Reinsurance - Summary of the impact of funds withheld (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Effects of Reinsurance [Line Items]
Net investment income - Fortitude Re funds withheld assets	$ 3,296	$ 2,657	$ 9,208	$ 8,066
Net realized losses on Fortitude Re funds withheld assets	(2,327)	1,220	(3,394)	(558)
Income (loss) before income tax expense (benefit)	(1,594)	2,461	(122)	2,703
Income tax expense (benefit)	(407)	392	(103)	336
Net income (loss)	(1,187)	2,069	(19)	2,367
Comprehensive income (loss)	3,446	(2,046)	3,600	(57)
Fortitude Re funds withheld assets
Effects of Reinsurance [Line Items]
Net investment income - Fortitude Re funds withheld assets	515	233	1,172	897
Fortitude Holdings
Effects of Reinsurance [Line Items]
Net investment income - Fortitude Re funds withheld assets	515	233	1,172	897
Net realized losses on Fortitude Re funds withheld assets	(1,352)	852	(1,551)	(161)
Income (loss) before income tax expense (benefit)	(837)	1,085	(379)	736
Income tax expense (benefit)	(176)	228	(80)	155
Net income (loss)	(661)	857	(299)	581
Comprehensive income (loss)	(25)	37	5	47
Fortitude Holdings | Fortitude Re funds withheld assets
Effects of Reinsurance [Line Items]
Net realized losses on Fortitude Re funds withheld assets	157	(228)	(100)	(338)
Fortitude Holdings | Fortitude Re funds withheld assets | Embedded derivatives
Effects of Reinsurance [Line Items]
Net realized losses on Fortitude Re funds withheld assets	(1,509)	1,080	(1,451)	177
Fortitude Holdings | Other investments
Effects of Reinsurance [Line Items]
Change in unrealized appreciation (depreciation) of the invested assets supporting the Fortitude Re modco arrangement classified as available-for-sale	$ 636	$ (820)	$ 304	$ (534)