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Equity Compensation Plans - Additional Information (Detail) - USD ($)
3 Months Ended 12 Months Ended
Aug. 31, 2018
Aug. 31, 2017
May 31, 2018
Compensation expense related to share based awards $ 1,431,000 $ 1,401,000  
Weighted-average fair value per share of stock options granted     $ 14.47
Employee Stock Purchase Plan | 2011 Employee Stock Purchase Plan      
Annual maximum limit percentage of compensation to purchase shares 5.00%    
Minimum      
Stock option vesting period 3 years    
Stock option contractual terms 5 years    
Maximum      
Stock option vesting period 5 years    
Stock option contractual terms 10 years