Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Share-based Payment Arrangement, Option, Exercise Price Range (Details)

v3.20.4
Stockholders' Equity - Share-based Payment Arrangement, Option, Exercise Price Range (Details) - $ / shares
 6 Months Ended
Oct. 31, 2020
Oct. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Outstanding (in shares) 1,744,354 3,021,131
Exercisable (in shares) 1,439,330  
Warrant    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Outstanding (in shares) 374,174 566,223
Warrant    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Exercisable (in shares) 374,174  
Warrant | $4.89    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Minimum exercise price (in dollars per share) $ 4.89  
Maximum exercise price (in dollars per share) 4.89  
Weighted average exercise price (in dollars per share) $ 4.89  
Outstanding (in shares) 50,000  
Weighted average exercise price (in dollars per share) $ 4.89  
Weighted average remaining life in years 3 years 5 months 8 days  
Exercisable (in shares) 50,000  
Warrant | $6.00    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Minimum exercise price (in dollars per share) $ 6.00  
Maximum exercise price (in dollars per share) 6.00  
Weighted average exercise price (in dollars per share) $ 6.00  
Outstanding (in shares) 100,000  
Weighted average exercise price (in dollars per share) $ 6.00  
Weighted average remaining life in years 3 years 4 months 6 days  
Exercisable (in shares) 100,000  
Warrant | $6.87    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Minimum exercise price (in dollars per share) $ 6.87  
Maximum exercise price (in dollars per share) 6.87  
Weighted average exercise price (in dollars per share) $ 6.87  
Outstanding (in shares) 224,174  
Weighted average exercise price (in dollars per share) $ 6.87  
Weighted average remaining life in years 1 year 8 months 23 days  
Exercisable (in shares) 224,174