Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation Plans (Details 8)

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Stock-Based Compensation Plans (Details 8) (Unearned Performance Shares [Member], USD $)
In Millions, except Per Share data, unless otherwise specified
12 Months Ended
May 31, 2012
May 31, 2011
Unearned Performance Shares [Member]
   
Nonvested/unearned shares activity    
Nonvested/ unearned shares outstanding, Beginning balance 0.1   
Nonvested/ unearned shares, weighted-average grant date fair value per share, Beginning balance $ 23.90   
Granted 0.1 0.1
Granted, Weighted-average grant-date fair value per share $ 28.87 $ 23.85
Forfeited      
Forfeited, Weighted-average grant-date fair value per share $ 25.38 $ 23.55
Nonvested/ unearned shares outstanding, Weighted-average grant-date fair value per share, Ending balance $ 26.83 $ 23.90
Nonvested/ unearned shares outstanding, Ending balance 0.2 0.1