$	14.9	$	15.4	$	15.5	$	15.7	$	15.7	$	15.7	$	15.6	$	15.6
2014			26.3		38.9		39.7		40.1		40.7		42.0		42.8		42.7		43.0
2015					4.0		7.0		7.6		8.0		8.1		8.1		8.1		6.4
2016							3.2		7.9		9.1		9.9		10.3		10.3		8.5
2017									3.1		6.6		8.4		8.5		8.5		9.2
2018											2.7		8.2		10.0		10.4		11.8
2019													4.8		6.9		7.4		18.2
2020															5.2		10.6		13.0
2021																	5.1		24.1
2022																			16.0
																	Total		165.8
All outstanding liabilities before 2013, net of reinsurance																			.2
Loss and LAE reserves, net of reinsurance																			$	204.3


Specialty
	Average Annual Percentage Payout of Incurred Losses and LAE by Age, Net of Reinsurance
	Unaudited
Years	1	2	3	4	5	6	7	8	9	10
	25.8%	33.4%	7.8%	4.8%	5.9%	5.9%	1.4%	1.9%	(3.2)%	(0.8)%


Marine & Energy
$ in Millions
	Incurred Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,																				As of December 31, 2022
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022		Total IBNR plus expected development on reported claims		Cumulative number of reported claims
	Unaudited
2013	$	55.4	$	41.7	$	32.3	$	31.0	$	30.8	$	29.6	$	29.5	$	29.3	$	29.4	$	29.3	$	(.2)	2,638
2014			34.1		19.9		17.0		16.1		14.0		13.6		13.9		13.6		13.7		(.2)		2,572
2015					21.0		16.7		15.4		12.6		12.0		12.1		12.0		12.2		—		3,238
2016							23.1		19.2		15.4		14.3		14.0		14.5		13.8		—		3,764
2017									25.3		18.6		16.8		16.2		15.9		15.0		.2		4,117
2018											24.6		19.1		16.6		17.0		16.6		.2		3,205
2019													20.7		18.6		18.6		18.3		.6		2,331
2020															24.4		21.7		23.2		1.8		1,529
2021																	83.0		66.1		24.8		1,356
2022																			148.2		99.5		1,188
																	Total		$	356.4


Marine & Energy
Millions
	Cumulative Paid Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022
	Unaudited
2013	$	7.8	$	22.2	$	27.6	$	28.6	$	29.1	$	29.3	$	29.3	$	29.1	$	29.3	$	29.3
2014			5.8		12.1		13.2		14.0		14.1		13.4		13.6		13.5		13.7
2015					4.0		7.8		9.6		10.9		10.3		10.4		10.8		11.4
2016							5.5		10.0		12.6		13.0		13.1		13.7		13.4
2017									5.1		11.1		12.8		14.0		14.1		14.1
2018											2.7		12.5		14.0		14.7		15.4
2019													3.3		10.6		12.6		14.3
2020															3.1		12.7		16.0
2021																	6.3		24.2
2022																			12.2
																	Total		164.0
All outstanding liabilities before 2013, net of reinsurance																			4.0
Loss and LAE reserves, net of reinsurance																			$	196.4


Casualty - Active
$ in Millions
	Incurred Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,																				As of December 31, 2022
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022		Total IBNR plus expected development on reported claims		Cumulative number of reported claims
	Unaudited
2013	$	18.2	$	13.0	$	8.5	$	8.0	$	8.0	$	8.1	$	7.7	$	7.8	$	7.8	$	7.8	$	.1	1,144
2014			12.6		8.7		7.7		7.5		7.4		7.0		7.1		6.9		7.1		.2		1,385
2015					8.8		9.0		7.4		7.3		6.6		6.4		6.3		6.5		.2		1,280
2016							7.6		7.1		7.8		7.8		7.9		8.0		8.1		.3		1,528
2017									9.5		9.6		8.7		7.3		7.0		8.4		.9		1,580
2018											11.0		11.5		9.2		9.0		6.8		1.1		1,036
2019													11.6		10.4		9.1		7.3		2.4		834
2020															9.7		8.3		7.1		4.2		524
2021																	17.4		18.4		16.3		674
2022																			32.0		28.8		832
																	Total		$	109.5


Casualty - Active
Millions
	Cumulative Paid Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022
	Unaudited
2013	$	1.5	$	3.6	$	5.3	$	5.8	$	6.3	$	6.7	$	7.0	$	7.0	$	7.3	$	7.5
2014			1.3		3.5		4.2		4.7		5.2		5.5		5.9		6.0		6.2
2015					1.8		2.4		3.2		4.4		4.7		4.9		5.1		5.5
2016							.2		1.0		2.3		4.0		4.6		5.3		6.5
2017									.8		1.7		2.8		3.4		4.2		5.7
2018											.3		1.4		3.5		4.3		4.3
2019													.3		1.4		2.3		3.0
2020															.5		1.0		2.0
2021																	.5		.9
2022																			.4
																	Total		42.0
All outstanding liabilities before 2013, net of reinsurance																			4.0
Loss and LAE reserves, net of reinsurance																			$	71.5


Casualty - Runoff
$ in Millions
	Incurred Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,																				As of December 31, 2022
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022		Total IBNR plus expected development on reported claims		Cumulative number of reported claims
	Unaudited
2013	$	47.7	$	51.4	$	47.7	$	49.0	$	47.6	$	47.3	$	47.7	$	47.5	$	47.5	$	47.5	$	1.4	1,798
2014			45.8		45.3		47.8		50.9		54.5		56.0		56.0		55.8		55.6		1.3		1,941
2015					33.8		29.4		30.6		34.0		33.8		34.8		34.1		36.6		1.6		1,995
2016							28.6		28.3		36.5		34.7		34.9		34.6		33.8		1.7		2,150
2017									27.4		30.8		28.2		28.9		28.4		26.7		2.2		1,599
2018											29.4		23.9		23.0		22.3		21.9		3.3		1,267
2019													21.1		17.8		18.0		19.4		5.0		961
2020															11.3		7.6		9.3		3.9		558
2021																	8.2		4.8		2.7		277
2022																			.6		.1		76
																	Total		$	256.2


Casualty - Runoff
Millions
	Cumulative Paid Loss and LAE, Net of Reinsurance
	For the Years Ended December 31,
Accident Year	2013		2014		2015		2016		2017		2018		2019		2020		2021		2022
	Unaudited
2013	$	7.1	$	19.4	$	35.7	$	40.6	$	42.4	$	43.3	$	43.9	$	44.6	$	44.9	$	45.2
2014			6.4		23.1		29.5		36.4		43.1		46.9		48.5		49.3		51.8
2015					4.3		8.2		14.5		21.4		24.7		27.3		28.9		33.1
2016							3.9		10.2		17.7		22.7		25.4		27.8		28.7
2017									3.2		9.4		14.6		18.5		21.4		22.5
2018											3.4		7.4		12.6		14.9		16.3
2019													3.3		5.8		7.8		12.1
2020															.8		1.3		3.1
2021																	.5		1.7
2022																			.3
																	Total		214.8
All outstanding liabilities before 2013, net of reinsurance																			19.4
Loss and LAE reserves, net of reinsurance																			$	60.8

Short-duration Insurance Contracts, Schedule of Historical Claims Duration


Property and Accident & Health
	Average Annual Percentage Payout of Incurred Losses and LAE by Age, Net of Reinsurance
	Unaudited
Years	1	2	3	4	5	6	7	8	9	10
	31.4%	34.2%	19.3%	5.5%	1.2%	0.8%	0.8%	0.3%	—%	—%


Marine & Energy
	Average Annual Percentage Payout of Incurred Losses and LAE by Age, Net of Reinsurance
	Unaudited
Years	1	2	3	4	5	6	7	8	9	10
	17.4%	35.8%	19.9%	5.9%	4.3%	6.9%	0.3%	0.3%	(0.3)%	0.1%


Casualty - Active
	Average Annual Percentage Payout of Incurred Losses and LAE by Age, Net of Reinsurance
	Unaudited
Years	1	2	3	4	5	6	7	8	9	10
	6.8%	11.7%	16.7%	12.7%	8.0%	10.8%	4.9%	3.1%	1.2%	2.9%


Casualty - Runoff
	Average Annual Percentage Payout of Incurred Losses and LAE by Age, Net of Reinsurance
	Unaudited
Years	1	2	3	4	5	6	7	8	9	10
	9.4%	15.4%	17.2%	15.7%	9.0%	7.4%	6.3%	4.3%	2.8%	1.4%

Third-Party Reinsurance (Tables)

12 Months Ended

Dec. 31, 2022

Reinsurance Disclosures [Abstract]

Effects of Reinsurance

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


	Year Ended December 31,
Millions	2022		2021
Written premiums:
Gross	$	1,452.0	$	1,058.7


Ceded	(256.8)		(199.6)
Net written premiums	$	1,195.2	$	859.1
Earned premiums:
Gross	$	1,324.2	$	886.4


Ceded	(280.8)		(249.1)
Net earned premiums	$	1,043.4	$	637.3
Losses and LAE:
Gross	$	814.9	$	442.9


Ceded	(278.5)		(128.1)
Net Losses and LAE	$	536.4	$	314.8

The following table provides a listing of Ark’s remaining gross and net reinsurance recoverables, excluding amounts related to TPC Providers, by the reinsurer’s A.M. Best Company, Inc. (“A.M. Best”) rating and the percentage of total recoverables.


$ in Millions	As of December 31, 2022
A.M. Best Rating (1)	Gross		Collateral		Net		% of Total
A+ or better	$	190.0	$	—	$	190.0	67.4	%
A- to A	75.3		—		75.3		26.7
B++ or lower and not rated	125.4		108.9		16.5		5.9
Total	$	390.7	$	108.9	$	281.8	100.0	%

(1) A.M. Best ratings as detailed above are: “A+ or better” (Superior) “A- to A” (Excellent), “B++” (Good).

Debt (Tables)

12 Months Ended

Dec. 31, 2022

Debt Disclosure [Abstract]

Schedule of debt outstanding

The following table presents White Mountains’s debt outstanding as of December 31, 2022 and 2021:


	December 31,		Effective	December 31,		Effective
$ in Millions	2022		Rate (1)	2021		Rate (1)



HG Global Senior Notes	$	150.0	8.9%	$	—
Unamortized discount and issuance cost	(3.5)			—
HG Global Senior Notes, carrying value	146.5			—
Ark 2007 Subordinated Notes, carrying value	30.0			30.0
Ark 2021 Notes Tranche 1	41.3			44.2
Ark 2021 Notes Tranche 2	47.0			47.0
Ark 2021 Notes Tranche 3	70.0			70.0
Unamortized issuance cost	(4.6)			(5.3)
Ark 2021 Subordinated Notes, carrying value	153.7			155.9
Total Ark Subordinated Notes, carrying value	183.7		7.6%	185.9		6.9%




Kudu Credit Facility	215.2		6.1%	225.4		4.3%
Unamortized issuance cost	(6.9)			(7.2)
Kudu Credit Facility, carrying value	208.3			218.2






Other Operations debt	37.4		6.6%	17.1		7.5%
Unamortized issuance cost	(.7)			(.3)
Other Operations debt, carrying value	36.7			16.8
Total debt	$	575.2		$	420.9

(1) Effective rate includes the effect of the amortization of debt issuance costs and, where applicable, the original issue discount.

The following table presents the change in debt under the Kudu Bank Facility and Kudu Credit Facility for the years ended December 31, 2022, 2021 and 2020:


	Year Ended December 31,
Millions	2022		2021		2020
Kudu Bank Facility
Beginning balance	$	—	$	89.2	$	57.0
Term loans
Borrowings	—		3.0		32.2
Repayments	—		(92.2)		—
Ending balance	$	—	$	—	$	89.2

Kudu Credit Facility
Beginning balance	$	225.4	$	—	$	—
Term loans
Borrowings	35.0		232.0		—
Repayments	(45.2)		(6.6)		—
Ending balance	$	215.2	$	225.4	$	—

Schedule of contractual repayments of debt

The following table presents a schedule of contractual repayments of White Mountains’s debt as of December 31, 2022:


Millions	December 31, 2022
Due in one year or less	$	5.4
Due in two to three years	12.6
Due in four to five years	30.7
Due after five years	542.2
Total	$	590.9

- 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

+ Details

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2022

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, 2022, 2021 and 2020:


	Year Ended December 31,
Millions	2022		2021		2020
Current income tax (expense) benefit:
U.S. federal	$	(16.9)	$	(4.8)	$	(10.7)
State	(4.5)		(2.1)		(4.2)
Non-U.S.	(7.1)		(2.8)		(.8)
Total current income tax (expense) benefit	(28.5)		(9.7)		(15.7)
Deferred income tax (expense) benefit:
U.S. federal	(7.3)		(13.9)		21.0
State	(1.8)		(7.0)		10.1
Non-U.S.	(3.8)		(13.8)		(.6)
Total deferred income tax (expense) benefit	(12.9)		(34.7)		30.5
Total income tax (expense) benefit	$	(41.4)	$	(44.4)	$	14.8

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


	Year Ended December 31,
Millions	2022		2021		2020
Tax (expense) benefit at the U.S. statutory rate	$	31.4	$	57.5	$	(138.7)
Differences in taxes resulting from:
Non-U.S. earnings, net of foreign taxes	(41.2)		(78.2)		74.3
Change in valuation allowance	(19.6)		(2.0)		(26.6)
Member’s surplus contributions	(6.2)		(5.6)		(4.8)
Withholding tax	(3.1)		(.3)		(5.0)
State taxes	(2.8)		(7.3)		(8.9)
Officer compensation	(1.0)		(1.5)		(1.1)
Tax rate changes	(.4)		(10.9)		3.1



Tax exempt interest and dividends	.2		.2		.8
Reorganization	—		—		130.5
Tax reserve adjustments	—		—		1.9

Other, net	1.3		3.7		(10.7)


Total income tax (expense) benefit on pre-tax income (loss)	$	(41.4)	$	(44.4)	$	14.8

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	2022		2021
Deferred tax assets related to:
U.S. federal and state net operating and capital loss carryforwards	$	85.4	$	85.7
Non-U.S. net operating loss carryforwards	36.1		46.1
Incentive compensation	21.4		14.5

Accrued interest	8.8		7.8
Deferred acquisition costs	8.0		6.4
Net unrealized investment losses	4.7		—
Tax credit carryforwards	1.8		.2







Other items	.5		.4
Total gross deferred tax assets	166.7		161.1
Less: valuation allowances	94.3		85.6
Total net deferred tax assets	72.4		75.5
Deferred tax liabilities related to:

Member’s surplus contributions	71.3		60.4
Purchase accounting	43.9		43.9
Investment basis difference	33.9		26.8


Deferred underwriting	9.7		4.1
Net unrealized investment gains (losses)	—		10.7
Other items	1.4		1.8
Total deferred tax liabilities	160.2		147.7
Net deferred tax asset (liability)	$	(87.8)	$	(72.2)

Schedule of net operating and capital loss carryforwards

The following table presents net operating loss and capital loss carryforwards as of December 31, 2022, the expiration dates and the deferred tax assets thereon:


	December 31, 2022
Millions	United States		Luxembourg		United Kingdom		Israel		Total

2022-2026	$	—	$	—	$	—	$	—	$	—
2027-2031	.2		—		—		—		.2
2032-2041	250.8		59.5		—		—		310.3
No expiration date	148.5		—		4.9		87.2		240.6
Total	$	399.5	$	59.5	$	4.9	$	87.2	$	551.1
Gross deferred tax asset	$	85.4	$	14.8	$	1.2	$	20.1	$	121.5
Valuation allowance	(85.4)		(14.8)		(1.2)		(20.1)		(121.5)
Net deferred tax asset	$	—	$	—	$	—	$	—	$	—

Municipal Bond Guarantee Insurance (Tables)

12 Months Ended

Dec. 31, 2022

Insurance [Abstract]

Schedule of Insured Obligations

The following table presents a schedule of BAM’s insured obligations as of December 31, 2022 and 2021:


	December 31,
	2022		2021
Contracts outstanding	13,382		12,350
Remaining weighted average contract period (in years)	10.8		10.8
Contractual debt service outstanding (in millions):
Principal	$	99,996.9	$	89,196.5
Interest	48,880.6		41,486.5
Total debt service outstanding	$	148,877.5	$	130,683.0

Gross unearned insurance premiums (in millions)	$	298.3	$	266.3

Schedule of BAM’s future premium revenues

The following table presents a schedule of BAM’s future premium revenues as of December 31, 2022:


Millions	December 31, 2022
January 1, 2023 - March 31, 2023	$	7.0
April 1, 2023 - June 30, 2023	7.0
July 1, 2023 - September 30, 2023	6.8
October 1, 2023 - December 31, 2023	6.7
	27.5
2024	25.9
2025	24.2
2026	22.6
2027	21.0
2028 and thereafter	177.1
Total gross unearned insurance premiums	$	298.3

Schedule of Net Written Premiums

The following table presents a schedule of written premiums and earned premiums included in White Mountains’s HG Global/BAM segment for the years ended December 31, 2022, 2021 and 2020:


	December 31,
Millions	2022		2021		2020
Written premiums:
Direct	$	63.8	$	51.0	$	61.5
Assumed	1.3		4.6		.2
Gross written premiums (1)	$	65.1	$	55.6	$	61.7
Earned premiums:
Direct	$	28.6	$	23.2	$	19.4
Assumed	4.7		3.7		3.4
Gross earned premiums (1)	$	33.3	$	26.9	$	22.8

(1) There are no ceded premium amounts in the periods presented and Gross earned premium are equivalent to net written premiums and net earned premiums.

Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2022

Earnings Per Share [Abstract]

Schedule of earnings per share from continuing operations


	Year Ended December 31,
	2022		2021		2020
Basic and diluted earnings per share numerators (in millions):
Net income (loss) attributable to White Mountains’s common shareholders	$	792.8	$	(275.4)	$	708.7
Less: total income (loss) from discontinued operations, net of tax (1)	903.2		(3.9)		(11.8)
Less: net (income) loss from discontinued operations attributable to non-controlling interests	(.7)		1.0		.2
Net income (loss) from continuing operations attributable to White Mountains’s common shareholders	(109.7)		(272.5)		720.3
Allocation of (earnings) losses to participating restricted common shares (2)	1.3		3.2		(9.5)


Basic and diluted earnings (losses) per share numerators	$	(108.4)	$	(269.3)	$	710.8




Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period	2,862.4		3,079.0		3,122.2
Average unvested restricted common shares (3)	(36.2)		(36.5)		(40.8)
Basic earnings (losses) per share denominator	2,826.2		3,042.5		3,081.4
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period	2,862.4		3,079.0		3,122.2
Average unvested restricted common shares (3)	(36.2)		(36.5)		(40.8)

Diluted earnings (losses) per share denominator	2,826.2		3,042.5		3,081.4
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)	(39.34)		(89.52)		229.69
Basic and diluted earnings (losses) per share	$	(38.34)	$	(88.52)	$	230.69

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

(3) Restricted shares outstanding vest upon a stated date. See Note 12 — “Employee Share-Based Incentive Compensation Plans”.

Schedule of undistributed net earnings (losses) from continuing operations


	Year Ended December 31,
Millions		2022		2021		2020
Undistributed net earnings - continuing operations:
Net income (loss) attributable to White Mountains’s common shareholders, net of restricted common share amounts		$	(108.4)	$	(269.3)	$	710.8
Dividends declared, net of restricted common share amounts (1)		(3.0)		(3.1)		(3.1)
Total undistributed net earnings (losses), net of restricted common share amounts		$	(111.4)	$	(272.4)	$	707.7

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


Millions	December 31, 2021
Assets held for sale
Short-term investments, at fair value	$	7.8
Cash (restricted $89.2)	111.6
Premiums and commissions receivable	85.0
Goodwill and other intangible assets	725.4
Other assets	59.2

Total assets held for sale	$	989.0
Liabilities held for sale
Debt	$	272.1
Premiums payable	135.9
Contingent consideration	6.8
Other liabilities	80.5
Total liabilities held for sale	495.3
Net assets held for sale	$	493.7

Net Income (Loss) from Discontinued Operations


	December 31,
Millions	2022 (1)		2021		2020
Revenues
Commission revenues	$	176.9	$	258.0	$	232.5
Other revenues	48.1		72.4		52.6
Total revenues - NSM Group	225.0		330.4		285.1
Expenses
General and administrative expenses	126.8		190.4		179.5
Broker commission expenses	52.9		80.2		75.3
Change in fair value of contingent consideration	.1		1.0		(3.3)
Amortization of other intangible assets	9.1		35.2		26.7
Loss on assets held for sale	—		28.7		—
Interest expense	12.1		23.3		22.1
Total expenses - NSM Group	201.0		358.8		300.3
Pre-tax income (loss) from discontinued operations - NSM Group	24.0		(28.4)		(15.2)
Income tax (expense) benefit	(7.6)		5.8		5.7
Net income (loss) from discontinued operations, net tax - NSM Group	16.4		(22.6)		(9.5)
Net gain (loss) from sale of discontinued operations, net of tax - NSM Group	886.8		—		—
Net gain (loss) from sale of discontinued operations, net of tax - Sirius Group	—		18.7		(2.3)
Total income (loss) from discontinued operations, net of tax	903.2		(3.9)		(11.8)
Net (income) loss from discontinued operations attributable to non-controlling interests	(.7)		1.0		$	.2
Total income (loss) from discontinued operations attributable to White Mountains’s common shareholders	902.5		(2.9)		(11.6)
Other comprehensive income (loss) from discontinued operations, net of tax - NSM Group	(5.2)		.2		5.9
Net gain (loss) from foreign currency translation from sale of discontinued operations, net of tax - NSM Group	2.9		—		—
Comprehensive income (loss) from discontinued operations	900.2		(2.7)		(5.7)
Other comprehensive (income) loss from discontinued operations attributable to non-controlling interests	.2		(.1)		(.3)
Comprehensive income (loss) from discontinued operations attributable to White Mountains’s common shareholders	$	900.4	$	(2.8)	$	(6.0)

(1) As a result of the NSM Transaction, the results of operations for NSM Group are presented for the period from January 1, 2022 to August 1, 2022.

