$WTM
WHITE MOUNTAINS INSURANCE GROUP LTD Stock $wtm

$wtm Overview Financials Valuation SEC Filings Company Website

2024 Q1 Form 10-K Financial Statement

#000077686724000005 Filed on February 26, 2024

Income Statement

Concept	2024 Q1	2023 Q4	2023
Revenue	$647.3M	$736.8M	$2.167B
YoY Change	21.7%	68.37%	87.12%
Cost Of Revenue	$7.600M		$40.40M
YoY Change	-45.32%		-59.03%
Gross Profit	$639.7M		$2.126B
YoY Change	23.49%		100.73%
Gross Profit Margin	98.83%		98.14%
Selling, General & Admin	$142.1M	$141.3M	$473.0M
YoY Change	29.3%	-4.27%	-0.38%
% of Gross Profit	22.21%		22.25%
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$71.60M		$290.1M
YoY Change	-187.1%		6646.51%
% of Gross Profit	11.19%		13.64%
Operating Expenses	$399.5M	$391.2M	$1.539B
YoY Change	24.77%	32.25%	21.44%
Operating Profit	$240.2M		$587.7M
YoY Change	21.44%		-382.96%
Interest Expense	$15.20M	-$17.80M	$62.70M
YoY Change	-220.63%	39.06%	-255.58%
% of Operating Profit	6.33%		10.67%
Other Income/Expense, Net
YoY Change
Pretax Income	$232.6M	$327.8M	$565.4M
YoY Change	16.83%	154.11%	-478.45%
Income Tax	$10.80M	-$34.90M	-$15.50M
% Of Pretax Income	4.64%	-10.65%	-2.74%
Net Earnings	$236.4M	$282.4M	$509.2M
YoY Change	31.7%	15.93%	-28.52%
Net Earnings / Revenue	36.52%	38.33%	23.5%
Basic Earnings Per Share	$92.33		$198.60
Diluted Earnings Per Share	$92.33	$111.90	$198.60
COMMON SHARES
Basic Shares Outstanding	2.555M shares	2.560M shares	2.527M shares
Diluted Shares Outstanding	2.531M shares		2.527M shares

Balance Sheet

Concept	2024 Q1	2023 Q4	2023
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$225.3M	$122.4M
Short-Term Investments
Other Short-Term Assets
YoY Change
Inventory
Prepaid Expenses
Receivables
Other Receivables
Total Short-Term Assets
YoY Change
LONG-TERM ASSETS
Property, Plant & Equipment
YoY Change
Goodwill	$439.2M	$168.8M
YoY Change	160.19%	-4.36%
Intangibles	$297.4M	$201.8M
YoY Change	43.39%	-6.53%
Long-Term Investments	$6.328B	$6.389B	$6.389B
YoY Change	16.44%	23.57%	23.57%
Other Assets	$83.00M
YoY Change
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$9.590B	$8.386B	$8.386B
YoY Change	20.49%	13.49%	13.49%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses	$59.50M	$114.9M	$114.9M
YoY Change	14.2%	-18.63%	-18.63%
Deferred Revenue
YoY Change
Short-Term Debt	$0.00	$0.00	$0.00
YoY Change
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$59.50M	$114.9M	$114.9M
YoY Change	14.2%	-18.63%	-18.63%
LONG-TERM LIABILITIES
Long-Term Debt	$532.1M	$564.6M	$564.6M
YoY Change	-4.35%	-1.84%	-1.84%
Other Long-Term Liabilities	$438.2M	$389.2M	$389.2M
YoY Change	48.04%	44.79%	44.79%
Total Long-Term Liabilities	$970.3M	$953.8M	$953.8M
YoY Change	13.84%	13.01%	13.01%
TOTAL LIABILITIES
Total Short-Term Liabilities	$59.50M	$114.9M	$114.9M
Total Long-Term Liabilities	$970.3M	$953.8M	$953.8M
Total Liabilities	$4.700B	$3.824B	$4.145B
YoY Change	21.56%	10.71%	13.81%
SHAREHOLDERS EQUITY
Retained Earnings	$3.918B	$3.691B
YoY Change	16.35%	14.91%
Common Stock	$2.600M	$2.600M
YoY Change	0.0%	-99.52%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$4.470B	$4.241B	$4.241B
YoY Change
Total Liabilities & Shareholders Equity	$9.590B	$8.386B	$8.386B
YoY Change	20.49%	13.49%	13.49%

Cashflow Statement

Concept	2024 Q1	2023 Q4	2023
OPERATING ACTIVITIES
Net Income	$236.4M	$282.4M	$509.2M
YoY Change	31.7%	15.93%	-28.52%
Depreciation, Depletion And Amortization	$71.60M		$290.1M
YoY Change	-187.1%		6646.51%
Cash From Operating Activities	$36.50M	$24.50M	$404.1M
YoY Change	-57.36%	-88.23%	10.71%
INVESTING ACTIVITIES
Capital Expenditures
YoY Change
Acquisitions	$231.8M		$0.00
YoY Change			-100.0%
Other Investing Activities	-$29.20M	-$88.90M	$3.400M
YoY Change	-360.71%	-41.51%	-22.73%
Cash From Investing Activities	$100.6M	-$88.90M	-$543.9M
YoY Change	-204.14%	-41.51%	-570.91%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net			$32.70M
YoY Change			-94.69%
Debt Paid & Issued, Net	$32.60M		$25.70M
YoY Change	63.0%		-54.67%
Cash From Financing Activities	-$34.20M	24.00M	$7.200M
YoY Change	-17.19%	-151.28%	-102.09%
NET CHANGE
Cash From Operating Activities	$36.50M	24.50M	$404.1M
Cash From Investing Activities	$100.6M	-88.90M	-$543.9M
Cash From Financing Activities	-$34.20M	24.00M	$7.200M
Net Change In Cash	$102.9M	-40.40M	-$132.6M
YoY Change	-296.75%	-534.41%	-223.58%
FREE CASH FLOW
Cash From Operating Activities	$36.50M	$24.50M	$404.1M
Capital Expenditures
Free Cash Flow
YoY Change

