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Equity Compensation Plans - Additional Information (Detail) (USD $)
In Thousands, except Per Share data, unless otherwise specified
3 Months Ended 6 Months Ended 12 Months Ended
Nov. 30, 2012
Nov. 30, 2011
Nov. 30, 2012
Nov. 30, 2011
May 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share based compensation $ 724 $ 472 $ 1,406 $ 1,072  
Weighted-average fair value of stock options granted     $ 13.81   $ 10.42
Employee stock purchase plan discount rate on market price     5.00%    
Employee and Director Stock Option
         
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Stock option vesting period     5 years    
Non-Qualified Options
         
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Stock option vesting period     10 years