Net Change in Cash from Discontinued Operations

The following summarizes the net change in cash associated with the businesses classified as discontinued operations for the year ended December 31, 2022, 2021 and 2020:


	Year Ended December 31,
Millions	2022		2021		2020
Net cash provided from (used for) operations	$	38.7	$	42.3	$	35.5
Net cash provided from (used for) investing activities	7.1		(56.5)		(124.9)
Net cash used from (used for) financing activities	(17.5)		(1.0)		128.8
Effect of exchange rate changes on cash	4.0		.2		(2.8)
Net change in cash during the period	32.3		(15.0)		36.6
Cash balances at beginning of period (includes restricted cash of $89.2, $78.4 and $56.3)	111.6		126.6		90.0
Cash sold as part of the sale of NSM Group (includes restricted cash of $105.1, $0.0 and $0.0)	(143.9)		—		—
Cash balances at end of period (includes restricted cash of $0.0, $89.2 and $78.4)	—		111.6		126.6
Supplemental cash flows information:
Interest paid	$	(12.0)	$	(16.6)	$	(20.9)
Net income tax payments	$	—	$	—	$	—

- Definition

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

+ References

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+ Details

Employee Share-Based Incentive Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2022

Share-Based Payment Arrangement [Abstract]

Schedule of performance share activity

The following table presents performance share activity for the years ended December 31, 2022, 2021 and 2020 for performance shares granted under the WTM Incentive Plan:


	Year Ended December 31,
	2022			2021			2020
$ in Millions	Target Performance Shares Outstanding	Accrued Expense		Target Performance Shares Outstanding	Accrued Expense		Target Performance Shares Outstanding	Accrued Expense
Beginning of period	40,828	$	42.2	42,458	$	56.3	42,473	$	43.7
Shares paid or expired (1)	(14,625)	(26.4)		(14,336)	(35.2)		(14,070)	(27.7)
New grants	13,225	—		13,475	—		14,055	—
Forfeitures and cancellations (2)	21	(.4)		(769)	.4		—	(.4)

Expense recognized	—	52.1		—	20.7		—	40.7
End of period	39,449	$	67.5	40,828	$	42.2	42,458	$	56.3

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

Schedule of performance shares outstanding and accrued expense for performance shares awarded

The following table presents performance shares outstanding and accrued expense for performance shares awarded under the WTM Incentive Plan as of December 31, 2022 for each performance cycle:


	December 31, 2022
$ in Millions	Target Performance Shares Outstanding	Accrued Expense
Performance cycle:
2022 – 2024	13,225	$	11.0
2021 – 2023	13,475	19.7
2020 – 2022	13,350	37.8
Sub-total	40,050	68.5
Assumed forfeitures	(601)	(1.0)
Total	39,449	$	67.5

Schedule of unrecognized compensation costs associated with outstanding restricted share awards

der the WTM Incentive Plan for the years ended December 31, 2022, 2021 and 2020:


	Year Ended December 31,
	2022			2021			2020
$ 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	37,850	$	15.9	43,105	$	15.2	43,395	$	16.7
Issued	13,225	13.8		13,475	16.1		14,055	15.1
Vested	(12,725)	—		(17,936)	—		(14,345)	—
Forfeited	—	—		(794)	(.8)		—	—

Expense recognized	—	(14.2)		—	(14.6)		—	(16.6)
End of period	38,350	$	15.5	37,850	$	15.9	43,105	$	15.2

Leases (Tables)

12 Months Ended

Dec. 31, 2022

Leases [Abstract]

Schedule of net lease expense

The following table summarizes net lease expense recognized in White Mountains’s consolidated statement of operations for the years ended December 31, 2022 and 2021:


	December 31,
Millions	2022		2021
Lease cost	$	8.0	$	6.7
Less: sublease income	.7		.4
Net lease cost	$	7.3	$	6.3

Schedule of contractual maturities of lease liabilities

The following table presents the contractual maturities of the lease liabilities associated with White Mountains’s operating lease agreements as of December 31, 2022:


Millions	December 31, 2022
2023	$	8.7
2024	7.6
2025	5.1
2026	2.8
2027	1.6
Thereafter	3.9
Total undiscounted lease payments	29.7
Less: present value adjustment	(2.6)
Operating lease liability	$	27.1

Schedule of lease related assets and liabilities

The following table presents lease related assets and liabilities by reportable segment as of December 31, 2022 and 2021:


	As of December 31, 2022
$ in Millions	HG/BAM		Ark		Kudu		Other Operations		Total		Weighted Average Incremental Borrowing Rate (1)
ROU lease asset	$	5.7	$	6.6	$	5.8	$	7.1	$	25.2	4.1%
Lease liability	$	6.2	$	6.6	$	6.5	$	7.8	$	27.1

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


	As of December 31, 2021
$ in Millions	HG/BAM		Ark		Kudu		Other Operations		Total		Weighted Average Incremental Borrowing Rate (1)
ROU lease asset	$	7.6	$	7.0	$	6.4	$	7.1	28.1		4.0%
Lease liability	$	8.1	$	7.0	$	7.1	$	7.8	$	30.0

(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 (Tables)

12 Months Ended

Dec. 31, 2022

Stockholders' Equity Note [Abstract]

Schedule of noncontrolling interest


	December 31, 2022				December 31, 2021
$ in Millions	Non-controlling Percentage (1)		Non-controlling Equity		Non-controlling Percentage (1)		Non-controlling Equity
Non-controlling interests, excluding BAM
HG Global	3.1	%	$	(.6)	3.1	%	$	8.9
Ark	28.0	%	247.9		28.0	%	230.7
Kudu	10.8	%	75.1		2.5	%	12.4
NSM (2)	—	%	—		3.5	%	16.7


Other	various		20.4		various		11.9
Total, excluding BAM			342.8				280.6

BAM	100.0	%	(154.7)		100.0	%	(124.0)
Total non-controlling interests			$	188.1			$	156.6

(2) As a result of the NSM Transaction, NSM has been classified as discontinued operations through the closing of the transaction. See Note 21 — “Held for Sale and Discontinued Operations.”

Segment Information (Tables)

12 Months Ended

Dec. 31, 2022

Segment Reporting [Abstract]

Schedule of financial information for segments

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


Millions	HG Global/BAM (1)		Ark		Kudu		Other Operations		Total
Year Ended December 31, 2022
Earned insurance premiums (2)	$	33.3	$	1,043.4	$	—	$	—	$	1,076.7
Net investment income	21.5		16.3		54.4		32.2		124.4

Net realized and unrealized investment gains (losses)	(105.8)		(55.2)		64.1		(1.6)		(98.5)
Net realized and unrealized investment gains (losses) from investment in MediaAlpha	—		—		—		(93.0)		(93.0)
Commission revenues	—		—		—		11.5		11.5
Other revenues	4.6		5.0		—		127.2		136.8
Total revenues	(46.4)		1,009.5		118.5		76.3		1,157.9

Loss and loss adjustment expenses	—		536.4		—		—		536.4
Insurance acquisition expenses	11.2		239.4		—		—		250.6

Cost of sales	—		—		—		98.6		98.6
General and administrative expenses	69.1		123.5		14.4		169.2		376.2


Amortization of other intangible assets	—		—		.3		4.9		5.2

Interest expense	8.3		15.1		15.0		1.9		40.3
Total expenses	88.6		914.4		29.7		274.6		1,307.3
Pre-tax income (loss)	$	(135.0)	$	95.1	$	88.8	$	(198.3)	$	(149.4)

(2) Ark’s earned insurance premiums based on the location of Ark’s underwriting offices in the United Kingdom and Bermuda are $638.5 and $404.9.


Millions	HG Global/BAM (1)		Ark		Kudu		Other Operations		Total
Year Ended December 31, 2021
Earned insurance premiums (2)	$	26.9	$	637.3	$	—	$	—	$	664.2
Net investment income	17.5		2.9		43.9		18.2		82.5

Net realized and unrealized investment gains (losses)	(22.9)		16.5		89.9		50.7		134.2
Net realized and unrealized investment gains (losses) from investment in MediaAlpha	—		—		—		(380.3)		(380.3)

Commission revenues	—		—		—		9.6		9.6
Other revenues	1.5		11.8		.2		90.7		104.2
Total revenues	23.0		668.5		134.0		(211.1)		614.4
Losses and loss adjustment expenses	—		314.8				—		314.8
Insurance acquisition expenses	8.3		178.0		—		—		186.3

Cost of sales	—		—		—		69.3		69.3
General and administrative expenses	57.1		115.5		14.5		105.4		292.5


Amortization of other intangible assets	—		—		.3		4.3		4.6
Interest expense	—		7.3		11.7		1.5		20.5
Total expenses	65.4		615.6		26.5		180.5		888.0
Pre-tax income (loss)	$	(42.4)	$	52.9	$	107.5	$	(391.6)	$	(273.6)

(2) Ark’s earned insurance premiums based on the location of Ark’s underwriting offices in the United Kingdom and Bermuda are $459.3 and $178.0.


Millions	HG Global/BAM (1)		Kudu		Other Operations		Total
Year Ended December 31, 2020
Earned insurance premiums	$	22.8	$	—	$	—	$	22.8
Net investment income	19.5		29.5		82.0		131.0
Net realized and unrealized investment gains (losses)	23.7		15.9		(8.8)		30.8
Net realized and unrealized investment gains from investment in MediaAlpha	—		—		686.0		686.0

Commission revenues	—		—		8.3		8.3
Other revenues	2.5		.3		13.9		16.7
Total revenues	68.5		45.7		781.4		895.6

Insurance acquisition expenses	7.0		—		—		7.0

Cost of sales	—		—		11.3		11.3
General and administrative expenses	56.8		11.8		139.3		207.9


Amortization of other intangible assets	—		.3		1.3		1.6
Interest expense	—		6.0		1.4		7.4
Total expenses	63.8		18.1		153.3		235.2
Pre-tax income (loss)	$	4.7	$	27.6	$	628.1	$	660.4

Schedule of selected balance sheet data by segment


Millions Selected Balance Sheet Data	HG Global/BAM			Ark		Kudu		Other Operations			Held for Sale		Total
December 31, 2022:
Total investments	$	975.8		$	1,761.9	$	695.9	$	1,736.4		$	—	$	5,170.0


Total assets	$	1,058.5	(1)	$	3,486.2	$	825.9	$	2,018.7	(2)	$	—	$	7,389.3


Total liabilities	$	501.8	(2)	$	2,520.9	$	273.3	$	158.3		$	—	$	3,454.3
Total White Mountains’s common shareholders’ equity	$	712.0	(2)	$	717.4	$	477.5	$	1,840.0	(2)	$	—	$	3,746.9
Non-controlling interest	$	(155.3)		$	247.9	$	75.1	$	20.4		$	—	$	188.1
December 31, 2021:
Total investments	$	966.5		$	1,562.1	$	669.5	$	1,059.4		$	—	$	4,257.5


Total assets	$	1,044.8	(1)	$	3,027.0	$	727.1	$	1,196.7	(2)	$	1,005.1	$	7,000.7


Total liabilities	$	321.9	(2)	$	2,122.4	$	261.0	$	95.4		$	495.3	$	3,296.0
Total White Mountains’s common shareholders’ equity	$	838.0	(2)	$	673.9	$	453.7	$	1,089.4	(2)	$	493.1	$	3,548.1
Non-controlling interest	$	(115.1)		$	230.7	$	12.4	$	11.9		$	16.7	$	156.6

Schedule of revenue by revenue source

Equity Method Eligible Investments (Tables)

12 Months Ended

Dec. 31, 2022

Equity Method Investments and Joint Ventures [Abstract]

Schedule of equity method eligible investments

The following table presents the ownership interests and carrying values of equity method eligible investments as of December 31, 2022 and 2021:


	December 31, 2022				December 31, 2021
$ in Millions	Ownership Interest		Carrying Value		Ownership Interest		Carrying Value
Kudu Participation Contracts (1)	4.1 - 30.0%		$	695.9	3.2 - 32.0%		$	669.5
Investment in MediaAlpha	27.1	%	168.6		28.0	%	261.6
PassportCard/DavidShield	53.8	%	135.0		53.8	%	120.0
Elementum Holdings, L.P.	29.7	%	30.0		29.7	%	45.0
Other equity method eligible investments, at fair value	Under 50.0%		84.4		Under 50.0%		109.3
Other equity method eligible investments, at fair value	50.0% and over		—		50.0% and over		17.8

Schedule of significant equity method eligible investments


	December 31,
Millions	2022		2021
Balance sheet data:
Total assets	$	170.1	$	289.8
Total liabilities	$	256.2	$	351.4


	Year Ended December 31,
Millions	2022		2021		2020
Income statement data:
Total revenues	$	459.1	$	645.3	$	584.8
Total expenses	$	531.5	$	653.8	$	574.2
Net income (loss)	$	(72.4)	$	(8.5)	$	10.6

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


	December 31,
Millions	2022		2021
Balance sheet data(1):
Total assets	$	2,252.5	$	1,845.7
Total liabilities	$	526.9	$	373.4

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


	Year Ended December 31,
Millions	2022		2021		2020
Income statement data(1):
Total revenues	$	735.3	$	987.4	$	526.5
Total expenses	$	515.9	$	418.7	$	325.9
Net income (loss)	$	219.4	$	568.7	$	200.6

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

Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2022

Fair Value Disclosures [Abstract]

Schedule of the fair value and carrying value of financial instruments

The following table presents the fair value and carrying value of these financial instruments as of December 31, 2022 and 2021:


	December 31, 2022				December 31, 2021
Millions	Fair Value		Carrying Value		Fair Value		Carrying Value
HG Global Senior Notes	$	155.7	$	146.5	$	—	$	—
Ark 2007 Subordinated Notes	$	28.4	$	30.0	$	27.6	$	30.0
Ark 2021 Subordinated Notes	$	163.1	$	153.7	$	162.8	$	155.9
Kudu Credit Facility	$	223.9	$	208.3	$	246.8	$	218.2
Other Operations debt	$	38.2	$	36.7	$	17.7	$	16.8

Held for Sale and Discontinued Operations (Tables)

12 Months Ended

Dec. 31, 2022

Discontinued Operations and Disposal Groups [Abstract]

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


	Year Ended December 31,
Millions		2022		2021		2020
Undistributed net earnings - continuing operations:
Net income (loss) attributable to White Mountains’s common shareholders, net of restricted common share amounts		$	(108.4)	$	(269.3)	$	710.8
Dividends declared, net of restricted common share amounts (1)		(3.0)		(3.1)		(3.1)
Total undistributed net earnings (losses), net of restricted common share amounts		$	(111.4)	$	(272.4)	$	707.7

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


Millions	December 31, 2021
Assets held for sale
Short-term investments, at fair value	$	7.8
Cash (restricted $89.2)	111.6
Premiums and commissions receivable	85.0
Goodwill and other intangible assets	725.4
Other assets	59.2

Total assets held for sale	$	989.0
Liabilities held for sale
Debt	$	272.1
Premiums payable	135.9
Contingent consideration	6.8
Other liabilities	80.5
Total liabilities held for sale	495.3
Net assets held for sale	$	493.7

Net Income (Loss) from Discontinued Operations


	December 31,
Millions	2022 (1)		2021		2020
Revenues
Commission revenues	$	176.9	$	258.0	$	232.5
Other revenues	48.1		72.4		52.6
Total revenues - NSM Group	225.0		330.4		285.1
Expenses
General and administrative expenses	126.8		190.4		179.5
Broker commission expenses	52.9		80.2		75.3
Change in fair value of contingent consideration	.1		1.0		(3.3)
Amortization of other intangible assets	9.1		35.2		26.7
Loss on assets held for sale	—		28.7		—
Interest expense	12.1		23.3		22.1
Total expenses - NSM Group	201.0		358.8		300.3
Pre-tax income (loss) from discontinued operations - NSM Group	24.0		(28.4)		(15.2)
Income tax (expense) benefit	(7.6)		5.8		5.7
Net income (loss) from discontinued operations, net tax - NSM Group	16.4		(22.6)		(9.5)
Net gain (loss) from sale of discontinued operations, net of tax - NSM Group	886.8		—		—
Net gain (loss) from sale of discontinued operations, net of tax - Sirius Group	—		18.7		(2.3)
Total income (loss) from discontinued operations, net of tax	903.2		(3.9)		(11.8)
Net (income) loss from discontinued operations attributable to non-controlling interests	(.7)		1.0		$	.2
Total income (loss) from discontinued operations attributable to White Mountains’s common shareholders	902.5		(2.9)		(11.6)
Other comprehensive income (loss) from discontinued operations, net of tax - NSM Group	(5.2)		.2		5.9
Net gain (loss) from foreign currency translation from sale of discontinued operations, net of tax - NSM Group	2.9		—		—
Comprehensive income (loss) from discontinued operations	900.2		(2.7)		(5.7)
Other comprehensive (income) loss from discontinued operations attributable to non-controlling interests	.2		(.1)		(.3)
Comprehensive income (loss) from discontinued operations attributable to White Mountains’s common shareholders	$	900.4	$	(2.8)	$	(6.0)

(1) As a result of the NSM Transaction, the results of operations for NSM Group are presented for the period from January 1, 2022 to August 1, 2022.

Net Change in Cash from Discontinued Operations

The following summarizes the net change in cash associated with the businesses classified as discontinued operations for the year ended December 31, 2022, 2021 and 2020:


	Year Ended December 31,
Millions	2022		2021		2020
Net cash provided from (used for) operations	$	38.7	$	42.3	$	35.5
Net cash provided from (used for) investing activities	7.1		(56.5)		(124.9)
Net cash used from (used for) financing activities	(17.5)		(1.0)		128.8
Effect of exchange rate changes on cash	4.0		.2		(2.8)
Net change in cash during the period	32.3		(15.0)		36.6
Cash balances at beginning of period (includes restricted cash of $89.2, $78.4 and $56.3)	111.6		126.6		90.0
Cash sold as part of the sale of NSM Group (includes restricted cash of $105.1, $0.0 and $0.0)	(143.9)		—		—
Cash balances at end of period (includes restricted cash of $0.0, $89.2 and $78.4)	—		111.6		126.6
Supplemental cash flows information:
Interest paid	$	(12.0)	$	(16.6)	$	(20.9)
Net income tax payments	$	—	$	—	$	—

Schedule of earnings per share for discontinued operations

The following table presents the Company’s computation of earnings per share for discontinued operations for the years ended December 31, 2022, 2021 and 2020:


	Year Ended December 31,
	2022		2021		2020
Basic and diluted earnings per share numerators (in millions):
Net income (loss) attributable to White Mountains’s common shareholders	$	792.8	$	(275.4)	$	708.7
Less: net income (loss) from continuing operations	(190.8)		(318.0)		675.2
Less: net (income) loss from continuing operations attributable to non-controlling interest	81.1		45.5		45.1
Total income (loss) from discontinued operations attributable to White Mountains’s common shareholders (1)	902.5		(2.9)		(11.6)
Allocation of (earnings) losses to participating restricted common shares (2)	(11.4)		—		.2
Basic and diluted (loss) earnings per share numerators	$	891.1	$	(2.9)	$	(11.4)
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period	2,862.4		3,079.0		3,122.2
Average unvested restricted common shares (3)	(36.2)		(36.5)		(40.8)
Basic earnings (loss) per share denominator	2,826.2		3,042.5		3,081.4
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period	2,862.4		3,079.0		3,122.2
Average unvested restricted common shares (3)	(36.2)		(36.5)		(40.8)

Diluted earnings (loss) per share denominator	2,826.2		3,042.5		3,081.4
Basic (loss) earnings per share (in dollars) - discontinued operations:	$	315.30	$	(.94)	$	(3.72)
Diluted (loss) earnings per share (in dollars) - discontinued operations:	$	315.30	$	(.94)	$	(3.72)

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

(3) Restricted shares outstanding vest upon a stated date. See Note 12 — “Employee Share-Based Incentive Compensation Plans.”

- Definition

+ References

+ Details

Basis of Presentation and Significant Accounting Policies - Reportable Segments (Details) $ in Millions		12 Months Ended
	Jan. 01, 2021	Dec. 31, 2022 segment	Dec. 31, 2021	Dec. 31, 2012 USD ($)
Basis of Presentation
Number of operating segments \| segment		3
Ark
Basis of Presentation
Percent of shares outstanding	12.50%	12.50%
HG Global
Basis of Presentation
Percentage of par value of policy reinsured		15.00%
Surplus notes \| $				$ 503.0
HG Global \| Preferred stocks
Basis of Presentation
Ownership interest (as a percent)		96.90%	96.90%
HG Global \| Common equity securities
Basis of Presentation
Ownership interest (as a percent)		88.40%	88.40%
Ark \| Ark
Basis of Presentation
Ownership interest (as a percent)		72.00%	72.00%
Fully diluted ownership interest (as a percent)		63.00%	63.00%
NSM
Basis of Presentation
Ownership interest (as a percent)			96.50%
Fully diluted ownership interest (as a percent)			87.30%
Kudu
Basis of Presentation
Ownership interest (as a percent)		89.30%	99.30%
Fully diluted ownership interest (as a percent)		76.10%	84.70%

Basis of Presentation and Significant Accounting Policies - Held for Sale and Discontinued Operations (Details) - NSM	Dec. 31, 2021
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest (as a percent)	96.50%
Fully diluted ownership interest (as a percent)	87.30%

Basis of Presentation and Significant Accounting Policies - Investment Securities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Percentage of investments recorded at fair value	72.00%	68.00%
Variance threshold for outliers	$ 0.5
Variance threshold for outliers (as a percent)	5.00%

Basis of Presentation and Significant Accounting Policies - Fair Value Measurements and Other Long-Term Investments (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Fair value measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value investments	$ 5,170.0	$ 4,265.3
Fair value measured on a recurring basis \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value investments	911.6	890.6
Other long-term investments \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value investments	911.6	890.6	$ 614.2
Other long-term investments \| Fair value measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value investments	926.4	895.3
Other long-term investments \| Fair value measured on a recurring basis \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value investments	911.6	890.6
Other long-term investments — NAV \| Fair value measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value investments	561.6	482.5
Other long-term investments — NAV \| Fair value measured on a recurring basis \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value investments	$ 0.0	$ 0.0

Basis of Presentation and Significant Accounting Policies - Property and Casualty Insurance and Reinsurance (Details)	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Ark \| Amount attributable to TPC Providers
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Percent of underwriting capital provided by third parties	0.00%	0.00%	42.80%	58.30%	57.60%	60.00%	59.60%	70.00%	66.20%	0.00%

Basis of Presentation and Significant Accounting Policies - Foreign Currency Exchange (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Net unrealized foreign currency translation gain (losses)	$ (3.5)	$ 5.1

Basis of Presentation and Significant Accounting Policies - Municipal Bond Guarantee Insurance (Details)	Dec. 31, 2022
Third Point Re \| Ark
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Annual crediting rate	3.00%

Significant Transactions - NSM (Details) - USD ($) $ in Millions		12 Months Ended
	Aug. 01, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Other Significant Noncash Transactions [Line Items]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal, Statement of Income or Comprehensive Income [Extensible Enumeration]		Net gain (loss) from sale of discontinued operations, net of tax
Net gain (loss) from foreign currency translation from sale of discontinued operations, net of tax - NSM Group		$ 2.9	$ 0.0	$ 0.0
NSM
Other Significant Noncash Transactions [Line Items]
Net gain (loss) from sale of discontinued operations, net of tax		$ 886.8	$ 0.0	$ 0.0
Discontinued Operations, Disposed of by Sale \| NSM
Other Significant Noncash Transactions [Line Items]
Disposal group, consideration	$ 1,400.0
Gain (loss) on assets held for sale	875.7
Net gain (loss) from sale of discontinued operations, net of tax	886.8
Net gain (loss) from foreign currency translation from sale of discontinued operations, net of tax - NSM Group	2.9
Compensation and other costs	$ 14.0

Significant Transactions - Ark (Details) - USD ($) $ in Millions			3 Months Ended	12 Months Ended
	Jan. 01, 2021	Oct. 01, 2020	Mar. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2020
Other Operations
Other Significant Noncash Transactions [Line Items]
Cash pre-funded/placed in escrow for Ark Transaction							$ 646.3
Goodwill and other intangible assets				$ 91.3	$ 39.1
Ark
Other Significant Noncash Transactions [Line Items]
Cash pre-funded/placed in escrow for Ark Transaction							366.3
Goodwill and other intangible assets				292.5	292.5
Contingent consideration				45.3	28.0
Purchase price adjustment				17.3	5.5
Ark \| In-force Business Acquired
Other Significant Noncash Transactions [Line Items]
Amortization				$ 7.5	$ 64.2
Ark \| Lloyd
Other Significant Noncash Transactions [Line Items]
Cash pre-funded/placed in escrow for Ark Transaction							$ 280.0
Ark
Other Significant Noncash Transactions [Line Items]
Merger agreement, equity capital contributed	$ 605.4	$ 605.4
Equity capital, pre money valuation amount		300.0
Additional equity purchase from shareholders		40.9
Investment, potential additional contribution of equity capital	$ 200.0	$ 200.0
Ownership interest after all transactions (as a percent)	72.00%
Ownership interest on fully-diluted basis (as a percent)	63.00%
Percent of shares outstanding	12.50%			12.50%
Assets acquired	$ 2,500.0
Goodwill and other intangible assets	292.5
Liabilities acquired	1,700.0
Contingent consideration	22.5
Noncontrolling interest acquired	$ 220.2
Transaction costs			$ 25.3
Ark \| Group Ark Insurance Limited \| Unsecured Subordinated Debt
Other Significant Noncash Transactions [Line Items]
Notes issued						$ 163.3

Significant Transactions - Schedule of Assets Acquired and Liabilities Assumed, Ark (Details) - USD ($) $ in Millions	Jan. 01, 2021	Oct. 01, 2020	Dec. 31, 2022	Dec. 31, 2021
Other Significant Transactions [Line Items]
Goodwill			$ 176.5	$ 142.3
Ark
Other Significant Transactions [Line Items]
Investments	$ 594.3
Cash	52.0
Reinsurance recoverables	433.4
Insurance premiums receivable	236.7
Ceded unearned premiums	170.2
Value of in-force business acquired	71.7
Other assets	88.9
Loss and loss adjustment expense reserves	(696.0)
Unearned insurance premiums	(326.1)
Debt	(46.4)
Ceded reinsurance payable	(528.3)
Other liabilities	(25.9)
Net tangible assets acquired	24.5
Goodwill	116.8
Other intangible assets - syndicate underwriting capacity	175.7
Deferred tax liability on other intangible assets	(33.4)
Net assets acquired	283.6
Merger agreement, equity capital contributed	$ 605.4	$ 605.4

Significant Transactions - Outrigger Re (Details) - USD ($) $ in Millions			3 Months Ended	12 Months Ended
	Dec. 20, 2022	Jan. 01, 2021	Dec. 31, 2022	Dec. 31, 2022
Ark
Other Significant Transactions [Line Items]
Ownership interest after all transactions (as a percent)		72.00%
Outrigger Re
Other Significant Transactions [Line Items]
Issuance of redeemable preference shares	$ 250.0
Outrigger Re \| Cash and Short Term Investments
Other Significant Transactions [Line Items]
Investment owned, balance			$ 203.7	$ 203.7
Assets held in trust, expenses				$ 1.3
Outrigger Re
Other Significant Transactions [Line Items]
Purchase price			$ 205.0
Ownership interest after all transactions (as a percent)			100.00%

Significant Transactions - MediaAlpha (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions			12 Months Ended
	Mar. 23, 2021	Oct. 30, 2020	Dec. 31, 2022	Dec. 31, 2021
MediaAlpha
Other Significant Noncash Transactions [Line Items]
Ownership interest (as a percent)			27.10%	28.00%
Share price (in USD per share)			$ 9.95
Investment in MediaAlpha, at fair value			$ 168.6
Other Operations
Other Significant Noncash Transactions [Line Items]
Investment in MediaAlpha, at fair value			$ 168.6	$ 261.6
Secondary Offering \| MediaAlpha
Other Significant Noncash Transactions [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	8,050
Sale of stock, price per share (in USD per share)	$ 46.00
Sale of stock, price per share net of underwriting fees (in dollars per share)	$ 44.62
MediaAlpha
Other Significant Noncash Transactions [Line Items]
Investment owned (in shares)			16,900
Fully diluted ownership interest (as a percent)			25.10%
MediaAlpha \| IPO
Other Significant Noncash Transactions [Line Items]
Sale of stock, number of shares issued in transaction (in shares)		3,600
Sale of stock, price per share (in USD per share)		$ 19.00
Sale of stock, price per share net of underwriting fees (in dollars per share)		$ 17.67
Sale of stock, consideration received in transaction		$ 63.8
Proceeds from dividends received		$ 55.0
Increase in investment owned (in dollars per share)			$ 1.00
Increase in book value per share (in dollars per share)			$ 6.60
MediaAlpha \| Secondary Offering
Other Significant Noncash Transactions [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	3,600
Sale of stock, consideration received in transaction	$ 160.3

Significant Transactions - Kudu (Details) $ in Millions		12 Months Ended
Significant Transactions - Kudu (Details) $ in Millions	May 26, 2022 USD ($)	Dec. 31, 2021 USD ($)	May 25, 2022
Kudu
Other Significant Noncash Transactions [Line Items]
Basic ownership	89.30%		99.10%
Kudu
Other Significant Noncash Transactions [Line Items]
Pre-money valuation	1.3
Pre-money valuation, amount	$ 114.0
Enterprise value excluded		$ 54.3
Mass Mutual
Other Significant Noncash Transactions [Line Items]
Equity capital raised	64.1
White Mountains
Other Significant Noncash Transactions [Line Items]
Equity capital raised	50.0
Kudu
Other Significant Noncash Transactions [Line Items]
Equity capital raised	0.4
Kudu
Other Significant Noncash Transactions [Line Items]
Equity capital raised	$ 114.5

Investment Securities - Net Investment Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Investment income:
Total investment income	$ 126.5	$ 84.8	$ 132.2
Third-party investment expenses	(2.1)	(2.3)	(1.2)
Net investment income, pre-tax	124.4	82.5	131.0
Fixed maturity investments
Investment income:
Total investment income	41.4	28.8	29.0
Short-term investments
Investment income:
Total investment income	16.4	0.6	1.1
Common equity securities
Investment income:
Total investment income	1.6	0.1	6.6
MediaAlpha
Investment income:
Total investment income	0.0	0.0	59.9
Other long-term investments
Investment income:
Total investment income	68.1	56.3	35.6
Amount attributable to TPC Providers
Investment income:
Amount attributable to TPC Providers	$ (1.0)	$ (1.0)	$ 0.0

Investment Securities - Net Realized and Unrealized Investment Gains and Losses - (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Realized investment gains (losses)	$ 115.1	$ 156.8	$ 187.1
Unrealized investment gains (losses)	(313.4)	(395.2)	529.7
Net realized and unrealized investment gains (losses)	(93.0)	(380.3)	686.0
Gain (loss) on investments related to foreign currency exchange	(29.3)	(7.7)	4.0
Gross realized investment gains	129.9	212.3	214.4
Gross realized investment losses	14.8	55.5	27.3
Investments Held
Debt Securities, Available-for-sale [Line Items]
Net realized and unrealized investment gains (losses)	(191.5)	(246.1)	716.8
Fixed maturity investments
Debt Securities, Available-for-sale [Line Items]
Realized investment gains (losses)	(11.9)	3.9	10.9
Unrealized investment gains (losses)	(168.4)	(42.2)	27.5
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Realized investment gains (losses)	(1.4)	(0.1)	0.4
Unrealized investment gains (losses)	(1.1)	0.0	0.0
Common equity securities
Debt Securities, Available-for-sale [Line Items]
Realized investment gains (losses)	0.0	0.4	137.2
Unrealized investment gains (losses)	(7.1)	14.9	(130.6)
Net realized and unrealized investment gains (losses)	(7.1)	15.3	6.6
MediaAlpha
Debt Securities, Available-for-sale [Line Items]
Realized investment gains (losses)	0.0	160.3	63.8
Unrealized investment gains (losses)	(93.0)	(540.6)	622.2
Net realized and unrealized investment gains (losses)	(93.0)	(380.3)	686.0
Other long-term investments
Debt Securities, Available-for-sale [Line Items]
Realized investment gains (losses)	128.4	(7.7)	(25.2)
Unrealized investment gains (losses)	(43.8)	172.7	10.6
Total Investments
Debt Securities, Available-for-sale [Line Items]
Net realized and unrealized investment gains (losses)	(198.3)	(238.4)	716.8
Amount attributable to TPC Providers
Debt Securities, Available-for-sale [Line Items]
Net realized and unrealized investment gains (losses)	6.8	(7.7)	0.0
Fixed maturity and short-term investments
Debt Securities, Available-for-sale [Line Items]
Net realized and unrealized investment gains (losses)	(182.8)	(38.4)	38.8
Less: net realized and unrealized gains (losses) on investment securities sold during the period	(2.9)	(8.4)	(8.7)
Fixed maturity and short-term investments \| Investments Held
Debt Securities, Available-for-sale [Line Items]
Net realized and unrealized investment gains (losses)	(179.9)	(30.0)	47.5
Common equity securities and investment in MediaAlpha
Debt Securities, Available-for-sale [Line Items]
Net realized and unrealized investment gains (losses)	(100.1)	(365.0)	692.6
Less: net realized and unrealized gains (losses) on investment securities sold during the period	0.0	20.3	38.3
Common equity securities and investment in MediaAlpha \| Investments Held
Debt Securities, Available-for-sale [Line Items]
Net realized and unrealized investment gains (losses)	$ (100.1)	$ (385.3)	$ 654.3

Investment Securities - Investment Gains and Losses For Level 3 (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Investment securities
Unrealized investment gains (losses)	$ (313.4)	$ (395.2)	$ 529.7
Proceeds from sale and maturity of investments	500.0	800.0	1,400.0
Level 3
Investment securities
Unrealized investment gains	$ 56.5	$ 98.9	276.0
MediaAlpha
Investment securities
Unrealized investment gains (losses)			$ 278.7

Investment Securities - Investment Holdings (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
U.S. Government and agency obligations
Investment securities
Cost or Amortized Cost	$ 216.6	$ 212.1
Gross Unrealized Gains	0.0	0.5
Gross Unrealized Losses	(10.2)	(1.1)
Net Foreign Currency Gains (Losses)	0.0	0.0
Carrying Value	206.4	211.5
Debt securities issued by corporations
Investment securities
Cost or Amortized Cost	1,098.3	993.3
Gross Unrealized Gains	0.6	8.7
Gross Unrealized Losses	(78.3)	(8.7)
Net Foreign Currency Gains (Losses)	(1.8)	(0.4)
Carrying Value	1,018.8	992.9
Municipal obligations
Investment securities
Cost or Amortized Cost	281.6	276.4
Gross Unrealized Gains	0.4	16.8
Gross Unrealized Losses	(23.4)	(1.3)
Net Foreign Currency Gains (Losses)	0.0	0.0
Carrying Value	258.6	291.9
Mortgage and asset-backed securities
Investment securities
Cost or Amortized Cost	288.7	277.2
Gross Unrealized Gains	0.0	2.9
Gross Unrealized Losses	(34.5)	(2.5)
Net Foreign Currency Gains (Losses)	0.0	0.0
Carrying Value	254.2	277.6
Collateralized loan obligations
Investment securities
Cost or Amortized Cost	190.8	136.5
Gross Unrealized Gains	0.1	0.0
Gross Unrealized Losses	(6.0)	(0.4)
Net Foreign Currency Gains (Losses)	(2.0)	(1.1)
Carrying Value	182.9	135.0
Total fixed maturity investments
Investment securities
Cost or Amortized Cost	2,076.0	1,895.5
Gross Unrealized Gains	1.1	28.9
Gross Unrealized Losses	(152.4)	(14.0)
Net Foreign Currency Gains (Losses)	(3.8)	(1.5)
Carrying Value	$ 1,920.9	$ 1,908.9
Including short term fixed
Investment securities
Duration of fixed maturities (years)	2 years 3 months 18 days
Excluding short term investments
Investment securities
Duration of fixed maturities (years)	3 years 4 months 24 days

Investment Securities - Cost and Amortized Cost Maturity Schedule (Details) $ in Millions	Dec. 31, 2022 USD ($)
Cost or Amortized Cost
Total fixed maturity investments	$ 2,076.0
Carrying Value
Total fixed maturity investments	1,920.9
Fixed Maturities and Convertible Fixed Maturities Excluding Mortgage Backed Securities
Cost or Amortized Cost
Due in one year or less	204.8
Due after one year through five years	914.0
Due after five years through ten years	374.4
Due after ten years	103.3
Carrying Value
Due in one year or less	201.2
Due after one year through five years	853.2
Due after five years through ten years	337.4
Due after ten years	92.0
Mortgage and asset-backed securities
Cost or Amortized Cost
Mortgage and asset-backed securities and collateralized loan obligations	479.5
Carrying Value
Mortgage and asset-backed securities and collateralized loan obligations	$ 437.1

Investment Securities - Cost or Amortized Cost, Gross Unrealized Investment Gains and Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Common equity securities
Investment securities
Cost or Amortized Cost	$ 660.6	$ 236.3
Gross Unrealized Gains	26.7	16.1
Gross Unrealized Losses	(8.4)	0.0
Net Foreign Currency Gains (Losses)	(10.5)	(1.3)
Common equity securities, at fair value	668.4	251.1
MediaAlpha
Investment securities
Cost or Amortized Cost	0.0	0.0
Gross Unrealized Gains	168.6	261.6
Gross Unrealized Losses	0.0	0.0
Net Foreign Currency Gains (Losses)	0.0	0.0
Common equity securities, at fair value	168.6	261.6
Other long-term investments
Investment securities
Cost or Amortized Cost	1,340.8	1,186.7
Gross Unrealized Gains	271.1	239.0
Gross Unrealized Losses	(107.1)	(44.1)
Net Foreign Currency Gains (Losses)	(16.8)	(3.8)
Common equity securities, at fair value	$ 1,488.0	$ 1,377.8

Investment Securities - Investments Held on Deposit or as Collateral (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Investment securities
Percentage of investments recorded at fair value	72.00%	68.00%
Investments held in trusts	$ 500.5	$ 479.5
Assets held by insurance regulators	4.6	4.8
Outrigger Re \| Cash and Short Term Investments
Investment securities
Investment owned, balance	203.7
HG Global Senior Notes \| Secured Debt
Investment securities
Interest reserve account	31.2
Letter of Credit \| Short-term investments \| Asset Pledged as Collateral
Investment securities
Investments pledged as collateral	90.3	50.0
Lloyds Bank
Investment securities
Investments held in trusts	137.4	113.8
Fair value investments	$ 319.2	$ 342.8

Investment Securities - Debt Securities Issued By Corporation (Details) - Debt securities issued by corporations - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Investment securities
Fair value investments	$ 1,018.8	$ 992.9
AAA
Investment securities
Fair value investments	11.3	12.0
AA
Investment securities
Fair value investments	96.0	85.0
A
Investment securities
Fair value investments	567.9	490.4
BBB
Investment securities
Fair value investments	337.7	396.8
Other
Investment securities
Fair value investments	$ 5.9	$ 8.7

Investment Securities - Mortgage-backed Asset Securities (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Total mortgage-backed securities
Investment securities
Fair value investments	$ 231.9	$ 256.5
Total mortgage-backed securities \| Level 2
Investment securities
Fair value investments	231.9	256.5
Total mortgage-backed securities \| Level 3
Investment securities
Fair value investments	0.0	0.0
Total mortgage-backed securities \| FNMA
Investment securities
Fair value investments	124.5	125.4
Total mortgage-backed securities \| FNMA \| Level 2
Investment securities
Fair value investments	124.5	125.4
Total mortgage-backed securities \| FNMA \| Level 3
Investment securities
Fair value investments	0.0	0.0
Total mortgage-backed securities \| FHLMC
Investment securities
Fair value investments	78.8	90.5
Total mortgage-backed securities \| FHLMC \| Level 2
Investment securities
Fair value investments	78.8	90.5
Total mortgage-backed securities \| FHLMC \| Level 3
Investment securities
Fair value investments	0.0	0.0
Total mortgage-backed securities \| GNMA
Investment securities
Fair value investments	28.3	40.1
Total mortgage-backed securities \| GNMA \| Level 2
Investment securities
Fair value investments	28.3	40.1
Total mortgage-backed securities \| GNMA \| Level 3
Investment securities
Fair value investments	0.0	0.0
Total mortgage-backed securities \| Total agency
Investment securities
Fair value investments	231.6	256.0
Total mortgage-backed securities \| Total agency \| Level 2
Investment securities
Fair value investments	231.6	256.0
Total mortgage-backed securities \| Total agency \| Level 3
Investment securities
Fair value investments	0.0	0.0
Total mortgage-backed securities \| Non-agency: Residential
Investment securities
Fair value investments	0.3	0.5
Total mortgage-backed securities \| Non-agency: Residential \| Level 2
Investment securities
Fair value investments	0.3	0.5
Total mortgage-backed securities \| Non-agency: Residential \| Level 3
Investment securities
Fair value investments	0.0	0.0
Total mortgage-backed securities \| Total non-agency
Investment securities
Fair value investments	0.3	0.5
Total mortgage-backed securities \| Total non-agency \| Level 2
Investment securities
Fair value investments	0.3	0.5
Total mortgage-backed securities \| Total non-agency \| Level 3
Investment securities
Fair value investments	0.0	0.0
Total other asset-backed securities
Investment securities
Fair value investments	22.3	21.1
Total other asset-backed securities \| Level 2
Investment securities
Fair value investments	22.3	21.1
Total other asset-backed securities \| Level 3
Investment securities
Fair value investments	0.0	0.0
Total other asset-backed securities \| Credit card receivables
Investment securities
Fair value investments	11.9	12.3
Total other asset-backed securities \| Credit card receivables \| Level 2
Investment securities
Fair value investments	11.9	12.3
Total other asset-backed securities \| Credit card receivables \| Level 3
Investment securities
Fair value investments	0.0	0.0
Total other asset-backed securities \| Vehicle receivables
Investment securities
Fair value investments	10.4	8.8
Total other asset-backed securities \| Vehicle receivables \| Level 2
Investment securities
Fair value investments	10.4	8.8
Total other asset-backed securities \| Vehicle receivables \| Level 3
Investment securities
Fair value investments	0.0	0.0
Mortgage and asset-backed securities
Investment securities
Fair value investments	254.2	277.6
Carrying Value	254.2	277.6
Mortgage and asset-backed securities \| Level 2
Investment securities
Fair value investments	254.2	277.6
Mortgage and asset-backed securities \| Level 3
Investment securities
Fair value investments	0.0	0.0
Collateralized loan obligations
Investment securities
Fair value investments	182.9	135.0
Carrying Value	182.9	135.0
Collateralized loan obligations \| Level 2
Investment securities
Fair value investments	182.9	135.0
Collateralized loan obligations \| Level 3
Investment securities
Fair value investments	0.0	0.0
Total mortgage and asset-backed securities and collateralized loan obligations
Investment securities
Fair value investments	437.1	412.6
Total mortgage and asset-backed securities and collateralized loan obligations \| Level 2
Investment securities
Fair value investments	437.1	412.6
Total mortgage and asset-backed securities and collateralized loan obligations \| Level 3
Investment securities
Fair value investments	$ 0.0	$ 0.0

