Stockholders' Equity - Earnings per Share (Details) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings per Share
As reported shares	878	876	874	872
Effect of options and performance share award units	3	7	5	8
Diluted shares	881	883	879	880
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	16		1