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
	Mar. 31, 2025	Mar. 31, 2024
Assets
Balance at beginning of period	$ 802	$ 676
Total gains (losses) included in: Net income	12	7
Total gains (losses) included in: OCI	1	2
Transfers Into Level 3	26	0
Transfers Out of Level 3	(7)	0
Purchases	25	20
Sales	(13)	(9)
Settlements	(1)	(2)
Balance at end of period	$ 845	$ 694
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
Gain (loss) included in earnings	$ 13	$ 0
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
Gain (loss) included in earnings	$ (1)	$ 5
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
Gain (loss) included in earnings	$ 0	$ 2
Municipal
Assets
Balance at beginning of period	2	11
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	0	0
Sales	0	(1)
Settlements	0	(2)
Balance at end of period	2	8
Corporate - public
Assets
Balance at beginning of period	22	26
Total gains (losses) included in: Net income	(1)	0
Total gains (losses) included in: OCI	1	2
Transfers Into Level 3	0	0
Transfers Out of Level 3	(7)	0
Purchases	20	0
Sales	0	(5)
Settlements	0	0
Balance at end of period	35	23
Corporate - privately placed
Assets
Balance at beginning of period	110	58
Total gains (losses) included in: Net income	(1)	(4)
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 end of period	109	54
Asset-backed securities (“ABS”)
Assets
Balance at beginning of period	114	58
Total gains (losses) included in: Net income	0	0
Total gains (losses) included in: OCI	0	0
Transfers Into Level 3	26	0
Transfers Out of Level 3	0	0
Purchases	0	0
Sales	0	0
Settlements	(1)	0
Balance at end of period	139	58
Fixed income securities
Assets
Balance at beginning of period	248	153
Total gains (losses) included in: Net income	(2)	(4)
Total gains (losses) included in: OCI	1	2
Transfers Into Level 3	26	0
Transfers Out of Level 3	(7)	0
Purchases	20	0
Sales	0	(6)
Settlements	(1)	(2)
Balance at end of period	285	143
Equity securities
Assets
Balance at beginning of period	407	402
Total gains (losses) included in: Net income	14	9
Total gains (losses) included in: OCI	0	0
Transfers Into Level 3	0	0
Transfers Out of Level 3	0	0
Purchases	4	0
Sales	(9)	(3)
Settlements	0	0
Balance at end of period	416	408
Short-term investments
Assets
Balance at beginning of period	5	1
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	1	20
Sales	(4)	0
Settlements	0	0
Balance at end of period	2	21
Other investments
Assets
Balance at beginning of period	1	2
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	0	0
Sales	0	0
Settlements	0	0
Balance at end of period	1	2
Other assets
Assets
Balance at beginning of period	134	118
Total gains (losses) included in: Net income	0	2
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 end of period	134	$ 120
Assets held for sale
Assets
Balance at beginning of period	7
Total gains (losses) included in: Net income	0
Total gains (losses) included in: OCI	0
Transfers Into Level 3	0
Transfers Out of Level 3	0
Purchases	0
Sales	0
Settlements	0
Balance at end of period	$ 7