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Income Taxes (Tables)

12 Months Ended

Dec. 31, 2024

Income Tax Disclosure [Abstract]

Schedule of total income tax benefit (expense)

The following table presents the total income tax (expense) benefit for the years ended December 31, 2024, 2023 and 2022:

						Year Ended December 31,
Millions						2024						2023						2022
Current income tax (expense) benefit:
U.S. federal						$	(6.3)					$	(12.6)					$	(16.9)
State						(.4)						(2.2)						(4.5)
Non-U.S.						(14.8)						(16.6)						(7.1)
Total current income tax (expense) benefit						(21.5)						(31.4)						(28.5)
Deferred income tax (expense) benefit:
U.S. federal						(18.8)						(13.2)						(7.3)
State						2.7						(3.8)						(1.8)
Non-U.S.						5.0						63.9						(3.8)
Total deferred income tax (expense) benefit						(11.1)						46.9						(12.9)
Total income tax (expense) benefit						$	(32.6)					$	15.5					$	(41.4)

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

The following table presents a reconciliation of taxes calculated for 2024, 2023 and 2022 using the 21% U.S. federal statutory rate (the tax rate at which the majority of White Mountains’s worldwide operations are taxed) to the income tax (expense) benefit on pre-tax income (loss):

						Year Ended December 31,
Millions						2024						2023						2022
Tax (expense) benefit at the U.S. statutory rate						$	(66.5)					$	(118.7)					$	31.4
Differences in taxes resulting from:
Non-U.S. earnings, net of foreign taxes						40.2						103.7						(41.2)
Change in valuation allowance						(8.1)						(30.2)						(19.6)
Bermuda corporate income tax						5.0						68.0						—
Noncontrolling interest						3.9						6.8						3.4
Tax rate changes						2.9						(.6)						(.4)
BAM member surplus contributions prior to deconsolidation						(2.8)						(5.7)						(6.2)
Withholding tax						(2.5)						(4.1)						(3.1)
State taxes						(1.8)						(8.2)						(2.8)
Tax exempt interest and dividends						.3						.2						.2
Officer compensation						—						(.2)						(1.0)
Other, net						(3.2)						4.5						(2.1)
Total income tax (expense) benefit on pre-tax income (loss)						$	(32.6)					$	15.5					$	(41.4)

Schedule of components of deferred income tax assets and liabilities

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

						December 31,
Millions						2024						2023
Deferred tax assets related to:
Non-U.S. net operating loss carryforwards						$	62.8					$	68.2
Intangible assets						51.5						51.5
Incentive compensation						23.8						25.4
Unearned premiums						20.5						18.2
Loss reserves						8.5						8.4
U.S. federal and state net operating and capital    loss carryforwards						6.4						87.6
Tax credit carryforwards						2.8						3.3
Accrued interest						.2						10.1
Deferred acquisition costs						—						3.7
Other items						.9						1.0
Total gross deferred tax assets						177.4						277.4
Less: valuation allowances						89.2						116.1
Total net deferred tax assets						88.2						161.3
Deferred tax liabilities related to:
Purchase accounting						43.9						43.9
Investment basis difference						43.5						40.9
Deferred underwriting						24.3						18.3
Net unrealized investment gains						19.0						15.5
Deferred acquisition costs						6.5						—
BAM member surplus contributions prior to deconsolidation						—						82.2
Other items						1.2						1.2
Total deferred tax liabilities						138.4						202.0
Net deferred tax asset (liability)						$	(50.2)					$	(40.7)

Schedule of net operating and capital loss carryforwards

The following table presents net operating loss and capital loss carryforwards as of December 31, 2024, the expiration dates and the deferred tax assets thereon:

						December 31, 2024
Millions						United States						Luxembourg																		United Kingdom						Israel						Total
2025-2029						$	.4					$	—																	$	—					$	—					$	.4
2030-2034						.3						—																		—						—						.3
2035-2044						8.8						177.1																		—						—						185.9
No expiration date						3.5						—																		—						88.1						91.6
Total						$	13.0					$	177.1																	$	—					$	88.1					$	278.2
Gross deferred tax asset						$	6.4					$	42.3																	$	—					$	20.3					$	69.0
Valuation allowance						(6.4)						(42.3)																		—						(20.3)						(69.0)
Net deferred tax asset						$	—					$	—																	$	—					$	—					$	—

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Tabular disclosure of the components of income tax expense attributable to continuing operations for each year presented including, but not limited to: current tax expense (benefit), deferred tax expense (benefit), investment tax credits, government grants, the benefits of operating loss carryforwards, tax expense that results from allocating certain tax benefits either directly to contributed capital or to reduce goodwill or other noncurrent intangible assets of an acquired entity, adjustments of a deferred tax liability or asset for enacted changes in tax laws or rates or a change in the tax status of the entity, and adjustments of the beginning-of-the-year balances of a valuation allowance because of a change in circumstances that causes a change in judgment about the realizability of the related deferred tax asset in future years.

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Tabular disclosure of the components of net deferred tax asset or liability recognized in an entity's statement of financial position, including the following: the total of all deferred tax liabilities, the total of all deferred tax assets, the total valuation allowance recognized for deferred tax assets.

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Tabular disclosure of the reconciliation using percentage or dollar amounts of the reported amount of income tax expense attributable to continuing operations for the year to the amount of income tax expense that would result from applying domestic federal statutory tax rates to pretax income from continuing operations.

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