Fair Value - Reconciliations of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Corporate bonds and other
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	$ 1,278	$ 1,045
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income	(6)	(1)
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in OCI	57	(15)
Purchases	197	352
Sales		(10)
Settlements	(101)	(104)
Transfers into Level 3	58	11
Transfers out of Level 3
Balance at end of period	1,483	1,278
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at December 31		(1)
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at December 31	57	(21)
States, municipalities and political subdivisions
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	42	44
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in OCI	3	(2)
Purchases
Sales
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance at end of period	45	42
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at December 31
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at December 31	3	(2)
Asset-backed
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	876	901
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income	17	9
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in OCI	(3)	(12)
Purchases	213	125
Sales		(14)
Settlements	(105)	(83)
Transfers into Level 3
Transfers out of Level 3		(50)
Balance at end of period	998	876
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at December 31
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at December 31	(1)	(12)
Fixed maturities available-for-sale
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	2,196	1,990
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income	11	8
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in OCI	57	(29)
Purchases	410	477
Sales	0	(24)
Settlements	(206)	(187)
Transfers into Level 3	58	11
Transfers out of Level 3	0	(50)
Balance at end of period	2,526	2,196
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at December 31	0	(1)
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at December 31	59	(35)
Equity securities
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	20	24
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income	4	12
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in OCI
Purchases	20	3
Sales	(7)	(19)
Settlements	(4)
Transfers into Level 3
Transfers out of Level 3
Balance at end of period	33	20
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at December 31	2	8
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at December 31