Investment Securities - Investment in MediaAlpha (Details) - MediaAlpha $ / shares in Units, $ in Millions	Dec. 31, 2022 USD ($) $ / shares
Investment securities
Share price (in USD per share) \| $ / shares	$ 9.95
Fair value of investment \| $	$ 168.6

Investment Securities - Other Long-Term Investments (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Investment securities
Other long-term investments	$ 1,488.0	$ 1,377.8
Kudu
Investment securities
Other long-term investments	695.9	669.5
PassportCard/DavidShield
Investment securities
Other long-term investments	135.0	120.0
Elementum Holdings L.P.
Investment securities
Other long-term investments	30.0	45.0
Other unconsolidated entities
Investment securities
Other long-term investments	37.2	34.4
Total unconsolidated entities
Investment securities
Other long-term investments	898.1	868.9
Private equity funds and hedge funds
Investment securities
Other long-term investments	197.8	153.8
Bank loan fund
Investment securities
Other long-term investments	174.8	163.0
Lloyd’s trust deposits
Investment securities
Other long-term investments	137.4	113.8
ILS funds
Investment securities
Other long-term investments	49.3	51.9
Private debt instruments
Investment securities
Other long-term investments	9.6	14.1
Other
Investment securities
Other long-term investments	$ 21.0	$ 12.3

Investment Securities - Fair Value of Hedge Funds Subject to Restrictions on Redemption Frequency (Details) $ in Millions	Dec. 31, 2022 USD ($) fund	Dec. 31, 2021 USD ($)
Total private equity funds and hedge funds included in other long-term investments
Investment securities
Other long-term investments largest single investment	$ 49.0	$ 31.3
Trading security, fair value	197.8	153.8
Fair value unfunded commitments	$ 94.3	44.0
Private equity funds
Investment securities
Number of investments \| fund	16
Trading security, fair value	$ 140.6	141.8
Fair value unfunded commitments	94.3	44.0
Private equity funds \| Aerospace/Defense/Government
Investment securities
Trading security, fair value	59.4	69.8
Fair value unfunded commitments	37.5	11.8
Private equity funds \| Financial services
Investment securities
Trading security, fair value	77.1	67.7
Fair value unfunded commitments	54.3	29.3
Private equity funds \| Real estate
Investment securities
Trading security, fair value	4.1	4.3
Fair value unfunded commitments	$ 2.5	2.9
Hedge funds
Investment securities
Number of investments \| fund	2
Trading security, fair value	$ 57.2	12.0
Fair value unfunded commitments	0.0	0.0
Hedge funds \| Long/short equity financials and business services
Investment securities
Trading security, fair value	49.0	0.0
Fair value unfunded commitments	0.0	0.0
Hedge funds \| European small/mid cap
Investment securities
Trading security, fair value	8.2	12.0
Fair value unfunded commitments	$ 0.0	$ 0.0

Investment Securities - Investments In Private Equity Funds Subject to Lock-Up Periods (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Investment securities
Investments held in trusts	$ 500.5	$ 479.5
Lloyds Bank
Investment securities
Fair value investments	319.2	342.8
Investments held in trusts	137.4	$ 113.8
Bank loan fund
Investment securities
Fair value investments	174.8
ILS funds
Investment securities
Fair value investments	49.3
Commitments to funds	100.0
Insurance-Linked Securities Funds Receivable
Investment securities
Fair value investments	70.0
Private equity funds
Investment securities
Trading security, fair value	140.6
1 – 3 years \| Private equity funds
Investment securities
Trading security, fair value	4.2
3 – 5 years \| Private equity funds
Investment securities
Trading security, fair value	18.8
5 – 10 years \| Private equity funds
Investment securities
Trading security, fair value	113.9
>10 years \| Private equity funds
Investment securities
Trading security, fair value	$ 3.7

Investment Securities - Rollforward of Fair Value Measurements by Level (Details) - Level 3 - Other long-term investments - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 890.6	$ 614.2
Net realized and unrealized gains	60.4	117.3
Amortization/accretion	0.0	0.0
Purchases	129.8	225.4
Sales	(169.2)	(75.9)
Transfers in	0.0	0.0
Transfers out	0.0	0.0
Ending balance	911.6	890.6
Ark
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Effect of transfers	$ 0.0	$ 9.6

Investment Securities - Significant Unobservable Inputs (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Other long-term investments \| Standard Poors NR Rating \| Level 3
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	$ 41.1	$ 46.7
Kudu Participation Contracts \| Kudu
Quantitative information for Level 3 Fair Value Measurements Assets
Investments in trading securities	$ 99.8	$ 223.4
Measurement Input, Discount Rate \| Kudu's Participation Contracts \| Standard Poors NR Rating
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value, pretax discount rate	21.00%	20.00%
Measurement Input, Discount Rate \| Kudu's Participation Contracts \| Standard Poors NR Rating \| Minimum
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value, discount rate (as a percent)	18.00%	18.00%
Measurement Input, Discount Rate \| Kudu's Participation Contracts \| Standard Poors NR Rating \| Maximum
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value, discount rate (as a percent)	25.00%	23.00%
Measurement Input, Discount Rate \| PassportCard/DavidShield \| Standard Poors NR Rating \| Level 3
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value, discount rate (as a percent)	24.00%	23.00%
Measurement Input, Discount Rate \| Elementum Holdings, L.P. \| Standard Poors NR Rating \| Level 3
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value, discount rate (as a percent)	21.00%	17.00%
Measurement Input, Discount Rate \| Private debt instruments \| Standard Poors NR Rating \| Level 3
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value, discount rate (as a percent)	11.00%	8.00%
Measurement Input, Long-term Revenue Growth Rate \| PassportCard/DavidShield \| Standard Poors NR Rating \| Level 3
Quantitative information for Level 3 Fair Value Measurements Assets
Terminal revenue growth rate (as a percent)	4.00%	4.00%
Measurement Input, Long-term Revenue Growth Rate \| Elementum Holdings, L.P. \| Standard Poors NR Rating \| Level 3
Quantitative information for Level 3 Fair Value Measurements Assets
Terminal revenue growth rate (as a percent)	4.00%	4.00%
Terminal Multiple \| Kudu's Participation Contracts \| Standard Poors NR Rating
Quantitative information for Level 3 Fair Value Measurements Assets
Cash flow exit multiple, pretax	11.8	10.0
Terminal Multiple \| Kudu's Participation Contracts \| Standard Poors NR Rating \| Minimum
Quantitative information for Level 3 Fair Value Measurements Assets
Cash flow exit multiple	7	7
Terminal Multiple \| Kudu's Participation Contracts \| Standard Poors NR Rating \| Maximum
Quantitative information for Level 3 Fair Value Measurements Assets
Cash flow exit multiple	16	13
Discounted Cash Flow Valuation Technique \| Kudu's Participation Contracts \| Standard Poors NR Rating \| Level 3
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	$ 695.9	$ 669.5
Discounted Cash Flow Valuation Technique \| PassportCard/DavidShield \| Standard Poors NR Rating \| Level 3
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	135.0	120.0
Discounted Cash Flow Valuation Technique \| Elementum Holdings, L.P. \| Standard Poors NR Rating \| Level 3
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	30.0	45.0
Discounted Cash Flow Valuation Technique \| Private debt instruments \| Standard Poors NR Rating \| Level 3
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	9.6	9.4
Probability Weighted Expected Return Method \| Kudu's Participation Contracts \| Standard Poors NR Rating \| Level 3
Quantitative information for Level 3 Fair Value Measurements Assets
Assets, fair value	$ 189.0	$ 78.8

Goodwill and Other Intangible Assets - Summary of Goodwill and Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Goodwill [Line Items]
Goodwill, fair value	$ 176.5	$ 142.3
Goodwill	176.5	142.3
Other intangible assets, fair value	404.6	347.5
Other intangible assets, accumulated amortization	12.2	7.0
Ark
Goodwill [Line Items]
Goodwill, fair value	116.8	116.8
Goodwill	116.8	116.8
Other intangible assets, fair value	175.7	175.7
Other intangible assets, accumulated amortization	0.0	0.0
Other intangible assets, net	175.7	175.7
Kudu
Goodwill [Line Items]
Goodwill, fair value	7.6	7.6
Goodwill	7.6	7.6
Other Operations
Goodwill [Line Items]
Goodwill, fair value	52.1	17.9
Goodwill	52.1	17.9
Other intangible assets, fair value	50.2	27.3
Other intangible assets, accumulated amortization	11.0	6.1
Other intangible assets, net	$ 39.2	21.2
Trade names \| Kudu
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life (in years)	7 years
Other intangible assets, fair value	$ 2.2	2.2
Other intangible assets, accumulated amortization	1.2	0.9
Other intangible assets, net	$ 1.0	1.3
Trade names \| Other Operations
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life (in years)	15 years 10 months 24 days
Other intangible assets, fair value	$ 17.9	8.2
Other intangible assets, accumulated amortization	3.0	1.5
Other intangible assets, net	$ 14.9	6.7
Customer relationships \| Other Operations
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life (in years)	12 years 4 months 24 days
Other intangible assets, fair value	$ 29.5	18.8
Other intangible assets, accumulated amortization	7.5	4.5
Other intangible assets, net	$ 22.0	14.3
Other Operations \| Other Operations
Goodwill [Line Items]
Acquired other intangible assets, weighted average useful life (in years)	12 years 1 month 6 days
Other intangible assets, fair value	$ 2.8	0.3
Other intangible assets, accumulated amortization	0.5	0.1
Other intangible assets, net	2.3	0.2
Total other intangible assets
Goodwill [Line Items]
Other intangible assets, fair value	228.1	205.2
Other intangible assets, accumulated amortization	12.2	7.0
Other intangible assets, net	215.9	198.2
Total Equity
Goodwill [Line Items]
Goodwill and other intangible assets	392.4	340.5
Non-controlling Interests
Goodwill [Line Items]
Goodwill and other intangible assets	(102.7)	(91.8)
Total
Goodwill [Line Items]
Goodwill and other intangible assets	$ 289.7	$ 248.7

Goodwill and Other Intangible Assets - Schedule of Goodwill and Other Intangible Assets Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Goodwill [Roll Forward]
Beginning balance	$ 142.3
Amortization	(5.2)	$ (4.6)	$ (1.6)
Ending balance	176.5	142.3
Insurance licenses	7,389.3	7,000.7
Goodwill
Goodwill [Roll Forward]
Beginning balance	142.3	19.2
Acquisition of businesses	59.5	15.8
Attribution of acquisition date fair value estimates between goodwill and other intangible assets	(22.9)	(9.3)
Measurement period adjustments	(2.4)	(0.2)
Assets held for sale	0.0	0.0
Amortization	0.0	0.0
Ending balance	176.5	142.3	19.2
Goodwill \| Ark
Goodwill [Roll Forward]
Ark Transaction	0.0	116.8
Total other intangible assets
Goodwill [Roll Forward]
Beginning balance	198.2	26.4
Acquisition of businesses	0.0	0.0
Attribution of acquisition date fair value estimates between goodwill and other intangible assets	22.9	9.3
Measurement period adjustments	0.0	0.0
Assets held for sale	0.0	(8.6)
Amortization	(5.2)	(4.6)
Ending balance	215.9	198.2	26.4
Total other intangible assets \| Ark
Goodwill [Roll Forward]
Ark Transaction	0.0	175.7
Total Goodwill and Other Intangible Assets
Goodwill [Roll Forward]
Beginning balance	340.5	45.6
Acquisition of businesses	59.5	15.8
Attribution of acquisition date fair value estimates between goodwill and other intangible assets	0.0	0.0
Measurement period adjustments	(2.4)	(0.2)
Assets held for sale	0.0	(8.6)
Amortization	(5.2)	(4.6)
Ending balance	392.4	340.5	$ 45.6
Total Goodwill and Other Intangible Assets \| Ark
Goodwill [Roll Forward]
Ark Transaction	$ 0.0	292.5
Insurance Licenses \| Disposal Group, Held-for-sale, Not Discontinued Operations \| Other Operations
Goodwill [Roll Forward]
Insurance licenses		$ 8.6

Goodwill and Other Intangible Assets - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of other intangible assets	$ 5.2	$ 4.6	$ 1.6

Goodwill and Other Intangible Assets - Amortization Expense (Details) $ in Millions	Dec. 31, 2022 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2023	$ 7.1
2024	6.6
2025	5.7
2026	4.8
2027 and years after	16.0
Total	40.2
Indefinite-lived intangible assets	$ 175.7

Loss and Loss Adjustment Expense Reserves - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Ark \| Amount attributable to TPC Providers
Liability for Claims and Claims Adjustment Expense [Line Items]
Percent of underwriting capital provided by third parties	0.00%	0.00%	42.80%	58.30%	57.60%	60.00%	59.60%	70.00%	66.20%	0.00%
Group Ark Insurance Limited
Liability for Claims and Claims Adjustment Expense [Line Items]
Favorable prior loss reserve development	$ (51.7)	$ (21.5)
Group Ark Insurance Limited \| Property and Accident & Health
Liability for Claims and Claims Adjustment Expense [Line Items]
Favorable prior loss reserve development	(20.8)	8.9
Group Ark Insurance Limited \| Specialty
Liability for Claims and Claims Adjustment Expense [Line Items]
Favorable prior loss reserve development	(12.7)	3.3
Group Ark Insurance Limited \| Marine & Energy
Liability for Claims and Claims Adjustment Expense [Line Items]
Favorable prior loss reserve development	$ (18.8)
Group Ark Insurance Limited \| Casualty - Active
Liability for Claims and Claims Adjustment Expense [Line Items]
Favorable prior loss reserve development		3.7
Group Ark Insurance Limited \| Casualty - Runoff
Liability for Claims and Claims Adjustment Expense [Line Items]
Favorable prior loss reserve development		$ 3.3

Loss and Loss Adjustment Expense Reserves - LAE Reserve Activity (Details) - Group Ark Insurance Limited - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross beginning balance	$ 894.7	$ 696.0
Less: beginning reinsurance recoverable on unpaid losses	(428.9)	(433.4)
Net loss and LAE reserves	465.8	262.6
Losses and LAE incurred relating to:
Current Year	588.1	336.3
Prior Year	(51.7)	(21.5)
Net incurred losses and LAE	536.4	314.8
Loss and LAE paid relating to:
Current year losses	(98.9)	(43.9)
Prior year losses	(158.6)	(61.6)
Net paid losses and LAE	(257.5)	(105.5)
Change in TPC Providers’ participation	57.5	(2.2)
Foreign currency translation and other adjustments to loss and LAE reserves	(10.7)	(3.9)
Net ending balance	791.5	465.8
Plus: ending reinsurance recoverable on unpaid losses	505.0	428.9
Gross ending balance	1,296.5	894.7
Amount attributable to TPC Providers
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Less: beginning reinsurance recoverable on unpaid losses	276.8	319.2
Loss and LAE paid relating to:
Plus: ending reinsurance recoverable on unpaid losses	$ (145.4)	$ (276.8)

Loss and Loss Adjustment Expense Reserves - Schedule of Ending Liabilities for Unpaid Loss and LAE, Net of Reinsurance (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total Reinsurance recoverables on unpaid losses	$ 505.0	$ 428.9
Ark
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Unpaid loss and LAE reserves, net of reinsurance recoverables on unpaid losses	791.5	465.8
Total Reinsurance recoverables on unpaid losses	505.0	428.9
Loss and loss adjustment expense reserves	1,296.5	894.7
Ark \| Property and Accident & Health
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Loss and LAE reserves, net of reinsurance	258.2	175.0
Total Reinsurance recoverables on unpaid losses	224.6	145.2
Ark \| Specialty
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Loss and LAE reserves, net of reinsurance	204.3	85.2
Total Reinsurance recoverables on unpaid losses	97.2	68.9
Ark \| Marine & Energy
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Loss and LAE reserves, net of reinsurance	196.4	99.3
Total Reinsurance recoverables on unpaid losses	79.8	70.2
Ark \| Casualty - Active
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Loss and LAE reserves, net of reinsurance	71.5	37.4
Total Reinsurance recoverables on unpaid losses	49.9	41.4
Ark \| Casualty - Runoff
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Loss and LAE reserves, net of reinsurance	60.8	68.4
Total Reinsurance recoverables on unpaid losses	53.5	103.2
Ark \| Other
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Loss and LAE reserves, net of reinsurance	$ 0.3	$ 0.5

Loss and Loss Adjustment Expense Reserves - TPC Participation (Details)	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Ark \| Amount attributable to TPC Providers
Liability for Claims and Claims Adjustment Expense [Line Items]
Percent of underwriting capital provided by third parties	0.00%	0.00%	42.80%	58.30%	57.60%	60.00%	59.60%	70.00%	66.20%	0.00%

