Investments - Realized capital gains and losses by asset type (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Realized capital gains and losses by asset type
Realized capital gains and losses	$ 197	$ 176	$ 1,183	$ 17
Fixed income securities
Realized capital gains and losses by asset type
Realized capital gains and losses	147	(30)	290	(153)
Equity securities
Realized capital gains and losses by asset type
Realized capital gains and losses	40	223	771	204
Mortgage loans
Realized capital gains and losses by asset type
Realized capital gains and losses	0	0	0	2
Limited partnership interests
Realized capital gains and losses by asset type
Realized capital gains and losses	(18)	(23)	75	(56)
Derivatives
Realized capital gains and losses by asset type
Realized capital gains and losses	40	5	16	20
Other
Realized capital gains and losses by asset type
Realized capital gains and losses	$ (12)	$ 1	$ 31	$ 0