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	$ (77)	$ 265	$ 143
Fixed income securities
Realized capital gains and losses by asset type
Realized capital gains and losses	(59)	309	(4)
Mortgage loans
Realized capital gains and losses by asset type
Realized capital gains and losses	0	6	2
Equity securities
Realized capital gains and losses by asset type
Realized capital gains and losses	(22)	(23)	134
Limited partnership interests
Realized capital gains and losses by asset type
Realized capital gains and losses	(5)	(32)	(4)
Derivatives
Realized capital gains and losses by asset type
Realized capital gains and losses	8	13	12
Other
Realized capital gains and losses by asset type
Realized capital gains and losses	$ 1	$ (8)	$ 3