Reinsurance - Summary of the Impact of Funds Withheld (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Effects of Reinsurance [Line Items]
Total net investment income	$ 1,466	$ 990	$ 2,571	$ 1,969
Net realized gains (losses) on Fortitude Re funds withheld assets	(258)	(180)	(361)	(267)
Income (loss) from continuing operations before income tax expense (benefit)	1,544	617	2,504	1,675
Income tax expense (benefit)	400	142	662	403
Net income (loss)	1,144	(3,884)	1,842	(2,284)
Change in unrealized appreciation (depreciation) on available for sale securities			805	349
Comprehensive income (loss)	2,060	2,810	3,394	3,353
Fortitude Re funds withheld assets
Effects of Reinsurance [Line Items]
Total net investment income	39	33	79	72
Fortitude Holdings
Effects of Reinsurance [Line Items]
Total net investment income	39	33	79	72
Net realized gains (losses) on Fortitude Re funds withheld assets	(66)	7	(109)	(21)
Income (loss) from continuing operations before income tax expense (benefit)	(27)	40	(30)	51
Income tax expense (benefit)	(5)	9	(6)	11
Net income (loss)	(22)	31	(24)	40
Comprehensive income (loss)	3	(3)	(1)	(2)
Fortitude Holdings | Fortitude Re funds withheld assets
Effects of Reinsurance [Line Items]
Net realized gains (losses) on Fortitude Re funds withheld assets	(52)	(1)	(54)	(20)
Fortitude Holdings | Fortitude Re funds withheld assets | Embedded derivatives
Effects of Reinsurance [Line Items]
Net realized gains (losses) on Fortitude Re funds withheld assets	(14)	8	(55)	(1)
Fortitude Holdings | Other investments
Effects of Reinsurance [Line Items]
Change in unrealized appreciation (depreciation) on available for sale securities	$ 25	$ (34)	$ 23	$ (42)