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Stock-based Compensation - Additional Information (Details) - USD ($)
12 Months Ended
May 31, 2018
May 31, 2017
Jan. 31, 2017
May 31, 2016
Dec. 29, 2015
Aug. 31, 2015
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Securities remaining and available for future issuances (in shares)             1,005,706  
Stock Option Activity [Abstract]                
Stock option vesting period             4 years  
Stock option contractual term             10 years  
Stock option vesting provisions             12/48 of a granted award will vest after one year of service, while an additional 1/48 of the award will vest at the end of each month thereafter for 36 months, or 1/48 of the award will vest at the end of each month over a four-year period.  
Weighted Average Remaining Contractual Terms [Abstract]                
Stock options exercised             $ 0 $ 0
Dividend yield assumed             0  
Total unamortized compensation cost related to outstanding unvested stock options and restricted stock awards             $ 200,000  
Weighted average period for recognition of cost             1 year 6 months  
2014 Plan [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Common stock shares to be issued (in shares) 750,000 200,000   33,333   30,180 26,500  
Securities remaining and available for future issuances (in shares)             947,856  
2015 Plan [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Common stock shares to be issued (in shares)     25,000   6,666      
Securities remaining and available for future issuances (in shares)             171