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Intangible Assets - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Nov. 30, 2014
Nov. 30, 2013
Nov. 30, 2014
Nov. 30, 2013
Finite-Lived Intangible Assets [Line Items]        
Amortization expense $ 0.9us-gaap_AmortizationOfIntangibleAssets $ 0.9us-gaap_AmortizationOfIntangibleAssets $ 1.9us-gaap_AmortizationOfIntangibleAssets $ 1.9us-gaap_AmortizationOfIntangibleAssets