Derivative Instruments - Additional Information (Detail) - Forward Contracts - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Derivative [Line Items]
Notional amount of cash flow hedge instruments	$ 10.9	$ 18.6
Unrealized gain (loss) on cash flow hedges	0.5	(0.2)
Cost of Revenue and Operating Expenses
Derivative [Line Items]
Realized gains (losses) on cash flow hedge instruments	(0.6)	(0.7)	$ (0.5)
Designated as Hedging Instrument
Derivative [Line Items]
Derivative asset, current	$ 0.6
Derivative liability, current		$ 0.3