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Stock-Based Compensation - Summary of Non-vested Options Activity (Detail) - $ / shares
9 Months Ended
Feb. 28, 2017
Feb. 29, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]    
Number of Shares, Non-vested options, Beginning balance 225,000  
Number of Shares, Granted 49,000 225,000
Number of Shares, Vested (45,000)  
Number of Shares, Non-vested options, Ending balance 229,000 225,000
Weighted Average Grant-Date Fair Value, Non-vested options, Beginning balance $ 2.19  
Weighted Average Grant-Date Fair Value, Granted 7.58 $ 2.19
Weighted Average Grant-Date Fair Value, Vested 2.19  
Weighted Average Grant-Date Fair Value, Non-vested options, Ending balance $ 3.34 $ 2.19