Loss and Loss Adjustment Expense Reserves - Cumulative Paid Loss and Allocated LAE, Net of Reinsurance (Details) - Ark - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property and Accident & Health
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	$ 410.2
All outstanding liabilities before 2013, net of reinsurance	1.4
Loss and LAE reserves, net of reinsurance	258.2	$ 175.0
Property and Accident & Health \| 2013
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	59.2	59.2	$ 59.3	$ 59.3	$ 59.4	$ 59.1	$ 59.1	$ 58.1	$ 39.1	$ 15.4
Property and Accident & Health \| 2014
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	27.9	27.8	27.9	27.8	27.6	27.5	27.1	24.9	13.6
Property and Accident & Health \| 2015
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	15.0	15.0	14.8	14.6	14.6	13.4	12.2	6.9
Property and Accident & Health \| 2016
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	17.8	17.2	16.9	16.8	16.4	13.1	8.5
Property and Accident & Health \| 2017
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	27.3	29.6	32.8	31.6	25.8	16.8
Property and Accident & Health \| 2018
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	40.8	40.0	40.1	32.2	15.6
Property and Accident & Health \| 2019
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	18.5	18.3	16.7	6.8
Property and Accident & Health \| 2020
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	47.0	34.1	11.2
Property and Accident & Health \| 2021
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	86.7	30.8
Property and Accident & Health \| 2022
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	70.0
Marine & Energy
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	164.0
All outstanding liabilities before 2013, net of reinsurance	4.0
Loss and LAE reserves, net of reinsurance	196.4	99.3
Marine & Energy \| 2013
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	29.3	29.3	29.1	29.3	29.3	29.1	28.6	27.6	22.2	7.8
Marine & Energy \| 2014
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	13.7	13.5	13.6	13.4	14.1	14.0	13.2	12.1	5.8
Marine & Energy \| 2015
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	11.4	10.8	10.4	10.3	10.9	9.6	7.8	4.0
Marine & Energy \| 2016
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	13.4	13.7	13.1	13.0	12.6	10.0	5.5
Marine & Energy \| 2017
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	14.1	14.1	14.0	12.8	11.1	5.1
Marine & Energy \| 2018
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	15.4	14.7	14.0	12.5	2.7
Marine & Energy \| 2019
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	14.3	12.6	10.6	3.3
Marine & Energy \| 2020
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	16.0	12.7	3.1
Marine & Energy \| 2021
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	24.2	6.3
Marine & Energy \| 2022
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	12.2
Specialty
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	165.8
All outstanding liabilities before 2013, net of reinsurance	0.2
Loss and LAE reserves, net of reinsurance	204.3	85.2
Specialty \| 2013
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	15.6	15.6	15.7	15.7	15.7	15.5	15.4	14.9	13.2	17.0
Specialty \| 2014
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	43.0	42.7	42.8	42.0	40.7	40.1	39.7	38.9	26.3
Specialty \| 2015
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	6.4	8.1	8.1	8.1	8.0	7.6	7.0	4.0
Specialty \| 2016
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	8.5	10.3	10.3	9.9	9.1	7.9	3.2
Specialty \| 2017
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	9.2	8.5	8.5	8.4	6.6	3.1
Specialty \| 2018
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	11.8	10.4	10.0	8.2	2.7
Specialty \| 2019
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	18.2	7.4	6.9	4.8
Specialty \| 2020
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	13.0	10.6	5.2
Specialty \| 2021
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	24.1	5.1
Specialty \| 2022
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	16.0
Casualty - Active
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	42.0
All outstanding liabilities before 2013, net of reinsurance	4.0
Loss and LAE reserves, net of reinsurance	71.5	37.4
Casualty - Active \| 2013
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	7.5	7.3	7.0	7.0	6.7	6.3	5.8	5.3	3.6	1.5
Casualty - Active \| 2014
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	6.2	6.0	5.9	5.5	5.2	4.7	4.2	3.5	1.3
Casualty - Active \| 2015
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	5.5	5.1	4.9	4.7	4.4	3.2	2.4	1.8
Casualty - Active \| 2016
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	6.5	5.3	4.6	4.0	2.3	1.0	0.2
Casualty - Active \| 2017
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	5.7	4.2	3.4	2.8	1.7	0.8
Casualty - Active \| 2018
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	4.3	4.3	3.5	1.4	0.3
Casualty - Active \| 2019
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	3.0	2.3	1.4	0.3
Casualty - Active \| 2020
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	2.0	1.0	0.5
Casualty - Active \| 2021
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	0.9	0.5
Casualty - Active \| 2022
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	0.4
Casualty - Runoff
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	214.8
All outstanding liabilities before 2013, net of reinsurance	19.4
Loss and LAE reserves, net of reinsurance	60.8	68.4
Casualty - Runoff \| 2013
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	45.2	44.9	44.6	43.9	43.3	42.4	40.6	35.7	19.4	$ 7.1
Casualty - Runoff \| 2014
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	51.8	49.3	48.5	46.9	43.1	36.4	29.5	23.1	$ 6.4
Casualty - Runoff \| 2015
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	33.1	28.9	27.3	24.7	21.4	14.5	8.2	$ 4.3
Casualty - Runoff \| 2016
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	28.7	27.8	25.4	22.7	17.7	10.2	$ 3.9
Casualty - Runoff \| 2017
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	22.5	21.4	18.5	14.6	9.4	$ 3.2
Casualty - Runoff \| 2018
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	16.3	14.9	12.6	7.4	$ 3.4
Casualty - Runoff \| 2019
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	12.1	7.8	5.8	$ 3.3
Casualty - Runoff \| 2020
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	3.1	1.3	$ 0.8
Casualty - Runoff \| 2021
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	1.7	$ 0.5
Casualty - Runoff \| 2022
Claims Development [Line Items]
Cumulative Paid Loss and LAE, Net of Reinsurance	$ 0.3

Loss and Loss Adjustment Expense Reserves - Average Annual Percentage Payout of Incurred Losses and Allocated LAE by Age, Net of Reinsurance (Details) - Ark	Dec. 31, 2022
Property and Accident & Health
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	31.40%
2	34.20%
3	19.30%
4	5.50%
5	1.20%
6	0.80%
7	0.80%
8	0.30%
9	0.00%
10	0.00%
Marine & Energy
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	17.40%
2	35.80%
3	19.90%
4	5.90%
5	4.30%
6	6.90%
7	0.30%
8	0.30%
9	(0.30%)
10	0.10%
Specialty
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	25.80%
2	33.40%
3	7.80%
4	4.80%
5	5.90%
6	5.90%
7	1.40%
8	1.90%
9	(3.20%)
10	(0.80%)
Casualty - Active
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	6.80%
2	11.70%
3	16.70%
4	12.70%
5	8.00%
6	10.80%
7	4.90%
8	3.10%
9	1.20%
10	2.90%
Casualty - Runoff
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
1	9.40%
2	15.40%
3	17.20%
4	15.70%
5	9.00%
6	7.40%
7	6.30%
8	4.30%
9	2.80%
10	1.40%

Third-Party Reinsurance - Effects of Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Earned premiums:
Net earned premiums	$ 1,076.7	$ 664.2	$ 22.8
Ark
Written premiums:
Direct	1,452.0	1,058.7
Ceded	(256.8)	(199.6)
Net written premiums	1,195.2	859.1
Earned premiums:
Direct	1,324.2	886.4
Ceded	(280.8)	(249.1)
Net earned premiums	1,043.4	637.3
Losses and LAE:
Gross	814.9	442.9
Ceded	(278.5)	(128.1)
Net Losses and LAE	$ 536.4	$ 314.8

Third-Party Reinsurance - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2022
Reinsurance [Line Items]
Total Reinsurance recoverables on unpaid losses	$ 428.9	$ 505.0
Reinsurance recoverables on paid losses	19.5	31.1
Ark
Reinsurance [Line Items]
Total Reinsurance recoverables on unpaid losses	428.9	505.0
Reinsurance recoverables	448.4	$ 536.1
Ark \| Third Point Re
Reinsurance [Line Items]
Annual crediting rate		3.00%
Decrease in investment	31.7
Value of investment	20.4	$ 20.4
Amount attributable to TPC Providers
Reinsurance [Line Items]
Total Reinsurance recoverables on unpaid losses	$ 276.8	$ 145.4

Third-Party Reinsurance - Remaining Gross and Net Reinsurance Recoverables (Details) - All Entities Except TCP Providers $ in Millions	Dec. 31, 2022 USD ($)
Reinsurance [Line Items]
Gross	$ 390.7
Collateral	108.9
Net	$ 281.8
% of Total	100.00%
A+ or better
Reinsurance [Line Items]
Gross	$ 190.0
Collateral	0.0
Net	$ 190.0
% of Total	67.40%
A- to A
Reinsurance [Line Items]
Gross	$ 75.3
Collateral	0.0
Net	$ 75.3
% of Total	26.70%
B++ or lower and not rated
Reinsurance [Line Items]
Gross	$ 125.4
Collateral	108.9
Net	$ 16.5
% of Total	5.90%

Debt - Debt Outstanding (Details) € in Millions, $ in Millions	Dec. 31, 2022 USD ($)	Dec. 31, 2022 EUR (€)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Debt Instrument
Total debt	$ 575.2		$ 420.9
Ark Subordinated Notes
Debt Instrument
Unamortized issuance cost	(4.6)		(5.3)
Ark 2007 Notes \| Ark Subordinated Notes
Debt Instrument
Total debt	30.0		30.0
Ark 2021 Notes Tranche 1
Debt Instrument
Long-term debt, gross \| €		€ 39.1
Ark 2021 Notes Tranche 1 \| Ark Subordinated Notes
Debt Instrument
Long-term debt, gross	41.3		44.2
Ark 2021 Notes Tranche 2 \| Ark Subordinated Notes
Debt Instrument
Long-term debt, gross	47.0		47.0
Ark 2021 Notes Tranche 3 \| Ark Subordinated Notes
Debt Instrument
Long-term debt, gross	70.0		70.0
Ark 2021 Notes \| Ark Subordinated Notes
Debt Instrument
Total debt	$ 153.7		$ 155.9
Ark
Debt Instrument
Effective yield (as a percent)	7.60%	7.60%	6.90%
Ark \| Ark Subordinated Notes
Debt Instrument
Total debt	$ 183.7		$ 185.9
Kudu \| Kudu Credit Facility
Debt Instrument
Total debt	208.3		218.2
Other Operations \| Other Operations debt
Debt Instrument
Unamortized issuance cost	(0.7)		(0.3)
Total debt	36.7		16.8
Debt instrument at face value	$ 37.4		17.1
Effective yield (as a percent)	6.60%	6.60%
Secured Debt \| HG Global Senior Notes
Debt Instrument
Long-term debt, gross	$ 150.0		0.0
Unamortized issuance cost	(3.5)		0.0
Total debt	$ 146.5		$ 0.0
Effective yield (as a percent)	8.90%	8.90%
Term Loan \| Kudu Credit Facility
Debt Instrument
Effective yield (as a percent)	6.10%	6.10%	4.30%
Term Loan \| Other Operations debt
Debt Instrument
Long-term debt, gross	$ 36.7
Term Loan \| Kudu \| Kudu Credit Facility
Debt Instrument
Unamortized issuance cost	(6.9)		$ (7.2)
Total debt	215.2		225.4	$ 0.0	$ 0.0
Debt instrument at face value	$ 215.2		$ 225.4
Term Loan \| Other Operations \| Other Operations debt
Debt Instrument
Effective yield (as a percent)			7.50%

Debt - Schedule of Contractual Repayments (Details) $ in Millions	Dec. 31, 2022 USD ($)
Debt Disclosure [Abstract]
Due in one year or less	$ 5.4
Due in two to three years	12.6
Due in four to five years	30.7
Due after five years	542.2
Total	$ 590.9

Debt - HG Global Senior Notes (Details) - USD ($)		12 Months Ended
Debt - HG Global Senior Notes (Details) - USD ($)	Apr. 29, 2022	Dec. 31, 2022	Jun. 16, 2022	Dec. 31, 2021
Interest Rate Cap \| HG Global
Debt Instrument
Notational amount			$ 150,000,000
HG Global Senior Notes \| Secured Debt
Debt Instrument
Proceeds from borrowings	$ 150,000,000
Annual payments		$ 15,000,000
Interest reserve account		$ 31,200,000
Additional interest rate		1.00%
Long-term debt, gross		$ 150,000,000.0		$ 0
HG Global Senior Notes \| Secured Debt \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Debt Instrument
Basis spread on variable rate	6.30%

Debt - Ark Subordinated Notes Narrative (Details)				1 Months Ended	3 Months Ended
Debt - Ark Subordinated Notes Narrative (Details)	Sep. 08, 2021 USD ($)	Aug. 11, 2021 USD ($)	Jul. 13, 2021 USD ($)	Mar. 31, 2007 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2022 EUR (€)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 EUR (€)	Jul. 13, 2021 EUR (€)	Mar. 31, 2007 EUR (€)
Debt Instrument
Debt						$ 575,200,000		$ 420,900,000
Unsecured Subordinated Debt \| Group Ark Insurance Limited
Debt Instrument
Proceeds from borrowings					$ 157,800,000
Unsecured Subordinated Debt \| Ark \| Group Ark Insurance Limited
Debt Instrument
Notes issued					$ 163,300,000
Ark 2007 Notes, Tranche 1 \| Ark Subordinated Notes
Debt Instrument
Long-term debt, gross						30,000,000.0
Ark 2021 Notes Tranche 1
Debt Instrument
Long-term debt, gross \| €							€ 39,100,000
Ark 2021 Notes Tranche 1 \| Ark Subordinated Notes
Debt Instrument
Long-term debt, gross						41,300,000		44,200,000
Ark 2021 Notes Tranche 1 \| Unsecured Subordinated Debt \| Group Ark Insurance Limited
Debt Instrument
Notes issued			$ 46,300,000							€ 39,100,000
Ark 2021 Notes Tranche 1 \| Unsecured Subordinated Debt \| EURIBOR \| Group Ark Insurance Limited
Debt Instrument
Basis spread on variable rate			5.75%
Ark 2021 Notes Tranche 2 \| Ark Subordinated Notes
Debt Instrument
Long-term debt, gross						47,000,000.0		47,000,000.0
Ark 2021 Notes Tranche 2 \| Unsecured Subordinated Debt \| Group Ark Insurance Limited
Debt Instrument
Notes issued		$ 47,000,000
Ark 2021 Notes Tranche 2 \| Unsecured Subordinated Debt \| United States Dollar London Interbank Offered Rate LIBOR \| Group Ark Insurance Limited
Debt Instrument
Basis spread on variable rate		5.75%
Ark 2021 Notes Tranche 3 \| Ark Subordinated Notes
Debt Instrument
Long-term debt, gross						70,000,000.0		70,000,000.0
Ark 2021 Notes Tranche 3 \| Unsecured Subordinated Debt \| Group Ark Insurance Limited
Debt Instrument
Notes issued	$ 70,000,000
Additional interest rate	1.00%
Solvency capital requirement	120.00%
Debt to capital requirement	40.00%
Ark 2021 Notes Tranche 3 \| Unsecured Subordinated Debt \| United States Dollar London Interbank Offered Rate LIBOR \| Group Ark Insurance Limited
Debt Instrument
Basis spread on variable rate	6.10%
Ark \| Ark 2007 Notes, Tranche 1 \| Junior Notes
Debt Instrument
Long-term line of credit				$ 30,000,000
Debt						$ 30,000,000
Ark \| Ark 2007 Notes, Tranche 1 \| Junior Notes \| United States Dollar London Interbank Offered Rate LIBOR
Debt Instrument
Basis spread on variable rate				4.60%
Ark \| Ark 2007 Notes, Tranche 2 \| Junior Notes
Debt Instrument
Long-term line of credit \| €											€ 12,000,000
Debt								$ 13,500,000	€ 12,000,000
Ark \| Ark 2007 Notes, Tranche 2 \| Junior Notes \| EURIBOR
Debt Instrument
Basis spread on variable rate				4.60%

Debt - Ark Stand By Letters of Credit Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021
Citibank LOC Facility \| Short-term investments \| Asset Pledged as Collateral
Debt Instrument
Investments pledged as collateral	$ 80.3	$ 50.0
Lloyds LOC Facility \| Short-term investments \| Asset Pledged as Collateral
Debt Instrument
Investments pledged as collateral	10.0
Secured Debt \| Citibank LOC Facility
Debt Instrument
Amount outstanding	53.6
Secured Debt \| Lloyds LOC Facility
Debt Instrument
Amount outstanding	$ 6.8
Uncollateralized \| Letter of Credit \| Secured Debt \| Ark
Debt Instrument
Total commitment under revolving credit facility			$ 50.0
Collateralized \| Letter of Credit \| Secured Debt \| Ark
Debt Instrument
Total commitment under revolving credit facility			$ 100.0

Debt - Kudu Credit and Bank Facility (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Mar. 23, 2021
Debt Instrument
Debt covenant, maximum loan to value percent, period one	50.00%
Debt covenant, maximum loan to value percent, period two	40.00%
Debt covenant, maximum loan to value percent, period three	25.00%
Debt covenant, maximum loan to value percent, period four	15.00%
Debt covenant, maximum loan to value percent, period five	0.00%
Debt covenant, maximum loan to value percent	33.00%
Kudu Bank Facility \| Revolving Credit Facility
Debt Instrument
Effective yield (as a percent)	0.25%
Kudu Bank Facility \| Revolving Credit Facility \| London Interbank Offered Rate (LIBOR)
Debt Instrument
Basis spread on variable rate	4.30%
Kudu Bank Facility \| Kudu
Debt Instrument
Total commitment under revolving credit facility			$ 300,000,000
Kudu Bank Facility \| Kudu \| Revolving Credit Facility
Debt Instrument
Loss on debt extinguishment		$ 4,100,000
Kudu Bank Facility \| Kudu \| Line of Credit
Debt Instrument
Interest reserve	$ 12,200,000	$ 4,500,000
Kudu Bank Facility \| Kudu \| Term Loan
Debt Instrument
Percentage of borrowing base	35.00%
Undrawn amount on facility	$ 45,900,000

Debt - Schedule of the Change in Debt under the Kudu Facility (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument
Beginning balance	$ 420.9
Repayments	(56.7)	$ (120.1)	$ (1.9)
Ending balance	575.2	420.9
Kudu Bank Facility \| Kudu \| Term Loan
Debt Instrument
Beginning balance	0.0	89.2	57.0
Borrowings	0.0	3.0	32.2
Repayments	0.0	(92.2)	0.0
Ending balance	0.0	0.0	89.2
Kudu Credit Facility \| Kudu
Debt Instrument
Beginning balance	218.2
Ending balance	208.3	218.2
Kudu Credit Facility \| Kudu \| Term Loan
Debt Instrument
Beginning balance	225.4	0.0	0.0
Borrowings	35.0	232.0	0.0
Repayments	(45.2)	(6.6)	0.0
Ending balance	$ 215.2	$ 225.4	$ 0.0

- Definition

Amount, excluding unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References + Details

Debt - Other Debt (Details) $ in Millions	12 Months Ended
Debt - Other Debt (Details) $ in Millions	Dec. 31, 2022 USD ($) credit_facility	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Debt Instrument
Interest expense	$ 40.3	$ 20.5	$ 7.4
Interest paid	$ 30.5	$ 13.9	$ 6.1
Other Operations
Debt Instrument
Secured credit facilities \| credit_facility	5
Other Operations debt \| Term Loan
Debt Instrument
Long-term debt, gross	$ 36.7

Income Taxes - Income Tax (Benefit) Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Current income tax (expense) benefit:
U.S. federal	$ (16.9)	$ (4.8)	$ (10.7)
State	(4.5)	(2.1)	(4.2)
Non-U.S.	(7.1)	(2.8)	(0.8)
Total current income tax (expense) benefit	(28.5)	(9.7)	(15.7)
Deferred income tax (expense) benefit:
U.S. federal	(7.3)	(13.9)	21.0
State	(1.8)	(7.0)	10.1
Non-U.S.	(3.8)	(13.8)	(0.6)
Total deferred income tax (expense) benefit	(12.9)	(34.7)	30.5
Total income tax (expense) benefit	$ (41.4)	$ (44.4)	$ 14.8

Income Taxes - Effective Rate Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Tax Contingency [Line Items]
Tax (expense) benefit at the U.S. statutory rate	$ 31.4	$ 57.5	$ (138.7)
Differences in taxes resulting from:
Non-U.S. earnings, net of foreign taxes	(41.2)	(78.2)	74.3
Change in valuation allowance	(19.6)	(2.0)	(26.6)
Member’s surplus contributions	(6.2)	(5.6)	(4.8)
Withholding tax	(3.1)	(0.3)	(5.0)
State taxes	(2.8)	(7.3)	(8.9)
Officer compensation	(1.0)	(1.5)	(1.1)
Tax rate changes	(0.4)	(10.9)	3.1
Tax exempt interest and dividends	0.2	0.2	0.8
Reorganization	0.0	0.0	130.5
Tax reserve adjustments	0.0	0.0	1.9
Other, net	1.3	3.7	(10.7)
Total income tax (expense) benefit	(41.4)	(44.4)	14.8
Pre-tax income (loss)	(149.4)	(273.6)	660.4
Tax Payments and Receipts
Net income tax payments to US	10.3	(0.1)	15.9
Non-US
Differences in taxes resulting from:
Pre-tax income (loss)	$ (94.4)	$ (319.0)	$ 327.8

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets related to:
U.S. federal and state net operating and capital loss carryforwards	$ 85.4	$ 85.7
Non-U.S. net operating loss carryforwards	36.1	46.1
Incentive compensation	21.4	14.5
Accrued interest	8.8	7.8
Deferred acquisition costs	8.0	6.4
Net unrealized investment losses	4.7	0.0
Tax credit carryforwards	1.8	0.2
Other items	0.5	0.4
Total gross deferred tax assets	166.7	161.1
Less: valuation allowances	94.3	85.6
Total net deferred tax assets	72.4	75.5
Deferred tax liabilities related to:
Member’s surplus contributions	71.3	60.4
Purchase accounting	43.9	43.9
Investment basis difference	33.9	26.8
Deferred underwriting	9.7	4.1
Net unrealized investment gains (losses)	0.0	10.7
Other items	1.4	1.8
Total deferred tax liabilities	160.2	147.7
Net deferred tax asset (liability)	$ (87.8)	$ (72.2)

Income Taxes - Valuation Allowance (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Valuation Allowance [Line Items]
Valuation allowance	$ 94.3	$ 85.6
Change in valuation allowance	19.6	2.0	$ 26.6
Income tax expense (benefit)	41.4	44.4	$ (14.8)
U.S. losses and other federal deferred tax benefits
Valuation Allowance [Line Items]
Valuation allowance	56.6	38.2
Net operating losses in Israel subsidiaries
Valuation Allowance [Line Items]
Valuation allowance	20.4	21.9
Luxembourg \| U.S. losses and other federal deferred tax benefits
Valuation Allowance [Line Items]
Change in valuation allowance	9.2	1.6
United Kingdom \| Net operating losses in United Kingdom subsidiaries
Valuation Allowance [Line Items]
Change in valuation allowance	1.0	3.1
United States \| Net operating losses in US branches
Valuation Allowance [Line Items]
Income tax expense (benefit)		0.6
Israel \| Net operating losses in Israel subsidiaries
Valuation Allowance [Line Items]
Change in valuation allowance	1.5	1.9
Subsidiaries \| Luxembourg \| Net operating losses in Luxembourg subsidiaries
Valuation Allowance [Line Items]
Valuation allowance	16.0	25.2
Subsidiaries \| United Kingdom \| Net operating losses in Luxembourg subsidiaries
Valuation Allowance [Line Items]
Valuation allowance	1.3	0.3
Guilford Holdings, Inc. \| United States
Valuation Allowance [Line Items]
Change in valuation allowance	7.8
Income tax expense (benefit)		(3.6)
BAM \| United States
Valuation Allowance [Line Items]
Income tax expense (benefit)	17.5	7.8
BAM \| United States \| MSC
Valuation Allowance [Line Items]
Income tax expense (benefit)	(10.9)	$ (7.5)
BAM \| United States \| Foreign Tax Credits
Valuation Allowance [Line Items]
Income tax expense (benefit)	$ 4.0

