Reinsurance - Summary of the Composition of Pool of Assets (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2025	Dec. 31, 2024
Effects of Reinsurance [Line Items]
Fixed maturity securities - available for sale	$ 66,027	$ 64,006
Fixed maturity securities - fair value option	754	745
Short-term investments	10,601	14,462
Other	4,724	4,735
Total assets	161,864	161,322
Carrying Value
Effects of Reinsurance [Line Items]
Short-term investments	4,389	4,673
Other	13	15
Commercial mortgage loans
Effects of Reinsurance [Line Items]
Loans	3,292	3,305
Fortitude Holdings
Effects of Reinsurance [Line Items]
Change in net unrealized gains (losses), gross	(2)	(35)
Change in net unrealized gains (losses), net of tax	(2)	(28)
Derivative asset, Fair value of collateral	1	9
Derivative liability, Fair value of collateral	33	2
Fortitude Holdings | Carrying Value
Effects of Reinsurance [Line Items]
Fixed maturity securities - available for sale	1,918	1,918
Fixed maturity securities - fair value option	729	721
Short-term investments	22	15
Funds withheld investment assets	3,146	3,104
Derivative assets, net	0	1
Other	81	115
Total assets	3,227	3,220
Fortitude Holdings | Estimated Fair Value
Effects of Reinsurance [Line Items]
Fixed maturity securities - available for sale	1,918	1,918
Fixed maturity securities - fair value option	729	721
Short-term investments	22	15
Funds withheld investment assets	3,134	3,091
Derivative assets, net	0	1
Other, fair value	81	115
Total	3,215	3,207
Fortitude Holdings | Commercial mortgage loans | Carrying Value
Effects of Reinsurance [Line Items]
Loans	477	450
Fortitude Holdings | Commercial mortgage loans | Estimated Fair Value
Effects of Reinsurance [Line Items]
Loans, fair value	$ 465	$ 437