Investments - Components of net investment income (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Net Investment Income [Line Items]
Total investment income	$ 3,183	$ 2,859	$ 6,282	$ 5,715
Investment expenses	195	145	370	306
Net investment income	2,988	2,714	5,912	5,409
Excluding Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	2,849	2,583	5,608	5,036
Investment expenses	186	139	353	291
Net investment income	2,663	2,444	5,255	4,745
Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	334	276	674	679
Investment expenses	9	6	17	15
Net investment income	325	270	657	664
Available-for-sale fixed maturity securities, including short-term investments
Net Investment Income [Line Items]
Total investment income	2,357	2,113	4,736	4,226
Available-for-sale fixed maturity securities, including short-term investments \| Excluding Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	2,174	1,905	4,358	3,801
Available-for-sale fixed maturity securities, including short-term investments \| Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	183	208	378	425
Other bond securities
Net Investment Income [Line Items]
Total investment income	91	14	175	129
Other bond securities \| Excluding Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	13	8	26	18
Other bond securities \| Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	78	6	149	111
Equity securities
Net Investment Income [Line Items]
Total investment income	(7)	3	3	32
Equity securities \| Excluding Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	(7)	3	3	32
Equity securities \| Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	0	0	0	0
Interest on mortgage and other loans
Net Investment Income [Line Items]
Total investment income	640	613	1,268	1,175
Interest on mortgage and other loans \| Excluding Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	592	564	1,172	1,076
Interest on mortgage and other loans \| Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	48	49	96	99
Alternative investments
Net Investment Income [Line Items]
Total investment income	78	93	59	123
Alternative investments \| Excluding Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	52	80	0	79
Alternative investments \| Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	26	13	59	44
Real estate
Net Investment Income [Line Items]
Total investment income	9	15	14	19
Real estate \| Excluding Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	10	15	22	19
Real estate \| Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	(1)	0	(8)	0
Other investments
Net Investment Income [Line Items]
Total investment income	15	8	27	11
Other investments \| Excluding Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	15	8	27	11
Other investments \| Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	$ 0	$ 0	$ 0	$ 0