Investments - Repurchase Agreements (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Schedule of Repurchase Agreements [Line Items]
Payables for repurchase agreements	$ 3,573	$ 6,043
Amortized Cost	4,290	6,528
Fair Value	3,722	6,225
Repurchase Agreements Net of Reverse Repurchase Agreements		907
Less than 30 days
Schedule of Repurchase Agreements [Line Items]
Payables for repurchase agreements	0	2,796
91 days to 1 year
Schedule of Repurchase Agreements [Line Items]
Payables for repurchase agreements	1,269	0
Greater than 1 year
Schedule of Repurchase Agreements [Line Items]
Payables for repurchase agreements	1,975	3,247
Maturity Overnight and on Demand
Schedule of Repurchase Agreements [Line Items]
Payables for repurchase agreements	329	0
U.S. government and agencies
Schedule of Repurchase Agreements [Line Items]
Amortized Cost	0	2,780
Fair Value	0	2,787
Foreign governments
Schedule of Repurchase Agreements [Line Items]
Amortized Cost	259	241
Fair Value	171	185
Corporate
Schedule of Repurchase Agreements [Line Items]
Amortized Cost	2,630	2,022
Fair Value	2,180	1,785
Collateralized Loan Obligations
Schedule of Repurchase Agreements [Line Items]
Amortized Cost	578	611
Fair Value	572	608
ABS
Schedule of Repurchase Agreements [Line Items]
Amortized Cost	516	584
Fair Value	492	568
CMBS
Schedule of Repurchase Agreements [Line Items]
Amortized Cost	219	197
Fair Value	220	198
RMBS
Schedule of Repurchase Agreements [Line Items]
Amortized Cost	88	93
Fair Value	$ 87	$ 94