Investments - Components of net investment income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Net Investment Income [Line Items]
Total investment income	$ 3,099	$ 2,856
Investment expenses	175	161
Net investment income	2,924	2,695
Excluding Fortitude Re Funds withheld assets
Net Investment Income [Line Items]
Total investment income	2,759	2,453
Investment expenses	167	152
Net investment income	2,592	2,301
Fortitude
Net Investment Income [Line Items]
Total investment income	340	403
Investment expenses	8	9
Net investment income	332	394
Available-for-sale fixed maturity securities, including short-term investments
Net Investment Income [Line Items]
Total investment income	2,379	2,113
Available-for-sale fixed maturity securities, including short-term investments | Excluding Fortitude Re Funds withheld assets
Net Investment Income [Line Items]
Total investment income	2,184	1,896
Available-for-sale fixed maturity securities, including short-term investments | Fortitude
Net Investment Income [Line Items]
Total investment income	195	217
Other bond securities
Net Investment Income [Line Items]
Total investment income	84	115
Other bond securities | Excluding Fortitude Re Funds withheld assets
Net Investment Income [Line Items]
Total investment income	13	10
Other bond securities | Fortitude
Net Investment Income [Line Items]
Total investment income	71	105
Equity securities
Net Investment Income [Line Items]
Total investment income	10	29
Equity securities | Excluding Fortitude Re Funds withheld assets
Net Investment Income [Line Items]
Total investment income	10	29
Equity securities | Fortitude
Net Investment Income [Line Items]
Total investment income	0	0
Interest on mortgage and other loans
Net Investment Income [Line Items]
Total investment income	628	562
Interest on mortgage and other loans | Excluding Fortitude Re Funds withheld assets
Net Investment Income [Line Items]
Total investment income	580	512
Interest on mortgage and other loans | Fortitude
Net Investment Income [Line Items]
Total investment income	48	50
Alternative investments
Net Investment Income [Line Items]
Total investment income	(19)	30
Alternative investments | Excluding Fortitude Re Funds withheld assets
Net Investment Income [Line Items]
Total investment income	(52)	(1)
Alternative investments | Fortitude
Net Investment Income [Line Items]
Total investment income	33	31
Real estate
Net Investment Income [Line Items]
Total investment income	5	4
Real estate | Excluding Fortitude Re Funds withheld assets
Net Investment Income [Line Items]
Total investment income	12	4
Real estate | Fortitude
Net Investment Income [Line Items]
Total investment income	(7)	0
Other investments
Net Investment Income [Line Items]
Total investment income	12	3
Other investments | Excluding Fortitude Re Funds withheld assets
Net Investment Income [Line Items]
Total investment income	12	3
Other investments | Fortitude
Net Investment Income [Line Items]
Total investment income	$ 0	$ 0