Investments - Realized capital gains and losses by asset type (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Realized capital gains and losses by asset type
Realized capital gains (losses)	$ 440	$ 197	$ 682	$ 1,183
Fixed income securities
Realized capital gains and losses by asset type
Realized capital gains (losses)	236	147	798	290
Equity securities
Realized capital gains and losses by asset type
Realized capital gains (losses)	202	40	(68)	771
Mortgage loans
Realized capital gains and losses by asset type
Realized capital gains (losses)	1	0	(40)	0
Limited partnership interests
Realized capital gains and losses by asset type
Realized capital gains (losses)	30	(18)	(53)	75
Derivatives
Realized capital gains and losses by asset type
Realized capital gains (losses)	(34)	40	72	16
Other
Realized capital gains and losses by asset type
Realized capital gains (losses)	$ 5	$ (12)	$ (27)	$ 31