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Net Income per Common Share - Additional Informations (Detail) - shares
12 Months Ended
Jul. 31, 2018
Jul. 31, 2017
Jul. 31, 2016
Earnings Per Share [Line Items]      
Anti-dilutive shares excluded from computations of diluted earnings per share 751,200 669,036  
Class A Nonvoting Common Stock [Member]      
Earnings Per Share [Line Items]      
Anti-dilutive shares excluded from computations of diluted earnings per share     3,172,755