Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity (Schedule of Assumptions Used to Value Stock Options) (Details)

v3.19.1
Stockholders' Equity (Schedule of Assumptions Used to Value Stock Options) (Details) - Stock Incentive Plan and Stock Option Grants to Employees and Directors [Member]
9 Months Ended
Jan. 31, 2019
Jan. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life (years) 3 years 6 months  
Expected volatility 51.00%  
Expected volatility, minimum   40.00%
Expected volatility, maximum   43.00%
Risk-free interest rate 2.70% 0.38%
Dividend yield 0.00% 0.00%
Expected forfeiture rate
Minimum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life (years)   4 years
Maximum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life (years)   6 years 6 months