Annual report pursuant to Section 13 and 15(d)

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

v3.7.0.1
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, 2017
Apr. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected volatility, minimum 40.00% 40.00%
Expected volatility, maximum 43.00% 43.00%
Weighted-average volatility 0.38% 0.40%
Risk-free interest rate 0.00% 0.38%
Dividend yield 0.00% 0.00%
Minimum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life (years) 4 years 4 years
Maximum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life (years) 6 years 6 months 6 years 6 months