Acquisition (Details) - USD ($) $ in Millions		Aug. 01, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Liabilities Acquired
Goodwill			$ 571	$ 345	$ 342
Deferred tax asset, goodwill and intangibles			$ 1,034	$ 1,020
US MidCorp and Entertainment
Purchase price
Business acquisition, cash paid		$ 450
Assets Acquired
Cash and investments, at fair value		2,332
Premiums receivable, net of commissions		265
Other assets acquired		167
Total assets acquired		3,327
Liabilities Acquired
Reserves for losses and loss adjustment expenses		2,418
Unearned premiums		636
Other liabilities acquired		69
Total liabilities acquired		3,123
Identifiable net assets acquired		204
Goodwill		246
Deferred tax asset, goodwill and intangibles		565
Net deferred tax asset, loss reserves and unearned premiums		24
US MidCorp and Entertainment | Reserves For Losses And Loss Adjustment Expenses
Liabilities Acquired
Loss reserves, fair value adjustment		128
US MidCorp and Entertainment | Distribution relationships
Assets Acquired
Intangible assets		$ 220
Useful life		10 years
US MidCorp and Entertainment | Value of business acquired
Assets Acquired
Intangible assets		$ 165
US MidCorp and Entertainment | Value of business acquired | Minimum
Assets Acquired
Useful life		1 year
US MidCorp and Entertainment | Value of business acquired | Maximum
Assets Acquired
Useful life		2 years
US MidCorp and Entertainment | Other intangible assets
Assets Acquired
Intangible assets	[1]	$ 178
US MidCorp and Entertainment | Other intangible assets | Minimum
Assets Acquired
Useful life		5 years
US MidCorp and Entertainment | Other intangible assets | Maximum
Assets Acquired
Useful life		7 years

[1] Includes $128 million related to the net fair value adjustment to reserves for loss and loss adjustment expenses on August 1, 2024.