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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]
6 Months Ended
Oct. 31, 2018
Oct. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life (years) 3 years 6 months 3 years 6 months
Expected volatility 46.00%  
Expected volatility, minimum 40.00%
Expected volatility, maximum 43.00%
Risk-free interest rate 38.00% 38.00%
Dividend yield 0.00% 0.00%
Expected forfeiture rate