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Stockholders' Equity - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
May 15, 2015
Jul. 31, 2017
Jul. 31, 2016
Jul. 31, 2015
Stock Based Compensation And Stockholders Equity [Line Items]        
Common stock purchased, shares 1,000,000      
Common stock price per share $ 60.00      
Aggregate purchase price of common stock $ 60,000     $ 60,000
Closing price of common stock $ 61.29      
Percentage of issued and outstanding common stock prior to repurchase 1.90%      
Total unrecognized compensation costs   $ 16,679    
Period for recognition of compensation cost not yet recognized   2 years 3 months 11 days    
Stock-based compensation   $ 12,500 $ 9,387 6,776
Tax benefits from stock compensation expense   4,625 3,473 2,507
Restricted Stock Units (RSUs)        
Stock Based Compensation And Stockholders Equity [Line Items]        
Total compensation expenses   $ 12,399 9,272 6,661
2010 Equity Incentive Plan        
Stock Based Compensation And Stockholders Equity [Line Items]        
Number of shares authorized under stock option plan   2,000,000    
Number of shares available to be granted   1,211,385    
2016 Equity Incentive Plan        
Stock Based Compensation And Stockholders Equity [Line Items]        
Number of shares authorized under stock option plan   2,000,000    
Number of shares available to be granted   1,834,021    
Restricted Stock Awards        
Stock Based Compensation And Stockholders Equity [Line Items]        
Total compensation expenses   $ 101 $ 115 $ 115
Total unrecognized compensation costs   $ 0    
Share-based compensation arrangement by share-based payment award, award vesting period   5 years