Income Taxes - Net Operating and Capital Loss Carryforwards (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Net deferred tax assets
Total net deferred tax assets	$ 72.4	$ 75.5
Tax credit carryforwards, foreign	$ 1.8
Percentage of likelihood for realization of benefit upon ultimate settlement	50.00%
Domestic Tax Authority
Net deferred tax assets
Separate return limitation year operating loss carryforwards	$ 0.6
Operating and Capital Loss Carryforward
Net deferred tax assets
Operating loss carryforwards	551.1
Gross deferred tax asset	121.5
Valuation allowance	(121.5)
Total net deferred tax assets	0.0
Operating and Capital Loss Carryforward \| United States
Net deferred tax assets
Operating loss carryforwards	399.5
Gross deferred tax asset	85.4
Valuation allowance	(85.4)
Total net deferred tax assets	0.0
Operating and Capital Loss Carryforward \| Luxembourg
Net deferred tax assets
Operating loss carryforwards	59.5
Gross deferred tax asset	14.8
Valuation allowance	(14.8)
Total net deferred tax assets	0.0
Operating and Capital Loss Carryforward \| United Kingdom
Net deferred tax assets
Operating loss carryforwards	4.9
Gross deferred tax asset	1.2
Valuation allowance	(1.2)
Total net deferred tax assets	0.0
Operating and Capital Loss Carryforward \| Israel
Net deferred tax assets
Operating loss carryforwards	87.2
Gross deferred tax asset	20.1
Valuation allowance	(20.1)
Total net deferred tax assets	0.0
2022-2026 \| Operating and Capital Loss Carryforward
Net deferred tax assets
Operating loss carryforwards	0.0
2022-2026 \| Operating and Capital Loss Carryforward \| United States
Net deferred tax assets
Operating loss carryforwards	0.0
2022-2026 \| Operating and Capital Loss Carryforward \| Luxembourg
Net deferred tax assets
Operating loss carryforwards	0.0
2022-2026 \| Operating and Capital Loss Carryforward \| United Kingdom
Net deferred tax assets
Operating loss carryforwards	0.0
2022-2026 \| Operating and Capital Loss Carryforward \| Israel
Net deferred tax assets
Operating loss carryforwards	0.0
2027-2031 \| Operating and Capital Loss Carryforward
Net deferred tax assets
Operating loss carryforwards	0.2
2027-2031 \| Operating and Capital Loss Carryforward \| United States
Net deferred tax assets
Operating loss carryforwards	0.2
2027-2031 \| Operating and Capital Loss Carryforward \| Luxembourg
Net deferred tax assets
Operating loss carryforwards	0.0
2027-2031 \| Operating and Capital Loss Carryforward \| United Kingdom
Net deferred tax assets
Operating loss carryforwards	0.0
2027-2031 \| Operating and Capital Loss Carryforward \| Israel
Net deferred tax assets
Operating loss carryforwards	0.0
2032-2041 \| Operating and Capital Loss Carryforward
Net deferred tax assets
Operating loss carryforwards	310.3
2032-2041 \| Operating and Capital Loss Carryforward \| United States
Net deferred tax assets
Operating loss carryforwards	250.8
2032-2041 \| Operating and Capital Loss Carryforward \| Luxembourg
Net deferred tax assets
Operating loss carryforwards	59.5
2032-2041 \| Operating and Capital Loss Carryforward \| United Kingdom
Net deferred tax assets
Operating loss carryforwards	0.0
2032-2041 \| 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	240.6
No expiration date \| Operating and Capital Loss Carryforward \| United States
Net deferred tax assets
Operating loss carryforwards	148.5
No expiration date \| Operating and Capital Loss Carryforward \| Luxembourg
Net deferred tax assets
Operating loss carryforwards	0.0
No expiration date \| Operating and Capital Loss Carryforward \| United Kingdom
Net deferred tax assets
Operating loss carryforwards	4.9
No expiration date \| Operating and Capital Loss Carryforward \| Israel
Net deferred tax assets
Operating loss carryforwards	$ 87.2

Derivatives (Details) - Interest Rate Cap - HG Global - USD ($)		12 Months Ended
	Jun. 16, 2022	Dec. 31, 2022
Derivative [Line Items]
Notational amount	$ 150,000,000
Premiums paid	$ 3,300,000
Derivative, fair value, net		$ 4,100,000
Interest Expense
Derivative [Line Items]
Change in fair value of derivative instruments		$ 800,000
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Derivative [Line Items]
Derivative, cap interest rate	3.50%
3-month variable rate		4.60%

Municipal Bond Guarantee Insurance - Narrative (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended			12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2022	Sep. 30, 2022	Mar. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2018	Jan. 01, 2025	Jun. 30, 2020	Jan. 31, 2020	Dec. 31, 2012
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Percentage of risk premium ceded	60.00%		60.00%			60.00%
Insurance-linked securities, term			12 years				12 years	12 years
Insurance-linked securities, callable term			7 years				5 years	5 years
HG Re
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Percentage of par value of policy reinsured	15.00%		15.00%			15.00%
Trust balance	$ 288.6	$ 250.2	$ 288.6			$ 288.6	$ 250.2
HG Global
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Surplus notes												$ 503.0
Percentage of par value of policy reinsured	15.00%		15.00%			15.00%
Percent over a target trust balance						102.00%
Supplement trust target	$ 603.0		$ 603.0			$ 603.0
BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Principal	99,996.9	89,196.5	99,996.9	$ 42.5	$ 805.5	99,996.9	89,196.5			$ 36.9
HG Global
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Collateral held in supplement trust	856.9	852.0	856.9			856.9	852.0
Cash and investments included in collateral trust	503.3	481.7	503.3			503.3	481.7
Interest receivable	157.9	157.6	157.9			157.9	157.6
BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Surplus notes	340.0	364.6	340.0			340.0	364.6
Interest receivable	13.6	5.7	13.6			13.6	5.7
Accrued interest on surplus notes	157.9	157.6	157.9			157.9	157.6
Supplemental Trust \| BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Cash repayments on notes	24.6	23.6
Accrued interest on surplus notes	1.0	0.4	1.0			1.0	0.4
Surplus Note \| BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Cash repayments on notes	36.0	33.8
Accrued interest on surplus notes	10.4	9.8	$ 10.4			10.4	$ 9.8
BAM \| Fidus Re Ltd.
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Losses above retention, percentage of liability			90.00%				90.00%	90.00%
Fidus Re Ltd. \| BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Insurance linked securities	150.0	150.0	$ 150.0			150.0	$ 150.0	$ 100.0
Aggregate loss limit on contracts	110.0	135.0	110.0			110.0	135.0	165.0
Reimbursement guarantee under contracts	150.0	150.0	$ 150.0			$ 150.0	150.0	100.0
Percentage of financial guaranty policies covered			33.00%			32.00%
Percentage of quota share reinsurance agreement				100.00%	100.00%
Fidus Re Ltd. \| BAM \| 2018 Covered Portfolio
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Percentage of financial guaranty policies covered						27.00%
Maximum \| BAM \| HG Global
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Aggregate loss limit on contracts											$ 125.0
Maximum \| Fidus Re Ltd. \| BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Aggregate loss limit on contracts	276.7	301.7	$ 276.7			$ 276.7	301.7	$ 276.1
Series A BAM Surplus Note \| HG Global
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Trust balance	$ 568.3	$ 601.8	$ 568.3			$ 568.3	$ 601.8
Fixed interest rate \| Surplus Note \| BAM \| Forecast
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Interest rate									8.00%
U.S. treasury rate plus \| Surplus Note \| BAM
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Basis spread on variable rate						3.00%
Effective yield (as a percent)	7.70%		7.70%			7.70%

Municipal Bond Guarantee Insurance - Schedule of Municipal Bond Guarantee Insured Obligations (Details) - BAM $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) Contract	Dec. 31, 2021 USD ($) Contract	Sep. 30, 2022 USD ($)	Mar. 31, 2021 USD ($)	Jun. 30, 2020 USD ($)
Guarantor Obligations [Line Items]
Contracts outstanding \| Contract	13,382	12,350
Remaining weighted average contract period (in years)	10 years 9 months 18 days	10 years 9 months 18 days
Principal	$ 99,996.9	$ 89,196.5	$ 42.5	$ 805.5	$ 36.9
Interest	48,880.6	41,486.5
Total debt service outstanding	148,877.5	130,683.0
Gross unearned insurance premiums (in millions)	$ 298.3	$ 266.3

Municipal Bond Guarantee - Schedule of Municipal Guarantee Insurance Contracts, Premium Received Over Contract Period (Details) - BAM - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Guarantor Obligations [Line Items]
January 1, 2023 - March 31, 2023	$ 7.0
April 1, 2023 - June 30, 2023	7.0
July 1, 2023 - September 30, 2023	6.8
October 1, 2023 - December 31, 2023	6.7
Total 2021	27.5
2024	25.9
2025	24.2
2026	22.6
2027	21.0
2028 and thereafter	177.1
Total gross unearned insurance premiums	$ 298.3	$ 266.3

Municipal Bond Guarantee Insurance - Schedule of Net Written Premiums (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Earned premiums:
Net earned premiums	$ 1,076.7	$ 664.2	$ 22.8
HG/BAM
Written premiums:
Direct	63.8	51.0	61.5
Assumed	1.3	4.6	0.2
Net written premiums	65.1	55.6	61.7
Earned premiums:
Direct	28.6	23.2	19.4
Assumed	4.7	3.7	3.4
Net earned premiums	33.3	26.9	22.8
HG Global-BAM
Earned premiums:
Net earned premiums	$ 33.3	$ 26.9	$ 22.8

Earnings Per Share - Schedule of Earnings Per Share from Continuing Operations (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Basic and diluted earnings per share numerators (in millions):
Net income (loss) attributable to White Mountains’s common shareholders	$ 792.8	$ (275.4)	$ 708.7
Less: total income (loss) from discontinued operations, net of tax	903.2	(3.9)	(11.8)
Less: net (income) loss from discontinued operations attributable to non-controlling interests	(0.7)	1.0	0.2
Net income (loss) from continuing operations attributable to White Mountains’s common shareholders	(109.7)	(272.5)	720.3
Allocation of (earnings) losses to participating restricted common shares	1.3	3.2	(9.5)
Basic and diluted earnings (losses) per share numerators	$ (108.4)	$ (269.3)	$ 710.8
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period (in shares)	2,862,400	3,079,000	3,122,200
Average unvested restricted common shares (in shares)	(36,200)	(36,500)	(40,800)
Basic earnings (losses) per share denominator (in shares)	2,826,200	3,042,500	3,081,400
Diluted earnings per share denominator (in thousands):
Average outstanding dilutive options to acquire common shares (in shares)	2,862,400	3,079,000	3,122,200
Average unvested restricted common shares (in shares)	(36,200)	(36,500)	(40,800)
Diluted earnings (loss) per share denominator (in shares)	2,826,200	3,042,500	3,081,400
Diluted earnings per share (in dollars) - continuing operations:
Dividends declared and paid (usd per share)	$ 1.00	$ 1.00	$ 1.00
Undistributed earnings (losses) (usd per share)	(39.34)	(89.52)	229.69
Total consolidated operations (usd per share)	(38.34)	(88.52)	230.69
Total consolidated operations (usd per share)	$ (38.34)	$ (88.52)	$ 230.69

Earnings Per Share - Schedule of Undistributed Net Earnings (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Earnings Per Share [Abstract]
Net income (loss) attributable to White Mountains’s common shareholders, net of restricted common share amounts	$ (108.4)	$ (269.3)	$ 710.8
Dividends declared, net of restricted common share amounts	(3.0)	(3.1)	(3.1)
Total undistributed net earnings (losses), net of restricted common share amounts	$ (111.4)	$ (272.4)	$ 707.7

Employee Share-Based Incentive Compensation Plans - Narrative (Details) $ in Millions	12 Months Ended			36 Months Ended
	Dec. 31, 2022 USD ($) multiplier shares	Dec. 31, 2021 USD ($) shares	Dec. 31, 2020 USD ($) shares	Dec. 31, 2021 USD ($) shares	Dec. 31, 2019 USD ($)
Performance Shares
Share-based compensation arrangement by share-based payment award
Vesting period	3 years
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
New grants (in shares)	13,225	13,475	14,055
Unamortized grant date fair value \| $	$ 36.7
Performance Shares \| 2020 – 2022
Share-based compensation arrangement by share-based payment award
Targeted performance goal (as a percent)	7.00%
Payout for maximum growth target percentage	200.00%
Performance Shares \| 2021 – 2023
Share-based compensation arrangement by share-based payment award
Targeted performance goal (as a percent)	8.00%
Payout for maximum growth target percentage	200.00%
Performance Shares \| 2022 – 2024
Share-based compensation arrangement by share-based payment award
Targeted performance goal (as a percent)	9.00%
Payout for maximum growth target percentage	200.00%
Performance Shares \| Minimum \| 2020 – 2022
Share-based compensation arrangement by share-based payment award
Payout for minimum growth target percentage	2.00%
Performance Shares \| Minimum \| 2021 – 2023
Share-based compensation arrangement by share-based payment award
Payout for minimum growth target percentage	3.00%
Performance Shares \| Minimum \| 2022 – 2024
Share-based compensation arrangement by share-based payment award
Payout for minimum growth target percentage	4.00%
Performance Shares \| Maximum \| 2020 – 2022
Share-based compensation arrangement by share-based payment award
Payout for minimum growth target percentage	12.00%
Performance Shares \| Maximum \| 2021 – 2023
Share-based compensation arrangement by share-based payment award
Payout for minimum growth target percentage	13.00%
Performance Shares \| Maximum \| 2022 – 2024
Share-based compensation arrangement by share-based payment award
Payout for minimum growth target percentage	14.00%
Performance Shares \| W T M Incentive Plan
Share-based compensation arrangement by share-based payment award
New grants (in shares)				750
Restricted Stock
Share-based compensation arrangement by share-based payment award
Vesting period	34 months
Unamortized grant date fair value \| $	$ 15.5	$ 15.9	$ 15.2	$ 15.9	$ 16.7
Shares issued (in shares)	13,225	13,475	14,055
Restricted Share Cliff Vesting in January 2024 \| W T M Incentive and Phantom Plan
Share-based compensation arrangement by share-based payment award
Shares issued (in shares)	13,225
Restricted Share Cliff Vesting in January 2023 \| W T M Incentive and Phantom Plan
Share-based compensation arrangement by share-based payment award
Shares issued (in shares)		13,475
Restricted Share Cliff Vesting in January 2022 \| W T M Incentive and Phantom Plan
Share-based compensation arrangement by share-based payment award
Shares issued (in shares)			14,055

Employee Share-Based Incentive Compensation Plans - Performance Shares (Details) - Performance Shares - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Target Performance Shares Outstanding
Beginning of period (in shares)	40,828	42,458	42,473
Shares paid or expired (in shares)	(14,625)	(14,336)	(14,070)
New grants (in shares)	13,225	13,475	14,055
Forfeitures and cancellations (in shares)	21	(769)	0
Expense recognized (in shares)	0	0	0
End of period (in shares)	39,449	40,828	42,458
Accrued Expense
Beginning of period	$ 42.2	$ 56.3	$ 43.7
Shares paid or expired	(26.4)	(35.2)	(27.7)
New grants	0.0	0.0	0.0
Forfeitures and cancellations	(0.4)	0.4	(0.4)
Expense recognized	52.1	20.7	40.7
End of period	$ 67.5	$ 42.2	$ 56.3
Range Of Performance Cycle From 2019 to 2021 \| W T M Incentive and Phantom Plan
Accrued Expense
Payout for maximum growth target percentage	172.00%
Range Of Performance Cycle From 2018 to 2020 \| W T M Incentive and Phantom Plan
Accrued Expense
Payout for minimum growth target percentage		200.00%
Range Of Performance Cycle From 2017 to 2019 \| W T M Incentive and Phantom Plan
Accrued Expense
Payout for maximum growth target percentage			180.00%
Payout for minimum growth target percentage			174.00%

Employee Share-Based Incentive Compensation Plans - Performance Shares Granted (Details) - Performance Shares - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based compensation arrangement by share-based payment award
Number of nonvested options before forfeitures (in shares)	40,050
Incentive compensation payable before forfeitures	$ 68.5
Assumed forfeitures (in shares)	(601)
Assumed forfeitures	$ (1.0)
Shares outstanding (in shares)	39,449	40,828	42,458	42,473
Accrued incentive compensation	$ 67.5	$ 42.2	$ 56.3	$ 43.7
2022 – 2024
Share-based compensation arrangement by share-based payment award
Number of nonvested options before forfeitures (in shares)	13,225
Incentive compensation payable before forfeitures	$ 11.0
2021 – 2023
Share-based compensation arrangement by share-based payment award
Number of nonvested options before forfeitures (in shares)	13,475
Incentive compensation payable before forfeitures	$ 19.7
2020 – 2022
Share-based compensation arrangement by share-based payment award
Number of nonvested options before forfeitures (in shares)	13,350
Incentive compensation payable before forfeitures	$ 37.8

Employee Share-Based Incentive Compensation Plans - Restricted Shares (Details) - Restricted Stock - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Restricted Shares
Beginning of period (in shares)	37,850	43,105	43,395
Issued (in shares)	13,225	13,475	14,055
Vested (in shares)	(12,725)	(17,936)	(14,345)
Forfeited (in shares)	0	(794)	0
Expense recognized (in shares)	0	0	0
End of period (in shares)	38,350	37,850	43,105
Unamortized Issue Date Fair Value
Beginning of period	$ 15.9	$ 15.2	$ 16.7
Issued	13.8	16.1	15.1
Vested	0.0	0.0	0.0
Forfeited	0.0	(0.8)	0.0
Expense recognized	(14.2)	(14.6)	(16.6)
End of period	$ 15.5	$ 15.9	$ 15.2

Leases - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
ROU lease asset	$ 25.2	$ 28.1
Operating lease liability	$ 27.1	$ 30.0

Leases - Schedule of Lease Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
Lease cost	$ 8.0	$ 6.7
Less: sublease income	0.7	0.4
Net lease cost	$ 7.3	$ 6.3

Leases - Schedule of Future Minimum Payments on Operating Leases (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
2023	$ 8.7
2024	7.6
2025	5.1
2026	2.8
2027	1.6
Thereafter	3.9
Total undiscounted lease payments	29.7
Less: present value adjustment	(2.6)
Operating lease liability	$ 27.1	$ 30.0

Leases - Schedule of Right-of-Use Assets and Lease Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other assets	Other assets
ROU lease asset	$ 25.2	$ 28.1
Operating Lease, Liability, Statement of Financial Position [Extensible List]	Other liabilities	Other liabilities
Lease liability	$ 27.1	$ 30.0
Weighted Average Incremental Borrowing Rate	4.10%	4.00%
HG/BAM
Lessee, Lease, Description [Line Items]
ROU lease asset	$ 5.7	$ 7.6
Lease liability	6.2	8.1
Ark
Lessee, Lease, Description [Line Items]
ROU lease asset	6.6	7.0
Lease liability	6.6	7.0
Kudu
Lessee, Lease, Description [Line Items]
ROU lease asset	5.8	6.4
Lease liability	6.5	7.1
Other Operations
Lessee, Lease, Description [Line Items]
ROU lease asset	7.1	7.1
Lease liability	$ 7.8	$ 7.8

Common Shareholders’ Equity and Non-controlling Interests (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	Sep. 26, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Common Shares Repurchased and Retired
Value of common shares repurchased and retired	$ 460.8	$ 615.8	$ 107.5	$ 85.1
Value of each common share repurchased and retired (in usd per share)	$ 1,400	$ 1,335.11	$ 1,091.29	$ 858.81
Shares repurchased to satisfy employee income tax withholding		4,011	7,218	5,899
Common Shares Issued
Stock issued (in shares)		15,640	15,066	15,745
Dividends on Common Shares
Cash dividends declared and paid		$ 3.0	$ 3.1	$ 3.2
Dividends declared and paid (in usd per share)		$ 1.00
Non-controlling Equity		$ 188.1	$ 156.6
HG Global
Dividends on Common Shares
Non-controlling Percentage		3.10%	3.10%
Ark
Dividends on Common Shares
Non-controlling Percentage		28.00%	28.00%
Kudu
Dividends on Common Shares
Non-controlling Percentage		10.80%	2.50%
NSM
Dividends on Common Shares
Non-controlling Percentage		0.00%	3.50%
BAM
Dividends on Common Shares
Non-controlling Percentage		100.00%	100.00%
Common equity securities
Common Shares Repurchased and Retired
Common shares repurchased and retired (in shares)	327,795	461,256	98,511	99,087
Restricted Stock
Common Shares Issued
Stock issued (in shares)		13,225	13,475	14,055
General Board Authorization
Common Shares Repurchased and Retired
Additional authorized repurchase of common shares (in shares)		320,550
Common shares repurchased and retired (in shares)		129,450	91,293	93,188
Value of common shares repurchased and retired		$ 150.9	$ 100.0	$ 78.5
Value of each common share repurchased and retired (in usd per share)		$ 1,165.84	$ 1,095.37	$ 1,115.51
Directors \| Restricted Stock
Common Shares Issued
Shares issued to directors (in shares)		2,415	1,591	1,440
MediaAlpha \| Restricted Stock
Common Shares Issued
Stock issued (in shares)				250
HG Global
Dividends on Common Shares
Non-controlling Equity		$ (0.6)	$ 8.9
Ark
Dividends on Common Shares
Non-controlling Equity		247.9	230.7
Kudu
Dividends on Common Shares
Non-controlling Equity		75.1	12.4
NSM
Dividends on Common Shares
Non-controlling Equity		0.0	16.7
Other Operations
Dividends on Common Shares
Non-controlling Equity		20.4	11.9
BAM
Dividends on Common Shares
Non-controlling Equity		(154.7)	(124.0)
Total Non-Controlling Excluding Reciprocals
Dividends on Common Shares
Non-controlling Equity		$ 342.8	$ 280.6

