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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]
9 Months Ended
Jan. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Expected volatility, minimum 40.00%
Expected volatility, maximum 43.00%
Risk-free interest rate 0.00%
Dividend yield 0.00%
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