Investments (Components of other-than-temporary impairment losses recognized in earnings) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Other-than-temporary impairment losses recognized in earnings	$ 23	$ 12
Corporate and other bonds [Member]
Other-than-temporary impairment losses recognized in earnings	16	5
States, municipalities and political subdivisions [Member]
Other-than-temporary impairment losses recognized in earnings	0	5
Residential mortgage-backed [Member]
Other-than-temporary impairment losses recognized in earnings	0	1
Other asset-backed [Member]
Other-than-temporary impairment losses recognized in earnings	2	0
Total asset-backed [Member]
Other-than-temporary impairment losses recognized in earnings	2	1
Total fixed maturity securities available-for-sale [Member]
Other-than-temporary impairment losses recognized in earnings	18	11
Common stock [Member]
Other-than-temporary impairment losses recognized in earnings	5	1
Total equity securities available-for-sale [Member]
Other-than-temporary impairment losses recognized in earnings	$ 5	$ 1