Quarterly report pursuant to Section 13 or 15(d)

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

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Stockholders' Equity - Schedule of All Options and Exercisable Options (Details)
 3 Months Ended 6 Months Ended
Oct. 31, 2019
$ / shares
shares
Oct. 31, 2019
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Exercisable (in shares) | shares 1,902,579 1,902,579
$1.57 to $2.10    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Minimum exercise price (in dollars per share) $ 1.57  
Maximum exercise price (in dollars per share) 2.10  
Weighted average exercise price (in dollars per share) $ 1.99 $ 1.99
Outstanding (in shares) | shares 600,115 600,115
Weighted average exercise price (in dollars per share) $ 1.99 $ 1.99
Weighted average remaining life in years   1 year 2 months 4 days
Exercisable (in shares) | shares 600,115 600,115
$2.28 to $2.76    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Minimum exercise price (in dollars per share) $ 2.28  
Maximum exercise price (in dollars per share) 2.76  
Weighted average exercise price (in dollars per share) $ 2.31 $ 2.31
Outstanding (in shares) | shares 392,780 392,780
Weighted average exercise price (in dollars per share) $ 2.29 $ 2.29
Weighted average remaining life in years   10 months 13 days
Exercisable (in shares) | shares 400,486 400,486
$3.24 to $4.38    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Minimum exercise price (in dollars per share) $ 3.24  
Maximum exercise price (in dollars per share) 4.38  
Weighted average exercise price (in dollars per share) $ 3.90 $ 3.90
Outstanding (in shares) | shares 358,388 358,388
Weighted average exercise price (in dollars per share) $ 3.93 $ 3.93
Weighted average remaining life in years   2 years
Exercisable (in shares) | shares 235,904 235,904
$4.50 to $5.20    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Minimum exercise price (in dollars per share) $ 4.5  
Maximum exercise price (in dollars per share) 5.20  
Weighted average exercise price (in dollars per share) $ 4.93 $ 4.93
Outstanding (in shares) | shares 711,459 711,459
Weighted average exercise price (in dollars per share) $ 4.90 $ 4.90
Weighted average remaining life in years   2 years 6 months 10 days
Exercisable (in shares) | shares 336,611 336,611
$5.95 to $6.28    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Minimum exercise price (in dollars per share) $ 5.95  
Maximum exercise price (in dollars per share) 6.28  
Weighted average exercise price (in dollars per share) $ 6.07 $ 6.07
Outstanding (in shares) | shares 80,417 80,417
Weighted average exercise price (in dollars per share) $ 6.13 $ 6.13
Weighted average remaining life in years   2 years 8 months 4 days
Exercisable (in shares) | shares 36,806 36,806
$7.17 to $7.55    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Minimum exercise price (in dollars per share) $ 7.17  
Maximum exercise price (in dollars per share) 7.55  
Weighted average exercise price (in dollars per share) $ 7.39 $ 7.39
Outstanding (in shares) | shares 660,972 660,972
Weighted average exercise price (in dollars per share) $ 7.39 $ 7.39
Weighted average remaining life in years   3 years 8 months 23 days
Exercisable (in shares) | shares 220,324 220,324
$8.57 to $9.07    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Minimum exercise price (in dollars per share) $ 8.57  
Maximum exercise price (in dollars per share) 9.07  
Weighted average exercise price (in dollars per share) $ 8.98 $ 8.98
Outstanding (in shares) | shares 217,000 217,000
Weighted average exercise price (in dollars per share) $ 8.98 $ 8.98
Weighted average remaining life in years   3 years 5 months 8 days
Exercisable (in shares) | shares 72,333 72,333