Investments - Realized capital gains and losses by asset type (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Realized capital gains and losses by asset type
Realized capital gains and losses	$ 324	$ (25)	$ 986	$ (159)
Fixed income securities
Realized capital gains and losses by asset type
Realized capital gains and losses	79	(80)	143	(123)
Equity securities
Realized capital gains and losses by asset type
Realized capital gains and losses	178	74	731	(19)
Mortgage loans
Realized capital gains and losses by asset type
Realized capital gains and losses	0	2	0	2
Limited partnership interests
Realized capital gains and losses by asset type
Realized capital gains and losses	21	(43)	93	(33)
Derivatives
Realized capital gains and losses by asset type
Realized capital gains and losses	22	23	(24)	15
Other
Realized capital gains and losses by asset type
Realized capital gains and losses	$ 24	$ (1)	$ 43	$ (1)