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Stock Incentive Plan - Assumptions Used to Estimate Fair Value of ESPP Shares (Detail) - 2015 Employee Stock Purchase Plan [Member] - $ / shares
12 Months Ended
Jul. 31, 2016
Jul. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected term (in years) 6 months 8 months 12 days
Risk-free interest rate   0.10%
Expected volatility   30.00%
Dividend yield 0.00% 0.00%
Fair value of common stock   $ 17.00
Minimum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Risk-free interest rate 0.40%  
Expected volatility 36.00%  
Fair value of common stock $ 8.27  
Maximum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Risk-free interest rate 0.50%  
Expected volatility 40.00%  
Fair value of common stock $ 12.81