Financial Instruments - Effects of Derivative Instruments on Condensed Consolidated Statements of Operations (Detail) - Foreign Exchange Contracts - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017
Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in accumulated other comprehensive loss on derivatives (effective portion)	$ 19.6	$ (21.3)	$ 6.3
Amount and location of (loss) gain reclassified from accumulated other comprehensive loss into (loss) income (effective portion)	(12.1)	9.9	7.4
Designated as Hedging Instrument | Net revenue
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of (loss) gain reclassified from accumulated other comprehensive loss into (loss) income (effective portion)	(8.5)	8.0	9.2
Designated as Hedging Instrument | Operating expenses
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of (loss) gain reclassified from accumulated other comprehensive loss into (loss) income (effective portion)	(3.6)	1.9	(1.8)
Designated as Hedging Instrument | Interest and other expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of gain (loss) recognized in income (loss) on derivatives (ineffective portion and amount excluded from effectiveness testing)	0.2	(0.2)	(0.3)
Not Designated as Hedging Instrument | Interest and other expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of loss recognized in loss (income) on derivatives	$ 6.6	$ (19.1)	$ (11.1)