Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]
Preferred Stock, par value	$ 0.01	$ 0.01
Preferred Stock, share authorized	0.1	0.1
Preferred Stock, share issued	0	0
Preferred Stock, share outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	3,200	3,200
Common stock, shares issued	1,671	1,667
Common stock, shares outstanding	1,228	1,231
Treasury stock, shares	441	435
Shares held in trust, shares	1	1