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Intangible Assets - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Nov. 30, 2012
Nov. 30, 2011
Nov. 30, 2012
Nov. 30, 2011
Finite-Lived Intangible Assets [Line Items]        
Amortization expense $ 1.0 $ 0.5 $ 1.7 $ 1.0