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Stockholders' Equity - Additional Information (Detail) - Common Stock - 2015 Stock Repurchase Plan - USD ($)
3 Months Ended 6 Months Ended
Jan. 31, 2018
Jan. 31, 2018
Mar. 09, 2018
Sep. 03, 2015
Class of Stock [Line Items]        
Stock repurchase program, authorized amount       $ 30,000,000
Share repurchase program, term   The Company may suspend or discontinue the 2015 Plan at any time and the 2015 plan has no expiration date.    
Shares repurchased during period 0 0    
Subsequent Event        
Class of Stock [Line Items]        
Stock repurchased during period, shares     1,956,733  
Stock repurchased during period, value     $ 12,000,000