Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity (Schedule of Stock Options Activity) (Details)

v3.10.0.1
Stockholders' Equity (Schedule of Stock Options Activity) (Details) - Stock Incentive Plan and Stock Option Grants to Employees and Directors [Member]
3 Months Ended
Jul. 31, 2018
USD ($)
$ / shares
shares
Number of Shares  
Balance Outstanding, April 30, 2018 | shares 2,979,510
Granted | shares 560,000
Exercised | shares (11,023)
Forfeited | shares (13,417)
Expired | shares
Balance Outstanding, July 31, 2018 | shares 3,515,070
Exercisable, July 31, 2018 | shares 1,552,546
Weighted Average Exercise Price  
Balance Outstanding, April 30, 2018 | $ / shares $ 3.62
Granted | $ / shares 7.55
Exercised | $ / shares 2.43
Forfeited | $ / shares
Expired | $ / shares
Balance Outstanding, July 31, 2018 | $ / shares 4.23
Exercisable, July 31, 2018 | $ / shares $ 2.32
Balance Outstanding, July 31, 2018 3 years 2 months 27 days
Exercisable, July 31, 2018 2 years 3 months
Aggregate Intrinsic Value  
Balance Outstanding, April 30, 2018 | $ $ 16,558,373
Balance Outstanding, July 31, 2018 | $ 16,677,457
Exercisable, July 31, 2018 | $ $ 11,524,870