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Earnings Per Share (Details 1) (USD $)
In Millions, except Per Share data
3 Months Ended 6 Months Ended
Jun. 30, 2011
Jun. 30, 2010
Jun. 30, 2011
Jun. 30, 2010
Number of shares underlying stock options excluded from the computation of diluted earnings [Abstract]        
Anti-dilutive stock options 1.6 2.2 1.4 2.0
Average exercise price $ 56.74 $ 54.40 $ 56.55 $ 54.50