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Equity Incentive Plan - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Feb. 29, 2016
Feb. 28, 2015
Feb. 29, 2016
Feb. 28, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expected period to recognize the unrecognized share based compensation cost     3 years  
Selling, general and administrative expenses        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Allocated share based compensation $ 368 $ 319 $ 1,016 $ 968
Restricted Stock Units        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted stock units granted (in shares) 0 0 182,000 87,000
Unrecognized share based compensation cost $ 2,119   $ 2,119  
Expected period to recognize the unrecognized share based compensation cost     2 years 6 days  
Vested restricted stock units 232,000 401,000 232,000 401,000
Exercise of conversion right, period     5 years  
Total excess tax benefit (shortfall) realized     $ (40) $ 348
2005 Equity Incentive Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Maximum number of shares authorized 1,000,000   1,000,000