Investments - Net investment income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Net Investment Income:
Investment income, before expense	$ 681	$ 618	$ 1,331	$ 1,263
Investment expense	(71)	(56)	(146)	(107)
Net investment income	610	562	1,185	1,156
Fixed income securities
Net Investment Income:
Investment income, before expense	422	299	812	566
Equity securities
Net Investment Income:
Investment income, before expense	21	34	32	70
Mortgage loans
Net Investment Income:
Investment income, before expense	8	9	16	17
Limited partnership interests
Net Investment Income:
Investment income, before expense	122	224	256	516
Short-term investments
Net Investment Income:
Investment income, before expense	69	10	135	12
Other investments
Net Investment Income:
Investment income, before expense	$ 39	$ 42	$ 80	$ 82