Investments (Components of net other-than-temporary impairment losses recognized in earnings) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Net other-than-temporary impairment losses recognized in earnings	$ 16	$ 23	$ 34	$ 50
Corporate and other bonds [Member]
Net other-than-temporary impairment losses recognized in earnings	5	6	8	16
Residential mortgage-backed [Member]
Net other-than-temporary impairment losses recognized in earnings	3	15	3	29
Other asset-backed [Member]
Net other-than-temporary impairment losses recognized in earnings	1		1
Total asset-backed [Member]
Net other-than-temporary impairment losses recognized in earnings	4	15	4	29
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	9	21	12	46
Common stock [Member]
Net other-than-temporary impairment losses recognized in earnings	2	2	2	4
Preferred stock [Member]
Net other-than-temporary impairment losses recognized in earnings	5		20
Total equity securities available-for-sale [Member]
Net other-than-temporary impairment losses recognized in earnings	$ 7	$ 2	$ 22	$ 4