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
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CY2023	dei	Entity File Number EntityFileNumber	1-8993
CY2023	dei	Entity Registrant Name EntityRegistrantName	WHITE MOUNTAINS INSURANCE GROUP, LTD.
CY2023	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	D0
CY2023	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	94-2708455
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CY2021	wtm	Income Loss From Discontinued Operations Net Of Tax Including Portion Attributable To Noncontrolling Interest Excluding Gain Loss On Disposal IncomeLossFromDiscontinuedOperationsNetOfTaxIncludingPortionAttributableToNoncontrollingInterestExcludingGainLossOnDisposal	-22600000	usd
CY2023	us-gaap	Increase Decrease In Reinsurance Recoverable IncreaseDecreaseInReinsuranceRecoverable	-153300000	usd
CY2022	us-gaap	Increase Decrease In Reinsurance Recoverable IncreaseDecreaseInReinsuranceRecoverable	79800000	usd
CY2021	us-gaap	Increase Decrease In Reinsurance Recoverable IncreaseDecreaseInReinsuranceRecoverable	-88000000.0	usd
CY2023	us-gaap	Increase Decrease In Premiums Receivable IncreaseDecreaseInPremiumsReceivable	67000000.0	usd
CY2022	us-gaap	Increase Decrease In Premiums Receivable IncreaseDecreaseInPremiumsReceivable	127800000	usd
CY2021	us-gaap	Increase Decrease In Premiums Receivable IncreaseDecreaseInPremiumsReceivable	179300000	usd
CY2023	us-gaap	Increase Decrease In Deferred Policy Acquisition Costs IncreaseDecreaseInDeferredPolicyAcquisitionCosts	22200000	usd
CY2022	us-gaap	Increase Decrease In Deferred Policy Acquisition Costs IncreaseDecreaseInDeferredPolicyAcquisitionCosts	21900000	usd
CY2021	us-gaap	Increase Decrease In Deferred Policy Acquisition Costs IncreaseDecreaseInDeferredPolicyAcquisitionCosts	41800000	usd
CY2023	us-gaap	Increase Decrease In Liability For Claims And Claims Adjustment Expense Reserve IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve	308600000	usd
CY2022	us-gaap	Increase Decrease In Liability For Claims And Claims Adjustment Expense Reserve IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve	401800000	usd
CY2021	us-gaap	Increase Decrease In Liability For Claims And Claims Adjustment Expense Reserve IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve	198700000	usd
CY2023	us-gaap	Increase Decrease In Unearned Premiums IncreaseDecreaseInUnearnedPremiums	147900000	usd
CY2022	us-gaap	Increase Decrease In Unearned Premiums IncreaseDecreaseInUnearnedPremiums	159300000	usd
CY2021	us-gaap	Increase Decrease In Unearned Premiums IncreaseDecreaseInUnearnedPremiums	198600000	usd
CY2023	us-gaap	Increase Decrease In Reinsurance Payables IncreaseDecreaseInReinsurancePayables	-170000000.0	usd
CY2022	us-gaap	Increase Decrease In Reinsurance Payables IncreaseDecreaseInReinsurancePayables	-173000000.0	usd
CY2021	us-gaap	Increase Decrease In Reinsurance Payables IncreaseDecreaseInReinsurancePayables	-104200000	usd
CY2023	wtm	Payments For Participation Contracts PaymentsForParticipationContracts	163800000	usd
CY2022	wtm	Payments For Participation Contracts PaymentsForParticipationContracts	99800000	usd
CY2021	wtm	Payments For Participation Contracts PaymentsForParticipationContracts	223400000	usd
CY2023	wtm	Proceeds From Sale Of Participation Contracts ProceedsFromSaleOfParticipationContracts	75200000	usd
CY2022	wtm	Proceeds From Sale Of Participation Contracts ProceedsFromSaleOfParticipationContracts	137500000	usd
CY2021	wtm	Proceeds From Sale Of Participation Contracts ProceedsFromSaleOfParticipationContracts	44400000	usd
CY2023	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	3900000	usd
CY2022	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-80800000	usd
CY2021	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-10700000	usd
CY2023	us-gaap	Net Cash Provided By Used In Operating Activities Continuing Operations NetCashProvidedByUsedInOperatingActivitiesContinuingOperations	404100000	usd
CY2022	us-gaap	Net Cash Provided By Used In Operating Activities Continuing Operations NetCashProvidedByUsedInOperatingActivitiesContinuingOperations	326300000	usd
CY2021	us-gaap	Net Cash Provided By Used In Operating Activities Continuing Operations NetCashProvidedByUsedInOperatingActivitiesContinuingOperations	-3700000	usd
CY2023	us-gaap	Cash Provided By Used In Operating Activities Discontinued Operations CashProvidedByUsedInOperatingActivitiesDiscontinuedOperations	0	usd
CY2022	us-gaap	Cash Provided By Used In Operating Activities Discontinued Operations CashProvidedByUsedInOperatingActivitiesDiscontinuedOperations	38700000	usd
CY2021	us-gaap	Cash Provided By Used In Operating Activities Discontinued Operations CashProvidedByUsedInOperatingActivitiesDiscontinuedOperations	42300000	usd
CY2023	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	404100000	usd
CY2022	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	365000000.0	usd
CY2021	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	38600000	usd
CY2023	wtm	Payments For Proceeds From Other Short Term Investments PaymentsForProceedsFromOtherShortTermInvestments	495800000	usd
CY2022	wtm	Payments For Proceeds From Other Short Term Investments PaymentsForProceedsFromOtherShortTermInvestments	455100000	usd
CY2021	wtm	Payments For Proceeds From Other Short Term Investments PaymentsForProceedsFromOtherShortTermInvestments	-59800000	usd
CY2023	us-gaap	Proceeds From Sale Of Trading Securities Heldforinvestment ProceedsFromSaleOfTradingSecuritiesHeldforinvestment	195100000	usd
CY2022	us-gaap	Proceeds From Sale Of Trading Securities Heldforinvestment ProceedsFromSaleOfTradingSecuritiesHeldforinvestment	188700000	usd
CY2021	us-gaap	Proceeds From Sale Of Trading Securities Heldforinvestment ProceedsFromSaleOfTradingSecuritiesHeldforinvestment	286300000	usd
CY2023	us-gaap	Proceeds From Maturities Repayments And Calls Of Trading Securities Heldforinvestment ProceedsFromMaturitiesRepaymentsAndCallsOfTradingSecuritiesHeldforinvestment	266500000	usd
CY2022	us-gaap	Proceeds From Maturities Repayments And Calls Of Trading Securities Heldforinvestment ProceedsFromMaturitiesRepaymentsAndCallsOfTradingSecuritiesHeldforinvestment	198500000	usd
CY2021	us-gaap	Proceeds From Maturities Repayments And Calls Of Trading Securities Heldforinvestment ProceedsFromMaturitiesRepaymentsAndCallsOfTradingSecuritiesHeldforinvestment	199000000.0	usd
CY2023	us-gaap	Proceeds From Sale Of Equity Securities Fv Ni ProceedsFromSaleOfEquitySecuritiesFvNi	261600000	usd
CY2022	us-gaap	Proceeds From Sale Of Equity Securities Fv Ni ProceedsFromSaleOfEquitySecuritiesFvNi	0	usd
CY2021	us-gaap	Proceeds From Sale Of Equity Securities Fv Ni ProceedsFromSaleOfEquitySecuritiesFvNi	176800000	usd
CY2023	us-gaap	Proceeds From Sale And Maturity Of Other Investments ProceedsFromSaleAndMaturityOfOtherInvestments	116900000	usd
CY2022	us-gaap	Proceeds From Sale And Maturity Of Other Investments ProceedsFromSaleAndMaturityOfOtherInvestments	115400000	usd
CY2021	us-gaap	Proceeds From Sale And Maturity Of Other Investments ProceedsFromSaleAndMaturityOfOtherInvestments	106400000	usd
CY2023	us-gaap	Cash Divested From Deconsolidation CashDivestedFromDeconsolidation	800000	usd
CY2022	us-gaap	Cash Divested From Deconsolidation CashDivestedFromDeconsolidation	144400000	usd
CY2021	us-gaap	Cash Divested From Deconsolidation CashDivestedFromDeconsolidation	0.0	usd
CY2023	us-gaap	Proceeds From Divestiture Of Businesses Net Of Cash Divested ProceedsFromDivestitureOfBusinessesNetOfCashDivested	17300000	usd
CY2022	us-gaap	Proceeds From Divestiture Of Businesses Net Of Cash Divested ProceedsFromDivestitureOfBusinessesNetOfCashDivested	1392000000	usd
CY2021	us-gaap	Proceeds From Divestiture Of Businesses Net Of Cash Divested ProceedsFromDivestitureOfBusinessesNetOfCashDivested	0	usd
CY2023	wtm	Proceeds From Payments For Release Of Cash Placed In Escrow ProceedsFromPaymentsForReleaseOfCashPlacedInEscrow	0	usd
CY2022	wtm	Proceeds From Payments For Release Of Cash Placed In Escrow ProceedsFromPaymentsForReleaseOfCashPlacedInEscrow	0	usd
CY2021	wtm	Proceeds From Payments For Release Of Cash Placed In Escrow ProceedsFromPaymentsForReleaseOfCashPlacedInEscrow	646300000	usd
CY2023	wtm	Release Of Cash Pre Fundings For Managed Funds ReleaseOfCashPreFundingsForManagedFunds	-70000000.0	usd
CY2022	wtm	Release Of Cash Pre Fundings For Managed Funds ReleaseOfCashPreFundingsForManagedFunds	70000000.0	usd
CY2021	wtm	Release Of Cash Pre Fundings For Managed Funds ReleaseOfCashPreFundingsForManagedFunds	0	usd
CY2023	wtm	Payments To Acquire Trading Fixed Maturities Investments PaymentsToAcquireTradingFixedMaturitiesInvestments	592700000	usd
CY2022	wtm	Payments To Acquire Trading Fixed Maturities Investments PaymentsToAcquireTradingFixedMaturitiesInvestments	585500000	usd
CY2021	wtm	Payments To Acquire Trading Fixed Maturities Investments PaymentsToAcquireTradingFixedMaturitiesInvestments	1219400000	usd
CY2023	wtm	Payments To Acquire Equity Securities And Equity Method Investments PaymentsToAcquireEquitySecuritiesAndEquityMethodInvestments	114200000	usd
CY2022	wtm	Payments To Acquire Equity Securities And Equity Method Investments PaymentsToAcquireEquitySecuritiesAndEquityMethodInvestments	424500000	usd
CY2021	wtm	Payments To Acquire Equity Securities And Equity Method Investments PaymentsToAcquireEquitySecuritiesAndEquityMethodInvestments	203400000	usd
CY2023	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	265200000	usd
CY2022	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	178800000	usd
CY2021	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	218000000.0	usd
CY2023	us-gaap	Cash Acquired From Acquisition CashAcquiredFromAcquisition	0.0	usd
CY2022	us-gaap	Cash Acquired From Acquisition CashAcquiredFromAcquisition	300000	usd
CY2021	us-gaap	Cash Acquired From Acquisition CashAcquiredFromAcquisition	52200000	usd
CY2023	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	0	usd
CY2022	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	67900000	usd
CY2021	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	-10600000	usd
CY2023	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	3400000	usd
CY2022	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	4400000	usd
CY2021	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-3800000	usd
CY2023	us-gaap	Net Cash Provided By Used In Investing Activities Continuing Operations NetCashProvidedByUsedInInvestingActivitiesContinuingOperations	-543900000	usd
CY2022	us-gaap	Net Cash Provided By Used In Investing Activities Continuing Operations NetCashProvidedByUsedInInvestingActivitiesContinuingOperations	108400000	usd
CY2021	us-gaap	Net Cash Provided By Used In Investing Activities Continuing Operations NetCashProvidedByUsedInInvestingActivitiesContinuingOperations	-151800000	usd
CY2023	us-gaap	Cash Provided By Used In Investing Activities Discontinued Operations CashProvidedByUsedInInvestingActivitiesDiscontinuedOperations	0	usd
CY2022	us-gaap	Cash Provided By Used In Investing Activities Discontinued Operations CashProvidedByUsedInInvestingActivitiesDiscontinuedOperations	7100000	usd
CY2021	us-gaap	Cash Provided By Used In Investing Activities Discontinued Operations CashProvidedByUsedInInvestingActivitiesDiscontinuedOperations	-56500000	usd
CY2023	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-543900000	usd
CY2022	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	115500000	usd
CY2021	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-208300000	usd
CY2023	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	12400000	usd
CY2022	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	213800000	usd
CY2021	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	401700000	usd
CY2023	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	25700000	usd
CY2022	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	56700000	usd