Statutory Capital and Surplus (Details) - USD ($)	1 Months Ended		12 Months Ended
Statutory Capital and Surplus (Details) - USD ($)	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statutory Accounting Practices [Line Items]
Total assets	$ 7,389,300,000	$ 7,000,700,000	$ 7,389,300,000	$ 7,000,700,000
Outrigger Re
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	204,000,000		204,000,000
Lloyds Bank
Statutory Accounting Practices [Line Items]
Total assets	325,400,000		325,400,000
HG Global-BAM
Statutory Accounting Practices [Line Items]
Total assets	1,058,500,000	1,044,800,000	1,058,500,000	1,044,800,000
BAM
Statutory Accounting Practices [Line Items]
Accrued interest on surplus notes	157,900,000	157,600,000	157,900,000	157,600,000
Ark
Statutory Accounting Practices [Line Items]
Total assets	3,486,200,000	3,027,000,000	3,486,200,000	3,027,000,000
HG Global
Statutory Accounting Practices [Line Items]
Collateral held in supplement trust	856,900,000	852,000,000	856,900,000	852,000,000
HG Re \| HG Global-BAM
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	730,800,000		730,800,000
Minimum regulatory capital requirement	1		1
Cash and investments outside of collateral trusts	9,300,000		9,300,000
Accrued interest held in supplemental trust	111,700,000		111,700,000
BAM \| HG Global-BAM
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	283,400,000		283,400,000
Minimum regulatory capital requirement	66,000,000		66,000,000
Statutory net loss			(55,000,000)	(49,300,000)	$ (59,300,000)
Ark
Statutory Accounting Practices [Line Items]
Total assets	3,486,200,000	3,027,000,000	3,486,200,000	3,027,000,000
Ark \| Ark
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	877,600,000		877,600,000
Minimum regulatory capital requirement	$ 419,700,000		$ 419,700,000
Percent of statutory capital balance	15.00%		15.00%
Percent of statutory capital and surplus balance	25.00%		25.00%
Dividend or capital distributions, maximum			$ 113,200,000
Statutory surplus balance	$ 754,700,000		754,700,000
Outrigger Re \| Outrigger Re
Statutory Accounting Practices [Line Items]
Minimum regulatory capital requirement	1		1
Surplus Note \| BAM
Statutory Accounting Practices [Line Items]
Cash repayments on notes	36,000,000	33,800,000
Accrued interest on surplus notes	10,400,000	9,800,000	10,400,000	9,800,000
Supplemental Trust \| BAM
Statutory Accounting Practices [Line Items]
Cash repayments on notes	24,600,000	23,600,000
Accrued interest on surplus notes	$ 1,000,000	$ 400,000	$ 1,000,000	$ 400,000

Segment Information - Income Statement Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) segment	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Segment Reporting [Abstract]
Number of operating segments \| segment	3
Segment reporting information
Earned insurance premiums	$ 1,076.7	$ 664.2	$ 22.8
Net investment income	124.4	82.5	131.0
Net realized and unrealized investment gains (losses)	(98.5)	134.2	30.8
Net realized and unrealized investment gains (losses) from investment in MediaAlpha	(93.0)	(380.3)	686.0
Commission revenues	11.5	9.6	8.3
Other revenues	136.8	104.2	16.7
Total revenues	1,157.9	614.4	895.6
Loss and loss adjustment expenses	536.4	314.8
Insurance acquisition expenses	250.6	186.3	7.0
Cost of sales	98.6	69.3	11.3
General and administrative expenses	376.2	292.5	207.9
Amortization of other intangible assets	5.2	4.6	1.6
Interest expense	40.3	20.5	7.4
Total expenses	1,307.3	888.0	235.2
Pre-tax income (loss)	(149.4)	(273.6)	660.4
United Kingdom
Segment reporting information
Earned insurance premiums		459.3
BERMUDA
Segment reporting information
Earned insurance premiums		178.0
HG Global-BAM
Segment reporting information
Earned insurance premiums	33.3	26.9	22.8
Net investment income	21.5	17.5	19.5
Net realized and unrealized investment gains (losses)	(105.8)	(22.9)	23.7
Net realized and unrealized investment gains (losses) from investment in MediaAlpha	0.0	0.0	0.0
Commission revenues	0.0	0.0	0.0
Other revenues	4.6	1.5	2.5
Total revenues	(46.4)	23.0	68.5
Loss and loss adjustment expenses	0.0	0.0
Insurance acquisition expenses	11.2	8.3	7.0
Cost of sales	0.0	0.0	0.0
General and administrative expenses	69.1	57.1	56.8
Amortization of other intangible assets	0.0	0.0	0.0
Interest expense	8.3	0.0	0.0
Total expenses	88.6	65.4	63.8
Pre-tax income (loss)	(135.0)	(42.4)	4.7
Ark
Segment reporting information
Earned insurance premiums	1,043.4	637.3	0.0
Net investment income	16.3	2.9	0.0
Net realized and unrealized investment gains (losses)	(55.2)	16.5	0.0
Net realized and unrealized investment gains (losses) from investment in MediaAlpha	0.0	0.0
Commission revenues	0.0	0.0
Other revenues	5.0	11.8	0.0
Total revenues	1,009.5	668.5	0.0
Loss and loss adjustment expenses	536.4	314.8	0.0
Insurance acquisition expenses	239.4	178.0	0.0
Cost of sales	0.0	0.0
General and administrative expenses	123.5	115.5	0.0
Amortization of other intangible assets	0.0	0.0
Interest expense	15.1	7.3	0.0
Total expenses	914.4	615.6	0.0
Pre-tax income (loss)	95.1	52.9
Ark \| United Kingdom
Segment reporting information
Earned insurance premiums	638.5
Ark \| BERMUDA
Segment reporting information
Earned insurance premiums	404.9
Kudu
Segment reporting information
Earned insurance premiums	0.0	0.0	0.0
Net investment income	54.4	43.9	29.5
Net realized and unrealized investment gains (losses)	64.1	89.9	15.9
Net realized and unrealized investment gains (losses) from investment in MediaAlpha	0.0	0.0	0.0
Commission revenues	0.0	0.0	0.0
Other revenues	0.0	0.2	0.3
Total revenues	118.5	134.0	45.7
Loss and loss adjustment expenses	0.0
Insurance acquisition expenses	0.0	0.0	0.0
Cost of sales	0.0	0.0	0.0
General and administrative expenses	14.4	14.5	11.8
Amortization of other intangible assets	0.3	0.3	0.3
Interest expense	15.0	11.7	6.0
Total expenses	29.7	26.5	18.1
Pre-tax income (loss)	88.8	107.5	27.6
Other Operations
Segment reporting information
Earned insurance premiums	0.0	0.0	0.0
Net investment income	32.2	18.2	82.0
Net realized and unrealized investment gains (losses)	(1.6)	50.7	(8.8)
Net realized and unrealized investment gains (losses) from investment in MediaAlpha	(93.0)	(380.3)	686.0
Commission revenues	11.5	9.6	8.3
Other revenues	127.2	90.7	13.9
Total revenues	76.3	(211.1)	781.4
Loss and loss adjustment expenses	0.0	0.0
Insurance acquisition expenses	0.0	0.0	0.0
Cost of sales	98.6	69.3	11.3
General and administrative expenses	169.2	105.4	139.3
Amortization of other intangible assets	4.9	4.3	1.3
Interest expense	1.9	1.5	1.4
Total expenses	274.6	180.5	153.3
Pre-tax income (loss)	$ (198.3)	$ (391.6)	$ 628.1

Segment Information - Assets (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2012
Segment reporting information
Total investments	$ 5,170.0	$ 4,257.5
Total assets	7,389.3	7,000.7
Total liabilities	3,454.3	3,296.0
Total White Mountains’s common shareholders’ equity	3,746.9	3,548.1
Non-controlling interests	188.1	156.6
Held for Sale
Segment reporting information
Total investments	0.0	0.0
Total assets	0.0	1,005.1
Total liabilities	0.0	495.3
Total White Mountains’s common shareholders’ equity	0.0	493.1
Non-controlling interests	0.0	16.7
HG Global-BAM
Segment reporting information
Total investments	975.8	966.5
Total assets	1,058.5	1,044.8
Total liabilities	501.8	321.9
Total White Mountains’s common shareholders’ equity	712.0	838.0
Non-controlling interests	(155.3)	(115.1)
Ark
Segment reporting information
Total investments	1,761.9	1,562.1
Total assets	3,486.2	3,027.0
Total liabilities	2,520.9	2,122.4
Total White Mountains’s common shareholders’ equity	717.4	673.9
Non-controlling interests	247.9	230.7
Kudu
Segment reporting information
Total investments	695.9	669.5
Total assets	825.9	727.1
Total liabilities	273.3	261.0
Total White Mountains’s common shareholders’ equity	477.5	453.7
Non-controlling interests	75.1	12.4
Other Operations
Segment reporting information
Total investments	1,736.4	1,059.4
Total assets	2,018.7	1,196.7
Total liabilities	158.3	95.4
Total White Mountains’s common shareholders’ equity	1,840.0	1,089.4
Non-controlling interests	20.4	11.9
BAM
Segment reporting information
Surplus notes	340.0	364.6
Accrued interest on surplus notes	157.9	157.6
HG Global
Segment reporting information
Non-controlling interests	(0.6)	8.9
Surplus notes			$ 503.0
Preferred Dividends Payable \| HG Global
Segment reporting information
Total liabilities	$ 341.4	$ 400.5

Equity Method Eligible Investments - Carrying Value and Ownership Percentages (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	May 07, 2020	May 06, 2020	May 31, 2019
Investments in and Advances to Affiliates [Line Items]
Other long-term investments	$ 1,488.0	$ 1,377.8
Kudu
Investments in and Advances to Affiliates [Line Items]
Other long-term investments	695.9	669.5
MediaAlpha
Investments in and Advances to Affiliates [Line Items]
Common equity securities, at fair value	168.6	261.6
PassportCard/DavidShield
Investments in and Advances to Affiliates [Line Items]
Other long-term investments	135.0	120.0
Elementum Holdings, L.P.
Investments in and Advances to Affiliates [Line Items]
Other long-term investments	30.0	45.0
Other Investment Sector
Investments in and Advances to Affiliates [Line Items]
Other long-term investments	84.4	109.3
Equity Method Investments
Investments in and Advances to Affiliates [Line Items]
Other long-term investments	$ 0.0	$ 17.8
Kudu's Participation Contracts \| Minimum
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	4.10%	3.20%
Kudu's Participation Contracts \| Maximum
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	30.00%	32.00%
MediaAlpha
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	27.10%	28.00%
PassportCard/DavidShield
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	53.80%	53.80%	53.80%	50.00%
Elementum Holdings, L.P.
Investments in and Advances to Affiliates [Line Items]
Ownership interest (as a percent)	29.70%	29.70%			30.00%

Equity Method Eligible Investments - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Equity Method Investee
Schedule of Equity Method Investments [Line Items]
Proceeds from dividends received	$ 68.9	$ 56.2	$ 95.0

Equity Method Eligible Investments - Balance Sheet and Income Statement Tables (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Investments in unconsolidated affiliates
Total assets	$ 7,389.3	$ 7,000.7
Total liabilities	3,454.3	3,296.0
Total revenues	1,157.9	614.4	$ 895.6
Net income (loss)	792.8	(275.4)	708.7
White Mountains
Investments in unconsolidated affiliates
Total assets	2,252.5	1,845.7
Total liabilities	526.9	373.4
Total revenues	735.3	987.4	526.5
Total expenses	515.9	418.7	325.9
Net income (loss)	219.4	568.7	200.6
MediaAlpha
Investments in unconsolidated affiliates
Total assets	170.1	289.8
Total liabilities	256.2	351.4
Total revenues	459.1	645.3	584.8
Total expenses	531.5	653.8	574.2
Net income (loss)	$ (72.4)	$ (8.5)	$ 10.6

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(11))
-URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 55
-Paragraph 10
-URI https://asc.fasb.org/extlink&oid=84165509&loc=d3e56426-112766

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8736-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(12))
-URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124433192&loc=SL2890621-112765

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
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Variable Interest Entities (Details) $ in Millions			3 Months Ended	12 Months Ended
Variable Interest Entities (Details) $ in Millions	May 07, 2020 USD ($)	Jan. 24, 2018 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2022 USD ($) director	Dec. 31, 2021 USD ($)	May 06, 2020	May 31, 2019 USD ($)
Private equity funds
Variable Interest Entity [Line Items]
Trading security, fair value			$ 140.6	$ 140.6	$ 141.8
Outrigger Re
Variable Interest Entity [Line Items]
Purchase price			$ 205.0
Ownership interest after all transactions (as a percent)			100.00%
BAM
Variable Interest Entity [Line Items]
Number directors to designate for election \| director				2
First Loss Reinsurance Treaty \| HG Global
Variable Interest Entity [Line Items]
Percentage of par value of policy reinsured			15.00%	15.00%
First Loss Reinsurance Treaty \| BAM
Variable Interest Entity [Line Items]
Percentage of premiums			60.00%	60.00%
Elementum Holdings, L.P.
Variable Interest Entity [Line Items]
Ownership interest (as a percent)			29.70%	29.70%	29.70%		30.00%
Other investments			$ 30.0	$ 30.0			$ 55.1
DavidShield
Variable Interest Entity [Line Items]
Ownership interest (as a percent)		50.00%
PassportCard
Variable Interest Entity [Line Items]
Ownership interest (as a percent)		50.00%
PassportCard/DavidShield
Variable Interest Entity [Line Items]
Ownership interest (as a percent)	53.80%		53.80%	53.80%	53.80%	50.00%
Other investments			$ 144.6	$ 144.6
Payments to acquire businesses, gross		$ 41.8
Payments to acquire business		$ 28.3
Additional investment in acquisition	$ 15.0

Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	$ 575.2	$ 420.9
Fair value \| HG Global Senior Notes
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	155.7	0.0
Fair value \| Ark 2007 Notes
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	28.4	27.6
Fair value \| Ark 2021 Notes
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	163.1	162.8
Fair value \| Kudu Credit Facility
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	223.9	246.8
Fair value \| Other Operations
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	38.2	17.7
Carrying Value \| HG Global Senior Notes
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	146.5	0.0
Carrying Value \| Ark 2007 Notes
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	30.0	30.0
Carrying Value \| Ark 2021 Notes
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	153.7	155.9
Carrying Value \| Kudu Credit Facility
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	208.3	218.2
Carrying Value \| Other Operations
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	$ 36.7	$ 16.8

Held for Sale and Discontinued Operations - Narrative (Details) - USD ($) $ in Millions		12 Months Ended
	May 12, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2018
Discontinued Operations
Total assets		$ 7,389.3	$ 7,000.7
Other Operations
Discontinued Operations
Liabilities held for sale - NSM Group		0.0	495.3
Total assets		2,018.7	2,201.8
Assets held for sale - Other		0.0	16.1
Sirius Group
Discontinued Operations
Gain (loss) on sale of discontinued operations		$ 0.0	18.7	$ (2.3)
Sirius Group \| Discontinued Operations, Disposed of by Sale
Discontinued Operations
Gain (loss) on sale of discontinued operations			17.6		$ 17.3
Liabilities held for sale - NSM Group				$ 18.7
Net (income) loss from discontinued operations attributable to non-controlling interests			1.1
Other Operations \| Discontinued Operations, Disposed of by Sale
Discontinued Operations
Proceeds from sale of segment	$ 19.5
Gain on sale of segment	$ 3.7
Other Operations \| Disposal Group, Held-for-sale, Not Discontinued Operations
Discontinued Operations
Total assets			$ 16.1

Held for Sale and Discontinued Operations - Financial Statement Disclosure (Details) - USD ($) $ in Millions		12 Months Ended
	Aug. 01, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2018	Dec. 31, 2019
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Net income (loss) from discontinued operations, net of tax - NSM Group		$ 16.4	$ (22.6)	$ (9.5)
Total income (loss) from discontinued operations attributable to White Mountains’s common shareholders		(903.2)	3.9	11.8
Net (income) loss from discontinued operations attributable to non-controlling interests		(0.7)	1.0	0.2
Other comprehensive income (loss) from discontinued operations, net of tax - NSM Group		(5.2)	0.2	5.9
Net gain (loss) from foreign currency translation from sale of discontinued operations, net of tax - NSM Group		2.9	0.0	0.0
Net Cash Provided by (Used in) Discontinued Operations [Abstract]
Net cash provided from (used for) operations		38.7	42.3	35.5
Net cash provided from (used for) investing activities		7.1	(56.5)	(124.9)
Net cash used from (used for) financing activities		(17.5)	(1.0)	128.8
Net decrease in cash during the year		107.3	63.1	13.6
Cash balance at beginning of year		147.7	84.6	71.0
Cash balance at end of year		255.0	147.7	84.6
Net income tax payments to US		10.3	(0.1)	15.9
NSM
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Net income (loss) from discontinued operations, net of tax - NSM Group		16.4	(22.6)	(9.5)
Gain (loss) on sale of discontinued operations		886.8	0.0	0.0
Net Cash Provided by (Used in) Discontinued Operations [Abstract]
Cash sold as part of the sale of NSM Group (includes restricted cash of $105.1 and $0.0)		(143.9)	(0.0)	(0.0)
Sirius Group
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Gain (loss) on sale of discontinued operations		0.0	18.7	(2.3)
Held for Sale
Net Cash Provided by (Used in) Discontinued Operations [Abstract]
Restricted cash balance		0.0	89.2	78.4		$ 56.3
Held for Sale \| NSM
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Short-term investments, at fair value			7.8
Cash held for sale			111.6
Restricted cash			89.2
Premiums and commissions receivable			85.0
Goodwill and other intangible assets			725.4
Other assets			59.2
Total assets held for sale			989.0
Debt			272.1
Premiums payable			135.9
Contingent consideration			6.8
Other liabilities			80.5
Total liabilities held for sale			495.3
Net assets held for sale			493.7
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Commission revenues		176.9	258.0	232.5
Other revenues		48.1	72.4	52.6
Total revenues - NSM Group		225.0	330.4	285.1
General and administrative expenses		126.8	190.4	179.5
Broker commission expenses		52.9	80.2	75.3
Change in fair value of contingent consideration		0.1	1.0	(3.3)
Amortization of other intangible assets		9.1	35.2	26.7
Loss on assets held for sale		0.0	(28.7)	0.0
Interest expense		12.1	23.3	22.1
Total expenses - NSM Group		201.0	358.8	300.3
Pre-tax income (loss) from discontinued operations - NSM Group		24.0	(28.4)	(15.2)
Income tax (expense) benefit		(7.6)	5.8	5.7
Net income (loss) from discontinued operations, net of tax - NSM Group		16.4	(22.6)	(9.5)
Gain (loss) on sale of discontinued operations		886.8	0.0	0.0
Total income (loss) from discontinued operations attributable to White Mountains’s common shareholders		903.2	(3.9)	(11.8)
Net (income) loss from discontinued operations attributable to non-controlling interests		(0.7)	1.0	0.2
Total income (loss) from discontinued operations attributable to White Mountains’s common shareholders		902.5	(2.9)	(11.6)
Other comprehensive income (loss) from discontinued operations, net of tax - NSM Group		(5.2)	0.2	5.9
Comprehensive income (loss) from discontinued operations		900.2	(2.7)	(5.7)
Other comprehensive income (loss) from discontinued operations attributable to non-controlling interests		0.2	(0.1)	(0.3)
Comprehensive income (loss) from discontinued operations attributable to White Mountains’s common shareholders		900.4	(2.8)	(6.0)
Net Cash Provided by (Used in) Discontinued Operations [Abstract]
Net cash provided from (used for) operations		38.7	42.3	35.5
Net cash provided from (used for) investing activities		7.1	(56.5)	(124.9)
Net cash used from (used for) financing activities		(17.5)	(1.0)	128.8
Effect of exchange rate changes on cash		4.0	0.2	(2.8)
Net decrease in cash during the year		32.3	(15.0)	36.6
Cash balance at beginning of year		111.6	126.6	90.0
Cash sold as part of the sale of NSM Group (includes restricted cash of $105.1 and $0.0)		(143.9)	0.0	0.0
Cash balance at end of year		0.0	111.6	126.6
Interest paid		(12.0)	(16.6)	(20.9)
Net income tax payments to US		0.0	0.0	0.0
Held for Sale \| Sirius Group
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Gain (loss) on sale of discontinued operations		0.0	18.7	(2.3)
Discontinued Operations, Disposed of by Sale \| NSM
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Loss on assets held for sale	$ (875.7)
Gain (loss) on sale of discontinued operations	886.8
Net gain (loss) from foreign currency translation from sale of discontinued operations, net of tax - NSM Group	$ 2.9
Net Cash Provided by (Used in) Discontinued Operations [Abstract]
Restricted cash balance		$ 105.1	0.0	0.0
Discontinued Operations, Disposed of by Sale \| Sirius Group
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Total liabilities held for sale				$ 18.7
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Gain (loss) on sale of discontinued operations			$ 17.6		$ 17.3

