Annual report pursuant to Section 13 and 15(d)

Stock Based Compensation Plans (Details 1)

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Stock Based Compensation Plans (Details 1) (Employee Stock Option [Member], USD $)
In Millions, except Per Share data, unless otherwise specified
12 Months Ended
May 31, 2011
May 31, 2010
May 31, 2009
May 31, 2008
Employee Stock Option [Member]
       
Stock option activity        
Options outstanding, Beginning Balance, Shares 14.2 14.0 14.3  
Options outstanding, Beginning balance, Weighted-average exercise price per share $ 34.14 $ 34.31 $ 34.84 $ 35.00
Options granted 0.5 1.4 1.0  
Options granted, Weighted-average exercise price $ 26.83 $ 26.34 $ 30.10  
Options exercised (0.4) (0.4) (0.4)  
Options exercised, Weighted-average exercise price per share $ 28.58 $ 23.12 $ 23.41  
Options forfeited (0.8) (0.4) (0.6)  
Options forfeited, Weighted--average exercise price per share $ 29.68 $ 33.35 $ 36.11  
Options expired (1.0) (0.4) (0.3)  
Options expired, Weighted-average exercise price per share $ 39.41 $ 36.18 $ 37.56  
Options outstanding, Ending balance, Shares 12.5 14.2 14.0  
Options outstanding, Ending balance, Weighted-average exercise price per share $ 34.14 $ 34.31 $ 34.84 $ 35.00
Options outstanding, Ending balance, Weighted-average remaining contractual term 4.6      
Options outstanding, Ending balance, Aggregate intrinsic value $ 12.2      
Options exercisable, Ending balance, Shares 10.4      
Options exercisable, Ending balance, Weighted-average exercise price per share $ 34.76      
Options exercisable, Ending balance, Weighted-average remaining contractual term 4.0      
Options exercisable, Ending balance, Aggregate intrinsic value $ 5.4