Investments - Debt Securities (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 28,600	$ 26,562
Gross Unrealized Gains	449	178
Gross Unrealized Losses	(331)	(707)
Fair Value	28,718	26,033
Allowance for expected credit losses	0	0
U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,691	2,826
Gross Unrealized Gains	39	7
Gross Unrealized Losses	(8)	(38)
Fair Value	2,722	2,795
States, municipalities and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	296	712
Gross Unrealized Gains	3	4
Gross Unrealized Losses	(7)	(18)
Fair Value	292	698
U.S. corporate securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	14,657	13,043
Gross Unrealized Gains	262	94
Gross Unrealized Losses	(231)	(412)
Fair Value	14,688	12,725
Foreign securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,981	2,608
Gross Unrealized Gains	78	27
Gross Unrealized Losses	(31)	(111)
Fair Value	3,028	2,524
Residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,065	792
Gross Unrealized Gains	14	2
Gross Unrealized Losses	(29)	(54)
Fair Value	1,050	740
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,974	1,731
Gross Unrealized Gains	28	9
Gross Unrealized Losses	(23)	(67)
Fair Value	1,979	1,673
Other asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,921	4,834
Gross Unrealized Gains	25	35
Gross Unrealized Losses	(2)	(7)
Fair Value	4,944	4,862
Redeemable preferred securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	15	16
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	15	16
Supporting experience-rated products
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Gains	10	5
Gross Unrealized Losses	(16)	(30)
Fair Value	$ 475	$ 543