Held for Sale and Discontinued Operations - Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Basic and diluted earnings per share numerators (in millions):
Net income (loss) attributable to White Mountains’s common shareholders	$ 792.8	$ (275.4)	$ 708.7
Net income (loss) from continuing operations attributable to White Mountains’s common shareholders	(109.7)	(272.5)	720.3
Total income (loss) from discontinued operations attributable to White Mountains’s common shareholders	(903.2)	3.9	11.8
Allocation of (earnings) losses to participating restricted common shares	1.3	3.2	(9.5)
Basic and diluted earnings (losses) per share numerators	$ (108.4)	$ (269.3)	$ 710.8
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period (in shares)	2,862,400	3,079,000	3,122,200
Average unvested restricted common shares (in shares)	(36,200)	(36,500)	(40,800)
Basic earnings (losses) per share denominator (in shares)	2,826,200	3,042,500	3,081,400
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period (in shares)	2,862,400	3,079,000	3,122,200
Average unvested restricted common shares (in shares)	(36,200)	(36,500)	(40,800)
Diluted earnings (loss) per share denominator (in shares)	2,826,200	3,042,500	3,081,400
Basic (losses) earnings per share (in usd per share)	$ 276.96	$ (89.46)	$ 226.97
Diluted (losses) earnings per share (in usd per share)	$ 276.96	$ (89.46)	$ 226.97
Discontinued Operations
Basic and diluted earnings per share numerators (in millions):
Net income (loss) attributable to White Mountains’s common shareholders	$ 792.8	$ (275.4)	$ 708.7
Net income (loss) from continuing operations attributable to White Mountains’s common shareholders	(190.8)	(318.0)	675.2
Less: net (income) loss from continuing operations attributable to non-controlling interest	81.1	45.5	45.1
Total income (loss) from discontinued operations attributable to White Mountains’s common shareholders	902.5	(2.9)	(11.6)
Allocation of (earnings) losses to participating restricted common shares	(11.4)	0.0	0.2
Basic and diluted earnings (losses) per share numerators	$ 891.1	$ (2.9)	$ (11.4)
Basic earnings per share denominators (in thousands):
Total average common shares outstanding during the period (in shares)	2,862,400	3,079,000	3,122,200
Average unvested restricted common shares (in shares)	(36,200)	(36,500)	(40,800)
Basic earnings (losses) per share denominator (in shares)	2,826,200	3,042,500	3,081,400
Diluted earnings per share denominator (in thousands):
Total average common shares outstanding during the period (in shares)	2,862,400	3,079,000	3,122,200
Average unvested restricted common shares (in shares)	(36,200)	(36,500)	(40,800)
Diluted earnings (loss) per share denominator (in shares)	2,826,200	3,042,500	3,081,400
Basic (losses) earnings per share (in usd per share)	$ 315.30	$ (0.94)	$ (3.72)
Diluted (losses) earnings per share (in usd per share)	$ 315.30	$ (0.94)	$ (3.72)

SCHEDULE I SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES (Details) $ in Millions	Dec. 31, 2022 USD ($)
Summary of investments other than investments in related parties
Cost	$ 5,002.6
Carrying Value	5,170.0
Fair Value	5,170.0
Fixed maturity investments
Summary of investments other than investments in related parties
Cost	2,076.0
Carrying Value	1,920.9
Fair Value	1,920.9
U.S. Government and agency obligations
Summary of investments other than investments in related parties
Cost	216.6
Carrying Value	206.4
Fair Value	206.4
Debt securities issued by corporations
Summary of investments other than investments in related parties
Cost	1,098.3
Carrying Value	1,018.8
Fair Value	1,018.8
Municipal obligations
Summary of investments other than investments in related parties
Cost	281.6
Carrying Value	258.6
Fair Value	258.6
Mortgage and asset-backed securities
Summary of investments other than investments in related parties
Cost	288.7
Carrying Value	254.2
Fair Value	254.2
Collateralized loan obligations
Summary of investments other than investments in related parties
Cost	190.8
Carrying Value	182.9
Fair Value	182.9
Short-term investments
Summary of investments other than investments in related parties
Cost	925.2
Carrying Value	924.1
Fair Value	924.1
Investment in MediaAlpha
Summary of investments other than investments in related parties
Cost	0.0
Carrying Value	168.6
Fair Value	168.6
Common equity securities - Industrial, Miscellaneous, and Other
Summary of investments other than investments in related parties
Cost	324.3
Carrying Value	334.6
Fair Value	334.6
Exchange traded funds
Summary of investments other than investments in related parties
Cost	336.3
Carrying Value	333.8
Fair Value	333.8
Total common equity securities
Summary of investments other than investments in related parties
Cost	660.6
Carrying Value	668.4
Fair Value	668.4
Other long-term investments
Summary of investments other than investments in related parties
Cost	1,340.8
Carrying Value	1,488.0
Fair Value	$ 1,488.0

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT - Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Assets
Other long-term investments	$ 1,488.0	$ 1,377.8
Total assets	7,389.3	7,000.7
Liabilities
Total liabilities	3,454.3	3,296.0
Total White Mountains’s common shareholders’ equity	3,746.9	3,548.1
Non-controlling interests	188.1	156.6
Total liabilities and equity	7,389.3	7,000.7
White Mountains Insurance Group Ltd.
Assets
Cash	0.1	0.6
Fixed maturity investments, at fair value	49.2	0.0
Common equity securities, at fair value	342.8	0.0
Other long-term investments	49.3	0.0
Short-term investments, at fair value	105.2	6.7
Other assets	75.3	3.0
Investments in consolidated subsidiaries	3,026.6	3,661.3
Total assets	3,648.5	3,671.6
Liabilities
Net Payable to subsidiary	(125.2)	104.9
Other liabilities	27.4	9.6
Total liabilities	(97.8)	114.5
Total White Mountains’s common shareholders’ equity	3,746.9	3,548.1
Non-controlling interests	(0.6)	9.0
Total liabilities and equity	$ 3,648.5	$ 3,671.6

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT - Statement of Operations and Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Revenues (loss) (including realized and unrealized gains and losses)	$ 1,157.9	$ 614.4	$ 895.6
Expenses	1,307.3	888.0	235.2
Pre-tax income (loss) from continuing operations	(149.4)	(273.6)	660.4
Income tax (expense) benefit	(41.4)	(44.4)	14.8
Net income (loss) from continuing operations	(190.8)	(318.0)	675.2
Net (income) loss attributable to non-controlling interests	80.4	46.5	45.3
Net income (loss) attributable to White Mountains’s common shareholders	792.8	(275.4)	708.7
Other comprehensive income (loss), net of tax	(3.8)	1.7	1.4
Other comprehensive income (loss) from discontinued operations, net of tax - NSM Group	(5.2)	0.2	5.9
Net gain (loss) from foreign currency translation from sale of discontinued operations, net of tax - NSM Group	2.9	0.0	0.0
Comprehensive income (loss)	786.7	(273.5)	716.0
Comprehensive (income) loss attributable to non-controlling interests	0.9	0.2	(0.5)
Comprehensive income (loss) attributable to White Mountains’s common shareholders	787.6	(273.3)	715.5
White Mountains Insurance Group Ltd.
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Revenues (loss) (including realized and unrealized gains and losses)	(0.4)	(0.2)	(8.7)
Expenses	67.1	39.0	61.0
Pre-tax income (loss) from continuing operations	(67.5)	(39.2)	(69.7)
Income tax (expense) benefit	(0.9)	0.0	(0.3)
Net income (loss) from continuing operations	(68.4)	(39.2)	(70.0)
Equity in earnings from consolidated subsidiaries, net of tax	853.8	(257.4)	782.0
Net (income) loss attributable to non-controlling interests	7.4	2.5	(1.0)
Net income (loss) attributable to White Mountains’s common shareholders	792.8	(275.4)	708.7
Other comprehensive income (loss), net of tax	(3.8)	1.7	1.4
Other comprehensive income (loss) from discontinued operations, net of tax - NSM Group	(5.2)	0.2	5.9
Net gain (loss) from foreign currency translation from sale of discontinued operations, net of tax - NSM Group	2.9	0.0	0.0
Comprehensive income (loss)	786.7	(273.5)	716.0
Comprehensive (income) loss attributable to non-controlling interests	0.9	0.2	(0.5)
Comprehensive income (loss) attributable to White Mountains’s common shareholders	787.6	(273.3)	715.5
Sirius Group
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Net gain (loss) from sale of discontinued operations, net of tax - Sirius Group	0.0	18.7	(2.3)
Sirius Group \| White Mountains Insurance Group Ltd.
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Net gain (loss) from sale of discontinued operations, net of tax - Sirius Group	$ 0.0	18.7	(2.3)
Swedish Tax Authority \| Sirius Group
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Loss contingency accrual, period increase (decrease)		18.7	(2.3)
Swedish Tax Authority \| Sirius Group \| White Mountains Insurance Group Ltd.
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Loss contingency accrual, period increase (decrease)		$ 18.7	$ (2.3)

SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT - Statement of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Net income (loss) attributable to White Mountains’s common shareholders	$ 792.8	$ (275.4)	$ 708.7
Charges (credits) to reconcile net income to net cash from operations:
Net realized and unrealized investment (gains) losses	93.0	380.3	(686.0)
Net change in other assets and liabilities	90.4	11.7	34.8
Net cash provided from (used for) operations	365.0	38.6	(60.6)
Cash flows from investing activities:
Net change in short-term investments	(455.1)	59.8	60.9
Cash pre-funded for ILS funds managed by Elementum	(70.0)	0.0	0.0
Purchases of consolidated subsidiaries, net of cash acquired	(67.9)	10.6	(9.1)
Net cash provided from (used for) investing activities	115.5	(208.3)	64.6
Cash flows from financing activities:
Repurchases and retirement of common shares	(615.8)	(107.5)	(85.2)
Dividends paid on common shares	(3.0)	(3.1)	(3.2)
Net cash provided from (used for) financing activities – continuing operations	(344.9)	217.6	49.0
Net decrease in cash during the year	107.3	63.1	13.6
Cash balance at beginning of year	147.7	84.6	71.0
Cash balance at end of year	255.0	147.7	84.6
Other long-term investments	1,488.0	1,377.8
Amortization of restricted share awards	14.0	14.7	16.6
Net income (loss) attributable to non-controlling interests	(80.4)	(46.5)	(45.3)
Net change in (receivables) payables to subsidiaries	3.3	6.5	4.8
White Mountains Insurance Group Ltd.
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Net income (loss) attributable to White Mountains’s common shareholders	792.8	(275.4)	708.7
Charges (credits) to reconcile net income to net cash from operations:
Net realized and unrealized investment (gains) losses	5.6	0.1	10.1
Undistributed earnings from consolidated subsidiaries	(853.8)	257.4	(782.0)
Other non-cash reconciling items	(0.4)	14.1	19.0
Accumulated earnings distributed from subsidiary in cash	7.0	0.0	0.0
Net change in other assets and liabilities	17.2	(5.7)	(2.5)
Net cash provided from (used for) operations	(31.6)	(28.2)	(44.4)
Cash flows from investing activities:
Net change in short-term investments	1,165.6	17.7	(127.4)
Purchases of investment securities	(359.2)	0.0	(6.7)
Sales and maturities of investment securities	15.7	0.0	189.7
Purchases of investment securities from subsidiaries	(14.0)	(26.4)	0.0
Sales of investment securities to subsidiaries	0.0	36.4	0.0
Cash pre-funded for ILS funds managed by Elementum	(70.0)	0.0	0.0
Net issuance of debt (to) from subsidiaries	(142.0)	94.0	(44.5)
Net repayment of debt to (from) subsidiaries	(15.0)	0.0	92.6
Purchases of consolidated subsidiaries, net of cash acquired	49.3	17.0	29.1
Proceeds from the sale of Other Operating Businesses, net of cash sold of $0.5 $0.0 and $0.0	19.5	0.0	0.0
Net cash provided from (used for) investing activities	649.9	138.7	132.8
Cash flows from financing activities:
Repurchases and retirement of common shares	(615.8)	(107.5)	(85.2)
Dividends paid on common shares	(3.0)	(3.1)	(3.2)
Net cash provided from (used for) financing activities – continuing operations	(618.8)	(110.6)	(88.4)
Net decrease in cash during the year	(0.5)	(0.1)	0.0
Cash balance at beginning of year	0.6	0.7	0.7
Cash balance at end of year	0.1	0.6	0.7
Investments in consolidated subsidiaries	3,026.6	3,661.3
Fixed maturity investments, at fair value	49.2	0.0
Other long-term investments	49.3	0.0
Short-term investments at carrying value	105.2	6.7
Other assets	75.3	3.0
Net income (loss) attributable to non-controlling interests	(7.4)	(2.5)	1.0
Bridge Holdings, Ltd.
Cash flows from investing activities:
Net issuance of debt (to) from subsidiaries	(69.0)
Net repayment of debt to (from) subsidiaries	15.0
Cash flows from financing activities:
Carrying value of stock transferred	3,540.6
Intercompany note receivable	76.4
Investments in consolidated subsidiaries	2,003.6
Fixed maturity investments, at fair value	28.6
Common equity securities, at fair value	8.1
Other long-term investments	52.2
Short-term investments at carrying value	1,358.7
Other assets	6.0
Cash	7.0
Distribution received from subsidiaries		12.6
Bridge Holdings, Ltd. \| White Mountains Insurance Group Ltd.
Cash flows from investing activities:
Net repayment of debt to (from) subsidiaries		200.0
Purchases of consolidated subsidiaries, net of cash acquired		18.0
Bridge Holdings, Ltd. \| White Mountains Insurance Group Ltd. \| Short-term investments
Cash flows from investing activities:
Purchases of consolidated subsidiaries, net of cash acquired		17.9
Bridge Holdings, Ltd. \| White Mountains Insurance Group Ltd. \| Cash
Cash flows from investing activities:
Purchases of consolidated subsidiaries, net of cash acquired		0.1
White Mountains Adams, Inc.
Cash flows from financing activities:
Contribution to subsidiary	25.0
White Mountains Adams, Inc. \| White Mountains Insurance Group Ltd.
Cash flows from investing activities:
Purchases of consolidated subsidiaries, net of cash acquired		(42.7)
White Mountains Adams, Inc. \| White Mountains Insurance Group Ltd. \| Short-term investments
Cash flows from investing activities:
Purchases of consolidated subsidiaries, net of cash acquired		(37.1)
White Mountains Adams, Inc. \| White Mountains Insurance Group Ltd. \| Cash
Cash flows from investing activities:
Purchases of consolidated subsidiaries, net of cash acquired		(5.6)
HG Global
Cash flows from investing activities:
Net issuance of debt (to) from subsidiaries	(6.0)
Cash flows from financing activities:
Distribution received from subsidiaries	116.3	22.3
White Mountains Investments Bermuda
Cash flows from investing activities:
Net issuance of debt (to) from subsidiaries	(205.0)
Cash flows from financing activities:
Contribution to subsidiary	51.0
White Mountains Investments Bermuda \| White Mountains Insurance Group Ltd.
Cash flows from investing activities:
Purchases of consolidated subsidiaries, net of cash acquired		(19.7)
White Mountains Investments Bermuda \| White Mountains Insurance Group Ltd. \| Short-term investments
Cash flows from investing activities:
Purchases of consolidated subsidiaries, net of cash acquired		19.1
White Mountains Investments Bermuda \| White Mountains Insurance Group Ltd. \| Cash
Cash flows from investing activities:
Purchases of consolidated subsidiaries, net of cash acquired		0.6
Group Ark Insurance Limited
Cash flows from financing activities:
Distribution received from subsidiaries	7.7
PSC Holdings, Ltd
Cash flows from financing activities:
Distribution received from subsidiaries	1.3	6.8
Non-cash reconciling item \| Bridge Holdings, Ltd.
Cash flows from financing activities:
Transfer to investments			169.6
Short-term investments \| White Mountains Insurance Group Ltd.
Cash flows from financing activities:
Transfer to investments			169.6
Short-term investments \| White Mountains Insurance Group Ltd. \| White Mountains Adams, Inc.
Cash flows from financing activities:
Transfer to investments	100.0
WM Lincoln
Cash flows from financing activities:
Carrying value of stock transferred		212.6
Sirius Group
Charges (credits) to reconcile net income to net cash from operations:
Net (gain) loss from sale of discontinued operations, net of tax - Sirius Group	0.0	(18.7)	2.3
Sirius Group \| White Mountains Insurance Group Ltd.
Charges (credits) to reconcile net income to net cash from operations:
Net (gain) loss from sale of discontinued operations, net of tax - Sirius Group	0.0	(18.7)	2.3
Other Operations
Cash flows from investing activities:
Proceeds from the sale of Other Operating Businesses, net of cash sold of $0.5 $0.0 and $0.0	19.5	0.0	0.0
Cash sold in subsidiary transaction	$ 0.5	0.0	0.0
Swedish Tax Authority \| Sirius Group
Cash flows from financing activities:
Loss contingency accrual, period increase (decrease)		18.7	(2.3)
Swedish Tax Authority \| Sirius Group \| White Mountains Insurance Group Ltd.
Cash flows from financing activities:
Loss contingency accrual, period increase (decrease)		$ 18.7	$ (2.3)

SCHEDULE III SUPPLEMENTARY INSURANCE INFORMATION (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
HG Global-BAM
SUPPLEMENTARY INSURANCE INFORMATION
Deferred Acquisition Costs	$ 36.0	$ 33.1	$ 27.8
Future Policy Benefits, Losses, Claims and Loss Expenses	0.0	0.0	0.0
Unearned Premiums	298.3	266.3	237.5
Other Policy Claims and Benefits Payable	0.0	0.0	0.0
Premiums Earned	33.3	26.9	22.8
Net Investment Income	21.5	17.5	19.5
Benefits, Claims, Losses and Settlement Expenses	0.0	0.0	0.0
Amortization of Deferred Acquisition Costs	11.2	8.3	7.0
Other Operating Expenses	0.4	0.4	0.4
Premiums Written	65.1	55.8	$ 61.7
Ark
SUPPLEMENTARY INSURANCE INFORMATION
Deferred Acquisition Costs	127.2	100.8
Future Policy Benefits, Losses, Claims and Loss Expenses	1,296.5	894.7
Unearned Premiums	623.2	495.9
Other Policy Claims and Benefits Payable	0.0	0.0
Premiums Earned	1,043.4	637.3
Net Investment Income	16.3	2.9
Benefits, Claims, Losses and Settlement Expenses	536.4	314.8
Amortization of Deferred Acquisition Costs	238.3	111.3
Other Operating Expenses	78.7	64.6
Premiums Written	$ 1,195.2	$ 859.1

SCHEDULE IV REINSURANCE (Details) - USD ($) $ in Millions	12 Months Ended
SCHEDULE IV REINSURANCE (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Premiums earned
Net earned premiums	$ 1,076.7	$ 664.2	$ 22.8
HG Global/BAM
Premiums earned
Gross Amount	28.6	23.2	19.4
Ceded to Other Companies	0.0	0.0	0.0
Assumed from Other Companies	4.7	3.7	3.4
Net earned premiums	$ 33.3	$ 26.9	$ 22.8
Percentage of Amount Assumed to Net	14.10%	13.80%	14.90%
Ark
Premiums earned
Gross Amount	$ 655.5	$ 556.0
Ceded to Other Companies	(280.8)	(249.1)
Assumed from Other Companies	668.7	330.4
Net earned premiums	$ 1,043.4	$ 637.3	$ 0.0
Percentage of Amount Assumed to Net	64.10%	51.80%

SCHEDULE V VALUATION AND QUALIFYING ACCOUNTS (Details) - Reinsurance recoverables: Allowance for uncollectible balances - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
VALUATION AND QUALIFYING ACCOUNTS
Balance at beginning of period	$ 3.6	$ 2.3
Charged to costs and expenses	4.6	1.3
Charged to other accounts	0.0	0.0
Deductions described	(0.4)	0.0
Balance at end of period	$ 7.8	$ 3.6

SCHEDULE VI SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS (Details) - Ark - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
SUPPLEMENTAL INFORMATION FOR PROPERTY AND CASUALTY INSURANCE UNDERWRITERS
Deferred acquisition costs	$ 127.2	$ 100.8
Reserves for Unpaid Claims and Claims Adjustment Expenses	1,296.5	894.7
Discount, if any, deducted in Column C	0.0	0.0
Unearned Premiums	623.2	495.9
Earned Premiums	1,043.4	637.3
Net investment income	16.3	2.9
Current Year	588.1	336.3
Prior Year	(51.7)	(21.5)
Amortization of deferred policy acquisition costs	238.3	111.3
Paid Claims and Claims Adjustment Expenses	257.5	0.0
Premiums written	$ 1,195.2	$ 859.1