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Stockholders' Equity - Additional Information (Detail) - USD ($)
3 Months Ended
Oct. 31, 2018
Oct. 31, 2017
Jun. 19, 2018
Stock Based Compensation And Stockholders Equity [Line Items]      
Total compensation expenses $ 4,530,000 $ 4,318,000  
Stock repurchase program authorized amount     $ 250,000,000
Stock repurchase program expiration date Jun. 19, 2020    
Obligation to repurchase common stock $ 0    
Regular dividend declared per common share $ 0.39    
Dividends declared but not paid $ 20,595,000    
Restricted Stock Units (RSUs)      
Stock Based Compensation And Stockholders Equity [Line Items]      
Withholding taxes payable $ 4,418,000