CY2021	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	120100000	usd
CY2023	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	2600000	usd
CY2022	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	3000000.0	usd
CY2021	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	3100000	usd
CY2023	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	32700000	usd
CY2022	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	615800000	usd
CY2021	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	107500000	usd
CY2023	us-gaap	Proceeds From Payments To Minority Shareholders ProceedsFromPaymentsToMinorityShareholders	-3000000.0	usd
CY2022	us-gaap	Proceeds From Payments To Minority Shareholders ProceedsFromPaymentsToMinorityShareholders	-21600000	usd
CY2021	us-gaap	Proceeds From Payments To Minority Shareholders ProceedsFromPaymentsToMinorityShareholders	700000	usd
CY2023	wtm	Proceeds From Payments To Discontinued Operations ProceedsFromPaymentsToDiscontinuedOperations	0	usd
CY2022	wtm	Proceeds From Payments To Discontinued Operations ProceedsFromPaymentsToDiscontinuedOperations	11600000	usd
CY2021	wtm	Proceeds From Payments To Discontinued Operations ProceedsFromPaymentsToDiscontinuedOperations	0	usd
CY2023	wtm	Proceeds From Issuance Of Equity To Noncontrolling Interests ProceedsFromIssuanceOfEquityToNoncontrollingInterests	0	usd
CY2022	wtm	Proceeds From Issuance Of Equity To Noncontrolling Interests ProceedsFromIssuanceOfEquityToNoncontrollingInterests	74600000	usd
CY2021	wtm	Proceeds From Issuance Of Equity To Noncontrolling Interests ProceedsFromIssuanceOfEquityToNoncontrollingInterests	6500000	usd
CY2023	wtm	Proceeds From Member Surplus Contributions ProceedsFromMemberSurplusContributions	72800000	usd
CY2022	wtm	Proceeds From Member Surplus Contributions ProceedsFromMemberSurplusContributions	81400000	usd
CY2021	wtm	Proceeds From Member Surplus Contributions ProceedsFromMemberSurplusContributions	62200000	usd
CY2023	wtm	Payments For Collateralized Financial Guarantee PaymentsForCollateralizedFinancialGuarantee	13600000	usd
CY2022	wtm	Payments For Collateralized Financial Guarantee PaymentsForCollateralizedFinancialGuarantee	10100000	usd
CY2021	wtm	Payments For Collateralized Financial Guarantee PaymentsForCollateralizedFinancialGuarantee	8800000	usd
CY2023	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-400000	usd
CY2022	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-1600000	usd
CY2021	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-13000000.0	usd
CY2023	us-gaap	Net Cash Provided By Used In Financing Activities Continuing Operations NetCashProvidedByUsedInFinancingActivitiesContinuingOperations	7200000	usd
CY2022	us-gaap	Net Cash Provided By Used In Financing Activities Continuing Operations NetCashProvidedByUsedInFinancingActivitiesContinuingOperations	-327400000	usd
CY2021	us-gaap	Net Cash Provided By Used In Financing Activities Continuing Operations NetCashProvidedByUsedInFinancingActivitiesContinuingOperations	218600000	usd
CY2023	us-gaap	Cash Provided By Used In Financing Activities Discontinued Operations CashProvidedByUsedInFinancingActivitiesDiscontinuedOperations	0	usd
CY2022	us-gaap	Cash Provided By Used In Financing Activities Discontinued Operations CashProvidedByUsedInFinancingActivitiesDiscontinuedOperations	-17500000	usd
CY2021	us-gaap	Cash Provided By Used In Financing Activities Discontinued Operations CashProvidedByUsedInFinancingActivitiesDiscontinuedOperations	-1000000.0	usd
CY2023	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	7200000	usd
CY2022	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-344900000	usd
CY2021	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	217600000	usd
CY2023	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect Continuing Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffectContinuingOperations	-132600000	usd
CY2022	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect Continuing Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffectContinuingOperations	107300000	usd
CY2021	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect Continuing Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffectContinuingOperations	63100000	usd
CY2022Q4	us-gaap	Restricted Cash And Cash Equivalents At Carrying Value RestrictedCashAndCashEquivalentsAtCarryingValue	18300000	usd
CY2021Q4	us-gaap	Restricted Cash And Cash Equivalents At Carrying Value RestrictedCashAndCashEquivalentsAtCarryingValue	4500000	usd
CY2020Q4	us-gaap	Restricted Cash And Cash Equivalents At Carrying Value RestrictedCashAndCashEquivalentsAtCarryingValue	0.0	usd
CY2022Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Disposal Group Including Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsDisposalGroupIncludingDiscontinuedOperations	0.0	usd
CY2021Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Disposal Group Including Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsDisposalGroupIncludingDiscontinuedOperations	111600000	usd
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Disposal Group Including Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsDisposalGroupIncludingDiscontinuedOperations	126600000	usd
CY2022Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	255000000.0	usd
CY2021Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	147700000	usd
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	84600000	usd
CY2023Q4	us-gaap	Restricted Cash And Cash Equivalents At Carrying Value RestrictedCashAndCashEquivalentsAtCarryingValue	700000	usd
CY2022Q4	us-gaap	Restricted Cash And Cash Equivalents At Carrying Value RestrictedCashAndCashEquivalentsAtCarryingValue	18300000	usd
CY2021Q4	us-gaap	Restricted Cash And Cash Equivalents At Carrying Value RestrictedCashAndCashEquivalentsAtCarryingValue	4500000	usd
CY2023Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Disposal Group Including Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsDisposalGroupIncludingDiscontinuedOperations	0.0	usd
CY2022Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Disposal Group Including Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsDisposalGroupIncludingDiscontinuedOperations	0.0	usd
CY2021Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Disposal Group Including Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsDisposalGroupIncludingDiscontinuedOperations	111600000	usd
CY2023Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	122400000	usd
CY2022Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	255000000.0	usd
CY2021Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	147700000	usd
CY2023	us-gaap	Use Of Estimates UseOfEstimates	<div><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:700;line-height:120%">Use of Estimates</span></div><div style="text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">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.</span></div>
CY2023	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	3	segment
CY2023Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	20300000	usd
CY2022Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	25200000	usd
CY2023Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	22000000	usd
CY2022Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	27100000	usd
CY2023Q4	us-gaap	Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax	-1600000	usd
CY2022Q4	us-gaap	Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Net Of Tax AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax	-3500000	usd
CY2020Q4	us-gaap	Escrow Deposit EscrowDeposit	646300000	usd
CY2021Q4	wtm	Number Of Portfolio Companies NumberOfPortfolioCompanies	2	portfoliocompany
CY2023	us-gaap	Gross Investment Income Operating GrossInvestmentIncomeOperating	196600000	usd
CY2022	us-gaap	Gross Investment Income Operating GrossInvestmentIncomeOperating	126500000	usd
CY2021	us-gaap	Gross Investment Income Operating GrossInvestmentIncomeOperating	84800000	usd
CY2022	us-gaap	Investment Income Investment Expense InvestmentIncomeInvestmentExpense	2100000	usd
CY2021	us-gaap	Investment Income Investment Expense InvestmentIncomeInvestmentExpense	2300000	usd
CY2021	us-gaap	Net Investment Income NetInvestmentIncome	82500000	usd
CY2023	wtm	Gain Loss On Investments Third Party Provider GainLossOnInvestmentsThirdPartyProvider	0	usd
CY2022	wtm	Gain Loss On Investments Third Party Provider GainLossOnInvestmentsThirdPartyProvider	6800000	usd
CY2021	wtm	Gain Loss On Investments Third Party Provider GainLossOnInvestmentsThirdPartyProvider	-7700000	usd
CY2021	us-gaap	Gain Loss On Investments GainLossOnInvestments	-246100000	usd
CY2023	us-gaap	Gain On Sale Of Investments GainOnSaleOfInvestments	113700000	usd
CY2022	us-gaap	Gain On Sale Of Investments GainOnSaleOfInvestments	129900000	usd
CY2021	us-gaap	Gain On Sale Of Investments GainOnSaleOfInvestments	212300000	usd
CY2023	us-gaap	Loss On Sale Of Investments LossOnSaleOfInvestments	16900000	usd
CY2022	us-gaap	Loss On Sale Of Investments LossOnSaleOfInvestments	14800000	usd
CY2021	us-gaap	Loss On Sale Of Investments LossOnSaleOfInvestments	55500000	usd
CY2023	us-gaap	Proceeds From Sale Maturity And Collection Of Longterm Investments ProceedsFromSaleMaturityAndCollectionOfLongtermInvestments	800000000	usd
CY2022	us-gaap	Proceeds From Sale Maturity And Collection Of Longterm Investments ProceedsFromSaleMaturityAndCollectionOfLongtermInvestments	500000000	usd
CY2021	us-gaap	Proceeds From Sale Maturity And Collection Of Longterm Investments ProceedsFromSaleMaturityAndCollectionOfLongtermInvestments	800000000	usd
CY2023	wtm	Debt Securities Weighted Average Portfolio Period DebtSecuritiesWeightedAveragePortfolioPeriod	P1Y10M24D
CY2023	wtm	Debt Securities Weighted Average Portfolio Period Excluding Short Term Investments DebtSecuritiesWeightedAveragePortfolioPeriodExcludingShortTermInvestments	P3Y3M18D
CY2023Q4	us-gaap	Equity Securities Fv Ni Cost EquitySecuritiesFvNiCost	483500000	usd
CY2023	us-gaap	Equity Securities Fv Ni Unrealized Gain EquitySecuritiesFvNiUnrealizedGain	62300000	usd
CY2023	us-gaap	Equity Securities Fv Ni Unrealized Loss EquitySecuritiesFvNiUnrealizedLoss	1200000	usd
CY2023	wtm	Equity Securities Fnni Net Foreign Currency Gain Loss EquitySecuritiesFNNINetForeignCurrencyGainLoss	-6200000	usd
CY2023Q4	us-gaap	Equity Securities Fv Ni Current And Noncurrent EquitySecuritiesFvNiCurrentAndNoncurrent	538400000	usd
CY2023Q4	wtm	Other Long Term Investments Cost OtherLongTermInvestmentsCost	1655700000	usd
CY2023	wtm	Other Long Term Investments Unrealized Gain OtherLongTermInvestmentsUnrealizedGain	446300000	usd
CY2023	wtm	Other Long Term Investments Unrealized Loss OtherLongTermInvestmentsUnrealizedLoss	94500000	usd
CY2023	wtm	Other Long Term Investments Net Foreign Currency Gain Loss OtherLongTermInvestmentsNetForeignCurrencyGainLoss	-9300000	usd
CY2023Q4	us-gaap	Other Long Term Investments OtherLongTermInvestments	1998200000	usd
CY2022Q4	us-gaap	Equity Securities Fv Ni Cost EquitySecuritiesFvNiCost	660600000	usd
CY2022	us-gaap	Equity Securities Fv Ni Unrealized Gain EquitySecuritiesFvNiUnrealizedGain	26700000	usd
CY2022	us-gaap	Equity Securities Fv Ni Unrealized Loss EquitySecuritiesFvNiUnrealizedLoss	8400000	usd
CY2022	wtm	Equity Securities Fnni Net Foreign Currency Gain Loss EquitySecuritiesFNNINetForeignCurrencyGainLoss	-10500000	usd
CY2022Q4	us-gaap	Equity Securities Fv Ni Current And Noncurrent EquitySecuritiesFvNiCurrentAndNoncurrent	668400000	usd
CY2022Q4	wtm	Other Long Term Investments Cost OtherLongTermInvestmentsCost	1340800000	usd
CY2022	wtm	Other Long Term Investments Unrealized Gain OtherLongTermInvestmentsUnrealizedGain	271100000	usd
CY2022	wtm	Other Long Term Investments Unrealized Loss OtherLongTermInvestmentsUnrealizedLoss	107100000	usd
CY2022	wtm	Other Long Term Investments Net Foreign Currency Gain Loss OtherLongTermInvestmentsNetForeignCurrencyGainLoss	-16800000	usd
