Investments (Details 7) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Investments [Abstract]
Net unrealized gains related to changes in valuation of fixed income securities subsequent to impairment measurement date	$ 221	$ 233
Other-than Impairment Losses Included in Accumulated Other Comprehensive Income
Amount of other-than-temporary impairment losses included in accumulated other comprehensive income for fixed income securities, not included in earnings	(133)	(147)
Municipal
Other-than Impairment Losses Included in Accumulated Other Comprehensive Income
Amount of other-than-temporary impairment losses included in accumulated other comprehensive income for fixed income securities, not included in earnings	(8)	(9)
Corporate
Other-than Impairment Losses Included in Accumulated Other Comprehensive Income
Amount of other-than-temporary impairment losses included in accumulated other comprehensive income for fixed income securities, not included in earnings	(7)	(7)
ABS
Other-than Impairment Losses Included in Accumulated Other Comprehensive Income
Amount of other-than-temporary impairment losses included in accumulated other comprehensive income for fixed income securities, not included in earnings	(21)	(23)
RMBS
Other-than Impairment Losses Included in Accumulated Other Comprehensive Income
Amount of other-than-temporary impairment losses included in accumulated other comprehensive income for fixed income securities, not included in earnings	(90)	(102)
CMBS
Other-than Impairment Losses Included in Accumulated Other Comprehensive Income
Amount of other-than-temporary impairment losses included in accumulated other comprehensive income for fixed income securities, not included in earnings	$ (7)	$ (6)