Reinsurance - Schedule of Assets in Support of Reserves (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024	Jun. 30, 2024	Dec. 31, 2023
Ceded Credit Risk [Line Items]
Fixed maturity AFS securities	$ 89,386	$ 87,111
Derivative investments	8,349	9,677
Other investments	6,611	6,588
Cash and invested cash	7,143	5,801	$ 5,475	$ 3,365
Accrued investment income	1,136	1,108
Fortitude Re
Ceded Credit Risk [Line Items]
Fixed maturity AFS securities	7,561	7,764
Derivative investments	22	30
Other investments	1,342	1,419
Cash and invested cash	80	28
Accrued investment income	93	96
Total	$ 9,098	$ 9,337