CY2022Q4	us-gaap	Other Long Term Investments OtherLongTermInvestments	1488000000	usd
CY2023Q4	wtm	Funds Held Under Reinsurance Agreements Assets Investments FundsHeldUnderReinsuranceAgreementsAssetsInvestments	585600000	usd
CY2022Q4	wtm	Funds Held Under Reinsurance Agreements Assets Investments FundsHeldUnderReinsuranceAgreementsAssetsInvestments	500500000	usd
CY2023Q4	us-gaap	Assets Held By Insurance Regulators AssetsHeldByInsuranceRegulators	4600000	usd
CY2022Q4	us-gaap	Assets Held By Insurance Regulators AssetsHeldByInsuranceRegulators	4600000	usd
CY2023Q4	us-gaap	Other Long Term Investments OtherLongTermInvestments	1998200000	usd
CY2022Q4	us-gaap	Other Long Term Investments OtherLongTermInvestments	1488000000	usd
CY2023Q4	wtm	Other Long Term Investments Remaining Period One To Three Years OtherLongTermInvestmentsRemainingPeriodOneToThreeYears	4500000	usd
CY2023Q4	wtm	Other Long Term Investments Remaining Period Three To Five Years OtherLongTermInvestmentsRemainingPeriodThreeToFiveYears	71000000.0	usd
CY2023Q4	wtm	Other Long Term Investments Remaining Period Five To Ten Years OtherLongTermInvestmentsRemainingPeriodFiveToTenYears	155400000	usd
CY2023Q4	wtm	Other Long Term Investments Remaining Period Greater Than10 Years OtherLongTermInvestmentsRemainingPeriodGreaterThan10Years	17700000	usd
CY2023Q4	us-gaap	Goodwill Goodwill	168800000	usd
CY2023Q4	us-gaap	Goodwill Goodwill	168800000	usd
CY2022Q4	us-gaap	Goodwill Goodwill	176500000	usd
CY2022Q4	us-gaap	Goodwill Goodwill	176500000	usd
CY2023Q4	us-gaap	Intangible Assets Gross Excluding Goodwill IntangibleAssetsGrossExcludingGoodwill	218800000	usd
CY2022Q4	us-gaap	Intangible Assets Gross Excluding Goodwill IntangibleAssetsGrossExcludingGoodwill	228100000	usd
CY2023Q4	wtm	Intangible Assets Gross Including Goodwill IntangibleAssetsGrossIncludingGoodwill	387600000	usd
CY2023Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	17000000.0	usd
CY2023Q4	us-gaap	Intangible Assets Net Including Goodwill IntangibleAssetsNetIncludingGoodwill	370600000	usd
CY2022Q4	wtm	Intangible Assets Gross Including Goodwill IntangibleAssetsGrossIncludingGoodwill	404600000	usd
CY2022Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	12200000	usd
CY2022Q4	us-gaap	Intangible Assets Net Including Goodwill IntangibleAssetsNetIncludingGoodwill	392400000	usd
CY2022Q4	us-gaap	Goodwill Goodwill	176500000	usd
CY2022Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	215900000	usd
CY2022Q4	us-gaap	Intangible Assets Net Including Goodwill IntangibleAssetsNetIncludingGoodwill	392400000	usd
CY2021Q4	us-gaap	Goodwill Goodwill	142300000	usd
CY2021Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	198200000	usd
CY2021Q4	us-gaap	Intangible Assets Net Including Goodwill IntangibleAssetsNetIncludingGoodwill	340500000	usd
CY2023	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	0	usd
CY2023	us-gaap	Indefinitelived Intangible Assets Acquired IndefinitelivedIntangibleAssetsAcquired	0	usd
CY2023	wtm	Goodwill And Indefinite Lived Intangible Assets Acquired During Period GoodwillAndIndefiniteLivedIntangibleAssetsAcquiredDuringPeriod	0	usd
CY2022	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	59500000	usd
CY2022	us-gaap	Indefinitelived Intangible Assets Acquired IndefinitelivedIntangibleAssetsAcquired	0	usd
CY2022	wtm	Goodwill And Indefinite Lived Intangible Assets Acquired During Period GoodwillAndIndefiniteLivedIntangibleAssetsAcquiredDuringPeriod	59500000	usd
CY2023	us-gaap	Goodwill Written Off Related To Sale Of Business Unit GoodwillWrittenOffRelatedToSaleOfBusinessUnit	6700000	usd
CY2023	us-gaap	Indefinite Lived Intangible Assets Written Off Related To Sale Of Business Unit IndefiniteLivedIntangibleAssetsWrittenOffRelatedToSaleOfBusinessUnit	6900000	usd
CY2023	wtm	Goodwill And Indefinite Lived Intangible Assets Written Off Related To Sale Of Business Unit GoodwillAndIndefiniteLivedIntangibleAssetsWrittenOffRelatedToSaleOfBusinessUnit	13600000	usd
CY2022	us-gaap	Goodwill Written Off Related To Sale Of Business Unit GoodwillWrittenOffRelatedToSaleOfBusinessUnit	0	usd
CY2022	us-gaap	Indefinite Lived Intangible Assets Written Off Related To Sale Of Business Unit IndefiniteLivedIntangibleAssetsWrittenOffRelatedToSaleOfBusinessUnit	0	usd
CY2022	wtm	Goodwill And Indefinite Lived Intangible Assets Written Off Related To Sale Of Business Unit GoodwillAndIndefiniteLivedIntangibleAssetsWrittenOffRelatedToSaleOfBusinessUnit	0	usd
CY2023	wtm	Goodwill Attribution Of Acquisition Adjustments GoodwillAttributionOfAcquisitionAdjustments	0	usd
CY2023	wtm	Finite Lived Intangible Assets Attribution Of Acquisition Adjustments FiniteLivedIntangibleAssetsAttributionOfAcquisitionAdjustments	0	usd
CY2023	wtm	Goodwill And Finite Lived Intangible Assets Attribution Of Acquisition Adjustments GoodwillAndFiniteLivedIntangibleAssetsAttributionOfAcquisitionAdjustments	0	usd
CY2022	wtm	Goodwill Attribution Of Acquisition Adjustments GoodwillAttributionOfAcquisitionAdjustments	-22900000	usd
CY2022	wtm	Finite Lived Intangible Assets Attribution Of Acquisition Adjustments FiniteLivedIntangibleAssetsAttributionOfAcquisitionAdjustments	22900000	usd
CY2022	wtm	Goodwill And Finite Lived Intangible Assets Attribution Of Acquisition Adjustments GoodwillAndFiniteLivedIntangibleAssetsAttributionOfAcquisitionAdjustments	0	usd
CY2023	us-gaap	Goodwill Purchase Accounting Adjustments GoodwillPurchaseAccountingAdjustments	-1000000.0	usd
CY2023	us-gaap	Goodwill Purchase Accounting Adjustments GoodwillPurchaseAccountingAdjustments	-1000000.0	usd
CY2022	us-gaap	Goodwill Purchase Accounting Adjustments GoodwillPurchaseAccountingAdjustments	-2400000	usd
CY2022	us-gaap	Goodwill Purchase Accounting Adjustments GoodwillPurchaseAccountingAdjustments	-2400000	usd
CY2023	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	7200000	usd
CY2023	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	7200000	usd
CY2022	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	5200000	usd
CY2022	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	5200000	usd
CY2023Q4	us-gaap	Goodwill Goodwill	168800000	usd
CY2023Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	201800000	usd
CY2023Q4	us-gaap	Intangible Assets Net Including Goodwill IntangibleAssetsNetIncludingGoodwill	370600000	usd
CY2022Q4	us-gaap	Goodwill Goodwill	176500000	usd
CY2022Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	215900000	usd
CY2022Q4	us-gaap	Intangible Assets Net Including Goodwill IntangibleAssetsNetIncludingGoodwill	392400000	usd
CY2023	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	7200000	usd
CY2022	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	5200000	usd
CY2021	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	4600000	usd
CY2023Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	5500000	usd
CY2023Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	4800000	usd
CY2023Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	4000000.0	usd
CY2023Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	3600000	usd
CY2023Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Five FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	8200000	usd
CY2023Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	26100000	usd
CY2023Q4	us-gaap	Indefinite Lived Intangible Assets Excluding Goodwill IndefiniteLivedIntangibleAssetsExcludingGoodwill	175700000	usd
CY2023	us-gaap	Schedule Of Liability For Unpaid Claims And Claims Adjustment Expense ScheduleOfLiabilityForUnpaidClaimsAndClaimsAdjustmentExpense	The following table summarizes the loss and LAE reserve activity of the Ark/WM Outrigger segment for the years ended December 31, 2023, 2022 and 2021:<div style="text-align:center"><table style="border-collapse:collapse;display:inline-table;margin-bottom:5pt;vertical-align:text-bottom;width:96.783%"><tr><td style="width:1.0%"></td><td style="width:61.135%"></td><td style="width:0.1%"></td><td style="width:0.1%"></td><td style="width:0.555%"></td><td style="width:0.1%"></td><td style="width:1.0%"></td><td style="width:10.833%"></td><td style="width:0.1%"></td><td style="width:0.1%"></td><td style="width:0.404%"></td><td style="width:0.1%"></td><td style="width:1.0%"></td><td style="width:10.833%"></td><td style="width:0.1%"></td><td style="width:0.1%"></td><td style="width:0.404%"></td><td style="width:0.1%"></td><td style="width:1.0%"></td><td style="width:10.836%"></td><td style="width:0.1%"></td></tr><tr><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td><td colspan="15" style="border-top:1pt solid #000;padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">Year Ended December 31,</span></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">Millions</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">2023</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">2022</span></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">2021</span></td></tr><tr><td colspan="3" style="border-top:1pt solid #000;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:9pt;font-weight:400;line-height:100%">Gross beginning balance</span></td><td colspan="3" style="padding:0 1pt"></td><td style="border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">$</span></td><td style="border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">1,296.5</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td style="border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">894.7 </span></td><td style="border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td style="border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">696.0 </span></td><td style="border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><div><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:9pt;font-weight:400;line-height:100%">Less: beginning reinsurance recoverable on unpaid losses </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:5.2pt;font-weight:400;line-height:100%;position:relative;top:-2.8pt;vertical-align:baseline">(1)</span></div></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">(505.0)</span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(428.9)</span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(433.4)</span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt 2px 7pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:9pt;font-weight:400;line-height:100%">Net loss and LAE reserves</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">791.5</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">465.8 </span></td><td style="border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">262.6 </span></td><td style="border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr style="height:3pt"><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:9pt;font-weight:400;line-height:100%">Losses and LAE incurred relating to:</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:9pt;font-weight:400;line-height:100%"> Current year losses</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">706.9</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">588.1 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">336.3 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:9pt;font-weight:400;line-height:100%"> Prior year losses</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">19.9</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(51.7)</span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(21.5)</span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:9pt;font-weight:400;line-height:100%">Net incurred losses and LAE</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">726.8</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">536.4 </span></td><td style="border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">314.8 </span></td><td style="border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr