Fair Value of Assets and Liabilities - Schedule of Rollforward of Level 3 Assets and Liabilities Held at Fair Value (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Assets
Balance at beginning of period	$ 618	$ 565	$ 832
Total gains (losses) included in: net income	40	76	128
Total gains (losses) included in: OCI	2	(2)	2
Transfers into Level 3	16	2	32
Transfers out of Level 3	0	(28)	(45)
Purchases	122	155	124
Sales	(101)	(121)	(405)
Issues	0	0	0
Settlements	(21)	(29)	(103)
Balance at end of period	$ 676	$ 618	$ 565
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Property-Liability net investment income, Net gains (losses) on investments and derivatives	Property-Liability net investment income, Net gains (losses) on investments and derivatives	Property-Liability net investment income, Net gains (losses) on investments and derivatives
Liabilities
Balance at beginning of period	$ 0	$ 0	$ (516)
Total gains (losses) included in: net income	0	0	35
Total gains (losses) included in: OCI	0	0	0
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	0	0
Purchases	0	0	0
Sales	0	0	492
Issues	0	0	(28)
Settlements	0	0	17
Balance at end of period	0	0	0
Net investment income
Fair value assets and liabilities measured on recurring basis, gain (loss) included in earnings
Gain (loss) included in earnings	$ (1)	$ 15	$ 1
Fair Value, Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Property-Liability net investment income	Property-Liability net investment income	Property-Liability net investment income
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Property-Liability net investment income	Property-Liability net investment income	Property-Liability net investment income
Net gains (losses) on investments and derivatives
Fair value assets and liabilities measured on recurring basis, gain (loss) included in earnings
Gain (loss) included in earnings	$ 41	$ 61	$ 124
Fair Value, Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net gains (losses) on investments and derivatives	Net gains (losses) on investments and derivatives	Net gains (losses) on investments and derivatives
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net gains (losses) on investments and derivatives	Net gains (losses) on investments and derivatives	Net gains (losses) on investments and derivatives
Liabilities held for sale
Liabilities
Balance at beginning of period		$ 0	$ (516)
Total gains (losses) included in: net income			35
Total gains (losses) included in: OCI			0
Transfers into Level 3			0
Transfers out of Level 3			0
Purchases			0
Sales			492
Issues			(28)
Settlements			17
Balance at end of period			0
Municipal
Assets
Balance at beginning of period	$ 21	18	17
Total gains (losses) included in: net income	3	0	0
Total gains (losses) included in: OCI	(1)	1	0
Transfers into Level 3	0	2	1
Transfers out of Level 3	0	0	0
Purchases	0	2	3
Sales	(10)	0	0
Issues	0	0	0
Settlements	(2)	(2)	(3)
Balance at end of period	11	21	18
Corporate - public
Assets
Balance at beginning of period	69	20	67
Total gains (losses) included in: net income	(1)	0	1
Total gains (losses) included in: OCI	2	(5)	(1)
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	0	0
Purchases	0	66	13
Sales	(44)	(10)	(53)
Issues	0	0	0
Settlements	0	(2)	0
Balance at end of period	26	69	20
Corporate - privately placed
Assets
Balance at beginning of period	55	66	63
Total gains (losses) included in: net income	(12)	19	(2)
Total gains (losses) included in: OCI	1	2	3
Transfers into Level 3	16	0	10
Transfers out of Level 3	0	0	0
Purchases	1	34	6
Sales	(3)	(65)	(23)
Issues	0	0	0
Settlements	0	(1)	(5)
Balance at end of period	58	55	66
ABS
Assets
Balance at beginning of period	28	40	79
Total gains (losses) included in: net income	0	1	0
Total gains (losses) included in: OCI	0	0	1
Transfers into Level 3	0	0	4
Transfers out of Level 3	0	(28)	(32)
Purchases	31	17	47
Sales	0	0	(5)
Issues	0	0	0
Settlements	(1)	(2)	(54)
Balance at end of period	58	28	40
Fixed income securities
Assets
Balance at beginning of period	173	144	226
Total gains (losses) included in: net income	(10)	20	(1)
Total gains (losses) included in: OCI	2	(2)	3
Transfers into Level 3	16	2	15
Transfers out of Level 3	0	(28)	(32)
Purchases	32	119	69
Sales	(57)	(75)	(81)
Issues	0	0	0
Settlements	(3)	(7)	(62)
Balance at end of period	153	173	144
Equity securities
Assets
Balance at beginning of period	333	349	304
Total gains (losses) included in: net income	36	16	61
Total gains (losses) included in: OCI	0	0	0
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	0	0
Purchases	77	13	43
Sales	(44)	(45)	(160)
Issues	0	0	0
Settlements	0	0	0
Balance at end of period	402	333	349
Short-term investments
Assets
Balance at beginning of period	6	5	35
Total gains (losses) included in: net income	0	0	0
Total gains (losses) included in: OCI	0	0	0
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	0	0
Purchases	13	23	5
Sales	0	0	0
Issues	0	0	0
Settlements	(18)	(22)	(35)
Balance at end of period	1	6	5
Other investments
Assets
Balance at beginning of period	3	2	0
Total gains (losses) included in: net income	(1)	2	0
Total gains (losses) included in: OCI	0	0	0
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	0	0
Purchases	0	0	3
Sales	0	(1)	(1)
Issues	0	0	0
Settlements	0	0	0
Balance at end of period	2	3	2
Other assets
Assets
Balance at beginning of period	103	65	0
Total gains (losses) included in: net income	15	38	65
Total gains (losses) included in: OCI	0	0	0
Transfers into Level 3	0	0	0
Transfers out of Level 3	0	0	0
Purchases	0	0	0
Sales	0	0	0
Issues	0	0	0
Settlements	0	0	0
Balance at end of period	$ 118	103	65
Assets held for sale
Assets
Balance at beginning of period		$ 0	267
Total gains (losses) included in: net income			3
Total gains (losses) included in: OCI			(1)
Transfers into Level 3			17
Transfers out of Level 3			(13)
Purchases			4
Sales			(163)
Issues			0
Settlements			(6)
Balance at end of period			$ 0