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Equity Compensation Plans - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended 12 Months Ended
Nov. 30, 2017
Nov. 30, 2016
Nov. 30, 2017
Nov. 30, 2016
May 31, 2018
May 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Compensation expense related to share based awards $ 1,264,000 $ 1,218,000 $ 2,666,000 $ 2,734,000    
Weighted-average fair value per share of stock options granted           $ 11.84
During fiscal 2018            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Weighted-average fair value per share of stock options granted         $ 14.69  
U.S. | ASU No. 2016-09            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Decrease in income tax expense $ 3,418,000   $ 3,794,000      
Employee Stock Purchase Plan | 2011 Employee Stock Purchase Plan            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Annual maximum limit percentage of compensation to purchase shares     5.00%      
Minimum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock option vesting period     3 years      
Stock option contractual terms     5 years      
Maximum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock option vesting period     5 years      
Stock option contractual terms     10 years