Investments (Components of other-than-temporary impairment losses recognized in earnings) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other-than-temporary impairment losses recognized in earnings	$ 77	$ 76	$ 150
Corporate and other bonds [Member]
Other-than-temporary impairment losses recognized in earnings	18	20	25
States, municipalities and political subdivisions [Member]
Other-than-temporary impairment losses recognized in earnings	46		34
Residential mortgage-backed [Member]
Other-than-temporary impairment losses recognized in earnings	5	19	48
Other asset-backed [Member]
Other-than-temporary impairment losses recognized in earnings	1	2
Total asset-backed [Member]
Other-than-temporary impairment losses recognized in earnings	6	21	48
U.S. Treasury and obligations of government-sponsored enterprises [Member]
Other-than-temporary impairment losses recognized in earnings			1
Total fixed maturity securities available-for-sale [Member]
Other-than-temporary impairment losses recognized in earnings	70	41	108
Common stock [Member]
Other-than-temporary impairment losses recognized in earnings	7	8	6
Preferred stock [Member]
Other-than-temporary impairment losses recognized in earnings		26	36
Total equity securities available-for-sale [Member]
Other-than-temporary impairment losses recognized in earnings	7	34	42
Short term investments [Member]
Other-than-temporary impairment losses recognized in earnings		$ 1