Investments - Realized capital gains and losses by asset type (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Realized capital gains and losses by asset type
Realized capital gains and losses	$ 1,885	$ (877)	$ 445
Fixed income securities
Realized capital gains and losses by asset type
Realized capital gains and losses	461	(237)	94
Equity securities
Realized capital gains and losses by asset type
Realized capital gains and losses	1,210	(594)	255
Mortgage loans
Realized capital gains and losses by asset type
Realized capital gains and losses	0	2	1
Limited partnership interests
Realized capital gains and losses by asset type
Realized capital gains and losses	200	(101)	132
Derivatives
Realized capital gains and losses by asset type
Realized capital gains and losses	(15)	46	(46)
Other
Realized capital gains and losses by asset type
Realized capital gains and losses	$ 29	$ 7	$ 9