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, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Assets
Balance at beginning of period	$ 773	$ 675	$ 802	$ 676
Total gains (losses) included in: Net income	2	12	33	16
Total gains (losses) included in: OCI	1	0	4	1
Transfers Into Level 3	1	0	27	0
Transfers Out of Level 3	(63)	0	(96)	0
Transfers (to) from held for sale		0		0
Purchases	59	39	102	94
Sales	(4)	(2)	(100)	(59)
Settlements	(3)	(1)	(6)	(5)
Balance at end of period	766	723	766	723
Liabilities
Balance at the beginning of the period	(1)	0	0	0
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
Transfers (to) from held for sale		0		0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Balance at the end of the period	$ (1)	$ 0	$ (1)	$ 0
Net investment income
Total Level 3 gains (losses) included in net income
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
Gain (loss) included in earnings	$ 1	$ 0	$ 1	$ 1
Net gains (losses) on investments and derivatives
Total Level 3 gains (losses) included in net income
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
Gain (loss) included in earnings	$ (2)	$ 10	$ 25	$ 10
Operating costs and expenses
Total Level 3 gains (losses) included in net income
Fair Value, Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Operating costs and expenses	Operating costs and expenses	Operating costs and expenses	Operating costs and expenses
Gain (loss) included in earnings	$ 3	$ 2	$ 6	$ 5
Other liabilities
Liabilities
Balance at the beginning of the period	(1)		0
Total gains (losses) included in: net income	0		(1)
Total gains (losses) included in: OCI	0		0
Transfers into Level 3	0		0
Transfers out of Level 3	0		0
Purchases	0		0
Sales	0		0
Settlements	0		0
Balance at the end of the period	(1)		(1)
Municipal
Assets
Balance at beginning of period	2	7	2	11
Total gains (losses) included in: Net income	0	(2)	0	(2)
Total gains (losses) included in: OCI	0	0	0	0
Transfers Into Level 3	1	0	1	0
Transfers Out of Level 3	0	0	0	0
Transfers (to) from held for sale		0		0
Purchases	0	0	0	0
Sales	0	0	0	(2)
Settlements	0	0	0	(2)
Balance at end of period	3	5	3	5
Corporate - public
Assets
Balance at beginning of period	35	30	22	26
Total gains (losses) included in: Net income	0	0	(1)	1
Total gains (losses) included in: OCI	0	0	1	1
Transfers Into Level 3	0	0	0	0
Transfers Out of Level 3	0	0	(7)	0
Transfers (to) from held for sale		(7)		(7)
Purchases	0	5	20	16
Sales	(1)	0	(1)	(9)
Settlements	0	0	0	0
Balance at end of period	34	28	34	28
Corporate - privately placed
Assets
Balance at beginning of period	109	50	110	58
Total gains (losses) included in: Net income	0	0	(1)	(6)
Total gains (losses) included in: OCI	1	0	2	0
Transfers Into Level 3	0	0	0	0
Transfers Out of Level 3	0	0	0	0
Transfers (to) from held for sale		0		0
Purchases	48	1	48	1
Sales	0	0	0	(2)
Settlements	(2)	0	(3)	0
Balance at end of period	156	51	156	51
ABS
Assets
Balance at beginning of period	39		26
Total gains (losses) included in: Net income	0		0
Total gains (losses) included in: OCI	0		0
Transfers Into Level 3	0		26
Transfers Out of Level 3	(15)		(41)
Purchases	0		15
Sales	0		0
Settlements	0		(2)
Balance at end of period	24		24
MBS
Assets
Balance at beginning of period	88		88
Total gains (losses) included in: Net income	0		0
Total gains (losses) included in: OCI	0		0
Transfers Into Level 3	0		0
Transfers Out of Level 3	0		0
Purchases	2		2
Sales	0		0
Settlements	(1)		(1)
Balance at end of period	89		89
ABS and MBS
Assets
Balance at beginning of period		71		58
Total gains (losses) included in: Net income		0		0
Total gains (losses) included in: OCI		0		0
Transfers Into Level 3		0		0
Transfers Out of Level 3		0		0
Transfers (to) from held for sale		0		0
Purchases		27		41
Sales		0		0
Settlements		(1)		(2)
Balance at end of period		97		97
Fixed income securities
Assets
Balance at beginning of period	273	158	248	153
Total gains (losses) included in: Net income	0	(2)	(2)	(7)
Total gains (losses) included in: OCI	1	0	3	1
Transfers Into Level 3	1	0	27	0
Transfers Out of Level 3	(15)	0	(48)	0
Transfers (to) from held for sale		(7)		(7)
Purchases	50	33	85	58
Sales	(1)	0	(1)	(13)
Settlements	(3)	(1)	(6)	(4)
Balance at end of period	306	181	306	181
Equity securities
Assets
Balance at beginning of period	358	393	407	402
Total gains (losses) included in: Net income	(1)	12	29	18
Total gains (losses) included in: OCI	0	0	0	0
Transfers Into Level 3	0	0	0	0
Transfers Out of Level 3	(48)	0	(48)	0
Transfers (to) from held for sale		0		0
Purchases	3	5	8	14
Sales	(2)	(2)	(86)	(26)
Settlements	0	0	0	0
Balance at end of period	310	408	310	408
Short-term investments
Assets
Balance at beginning of period	4	1	5	1
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
Transfers (to) from held for sale		0		0
Purchases	6	1	9	22
Sales	(1)	0	(5)	(20)
Settlements	0	0	0	(1)
Balance at end of period	9	2	9	2
Other investments
Assets
Balance at beginning of period	1	2	1	2
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
Transfers (to) from held for sale		0		0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Balance at end of period	1	2	1	2
Other assets
Assets
Balance at beginning of period	137	121	134	118
Total gains (losses) included in: Net income	3	2	6	5
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
Transfers (to) from held for sale		0		0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Balance at end of period	140	123	140	123
Assets held for sale
Assets
Balance at beginning of period		0	7	0
Total gains (losses) included in: Net income		0	0	0
Total gains (losses) included in: OCI		0	1	0
Transfers Into Level 3		0	0	0
Transfers Out of Level 3		0	0	0
Transfers (to) from held for sale		7		7
Purchases		0	0	0
Sales		0	(8)	0
Settlements		0	0	0
Balance at end of period	$ 0	$ 7	$ 0	$ 7