Investments (Components of other-than-temporary impairment losses recognized in earnings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other-than-temporary impairment losses recognized in earnings	$ 156	$ 77	$ 76
Corporate and other bonds [Member]
Other-than-temporary impairment losses recognized in earnings	104	18	20
States, municipalities and political subdivisions [Member]
Other-than-temporary impairment losses recognized in earnings	18	46	0
Residential mortgage-backed [Member]
Other-than-temporary impairment losses recognized in earnings	8	5	19
Other asset-backed [Member]
Other-than-temporary impairment losses recognized in earnings	1	1	2
Total asset-backed [Member]
Other-than-temporary impairment losses recognized in earnings	9	6	21
Total fixed maturity securities available-for-sale [Member]
Other-than-temporary impairment losses recognized in earnings	131	70	41
Common stock [Member]
Other-than-temporary impairment losses recognized in earnings	25	7	8
Preferred stock [Member]
Other-than-temporary impairment losses recognized in earnings	0	0	26
Total equity securities available-for-sale [Member]
Other-than-temporary impairment losses recognized in earnings	25	7	34
Short term investments [Member]
Other-than-temporary impairment losses recognized in earnings	$ 0	$ 0	$ 1