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Quarterly report pursuant to Section 13 or 15(d)

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

v3.20.4
Stockholders' Equity - Schedule of All Options and Exercisable Options (Details) - $ / shares
9 Months Ended
Jan. 31, 2021
Jan. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Ìý Ìý
Outstanding (in shares) 1,260,213 2,776,778
Exercisable (in shares) 1,038,024 Ìý
$1.57 to $2.10 Ìý Ìý
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Ìý Ìý
Minimum exercise price (in dollars per share) $ 1.57 Ìý
Maximum exercise price (in dollars per share) 2.10 Ìý
Weighted average exercise price (in dollars per share) $ 1.92 Ìý
Outstanding (in shares) 29,167 Ìý
Weighted average exercise price (in dollars per share) $ 1.92 Ìý
Weighted average remaining life in years 5 months 8 days Ìý
Exercisable (in shares) 29,167 Ìý
$2.28 to $2.76 Ìý Ìý
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Ìý Ìý
Minimum exercise price (in dollars per share) $ 2.28 Ìý
Maximum exercise price (in dollars per share) 2.76 Ìý
Weighted average exercise price (in dollars per share) $ 2.76 Ìý
Outstanding (in shares) 11,415 Ìý
Weighted average exercise price (in dollars per share) $ 2.76 Ìý
Weighted average remaining life in years 8 months 1 day Ìý
Exercisable (in shares) 11,415 Ìý
$3.24 to $4.38 Ìý Ìý
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Ìý Ìý
Minimum exercise price (in dollars per share) $ 3.24 Ìý
Maximum exercise price (in dollars per share) 4.38 Ìý
Weighted average exercise price (in dollars per share) $ 3.82 Ìý
Outstanding (in shares) 188,639 Ìý
Weighted average exercise price (in dollars per share) $ 3.75 Ìý
Weighted average remaining life in years 1 year 3 months 25 days Ìý
Exercisable (in shares) 146,804 Ìý
$4.50 to $5.20 Ìý Ìý
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Ìý Ìý
Minimum exercise price (in dollars per share) $ 4.50 Ìý
Maximum exercise price (in dollars per share) 5.20 Ìý
Weighted average exercise price (in dollars per share) $ 4.94 Ìý
Outstanding (in shares) 362,818 Ìý
Weighted average exercise price (in dollars per share) $ 4.95 Ìý
Weighted average remaining life in years 1 year 9 months 25 days Ìý
Exercisable (in shares) 297,714 Ìý
$5.95 to $6.28 Ìý Ìý
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Ìý Ìý
Minimum exercise price (in dollars per share) $ 5.95 Ìý
Maximum exercise price (in dollars per share) 6.28 Ìý
Weighted average exercise price (in dollars per share) $ 6.10 Ìý
Outstanding (in shares) 66,000 Ìý
Weighted average exercise price (in dollars per share) $ 6.10 Ìý
Weighted average remaining life in years 1 year 5 months 19 days Ìý
Exercisable (in shares) 66,000 Ìý
$7.17 to $7.55 Ìý Ìý
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Ìý Ìý
Minimum exercise price (in dollars per share) $ 7.17 Ìý
Maximum exercise price (in dollars per share) 7.55 Ìý
Weighted average exercise price (in dollars per share) $ 7.44 Ìý
Outstanding (in shares) 444,425 Ìý
Weighted average exercise price (in dollars per share) $ 7.43 Ìý
Weighted average remaining life in years 2 years 7 months 13 days Ìý
Exercisable (in shares) 329,175 Ìý
$8.57 to $9.07 Ìý Ìý
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Ìý Ìý
Minimum exercise price (in dollars per share) $ 8.57 Ìý
Maximum exercise price (in dollars per share) 9.07 Ìý
Weighted average exercise price (in dollars per share) $ 8.98 Ìý
Outstanding (in shares) 157,749 Ìý
Weighted average exercise price (in dollars per share) $ 8.98 Ìý
Weighted average remaining life in years 1 year 11 months 4 days Ìý
Exercisable (in shares) 157,749 Ìý