Investments (Details 4) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Realized capital gains and losses by asset type
Realized capital gains and losses	$ 103	$ 33	$ 318	$ (92)
Fixed income securities
Realized capital gains and losses by asset type
Realized capital gains and losses	41	(1)	78	(48)
Equity securities
Realized capital gains and losses by asset type
Realized capital gains and losses	57	45	182	(34)
Mortgage loans
Realized capital gains and losses by asset type
Realized capital gains and losses	1	0	1	1
Limited partnership interests
Realized capital gains and losses by asset type
Realized capital gains and losses	21	12	92	25
Derivatives
Realized capital gains and losses by asset type
Realized capital gains and losses	(17)	(15)	(40)	(22)
Other
Realized capital gains and losses by asset type
Realized capital gains and losses	$ 0	$ (8)	$ 5	$ (14)