Reinsurance - Summary of the Composition of Pool of Assets (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2025	Dec. 31, 2024
Effects of Reinsurance [Line Items]
Fixed maturity securities - available for sale	$ 68,860	$ 64,006
Fixed maturity securities - fair value option	722	745
Short-term investments	10,102	14,462
Other	4,552	4,735
Total assets	165,971	161,322
Carrying Value
Effects of Reinsurance [Line Items]
Short-term investments	4,746	4,673
Other	14	15
Commercial mortgage loans
Effects of Reinsurance [Line Items]
Loans	3,029	3,305
Fortitude Holdings
Effects of Reinsurance [Line Items]
Change in net unrealized gains (losses), gross	29	(35)
Change in net unrealized gains (losses), net of tax	23	(28)
Derivative asset, Fair value of collateral	1	9
Derivative liability, Fair value of collateral	35	2
Fortitude Holdings | Carrying Value
Effects of Reinsurance [Line Items]
Fixed maturity securities - available for sale	1,831	1,918
Fixed maturity securities - fair value option	718	721
Short-term investments	35	15
Funds withheld investment assets	3,053	3,104
Derivative assets, net	(1)	1
Other	68	115
Total assets	3,120	3,220
Fortitude Holdings | Estimated Fair Value
Effects of Reinsurance [Line Items]
Fixed maturity securities - available for sale	1,831	1,918
Fixed maturity securities - fair value option	718	721
Short-term investments	35	15
Funds withheld investment assets	3,042	3,091
Derivative assets, net	(1)	1
Other, fair value	68	115
Total	3,109	3,207
Fortitude Holdings | Commercial mortgage loans | Carrying Value
Effects of Reinsurance [Line Items]
Loans	469	450
Fortitude Holdings | Commercial mortgage loans | Estimated Fair Value
Effects of Reinsurance [Line Items]
Loans, fair value	$ 458	$ 437