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Stockholders' Equity - Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions (Details) - $ / shares
3 Months Ended 6 Months Ended
Oct. 31, 2015
Oct. 31, 2015
Expected term (years) 3 years  
Expected volatility 80.00%  
Expected volatility, minimum   79.00%
Expected volatility, maximum   80.00%
Dividend yield 0.00% 0.00%
Risk-free interest rate 1.01%  
Risk-free interest rate, minimum   0.90%
Risk-free interest rate, maximum   1.01%
Weighted average per share grant date fair value $ 0.78  
Minimum    
Expected term (years)   2 years 6 months
Weighted average per share grant date fair value   $ 0.78
Maximum    
Expected term (years)   3 years
Weighted average per share grant date fair value   $ 1.03