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Accounts Receivable - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Jul. 31, 2017
Jul. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Amount of accounts receivable factored $ 41.1 $ 0.9
London Interbank Offered Rate (LIBOR)    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Interest rate on the sale of receivables 0.85%