style="height:3pt"><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:9pt;font-weight:400;line-height:100%">Loss and LAE paid relating to:</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td></tr><tr><td colspan="3" style="padding:2px 1pt 2px 13pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:9pt;font-weight:400;line-height:100%">Current year losses</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">(51.3)</span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(98.9)</span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(43.9)</span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt 2px 7pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:9pt;font-weight:400;line-height:100%"> Prior year losses</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">(356.6)</span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(158.6)</span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(61.6)</span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:9pt;font-weight:400;line-height:100%">Net paid losses and LAE</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">(407.9)</span></td><td style="border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(257.5)</span></td><td style="border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(105.5)</span></td><td style="border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr style="height:3pt"><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><div><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:9pt;font-weight:400;line-height:100%">Change in TPC Providers’ participation </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:5.85pt;font-weight:400;line-height:100%;position:relative;top:-3.15pt;vertical-align:baseline">(2)</span></div></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">145.4</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">57.5 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(2.2)</span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:9pt;font-weight:400;line-height:100%">Foreign currency translation and other adjustments to loss and LAE reserves</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">8.5</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(10.7)</span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">(3.9)</span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr style="height:3pt"><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:9pt;font-weight:400;line-height:100%">Net ending balance</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">1,264.3</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">791.5 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">465.8 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><div style="padding-left:6pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:9pt;font-weight:400;line-height:100%">Plus: ending reinsurance recoverable on unpaid losses </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:5.2pt;font-weight:400;line-height:100%;position:relative;top:-2.8pt;vertical-align:baseline">(3)</span></div></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">340.8</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">505.0 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">428.9 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="border-bottom:3pt double #000;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:9pt;font-weight:400;line-height:100%">Gross ending balance</span></td><td colspan="3" style="border-bottom:3pt double #000;padding:0 1pt"></td><td style="border-bottom:3pt double #000;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">$</span></td><td style="border-bottom:3pt double #000;border-top:1pt solid #000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">1,605.1</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="border-bottom:3pt double #000;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="border-bottom:3pt double #000;padding:0 1pt"></td><td style="border-bottom:3pt double #000;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="border-bottom:3pt double #000;border-top:1pt solid #000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">1,296.5 </span></td><td style="border-bottom:3pt double #000;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="border-bottom:3pt double #000;padding:0 1pt"></td><td style="border-bottom:3pt double #000;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="border-bottom:3pt double #000;border-top:1pt solid #000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">894.7 </span></td><td style="border-bottom:3pt double #000;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr></table></div><div style="margin-top:3pt;padding-left:18pt;padding-right:9pt;text-indent:-9pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:5.2pt;font-weight:400;line-height:120%;position:relative;top:-2.8pt;vertical-align:baseline">(1)</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:120%"> The beginning reinsurance recoverable on unpaid losses includes amounts attributable to TPC Providers of $145.4, $276.8 and $319.2 as of December 31, 2022, 2021 and 2020.</span></div><div style="padding-left:18pt;padding-right:9pt;text-indent:-9pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:5.2pt;font-weight:400;line-height:120%;position:relative;top:-2.8pt;vertical-align:baseline">(2)</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:120%"> 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.</span></div><div style="padding-left:18pt;padding-right:9pt;text-indent:-9pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:5.2pt;font-weight:400;line-height:120%;position:relative;top:-2.8pt;vertical-align:baseline">(3)</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:120%"> The ending reinsurance recoverable on unpaid losses includes amounts attributable to TPC Providers of $0.0, $145.4 and $276.8 as of December 31, 2023, 2022 and 2021. </span></div><div style="text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The following table summarizes the unpaid loss and LAE reserves, net of reinsurance recoverables on unpaid losses, for each of the Ark/WM Outrigger segment’s major reserving lines of business as of December 31, 2023 and 2022:</span></div><div style="text-indent:18pt"><span><br/></span></div><div style="text-indent:18pt"><table style="border-collapse:collapse;display:inline-table;margin-bottom:5pt;vertical-align:text-bottom;width:96.491%"><tr><td style="width:1.0%"></td><td style="width:68.748%"></td><td style="width:0.1%"></td><td style="width:0.1%"></td><td style="width:0.557%"></td><td style="width:0.1%"></td><td style="width:1.0%"></td><td style="width:13.293%"></td><td style="width:0.1%"></td><td style="width:0.1%"></td><td style="width:0.406%"></td><td style="width:0.1%"></td><td style="width:1.0%"></td><td style="width:13.296%"></td><td style="width:0.1%"></td></tr><tr><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td><td colspan="9" style="border-top:1pt solid #000;padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">Year Ended December 31,</span></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%"><br/><br/></span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">Millions</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">2023</span></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">2022</span></td></tr><tr><td colspan="3" style="border-top:1pt solid #000;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Property and Accident & Health</span></td><td colspan="3" style="padding:0 1pt"></td><td style="border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">$</span></td><td style="border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">358.7</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td style="border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">258.2 </span></td><td style="border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Specialty</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">339.7</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">204.3 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Marine & Energy</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">331.7</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">196.4 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="display:none"></td><td colspan="3" style="display:none"></td><td colspan="3" style="display:none"></td><td colspan="3" style="display:none"></td><td colspan="3" style="display:none"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Casualty-Active </span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">137.1</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">71.5 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Casualty-Runoff</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">81.3</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">60.8 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:112%">WM Outrigger and Other</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">15.8</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">.3 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:112%"> Unpaid loss and LAE reserves, net of reinsurance recoverables on unpaid losses</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">1,264.3</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">791.5 </span></td><td style="border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><div><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Plus: Reinsurance recoverables on unpaid losses </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:6.5pt;font-weight:400;line-height:100%;position:relative;top:-3.5pt;vertical-align:baseline">(1)</span></div></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000;padding:0 1pt"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><div><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Property and Accident & Health</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:6.5pt;font-weight:400;line-height:100%;position:relative;top:-3.5pt;vertical-align:baseline"> (2)</span></div></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">126.9</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">224.6 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Specialty</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">77.6</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">97.2 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Marine & Energy</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">59.1</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">79.8 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Casualty-Active</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">74.8</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">49.9 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Casualty-Runoff</span></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">2.4</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">53.5 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><div style="text-indent:9pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:112%">Total Reinsurance recoverables on unpaid losses </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:6.5pt;font-weight:400;line-height:112%;position:relative;top:-3.5pt;vertical-align:baseline">(1) (2)</span></div></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">340.8</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="padding:0 1pt"></td><td colspan="2" style="border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">505.0 </span></td><td style="border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr><tr><td colspan="3" style="border-bottom:3pt double #000000;padding:2px 1pt 2px 13pt;text-align:left;text-indent:4.5pt;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">Total unpaid loss and LAE reserves</span></td><td colspan="3" style="border-bottom:3pt double #000000;padding:0 1pt"></td><td style="border-bottom:3pt double #000000;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">$</span></td><td style="border-bottom:3pt double #000000;border-top:1pt solid #000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:100%">1,605.1</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%"> </span></td><td style="border-bottom:3pt double #000000;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td><td colspan="3" style="border-bottom:3pt double #000;padding:0 1pt"></td><td style="border-bottom:3pt double #000000;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">$</span></td><td style="border-bottom:3pt double #000000;border-top:1pt solid #000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:100%">1,296.5 </span></td><td style="border-bottom:3pt double #000000;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></tr></table></div><div style="margin-top:3pt;padding-left:9pt;text-indent:9pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:5.2pt;font-weight:400;line-height:120%;position:relative;top:-2.8pt;vertical-align:baseline">(1)</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:120%"> The reinsurance recoverables on unpaid losses include amounts attributable to TPC Providers of $0.0 and $145.4 as of December 31, 2023 and 2022.