Investments (Components of other-than-temporary impairment losses recognized in earnings) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Other-than-temporary impairment losses recognized in earnings	$ 18	$ 56	$ 56	$ 99
Corporate and other bonds [Member]
Other-than-temporary impairment losses recognized in earnings	14	36	43	52
States, municipalities and political subdivisions [Member]
Other-than-temporary impairment losses recognized in earnings	0	0	0	18
Residential mortgage-backed [Member]
Other-than-temporary impairment losses recognized in earnings	0	1	1	7
Other asset-backed [Member]
Other-than-temporary impairment losses recognized in earnings	0	0	3	1
Total asset-backed [Member]
Other-than-temporary impairment losses recognized in earnings	0	1	4	8
Total fixed maturity securities available-for-sale [Member]
Other-than-temporary impairment losses recognized in earnings	14	37	47	78
Common stock [Member]
Other-than-temporary impairment losses recognized in earnings	4	19	9	20
Short term investments [Member]
Other-than-temporary impairment losses recognized in earnings	$ 0	$ 0	$ 0	$ 1