Investments - Net investment income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Net Investment Income [Line Items]
Investment income, before expense	$ 2,649	$ 3,464	$ 1,723
Investment expense	(246)	(171)	(133)
Net investment income	2,403	3,293	1,590
Fixed income securities
Net Investment Income [Line Items]
Investment income, before expense	1,255	1,148	1,232
Equity securities
Net Investment Income [Line Items]
Investment income, before expense	132	100	78
Mortgage loans
Net Investment Income [Line Items]
Investment income, before expense	33	43	34
Limited partnership interests
Net Investment Income [Line Items]
Investment income, before expense	985	1,973	238
Short-term investments
Net Investment Income [Line Items]
Investment income, before expense	82	5	17
Other investments
Net Investment Income [Line Items]
Investment income, before expense	$ 162	$ 195	$ 124