Investments - Schedule of Securities Pledged As Collateral For Repurchase Agreements (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 227,740	$ 199,895
Fair Value	218,684	184,167
Asset Pledged as Collateral \| Securities Sold under Agreements to Repurchase
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,305	6,841
Fair Value	3,031	5,878
U.S. government and agencies \| Asset Pledged as Collateral \| Securities Sold under Agreements to Repurchase
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	0	3,253
Fair Value	0	2,693
Foreign governments \| Asset Pledged as Collateral \| Securities Sold under Agreements to Repurchase
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	241	159
Fair Value	185	107
Corporate \| Asset Pledged as Collateral \| Securities Sold under Agreements to Repurchase
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,876	1,877
Fair Value	1,690	1,573
CLO \| Asset Pledged as Collateral \| Securities Sold under Agreements to Repurchase
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	587	587
Fair Value	587	588
ABS \| Asset Pledged as Collateral \| Securities Sold under Agreements to Repurchase
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	601	596
Fair Value	569	552
RMBS \| Asset Pledged as Collateral \| Securities Sold under Agreements to Repurchase
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	0	369
Fair Value	$ 0	$ 365