Fair Value of Assets and Liabilities - Schedule of Rollforward of Level 3 Assets and Liabilities Held at Fair Value (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Assets
Balance at beginning of period	$ 625	$ 676	$ 618	$ 565
Total gains (losses) included in: Net income	24	(19)	22	73
Total gains (losses) included in: OCI	(2)	(1)	0	(6)
Transfers Into Level 3	0	2	16	2
Transfers Out of Level 3	0	(1)	0	(28)
Purchases	14	56	92	168
Sales	(14)	(66)	(98)	(101)
Issues	0	0	0	0
Settlements	0	(2)	(3)	(28)
Balance at end of period	647	645	647	645
Net investment income
Total Level 3 gains (losses) included in net income
Gain (loss) included in earnings	$ (1)	$ 4	$ (3)	$ 17
Fair Value, Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net investment income	Net investment income	Net investment income	Net investment income
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net investment income	Net investment income	Net investment income	Net investment income
Net gains (losses) on investments and derivatives
Total Level 3 gains (losses) included in net income
Gain (loss) included in earnings	$ 25	$ (23)	$ 25	$ 56
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	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	Net gains (losses) on investments and derivatives
Municipal
Assets
Balance at beginning of period	$ 12	$ 18	$ 21	$ 18
Total gains (losses) included in: Net income	0	0	3	0
Total gains (losses) included in: OCI	0	0	(1)	1
Transfers Into Level 3	0	2	0	2
Transfers Out of Level 3	0	(1)	0	0
Purchases	0	0	0	0
Sales	(1)	0	(10)	0
Issues	0	0	0	0
Settlements	0	0	(2)	(2)
Balance at end of period	11	19	11	19
Corporate - public
Assets
Balance at beginning of period	26	77	69	20
Total gains (losses) included in: Net income	0	0	(1)	0
Total gains (losses) included in: OCI	(1)	(2)	1	(6)
Transfers Into Level 3	0	0	0	0
Transfers Out of Level 3	0	0	0	0
Purchases	0	0	0	66
Sales	0	(7)	(44)	(10)
Issues	0	0	0	0
Settlements	0	0	0	(2)
Balance at end of period	25	68	25	68
Corporate - privately placed
Assets
Balance at beginning of period	60	73	55	66
Total gains (losses) included in: Net income	0	1	(11)	20
Total gains (losses) included in: OCI	(1)	1	0	(1)
Transfers Into Level 3	0	0	16	0
Transfers Out of Level 3	0	0	0	0
Purchases	0	18	1	32
Sales	0	(22)	(2)	(46)
Issues	0	0	0	0
Settlements	0	0	0	0
Balance at end of period	59	71	59	71
ABS
Assets
Balance at beginning of period	34	18	28	40
Total gains (losses) included in: Net income	0	0	0	1
Total gains (losses) included in: OCI	0	0	0	0
Transfers Into Level 3	0	0	0	0
Transfers Out of Level 3	0	0	0	(28)
Purchases	4	30	11	37
Sales	0	0	0	0
Issues	0	0	0	0
Settlements	0	0	(1)	(2)
Balance at end of period	38	48	38	48
Fixed income securities
Assets
Balance at beginning of period	132	186	173	144
Total gains (losses) included in: Net income	0	1	(9)	21
Total gains (losses) included in: OCI	(2)	(1)	0	(6)
Transfers Into Level 3	0	2	16	2
Transfers Out of Level 3	0	(1)	0	(28)
Purchases	4	48	12	135
Sales	(1)	(29)	(56)	(56)
Issues	0	0	0	0
Settlements	0	0	(3)	(6)
Balance at end of period	133	206	133	206
Equity securities
Assets
Balance at beginning of period	381	372	333	349
Total gains (losses) included in: Net income	15	(16)	22	13
Total gains (losses) included in: OCI	0	0	0	0
Transfers Into Level 3	0	0	0	0
Transfers Out of Level 3	0	0	0	0
Purchases	0	8	70	10
Sales	(13)	(37)	(42)	(45)
Issues	0	0	0	0
Settlements	0	0	0	0
Balance at end of period	383	327	383	327
Short-term investments
Assets
Balance at beginning of period	6	8	6	5
Total gains (losses) included in: Net income	0	0	0	0
Total gains (losses) included in: OCI	0	0	0	0
Transfers Into Level 3	0	0	0	0
Transfers Out of Level 3	0	0	0	0
Purchases	10	0	10	23
Sales	0	0	0	0
Issues	0	0	0	0
Settlements	0	(2)	0	(22)
Balance at end of period	16	6	16	6
Other investments
Assets
Balance at beginning of period	2	2	3	2
Total gains (losses) included in: Net income	0	0	(1)	0
Total gains (losses) included in: OCI	0	0	0	0
Transfers Into Level 3	0	0	0	0
Transfers Out of Level 3	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Issues	0	0	0	0
Settlements	0	0	0	0
Balance at end of period	2	2	2	2
Other assets
Assets
Balance at beginning of period	104	108	103	65
Total gains (losses) included in: Net income	9	(4)	10	39
Total gains (losses) included in: OCI	0	0	0	0
Transfers Into Level 3	0	0	0	0
Transfers Out of Level 3	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Issues	0	0	0	0
Settlements	0	0	0	0
Balance at end of period	$ 113	$ 104	$ 113	$ 104