Investments - Components of net investment income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Net Investment Income [Line Items]
Total investment income	$ 3,485	$ 2,789	$ 9,767	$ 8,504
Investment expenses	189	132	559	438
Net investment income	3,296	2,657	9,208	8,066
Excluding Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	2,962	2,548	8,570	7,584
Investment expenses	181	124	534	415
Net investment income	2,781	2,424	8,036	7,169
Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	523	241	1,197	920
Investment expenses	8	8	25	23
Net investment income	515	233	1,172	897
Available-for-sale fixed maturity securities, including short-term investments
Net Investment Income [Line Items]
Total investment income	2,384	2,177	7,120	6,403
Available-for-sale fixed maturity securities, including short-term investments | Excluding Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	2,202	1,976	6,560	5,777
Available-for-sale fixed maturity securities, including short-term investments | Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	182	201	560	626
Other bond securities
Net Investment Income [Line Items]
Total investment income	252	(28)	427	101
Other bond securities | Excluding Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	22	7	48	25
Other bond securities | Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	230	(35)	379	76
Equity securities
Net Investment Income [Line Items]
Total investment income	2	9	5	41
Equity securities | Excluding Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	2	9	5	41
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	704	580	1,972	1,755
Interest on mortgage and other loans | Excluding Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	657	529	1,829	1,605
Interest on mortgage and other loans | Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	47	51	143	150
Alternative investments
Net Investment Income [Line Items]
Total investment income	119	18	178	141
Alternative investments | Excluding Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	59	(7)	59	72
Alternative investments | Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	60	25	119	69
Real estate
Net Investment Income [Line Items]
Total investment income	10	9	24	28
Real estate | Excluding Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	7	9	29	28
Real estate | Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	3	0	(5)	0
Other investments
Net Investment Income [Line Items]
Total investment income	14	24	41	35
Other investments | Excluding Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	13	25	40	36
Other investments | Fortitude Re Funds Withheld Assets
Net Investment Income [Line Items]
Total investment income	$ 1	$ (1)	$ 1	$ (1)