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Stockholders' Equity (Schedule of Assumptions Used to Value Stock Options) (Details) - Stock Incentive Plan and Stock Option Grants to Employees and Directors [Member]
12 Months Ended
Apr. 30, 2019
Apr. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life (years) 3 years 6 months  
Expected volatility 50.10%  
Expected volatility, minimum   40.00%
Expected volatility, maximum   43.00%
Risk-free interest rate 2.63% 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)   5 years