Investments (Components of other-than-temporary impairment losses recognized in earnings) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Other-than-temporary impairment losses recognized in earnings	$ 56	$ 10	$ 99	$ 17
Corporate and other bonds [Member]
Other-than-temporary impairment losses recognized in earnings	36	6	52	9
States, municipalities and political subdivisions [Member]
Other-than-temporary impairment losses recognized in earnings	0	0	18	0
Residential mortgage-backed [Member]
Other-than-temporary impairment losses recognized in earnings	1	2	7	4
Other asset-backed [Member]
Other-than-temporary impairment losses recognized in earnings	0	0	1	1
Total asset-backed [Member]
Other-than-temporary impairment losses recognized in earnings	1	2	8	5
Total fixed maturity securities available-for-sale [Member]
Other-than-temporary impairment losses recognized in earnings	37	8	78	14
Common Stock [Member]
Other-than-temporary impairment losses recognized in earnings	19	2	20	3
Short term investments [Member]
Other-than-temporary impairment losses recognized in earnings	$ 0	$ 0	$ 1	$ 0