Assets and Liabilities Carried at Fair Value and Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Apr. 30, 2017	Jul. 31, 2016	Apr. 30, 2016	Jul. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 158,633	$ 118,697	$ 128,124	$ 123,800
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	158,600	118,700
Plan assets for deferred compensation	6,700	5,900
Total assets at fair value	165,300	124,600
Contingent consideration		12,200
Foreign currency forward contracts	500	300
Total liabilities at fair value	500	12,500
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	158,600	118,700
Plan assets for deferred compensation	6,700	5,900
Total assets at fair value	165,300	124,600
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency forward contracts	500	300
Total liabilities at fair value	$ 500	300
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration		12,200
Total liabilities at fair value		$ 12,200