Income per Share (Tables)

9 Months Ended

Sep. 30, 2011

Income per Share [Abstract]

Reconciliation of the Number of Shares Used for the Basic and Diluted Income Per Share Calculations

	Three Months Ended				Nine Months Ended
	September 30				September 30
Millions of shares	2011		2010		2011		2010
Basic weighted average common shares outstanding		920		910		917		907
Dilutive effect of stock options		5		2		5		3
Diluted weighted average common shares outstanding		925		912		922		910