Investments - Repurchase Agreements (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Schedule of Repurchase Agreements [Line Items]
Payables for repurchase agreements	$ 4,512	$ 4,743
Amortized Cost	5,894	6,161
Fair Value	4,681	4,996
Less than 30 days
Schedule of Repurchase Agreements [Line Items]
Payables for repurchase agreements	533	608
30-90 days
Schedule of Repurchase Agreements [Line Items]
Payables for repurchase agreements	427	1,268
Greater than 1 year
Schedule of Repurchase Agreements [Line Items]
Payables for repurchase agreements	2,866	2,867
91 days to 1 year
Schedule of Repurchase Agreements [Line Items]
Payables for repurchase agreements	686	0
Available-for-sale Securities | Corporate
Schedule of Repurchase Agreements [Line Items]
Amortized Cost	2,899	1,940
Fair Value	2,285	1,605
Available-for-sale Securities | U.S. government and agencies
Schedule of Repurchase Agreements [Line Items]
Amortized Cost	1,353	2,559
Fair Value	962	1,941
Available-for-sale Securities | Collateralized Loan Obligations
Schedule of Repurchase Agreements [Line Items]
Amortized Cost	264	273
Fair Value	259	261
Available-for-sale Securities | Foreign governments
Schedule of Repurchase Agreements [Line Items]
Amortized Cost	152	146
Fair Value	101	107
Available-for-sale Securities | ABS
Schedule of Repurchase Agreements [Line Items]
Amortized Cost	1,226	1,243
Fair Value	$ 1,074	$ 1,082