Investments - Gross realized gains and losses on available for sale fixed maturity security investment transactions (Details) - Fixed maturities - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Gross realized gains and losses on the sale of available for sale fixed maturity security investments
Gross gains	$ 1	$ 5	$ 3
Gross losses	$ (5)	$ (38)	$ (18)

Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-9

Name:	us-gaap_DebtSecuritiesAvailableForSaleRealizedGain
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration