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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]
3 Months Ended 12 Months Ended
Jul. 31, 2019
Apr. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life (years) 3 years 3 years 6 months
Expected volatility 46.00% 50.10%
Risk-free interest rate 2.18% 2.63%
Dividend yield 0.00% 0.00%
Expected forfeiture rate