Investments (Details 4) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Realized capital gains and losses by asset type
Realized capital gains and losses	$ (90)	$ 30	$ 694
Fixed income securities
Realized capital gains and losses by asset type
Realized capital gains and losses	(91)	212	130
Equity securities
Realized capital gains and losses by asset type
Realized capital gains and losses	23	(50)	582
Mortgage loans
Realized capital gains and losses by asset type
Realized capital gains and losses	0	6	2
Limited partnership interests
Realized capital gains and losses by asset type
Realized capital gains and losses	(21)	(93)	13
Derivatives
Realized capital gains and losses by asset type
Realized capital gains and losses	3	(21)	(38)
Other
Realized capital gains and losses by asset type
Realized capital gains and losses	$ (4)	$ (24)	$ 5