Fair Value Measurements - Schedule of Components of Amounts Included in Purchases, Sales, Issuances and Settlements (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) [Abstract]
Purchases	$ 131	$ 246	$ 671	$ 821
Sales	(66)	(250)	(549)	(689)
Issuances	7	7	96	79
Settlements	(151)	(28)	(233)	(120)
Total	(79)	(25)	(15)	91
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases, (Sales), Issuances, (Settlements) [Abstract]
Purchases	0		0
Sales	0		0
Issuances	(395)		(863)
Settlements	505		867
Total	110		4
Funds withheld payable under reinsurance treaties
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases, (Sales), Issuances, (Settlements) [Abstract]
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	(360)	(374)	(731)	(752)
Settlements	505	440	867	791
Total	145	66	136	39
Market risk benefit liabilities
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases, (Sales), Issuances, (Settlements) [Abstract]
Purchases	0		0
Sales	0		0
Issuances	(35)		(132)
Settlements	0		0
Total	(35)		(132)
Debt securities \| Public utilities
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) [Abstract]
Purchases				0
Sales				(44)
Issuances				0
Settlements				0
Total				(44)
Debt securities \| Corporate securities
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) [Abstract]
Purchases	27	80	37	185
Sales	(1)	(81)	(196)	(89)
Issuances	0	0	0	0
Settlements	0	0	0	0
Total	26	(1)	(159)	96
Debt securities \| Commercial mortgage-backed
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) [Abstract]
Purchases	15		15
Sales	0		0
Issuances	0		0
Settlements	0		0
Total	15		15
Debt securities \| Residential mortgage-backed
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) [Abstract]
Purchases		4		4
Sales		(4)		(4)
Issuances		0		0
Settlements		0		0
Total		0		0
Debt securities \| Other asset-backed securities
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) [Abstract]
Purchases	78	75	154	445
Sales	(10)	(109)	(139)	(334)
Issuances	0	0	0	0
Settlements	0	0	0	0
Total	68	(34)	15	111
Mortgage loans
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) [Abstract]
Purchases	9	13	449	112
Sales	(55)	(55)	(214)	(217)
Issuances	0	0	0	0
Settlements	0	0	0	0
Total	(46)	(42)	235	(105)
Limited partnerships
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) [Abstract]
Purchases	2	74	16	75
Sales	0	(1)	0	(1)
Issuances	0	0	0	0
Settlements	0	0	0	0
Total	2	73	16	74
Policy loans
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) [Abstract]
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	7	7	96	79
Settlements	(151)	(28)	(233)	(120)
Total	$ (144)	$ (21)	$ (137)	$ (41)

Amount of issuances of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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