</span></div><div style="padding-left:27pt;text-indent:-9pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:5.2pt;font-weight:400;line-height:120%;position:relative;top:-2.8pt;vertical-align:baseline">(2)</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:120%"> The reinsurance recoverables on unpaid losses exclude $15.6 ceded by Ark to WM Outrigger Re as of December 31, 2023, which eliminate in White Mountains’s consolidated financial statements.</span></div>
CY2021	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	2800000	usd
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CY2021	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	9700000	usd
CY2023	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	13200000	usd
CY2022	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	7300000	usd
CY2023Q4	us-gaap	Long Term Debt LongTermDebt	564600000	usd
CY2022Q4	us-gaap	Long Term Debt LongTermDebt	575200000	usd
CY2023Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	3300000	usd
CY2023Q4	us-gaap	Long Term Debt Maturing In Years Two And Three LongTermDebtMaturingInYearsTwoAndThree	11200000	usd
CY2023Q4	us-gaap	Long Term Debt Maturing In Years Four And Five LongTermDebtMaturingInYearsFourAndFive	40600000	usd
CY2023Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal After Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive	523800000	usd
CY2023Q4	us-gaap	Debt Instrument Carrying Amount DebtInstrumentCarryingAmount	578900000	usd
CY2023	us-gaap	Interest Expense Debt InterestExpenseDebt	62700000	usd
CY2022	us-gaap	Interest Expense Debt InterestExpenseDebt	40300000	usd
CY2021	us-gaap	Interest Expense Debt InterestExpenseDebt	20500000	usd
CY2023	us-gaap	Interest Paid InterestPaid	42200000	usd
CY2022	us-gaap	Interest Paid InterestPaid	30500000	usd
CY2021	us-gaap	Interest Paid InterestPaid	13900000	usd
CY2023	us-gaap	Deferred Other Tax Expense Benefit DeferredOtherTaxExpenseBenefit	-68000000	usd
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CY2022	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	16900000	usd
CY2021	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	4800000	usd
CY2023	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	2200000	usd
CY2022	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	4500000	usd
CY2021	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	2100000	usd
CY2023	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	16600000	usd
CY2022	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	7100000	usd
CY2021	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	13900000	usd
CY2023	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	3800000	usd
CY2022	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	1800000	usd
CY2021	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	7000000.0	usd
CY2023	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-63900000	usd
CY2022	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	3800000	usd
CY2021	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	13800000	usd
CY2023	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-46900000	usd
CY2022	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	12900000	usd
CY2021	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	34700000	usd
CY2023	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-15500000	usd
CY2022	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	41400000	usd
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	44400000	usd
CY2023	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	118700000	usd
CY2022	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	-31400000	usd
CY2021	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	-57500000	usd
CY2023	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	-103700000	usd
CY2022	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	41200000	usd
CY2021	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	78200000	usd
CY2023	wtm	Effective Income Tax Rate Reconciliation Bermuda Corporate Income Tax Law Amount EffectiveIncomeTaxRateReconciliationBermudaCorporateIncomeTaxLawAmount	68000000.0	usd
CY2022	wtm	Effective Income Tax Rate Reconciliation Bermuda Corporate Income Tax Law Amount EffectiveIncomeTaxRateReconciliationBermudaCorporateIncomeTaxLawAmount	0	usd
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CY2023	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	30200000	usd
CY2022	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	19600000	usd
CY2021	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	2000000.0	usd
CY2023	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	8200000	usd
CY2022	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	2800000	usd
CY2021	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	7300000	usd
CY2023	us-gaap	Income Tax Reconciliation Minority Interest Income Expense IncomeTaxReconciliationMinorityInterestIncomeExpense	6800000	usd
CY2022	us-gaap	Income Tax Reconciliation Minority Interest Income Expense IncomeTaxReconciliationMinorityInterestIncomeExpense	3400000	usd
CY2021	us-gaap	Income Tax Reconciliation Minority Interest Income Expense IncomeTaxReconciliationMinorityInterestIncomeExpense	2100000	usd
CY2023	wtm	Effective Income Tax Rate Reconciliation Member Surplus Contribution Amount EffectiveIncomeTaxRateReconciliationMemberSurplusContributionAmount	5700000	usd
CY2022	wtm	Effective Income Tax Rate Reconciliation Member Surplus Contribution Amount EffectiveIncomeTaxRateReconciliationMemberSurplusContributionAmount	6200000	usd
CY2021	wtm	Effective Income Tax Rate Reconciliation Member Surplus Contribution Amount EffectiveIncomeTaxRateReconciliationMemberSurplusContributionAmount	5600000	usd
CY2023	wtm	Effective Income Tax Rate Reconciliation Withholding Tax Amount EffectiveIncomeTaxRateReconciliationWithholdingTaxAmount	4100000	usd
CY2022	wtm	Effective Income Tax Rate Reconciliation Withholding Tax Amount EffectiveIncomeTaxRateReconciliationWithholdingTaxAmount	3100000	usd
CY2021	wtm	Effective Income Tax Rate Reconciliation Withholding Tax Amount EffectiveIncomeTaxRateReconciliationWithholdingTaxAmount	300000	usd
CY2023	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	600000	usd
CY2022	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	400000	usd
CY2021	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	10900000	usd
CY2023	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	200000	usd
CY2022	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	1000000.0	usd
CY2021	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	1500000	usd
CY2023	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	200000	usd
CY2022	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	200000	usd
CY2021	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	200000	usd
CY2023	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-4500000	usd
CY2022	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	2100000	usd
CY2021	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-1600000	usd
CY2023	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-15500000	usd
CY2022	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	41400000	usd
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	44400000	usd
CY2023	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	450000000	usd
CY2022	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	-94400000	usd
CY2021	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	-319000000.0	usd
CY2023	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	42700000	usd
CY2022	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	10300000	usd
CY2021	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	-100000	usd
CY2023Q4	wtm	Deferred Tax Assets Operating Loss Carryforwards And Capital Loss Carryforwards Domestic DeferredTaxAssetsOperatingLossCarryforwardsAndCapitalLossCarryforwardsDomestic	87600000	usd
CY2022Q4	wtm	Deferred Tax Assets Operating Loss Carryforwards And Capital Loss Carryforwards Domestic DeferredTaxAssetsOperatingLossCarryforwardsAndCapitalLossCarryforwardsDomestic	85400000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards Foreign DeferredTaxAssetsOperatingLossCarryforwardsForeign	68200000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards Foreign DeferredTaxAssetsOperatingLossCarryforwardsForeign	36100000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Goodwill And Intangible Assets DeferredTaxAssetsGoodwillAndIntangibleAssets	51500000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Goodwill And Intangible Assets DeferredTaxAssetsGoodwillAndIntangibleAssets	0	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits	25400000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits	21400000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Unearned Premiums Reserve DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsUnearnedPremiumsReserve	18200000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Unearned Premiums Reserve DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsUnearnedPremiumsReserve	0	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Accrued Liabilities DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities	10100000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Accrued Liabilities DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities	8800000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Loss Reserves DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsLossReserves	8400000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Loss Reserves DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsLossReserves	0	usd
CY2023Q4	wtm	Deferred Tax Assets Deferred Expense Deferred Policy Acquisition Cost DeferredTaxAssetsDeferredExpenseDeferredPolicyAcquisitionCost	3700000	usd
CY2022Q4	wtm	Deferred Tax Assets Deferred Expense Deferred Policy Acquisition Cost DeferredTaxAssetsDeferredExpenseDeferredPolicyAcquisitionCost	8000000.0	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards DeferredTaxAssetsTaxCreditCarryforwards	3300000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Credit Carryforwards DeferredTaxAssetsTaxCreditCarryforwards	1800000	usd
CY2023Q4	wtm	Deferred Tax Assets Unrealized Investment Gains Losses Net DeferredTaxAssetsUnrealizedInvestmentGainsLossesNet	0	usd
CY2022Q4	wtm	Deferred Tax Assets Unrealized Investment Gains Losses Net DeferredTaxAssetsUnrealizedInvestmentGainsLossesNet	4700000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	1000000.0	usd
