Quarterly report pursuant to Section 13 or 15(d)

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

v3.20.1
Stockholders' Equity - Share-based Payment Arrangement, Option, Exercise Price Range (Details)
 9 Months Ended
Jan. 31, 2020
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Outstanding (in shares) | shares 2,776,778
Exercisable (in shares) | shares 1,824,684
Warrant  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Outstanding (in shares) | shares 566,223
Warrant  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Exercisable (in shares) | 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) | shares 50,000
Weighted average exercise price (in dollars per share) $ 4.89
Weighted average remaining life in years 4 years 2 months 8 days
Exercisable (in shares) | 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) | shares 92,049
Weighted average exercise price (in dollars per share) $ 5.85
Weighted average remaining life in years 3 years 9 months 3 days
Exercisable (in shares) | 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) | shares 200,000
Weighted average exercise price (in dollars per share) $ 6.00
Weighted average remaining life in years 4 years 1 month 6 days
Exercisable (in shares) | 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) | shares 224,174
Weighted average exercise price (in dollars per share) $ 6.87
Weighted average remaining life in years 2 years 5 months 23 days
Exercisable (in shares) | shares 224,174