Reinsurance - Schedule of Assets in Support of Reserves (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024	Sep. 30, 2024	Dec. 31, 2023
Ceded Credit Risk [Line Items]
Fixed maturity AFS securities	$ 90,680	$ 87,111
Derivative investments	10,427	9,677
Other investments	7,786	7,252
Cash and invested cash	10,668	5,801	$ 6,013	$ 3,365
Accrued investment income	1,172	1,108
Other assets	7,223	7,499
Fortitude Re
Ceded Credit Risk [Line Items]
Fixed maturity AFS securities	7,607	7,764
Derivative investments	25	30
Other investments	1,392	1,419
Cash and invested cash	10	28
Accrued investment income	91	96
Other assets	1	0
Total	$ 9,126	$ 9,337