Fair Value - Reconciliations of Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Corporate bonds and other
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	$ 1,045	$ 810
Included in Net Income
Included in OCI	(12)	24
Purchases	74	81
Sales
Settlements	(36)	(3)
Transfers into Level 3	11
Transfers out of Level 3
Balance at ending of period	1,082	912
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at March 31
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at March 31	(14)	24
States, municipalities and political subdivisions
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	44	43
Included in Net Income
Included in OCI	(1)	1
Purchases
Sales
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance at ending of period	43	44
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at March 31
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at March 31	(1)	1
Asset-backed
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	901	788
Included in Net Income	2	5
Included in OCI	(5)	7
Purchases	18	55
Sales	(9)
Settlements	(17)	(9)
Transfers into Level 3		23
Transfers out of Level 3	(19)	(10)
Balance at ending of period	871	859
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at March 31
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at March 31	(5)	7
Fixed maturities available-for-sale
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	1,990	1,641
Included in Net Income	2	5
Included in OCI	(18)	32
Purchases	92	136
Sales	(9)	0
Settlements	(53)	(12)
Transfers into Level 3	11	23
Transfers out of Level 3	(19)	(10)
Balance at ending of period	1,996	1,815
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at March 31	0	0
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at March 31	(20)	32
Equity securities
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	24	35
Included in Net Income	6	(6)
Included in OCI
Purchases
Sales	(19)
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance at ending of period	11	29
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at March 31	1	(6)
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at March 31