Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Per Share data	Sep. 30, 2011	Dec. 31, 2010
Condensed Consolidated Balance Sheets
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	0.1	0.1
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	3,200	3,200
Common stock, shares issued	1,636	1,624
Common stock, shares outstanding	1,308	1,363
Treasury stock, shares	326	259
Shares held in trust, shares	2	2