Fair Value Measurements - Summary Fair Value of Outstanding Derivative Instruments (Detail) - Foreign currency derivative contracts [Member] - Derivatives not designated as hedging instruments [Member] $ in Thousands	Jul. 31, 2017 USD ($)
Prepaid expenses and other current assets [Member]
Derivatives Fair Value [Line Items]
Derivative Assets	$ 46
Accrued expenses [Member]
Derivatives Fair Value [Line Items]
Derivative Liabilities	$ 253