Income per Share (Tables)

3 Months Ended

Mar. 31, 2012

Income per Share [Abstract]

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

	Three Months Ended March 31
Millions of shares	2012		2011
Basic weighted average common shares outstanding		923		914
Dilutive effect of employee stock plans		3		5
Diluted weighted average common shares outstanding		926		919