Reinsurance - Summary of the Impact of Funds Withheld (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Effects of Reinsurance [Line Items]
Total net investment income	$ 1,105	$ 979
Net realized losses on Fortitude Re funds withheld assets	(103)	(87)
Income (loss) from continuing operations before income tax expense (benefit)	960	1,058
Income tax expense (benefit)	262	261
Net income	698	1,600
Change in unrealized appreciation (depreciation) on available for sale securities	317	196
Comprehensive income (loss)	1,334	543
Fortitude Re funds withheld assets
Effects of Reinsurance [Line Items]
Total net investment income	40	39
Fortitude Holdings
Effects of Reinsurance [Line Items]
Total net investment income	40	39
Net realized losses on Fortitude Re funds withheld assets	(43)	(28)
Income (loss) from continuing operations before income tax expense (benefit)	(3)	11
Income tax expense (benefit)	(1)	2
Net income	(2)	9
Comprehensive income (loss)	(4)	1
Fortitude Holdings | Fortitude Re funds withheld assets
Effects of Reinsurance [Line Items]
Net realized losses on Fortitude Re funds withheld assets	(2)	(19)
Fortitude Holdings | Fortitude Re funds withheld assets | Embedded derivatives
Effects of Reinsurance [Line Items]
Net realized losses on Fortitude Re funds withheld assets	(41)	(9)
Fortitude Holdings | Other investments
Effects of Reinsurance [Line Items]
Change in unrealized appreciation (depreciation) on available for sale securities	$ (2)	$ (8)