Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.2
Stockholders' Equity (Schedule of All Warrants and Exercisable Warrants) (Details)
3 Months Ended
Jul. 31, 2019
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
ALL WARRANTS, Outstanding No. of Warrants | shares 3,237,840
EXERCISABLE WARRANTS, Exercisable No. of Warrants | shares 2,057,324
Warrant [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
ALL WARRANTS, Outstanding No. of Warrants | shares 687,292
EXERCISABLE WARRANTS, Exercisable No. of Warrants | shares 637,292
Warrant [Member] | $1.86 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
ALL WARRANTS, Exercise Price Upper Range $ 1.86
ALL WARRANTS, Weighted Average Exercise Price $ 1.86
ALL WARRANTS, Outstanding No. of Warrants | shares 88,710
EXERCISABLE WARRANTS, Weighted Average Exercise Price $ 1.86
EXERCISABLE WARRANTS, Weighted Average Remaining Life In Years 1 month 2 days
EXERCISABLE WARRANTS, Exercisable No. of Warrants | shares 88,710
Warrant [Member] | $2.28 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
ALL WARRANTS, Exercise Price Upper Range $ 2.28
ALL WARRANTS, Weighted Average Exercise Price $ 2.28
ALL WARRANTS, Outstanding No. of Warrants | shares 32,359
EXERCISABLE WARRANTS, Weighted Average Exercise Price $ 2.28
EXERCISABLE WARRANTS, Weighted Average Remaining Life In Years 1 month 6 days
EXERCISABLE WARRANTS, Exercisable No. of Warrants | shares 32,359
Warrant [Member] | $4.89 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
ALL WARRANTS, Exercise Price Upper Range $ 4.89
ALL WARRANTS, Weighted Average Exercise Price $ 4.89
ALL WARRANTS, Outstanding No. of Warrants | shares 50,000
EXERCISABLE WARRANTS, Weighted Average Exercise Price $ 4.89
EXERCISABLE WARRANTS, Weighted Average Remaining Life In Years 4 years 8 months 12 days
EXERCISABLE WARRANTS, Exercisable No. of Warrants | shares
Warrant [Member] | $5.85 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
ALL WARRANTS, Exercise Price Upper Range $ 5.85
ALL WARRANTS, Weighted Average Exercise Price $ 5.85
ALL WARRANTS, Outstanding No. of Warrants | shares 92,049
EXERCISABLE WARRANTS, Weighted Average Exercise Price $ 5.85
EXERCISABLE WARRANTS, Weighted Average Remaining Life In Years 4 years 3 months 8 days
EXERCISABLE WARRANTS, Exercisable No. of Warrants | shares 92,049
Warrant [Member] | $6.00 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
ALL WARRANTS, Exercise Price Upper Range $ 6.00
ALL WARRANTS, Weighted Average Exercise Price $ 6.00
ALL WARRANTS, Outstanding No. of Warrants | shares 200,000
EXERCISABLE WARRANTS, Weighted Average Exercise Price $ 6.00
EXERCISABLE WARRANTS, Weighted Average Remaining Life In Years 4 years 7 months 6 days
EXERCISABLE WARRANTS, Exercisable No. of Warrants | shares 200,000
Warrant [Member] | $6.87 [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
ALL WARRANTS, Exercise Price Upper Range $ 6.87
ALL WARRANTS, Weighted Average Exercise Price $ 6.87
ALL WARRANTS, Outstanding No. of Warrants | shares 224,174
EXERCISABLE WARRANTS, Weighted Average Exercise Price $ 6.87
EXERCISABLE WARRANTS, Weighted Average Remaining Life In Years 2 years 11 months 26 days
EXERCISABLE WARRANTS, Exercisable No. of Warrants | shares 224,174