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Fair Value Measurements - Additional Information (Detail) (USD $)
9 Months Ended
Feb. 28, 2015
Feb. 28, 2014
Fair Value Assets Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]    
Transfer in and out of Level 1, Level 2 or Level 3 measurements $ 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet $ 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet
Transfer of Liability from Level 1 to Level 2 0us-gaap_FairValueLiabilitiesLevel1ToLevel2TransfersAmount 0us-gaap_FairValueLiabilitiesLevel1ToLevel2TransfersAmount
Transfer of Liability from Level 2 to Level 1 $ 0us-gaap_FairValueLiabilitiesLevel2ToLevel1TransfersAmount $ 0us-gaap_FairValueLiabilitiesLevel2ToLevel1TransfersAmount