Investments - Net investment income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net Investment Income [Line Items]
Investment income, before expense	$ 3,464	$ 1,723	$ 1,900
Investment expense	(171)	(133)	(172)
Net investment income	3,293	1,590	1,728
Fixed income securities
Net Investment Income [Line Items]
Investment income, before expense	1,148	1,232	1,201
Equity securities
Net Investment Income [Line Items]
Investment income, before expense	100	78	175
Mortgage loans
Net Investment Income [Line Items]
Investment income, before expense	43	34	27
Limited partnership interests
Net Investment Income [Line Items]
Investment income, before expense	1,973	238	296
Short-term investments
Net Investment Income [Line Items]
Investment income, before expense	5	17	70
Other investments
Net Investment Income [Line Items]
Investment income, before expense	$ 195	$ 124	$ 131