Investments - Other-than-temporary Losses Included in AOCI (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Other-than-temporary 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	$ (48)	$ (53)
Municipal
Other-than-temporary 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	(4)	(4)
ABS
Other-than-temporary 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	(6)	(8)
RMBS
Other-than-temporary 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	(34)	(37)
CMBS
Other-than-temporary 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	$ (4)	$ (4)