Investments - Repurchase Agreements (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Schedule of Repurchase Agreements [Line Items]
Payables for repurchase agreements	$ 3,866	$ 3,853
Amortized Cost	4,857	4,659
Fair Value	3,997	4,071
Less than 30 days
Schedule of Repurchase Agreements [Line Items]
Payables for repurchase agreements	1,200	686
91 days to 1 year
Schedule of Repurchase Agreements [Line Items]
Payables for repurchase agreements	1,097	0
Greater than 1 year
Schedule of Repurchase Agreements [Line Items]
Payables for repurchase agreements	1,569	3,167
Corporate
Schedule of Repurchase Agreements [Line Items]
Amortized Cost	1,859	2,735
Fair Value	1,562	2,307
U.S. government and agencies
Schedule of Repurchase Agreements [Line Items]
Amortized Cost	1,665	0
Fair Value	1,204	0
Collateralized Loan Obligations
Schedule of Repurchase Agreements [Line Items]
Amortized Cost	584	580
Fair Value	587	579
Foreign governments
Schedule of Repurchase Agreements [Line Items]
Amortized Cost	141	137
Fair Value	95	99
ABS
Schedule of Repurchase Agreements [Line Items]
Amortized Cost	608	1,207
Fair Value	$ 549	$ 1,086