Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Schedule of All Warrants and Exercisable Warrants (Details)

v3.20.2
Stockholders' Equity - Schedule of All Warrants and Exercisable Warrants (Details) - $ / shares
 12 Months Ended
Apr. 30, 2020
Apr. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Outstanding (in shares) 2,734,899 3,408,154
Exercisable (in shares) 1,742,599  
Warrant    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Outstanding (in shares) 566,223 731,152
Warrant    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Exercisable (in shares) 566,223  
Warrant | Warrant    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Outstanding (in shares) 566,223  
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 10 months 6 days  
Exercisable (in shares) 50,000  
Warrant | $5.85    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Minimum exercise price (in dollars per share) $ 5.85  
Maximum exercise price (in dollars per share) 5.85  
Weighted average exercise price (in dollars per share) $ 5.85  
Outstanding (in shares) 92,049  
Weighted average exercise price (in dollars per share) $ 5.85  
Weighted average remaining life (in years) 3 years 9 months 25 days  
Exercisable (in shares) 92,049  
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) 200,000  
Weighted average exercise price (in dollars per share) $ 6.00  
Weighted average remaining life (in years) 3 years 10 months 6 days  
Exercisable (in shares) 200,000  
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) 2 years 2 months 26 days  
Exercisable (in shares) 224,174