Derivatives and Hedging Activities - Additional Information (Detail) $ in Thousands, £ in Millions	3 Months Ended		6 Months Ended
	Jan. 31, 2018 USD ($)	Jan. 31, 2017 USD ($)	Jan. 31, 2018 USD ($)	Jan. 31, 2017 USD ($)	Jul. 31, 2017 USD ($)	May 13, 2010 GBP (£)
Derivatives, Fair Value [Line Items]
Derivative Maturities			18 months
Derivative, Notional Amount	$ 18,236		$ 18,236		$ 81,195
Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months	(856)	$ (451)	(856)	$ (451)
Cash Flow Hedge Gain (Loss) Reclassified to Earnings	(158)	(10)	(182)	(415)
Total Outstanding Forward Foreign Exchange Contracts	15,043		15,043
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	$ (2)	$ (3,313)	$ 20	$ (5,046)
Senior Unsecured Notes [Member]
Derivatives, Fair Value [Line Items]
Derivative, Amount of Hedged Item | £						£ 45