Investments (Details 24) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Entity Sector Industry Classifications [Abstract]
Equity securities other than temporary impairment losses recognized in earnings	$ 47	$ 1	$ 53	$ 2
Non-redeemable preferred stock [Member]
Entity Sector Industry Classifications [Abstract]
Equity securities other than temporary impairment losses recognized in earnings	38	0	38	0
Common stock [Member]
Entity Sector Industry Classifications [Abstract]
Equity securities other than temporary impairment losses recognized in earnings	9	1	15	2
Perpetual hybrid securities [Member]
Entity Sector Industry Classifications [Abstract]
Equity securities other than temporary impairment losses recognized in earnings	38	0	38	0
Other industries [Member]
Entity Sector Industry Classifications [Abstract]
Equity securities other than temporary impairment losses recognized in earnings	$ 9	$ 1	$ 15	$ 2