Investments (Details 24) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Entity Sector Industry Classifications [Abstract]
Equity securities other than temporary impairment losses recognized in earnings	$ 5	$ 1	$ 58	$ 3
Equity Securities [Member]
Entity Sector Industry Classifications [Abstract]
Equity securities other than temporary impairment losses recognized in earnings	5	1	58	3
Non-redeemable preferred stock [Member]
Entity Sector Industry Classifications [Abstract]
Equity securities other than temporary impairment losses recognized in earnings	0	0	38	0
Common stock
Entity Sector Industry Classifications [Abstract]
Equity securities other than temporary impairment losses recognized in earnings	5	1	20	3
Financial Services Industry [Member]
Entity Sector Industry Classifications [Abstract]
Equity securities other than temporary impairment losses recognized in earnings	0	0	38	0
Other industries [Member]
Entity Sector Industry Classifications [Abstract]
Equity securities other than temporary impairment losses recognized in earnings	$ 5	$ 1	$ 20	$ 3