CY2022Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	1300000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	277400000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	167500000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	116100000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	94300000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	161300000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	73200000	usd
CY2023Q4	wtm	Deferred Tax Liabilities Members Surplus Contributions DeferredTaxLiabilitiesMembersSurplusContributions	82200000	usd
CY2022Q4	wtm	Deferred Tax Liabilities Members Surplus Contributions DeferredTaxLiabilitiesMembersSurplusContributions	71300000	usd
CY2023Q4	wtm	Deferred Tax Liabilities Purchase Accounting DeferredTaxLiabilitiesPurchaseAccounting	43900000	usd
CY2022Q4	wtm	Deferred Tax Liabilities Purchase Accounting DeferredTaxLiabilitiesPurchaseAccounting	43900000	usd
CY2023Q4	us-gaap	Deferred Tax Liabilities Investments DeferredTaxLiabilitiesInvestments	40900000	usd
CY2022Q4	us-gaap	Deferred Tax Liabilities Investments DeferredTaxLiabilitiesInvestments	33900000	usd
CY2023Q4	wtm	Deferred Tax Liabilities Deferred Underwriting DeferredTaxLiabilitiesDeferredUnderwriting	18300000	usd
CY2022Q4	wtm	Deferred Tax Liabilities Deferred Underwriting DeferredTaxLiabilitiesDeferredUnderwriting	9700000	usd
CY2023Q4	us-gaap	Deferred Tax Liabilities Unrealized Gains On Trading Securities DeferredTaxLiabilitiesUnrealizedGainsOnTradingSecurities	15500000	usd
CY2022Q4	us-gaap	Deferred Tax Liabilities Unrealized Gains On Trading Securities DeferredTaxLiabilitiesUnrealizedGainsOnTradingSecurities	0	usd
CY2023Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	1200000	usd
CY2022Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	2200000	usd
CY2023Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	202000000.0	usd
CY2022Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	161000000.0	usd
CY2023Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	40700000	usd
CY2022Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	87800000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	116100000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	94300000	usd
CY2023Q4	wtm	Operating And Capital Loss Carryforwards Not Subject To Expiration OperatingAndCapitalLossCarryforwardsNotSubjectToExpiration	94200000	usd
CY2023Q4	wtm	Operating And Capital Loss Carryforwards OperatingAndCapitalLossCarryforwards	677200000	usd
CY2023Q4	wtm	Deferred Tax Assets Operating And Capital Loss Carryforwards DeferredTaxAssetsOperatingAndCapitalLossCarryforwards	155800000	usd
CY2023Q4	wtm	Operating And Capital Loss Carryforwards Valuation Allowance OperatingAndCapitalLossCarryforwardsValuationAllowance	155800000	usd
CY2023Q4	wtm	Deferred Tax Assets Operating And Capital Loss Carryforwards Net DeferredTaxAssetsOperatingAndCapitalLossCarryforwardsNet	0	usd
CY2023Q4	wtm	Percentageof Risk Premium Ceded PercentageofRiskPremiumCeded	0.60
CY2022Q4	us-gaap	Funds Held Under Reinsurance Agreements Asset FundsHeldUnderReinsuranceAgreementsAsset	856900000	usd
CY2023Q4	wtm	Funds Held Under Reinsurance Agreements Assets Cash And Investments FundsHeldUnderReinsuranceAgreementsAssetsCashAndInvestments	588600000	usd
CY2022Q4	wtm	Funds Held Under Reinsurance Agreements Assets Cash And Investments FundsHeldUnderReinsuranceAgreementsAssetsCashAndInvestments	503300000	usd
CY2023Q4	wtm	Funds Held Under Reinsurance Agreements Assets Surplus Notes FundsHeldUnderReinsuranceAgreementsAssetsSurplusNotes	322200000	usd
CY2022Q4	wtm	Funds Held Under Reinsurance Agreements Assets Surplus Notes FundsHeldUnderReinsuranceAgreementsAssetsSurplusNotes	340000000	usd
CY2023Q4	wtm	Funds Held Under Reinsurance Agreements Assets Interest Receivable FundsHeldUnderReinsuranceAgreementsAssetsInterestReceivable	37700000	usd
CY2022Q4	wtm	Funds Held Under Reinsurance Agreements Assets Interest Receivable FundsHeldUnderReinsuranceAgreementsAssetsInterestReceivable	13600000	usd
CY2023	us-gaap	Net Income Loss NetIncomeLoss	509200000	usd
CY2022	us-gaap	Net Income Loss NetIncomeLoss	792800000	usd
CY2021	us-gaap	Net Income Loss NetIncomeLoss	-275400000	usd
CY2023	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	0	usd
CY2022	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	903200000	usd
CY2021	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Reporting Entity IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity	-3900000	usd
CY2023	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Noncontrolling Interest IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToNoncontrollingInterest	0	usd
CY2022	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Noncontrolling Interest IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToNoncontrollingInterest	700000	usd
CY2021	us-gaap	Income Loss From Discontinued Operations Net Of Tax Attributable To Noncontrolling Interest IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToNoncontrollingInterest	-1000000.0	usd
CY2023	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	509200000	usd
CY2022	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	-109700000	usd
CY2021	us-gaap	Income Loss From Continuing Operations IncomeLossFromContinuingOperations	-272500000	usd
CY2023	us-gaap	Undistributed Continuing Operation Earnings Loss Allocation To Participating Securities Basic UndistributedContinuingOperationEarningsLossAllocationToParticipatingSecuritiesBasic	7200000	usd
CY2022	us-gaap	Undistributed Continuing Operation Earnings Loss Allocation To Participating Securities Basic UndistributedContinuingOperationEarningsLossAllocationToParticipatingSecuritiesBasic	-1300000	usd
CY2021	us-gaap	Undistributed Continuing Operation Earnings Loss Allocation To Participating Securities Basic UndistributedContinuingOperationEarningsLossAllocationToParticipatingSecuritiesBasic	-3200000	usd
CY2023	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	502000000.0	usd
CY2023	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	502000000.0	usd
CY2022	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	-108400000	usd
CY2022	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	-108400000	usd
CY2021	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	-269300000	usd
CY2021	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	-269300000	usd
CY2023	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	2563300	shares
CY2022	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	2862400	shares
CY2021	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	3079000	shares
CY2023	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	36000.0	shares
CY2022	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	36200	shares
CY2021	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	36500	shares
CY2023	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	2527300	shares
CY2022	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	2826200	shares
CY2021	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	3042500	shares
CY2023	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	2563300	shares
CY2022	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	2862400	shares
CY2021	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	3079000	shares
CY2023	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	36000.0	shares
CY2022	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	36200	shares
CY2021	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	36500	shares
CY2023	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	2527300	shares
CY2022	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	2826200	shares
CY2021	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	3042500	shares
CY2023	us-gaap	Earnings Per Share Basic Distributed EarningsPerShareBasicDistributed	1.00
CY2023	us-gaap	Earnings Per Share Diluted Distributed EarningsPerShareDilutedDistributed	1.00
CY2022	us-gaap	Earnings Per Share Diluted Distributed EarningsPerShareDilutedDistributed	1.00
CY2022	us-gaap	Earnings Per Share Basic Distributed EarningsPerShareBasicDistributed	1.00
CY2021	us-gaap	Earnings Per Share Diluted Distributed EarningsPerShareDilutedDistributed	1.00
CY2021	us-gaap	Earnings Per Share Basic Distributed EarningsPerShareBasicDistributed	1.00
CY2023	us-gaap	Earnings Per Share Basic Undistributed EarningsPerShareBasicUndistributed	197.60
CY2023	us-gaap	Earnings Per Share Diluted Undistributed EarningsPerShareDilutedUndistributed	197.60
CY2022	us-gaap	Earnings Per Share Diluted Undistributed EarningsPerShareDilutedUndistributed	-39.34
CY2022	us-gaap	Earnings Per Share Basic Undistributed EarningsPerShareBasicUndistributed	-39.34
CY2021	us-gaap	Earnings Per Share Diluted Undistributed EarningsPerShareDilutedUndistributed	-89.52
CY2021	us-gaap	Earnings Per Share Basic Undistributed EarningsPerShareBasicUndistributed	-89.52
CY2023	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	198.60
CY2023	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	198.60
CY2022	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	-38.34
CY2022	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	-38.34
CY2021	us-gaap	Income Loss From Continuing Operations Per Basic Share IncomeLossFromContinuingOperationsPerBasicShare	-88.52
CY2021	us-gaap	Income Loss From Continuing Operations Per Diluted Share IncomeLossFromContinuingOperationsPerDilutedShare	-88.52
CY2021Q4	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiability	42200000	usd
CY2023	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesGrantsInPeriod	10895	shares
CY2022	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesGrantsInPeriod	13225	shares
CY2021	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesGrantsInPeriod	13475	shares
CY2023	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	502000000.0	usd
CY2022	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	-108400000	usd
CY2021	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	-269300000	usd
CY2023	wtm	Dividends Common Stock Cash Net Of Restricted Stock DividendsCommonStockCashNetOfRestrictedStock	2500000	usd
CY2022	wtm	Dividends Common Stock Cash Net Of Restricted Stock DividendsCommonStockCashNetOfRestrictedStock	3000000.0	usd
CY2021	wtm	Dividends Common Stock Cash Net Of Restricted Stock DividendsCommonStockCashNetOfRestrictedStock	3100000	usd
CY2023	us-gaap	Undistributed Continuing Operation Earnings Loss Basic UndistributedContinuingOperationEarningsLossBasic	499500000	usd
CY2022	us-gaap	Undistributed Continuing Operation Earnings Loss Basic UndistributedContinuingOperationEarningsLossBasic	-111400000	usd
CY2021	us-gaap	Undistributed Continuing Operation Earnings Loss Basic UndistributedContinuingOperationEarningsLossBasic	-272400000	usd
CY2022Q4	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceShares	39449	shares
CY2022Q4	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiability	67500000	usd
CY2021Q4	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceShares	40828	shares
CY2021Q4	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiability	42200000	usd
CY2020Q4	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceShares	42458	shares
CY2020Q4	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiability	56300000	usd
CY2023	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Shares Paid In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesSharesPaidInPeriod	13350	shares
CY2023	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability Shares Paid In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiabilitySharesPaidInPeriod	40800000	usd
CY2022	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Shares Paid In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesSharesPaidInPeriod	14625	shares
CY2022	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability Shares Paid In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiabilitySharesPaidInPeriod	26400000	usd
