| 
           Income Taxes (Details Textuals) (USD $) 
        In Millions  | 
        12 Months Ended | |
|---|---|---|
| 
           May 31, 2011 
         | 
        
           May 31, 2010 
         | 
      |
| Income Taxes (Textuals) [Abstract] | ||
| Total reserve for uncertain tax positions | $ 34.4 | $ 27.5 | 
| Impact of uncertain tax position in company's effective income tax rate | 29.2 | |
| Total reserve for uncertain tax positions which included in long-term liabilities on the consolidated balance sheets | $ 34.1 | $ 27.4 | 
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- Definition 
          Impact of uncertain tax position in company's effective income tax rate. 
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- Definition 
          Income taxes. 
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- Definition 
          Total reserve for uncertain tax positions. 
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- Definition 
          Carrying amount as of the balance sheet date of the unpaid sum of the known and estimated amounts payable to satisfy all domestic and foreign income tax obligations due beyond one year or the operating cycle, whichever is longer. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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