Reinsurance - Summary of the Impact of Funds Withheld (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Effects of Reinsurance [Line Items]
Total net investment income	$ 4,215	$ 4,255	$ 3,446
Net realized losses on Fortitude Re funds withheld assets	(1,202)	(548)	(1,078)
Income (loss) from continuing operations before income tax expense (benefit)	3,879	3,870	2,867
Income tax benefit	782	1,170	126
Net income (loss)	3,097	(926)	3,878
Change in unrealized appreciation on available for sale securities	423	571	(1,075)
Comprehensive loss	5,209	5,179	9,818
Fortitude Re funds withheld assets
Effects of Reinsurance [Line Items]
Total net investment income	149	144	180
Fortitude Holdings
Effects of Reinsurance [Line Items]
Total net investment income	149	144	180
Net realized losses on Fortitude Re funds withheld assets	(236)	(114)	(344)
Income (loss) from continuing operations before income tax expense (benefit)	(87)	30	(164)
Income tax benefit	(18)	6	(34)
Net income (loss)	(69)	24	(130)
Comprehensive loss	(2)	(4)	(38)
Fortitude Holdings | Fortitude Re funds withheld assets
Effects of Reinsurance [Line Items]
Net realized losses on Fortitude Re funds withheld assets	(70)	(39)	(71)
Fortitude Holdings | Fortitude Re funds withheld assets | Embedded derivatives
Effects of Reinsurance [Line Items]
Net realized losses on Fortitude Re funds withheld assets	(166)	(75)	(273)
Fortitude Holdings | Other investments
Effects of Reinsurance [Line Items]
Change in unrealized appreciation on available for sale securities	$ 67	$ (28)	$ 92