Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies (Details Textual)

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Commitments and Contingencies (Details Textual) (USD $)
In Millions, unless otherwise specified
9 Months Ended
Feb. 29, 2012
May 31, 2011
Commitments and Contingencies (Textual) [Abstract]    
Lines of credit amount outstanding $ 0  
Irrevocable standby letters of credit amount available 46.8 47.4
Irrevocable standby letters of credit amount outstanding 0  
Expiry date range of letters of credit July 2012 to December 2012  
Commitments to purchase capital assets $ 7.4 $ 6.0