Financial Instruments - Effects of Derivative Instruments on Condensed Consolidated Statements of Operations (Detail) - Foreign Exchange Contracts - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain recognized in accumulated other comprehensive income on derivatives (effective portion)	$ 6.3	$ 2.2	$ 46.4
Amount and location of gain reclassified from accumulated other comprehensive income into income (effective portion)	7.4	29.3	7.0
Designated as Hedging Instrument | Net revenue
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of gain reclassified from accumulated other comprehensive income into income (effective portion)	9.2	39.8	10.5
Designated as Hedging Instrument | Operating expenses
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of gain reclassified from accumulated other comprehensive income into income (effective portion)	(1.8)	(10.5)	(3.5)
Designated as Hedging Instrument | Interest and other expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of (loss) gain recognized in income on derivatives (ineffective portion and amount excluded from effectiveness testing)	(0.3)	(0.7)	0.9
Not Designated as Hedging Instrument | Interest and other expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of (loss) gain recognized in income on derivatives	$ (11.1)	$ (1.7)	$ (25.5)