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Fair Value Measurements - Additional Information (Detail) (USD $)
3 Months Ended
Aug. 31, 2014
Aug. 31, 2013
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 $ 0 $ 0
Transfer of Liability from Level 1 to Level 2 0 0
Transfer of Liability from Level 2 to Level 1 $ 0 $ 0