CY2021	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Shares Paid In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesSharesPaidInPeriod	14336	shares
CY2021	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability Shares Paid In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiabilitySharesPaidInPeriod	35200000	usd
CY2023	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesGrantsInPeriod	10895	shares
CY2023	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiabilityGrantsInPeriod	0	usd
CY2022	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesGrantsInPeriod	13225	shares
CY2022	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiabilityGrantsInPeriod	0	usd
CY2021	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesGrantsInPeriod	13475	shares
CY2021	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiabilityGrantsInPeriod	0	usd
CY2023	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Forfeited And Cancelled In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesForfeitedAndCancelledInPeriod	-37	shares
CY2023	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability Forfeited And Cancelled In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiabilityForfeitedAndCancelledInPeriod	100000	usd
CY2022	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Forfeited And Cancelled In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesForfeitedAndCancelledInPeriod	-21	shares
CY2022	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability Forfeited And Cancelled In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiabilityForfeitedAndCancelledInPeriod	400000	usd
CY2021	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Forfeited And Cancelled In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesForfeitedAndCancelledInPeriod	769	shares
CY2021	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability Forfeited And Cancelled In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiabilityForfeitedAndCancelledInPeriod	-400000	usd
CY2023	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability Expense In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiabilityExpenseInPeriod	42800000	usd
CY2022	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability Expense In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiabilityExpenseInPeriod	52100000	usd
CY2021	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability Expense In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiabilityExpenseInPeriod	20700000	usd
CY2023Q4	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceShares	37031	shares
CY2023Q4	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiability	69400000	usd
CY2022Q4	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceShares	39449	shares
CY2022Q4	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiability	67500000	usd
CY2021Q4	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceShares	40828	shares
CY2023Q4	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Nonvested Number Before Assumed Forfeitures ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesNonvestedNumberBeforeAssumedForfeitures	37595	shares
CY2023Q4	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability Before Assumed Forfeitures ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiabilityBeforeAssumedForfeitures	70500000	usd
CY2023	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Forfeited In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesForfeitedInPeriod	564	shares
CY2023	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability Forfeited In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiabilityForfeitedInPeriod	1100000	usd
CY2023Q4	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceShares	37031	shares
CY2023Q4	wtm	Share Based Compensation Arrangement By Share Based Payment Award Performance Shares Accrued Liability ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceSharesAccruedLiability	69400000	usd
CY2023Q4	wtm	Stock Repurchase Program Number Of Additional Shares Authorized To Be Repurchased StockRepurchaseProgramNumberOfAdditionalSharesAuthorizedToBeRepurchased	301014	shares
CY2023	us-gaap	Stock Repurchased And Retired During Period Shares StockRepurchasedAndRetiredDuringPeriodShares	24165	shares
CY2023	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	32700000	usd
CY2023	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	1354.88
CY2023	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	4629	shares
CY2022	us-gaap	Stock Repurchased And Retired During Period Shares StockRepurchasedAndRetiredDuringPeriodShares	461256	shares
CY2022	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	615800000	usd
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CY2022	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	4011	shares
CY2022Q3	us-gaap	Stock Repurchased And Retired During Period Shares StockRepurchasedAndRetiredDuringPeriodShares	327795	shares
CY2022Q3	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	1400
CY2022Q3	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	460800000	usd
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CY2021	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	107500000	usd
CY2021	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	1091.29
CY2021	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	7218	shares
CY2023	us-gaap	Stock Issued During Period Shares New Issues StockIssuedDuringPeriodSharesNewIssues	12461	shares
CY2022	us-gaap	Stock Issued During Period Shares New Issues StockIssuedDuringPeriodSharesNewIssues	15640	shares
CY2021	us-gaap	Stock Issued During Period Shares New Issues StockIssuedDuringPeriodSharesNewIssues	15066	shares
CY2023	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	2600000	usd
CY2022	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	3000000	usd
CY2021	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	3100000	usd
CY2023	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.00
CY2022	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.00
CY2021	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.00
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CY2021	us-gaap	Business Combination Contingent Consideration Arrangements Change In Amount Of Contingent Consideration Liability1 BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1	5500000	usd
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CY2023Q4	us-gaap	Minority Interest MinorityInterest	321100000	usd
CY2022Q4	us-gaap	Minority Interest MinorityInterest	188100000	usd
CY2023	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	3	segment
CY2023	us-gaap	Premiums Earned Net PremiumsEarnedNet	1440900000	usd
CY2023	us-gaap	Net Investment Income NetInvestmentIncome	194200000	usd
CY2023	us-gaap	Investment Income Net InvestmentIncomeNet	0	usd
CY2023	us-gaap	Insurance Commissions And Fees InsuranceCommissionsAndFees	13200000	usd
CY2023	us-gaap	Other Income OtherIncome	84200000	usd
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CY2023	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	726800000	usd
CY2023	us-gaap	Deferred Policy Acquisition Cost Amortization Expense DeferredPolicyAcquisitionCostAmortizationExpense	290100000	usd
CY2023	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	40400000	usd
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CY2023	us-gaap	Business Combination Contingent Consideration Arrangements Change In Amount Of Contingent Consideration Liability1 BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1	48700000	usd
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CY2023	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	1601300000	usd
CY2023	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	565400000	usd
CY2022	us-gaap	Premiums Earned Net PremiumsEarnedNet	1076700000	usd
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CY2022	us-gaap	Insurance Commissions And Fees InsuranceCommissionsAndFees	11500000	usd
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CY2022Q4	us-gaap	Minority Interest MinorityInterest	188100000	usd
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CY2021	us-gaap	Equity Method Investment Dividends Or Distributions EquityMethodInvestmentDividendsOrDistributions	56200000	usd
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CY2022	us-gaap	Income Loss From Continuing Operations Attributable To Noncontrolling Entity IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity	-81100000	usd
CY2021	us-gaap	Income Loss From Continuing Operations Attributable To Noncontrolling Entity IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity	-45500000	usd
CY2022	us-gaap	Income Loss From Discontinued Operations Net Of Tax IncomeLossFromDiscontinuedOperationsNetOfTax	902500000	usd
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CY2021	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	3079000	shares
CY2022	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	36200	shares
CY2021	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	36500	shares
CY2022	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	2826200	shares
CY2021	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	3042500	shares
CY2022	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	2862400	shares
CY2021	us-gaap	Weighted Average Number Of Shares Issued Basic WeightedAverageNumberOfSharesIssuedBasic	3079000	shares
CY2022	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	36200	shares
CY2021	us-gaap	Weighted Average Number Of Shares Restricted Stock WeightedAverageNumberOfSharesRestrictedStock	36500	shares
CY2022	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	2826200	shares
CY2021	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	3042500	shares
CY2022	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Basic Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare	315.30
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CY2022	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	315.30
CY2021	us-gaap	Income Loss From Discontinued Operations Net Of Tax Per Diluted Share IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare	-0.94
CY2023	dei	Auditor Name AuditorName	PricewaterhouseCoopers LLP
CY2023	dei	Auditor Location AuditorLocation	Atlanta, Georgia
CY2023Q4	us-gaap	Summary Of Investments Other Than Investments In Related Parties Cost SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost	5883800000	usd
CY2023Q4	us-gaap	Summary Of Investments Other Than Investments In Related Parties Carrying Amount SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount	6388700000	usd
CY2023Q4	us-gaap	Summary Of Investments Other Than Investments In Related Parties Fair Value SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue	6388700000	usd
CY2023	us-gaap	Share Based Compensation ShareBasedCompensation	15300000	usd
CY2022	us-gaap	Share Based Compensation ShareBasedCompensation	14000000.0	usd
CY2021	us-gaap	Share Based Compensation ShareBasedCompensation	14700000	usd
CY2023	wtm	Increase Decrease In Payables From Receivables To Affiliates IncreaseDecreaseInPayablesFromReceivablesToAffiliates	8400000	usd
CY2022	wtm	Increase Decrease In Payables From Receivables To Affiliates IncreaseDecreaseInPayablesFromReceivablesToAffiliates	3300000	usd
CY2021	wtm	Increase Decrease In Payables From Receivables To Affiliates IncreaseDecreaseInPayablesFromReceivablesToAffiliates	-6500000	usd

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$WTM
WHITE MOUNTAINS INSURANCE GROUP LTD Stock $wtm

2024 Q1 Form 10-K Financial Statement

#000077686724000005 Filed on February 26, 2024

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$WTM WHITE MOUNTAINS INSURANCE GROUP LTD Stock $wtm

2024 Q1 Form 10-K Financial Statement

#000077686724000005 Filed on February 26, 2024

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$WTM
WHITE MOUNTAINS INSURANCE GROUP LTD Stock $wtm