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Share-Based Compensation - Additional Information (Detail) - USD ($)
3 Months Ended
Aug. 31, 2015
Aug. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Awards outstanding to officers, directors and key employees 800,000  
Total number of shares cumulatively authorized to be issued under our stock incentive plans 7,120,000  
Share-based compensation $ 1,200,000 $ 1,000,000
Employee service share-based compensation, nonvested awards, compensation not yet recognized, share-based awards other than options $ 9,300,000  
Remaining weighted-average period 2 years 6 months  
Tax benefit related to share-based compensation $ 0 900,000
Weighted-average remaining contractual life of options exercisable 1 year 7 months 6 days  
Stock Options [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based compensation $ 0 0
Award vesting period 4 years  
Stock option year term 10 years  
Long Term Performance Stock Unit Awards [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based compensation $ 100,000  
Performance Period 3 years  
Service Period 3 years  
Settlement period 20 days  
Long Term Performance Stock Unit Awards [Member] | Minimum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Possible payouts 0.00%  
Long Term Performance Stock Unit Awards [Member] | Maximum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Possible payouts 300.00%  
Stock and Stock Units [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based compensation $ 1,000,000 800,000
Stock and Stock Units [Member] | Minimum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award vesting period 2 years  
Stock and Stock Units [Member] | Maximum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Award vesting period 4 years  
Performance Shares [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based compensation $ 100,000 $ 100,000
Award vesting period 4 years