Quarterly report pursuant to Section 13 or 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]
3 Months Ended
Jul. 31, 2017
Jul. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life (years) 3 years 6 months  
Expected volatility, minimum 40.00% 40.00%
Expected volatility, maximum 43.00% 43.00%
Weighted-average volatility 38.60% 40.00%
Risk-free interest rate 0.38% 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)   6 years 6 months