Financial Instruments (Effects of Derivative Instruments on Condensed Consolidated Statements of Operations) (Details) - Foreign currency contracts - USD ($) $ in Millions	3 Months Ended
	Apr. 30, 2018	Apr. 30, 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)	$ 6.9	$ (2.1)
Amount and location of (loss) gain reclassified from accumulated other comprehensive loss into (loss) income (effective portion)	0.8	(0.7)
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)	(2.5)	2.0
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)	3.3	(2.7)
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 (ineffective portion and amount excluded from effectiveness testing)	(0.2)	(0.2)
Derivatives not designated as hedging instruments | Interest and other expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of gain (loss) recognized on derivatives in net (loss) income	$ 4.6	$ (1.8)