Derivative Instruments - Additional Information (Detail) - Forward Contracts - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016	Jul. 31, 2016
Derivative [Line Items]
Unrealized loss on cash flow hedges	$ 0.0		$ 0.0		$ 0.2
Notional amount of cash flow hedge instruments	14.3		14.3		18.6
Cost of Revenue and Operating Expenses
Derivative [Line Items]
Realized gains (losses) on cash flow hedge instruments	(0.2)	$ (0.2)	(0.3)	$ (0.5)
Designated as Hedging Instrument
Derivative [Line Items]
Derivative liability, current	$ 0.0		$ 0.0		$ 0.3