Investments (Components of other-than-temporary impairment losses recognized in earnings) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Other-than-temporary impairment losses recognized in earnings	$ 15	$ 31	$ 38	$ 43
Corporate and other bonds [Member]
Other-than-temporary impairment losses recognized in earnings	13	11	29	16
States, municipalities and political subdivisions [Member]
Other-than-temporary impairment losses recognized in earnings	0	13	0	18
Residential mortgage-backed [Member]
Other-than-temporary impairment losses recognized in earnings	1	5	1	6
Other asset-backed [Member]
Other-than-temporary impairment losses recognized in earnings	1	1	3	1
Total asset-backed [Member]
Other-than-temporary impairment losses recognized in earnings	2	6	4	7
Total fixed maturity securities available-for-sale [Member]
Other-than-temporary impairment losses recognized in earnings	15	30	33	41
Common stock [Member]
Other-than-temporary impairment losses recognized in earnings	0	0	5	1
Short term investments [Member]
Other-than-temporary impairment losses recognized in earnings	$ 0	$ 1	$ 0	$ 1