Income per Share (Tables)

6 Months Ended

Jun. 30, 2011

Earnings Per Share [Abstract]

Reconciliation of the number of shares used for the basic and diluted income per share calculations

	Three Months Ended				Six Months Ended
	June 30				June 30
Millions of shares	2011		2010		2011		2010
Basic weighted average common shares outstanding		916		906		915		906
Dilutive effect of stock options		5		3		5		2
Diluted weighted average common shares outstanding		921		909		920		908