Investments (Components of net other-than-temporary impairment losses recognized in earnings) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net other-than-temporary impairment losses recognized in earnings	$ 17	$ 64	$ 51	$ 114
Corporate and other bonds [Member]
Net other-than-temporary impairment losses recognized in earnings	9	7	17	23
States, municipalities and political subdivisions [Member]
Net other-than-temporary impairment losses recognized in earnings		17		17
Residential mortgage-backed [Member]
Net other-than-temporary impairment losses recognized in earnings	2	20	5	49
Other asset-backed [Member]
Net other-than-temporary impairment losses recognized in earnings	1		2
Total asset-backed [Member]
Net other-than-temporary impairment losses recognized in earnings	3	20	7	49
U.S. Treasury and obligations of government-sponsored enterprises [Member]
Net other-than-temporary impairment losses recognized in earnings				1
Total fixed maturity securities available-for-sale [Member]
Net other-than-temporary impairment losses recognized in earnings	12	44	24	90
Common stock [Member]
Net other-than-temporary impairment losses recognized in earnings	3	1	5	5
Preferred stock [Member]
Net other-than-temporary impairment losses recognized in earnings	2	19	22	19
Total equity securities available-for-sale [Member]
Net other-than-temporary impairment losses recognized in earnings	$ 5	$ 20	$ 27	$ 24