Financial Instruments Effects of Derivative Instruments on Condensed Consolidated Statements of Operations (Details) - Foreign currency contracts - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Designated as hedging instrument
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in accumulated other comprehensive (loss) income on derivatives (effective portion)	$ 2.9	$ 1.8	$ (8.5)	$ (3.1)
Amount and location of gain (loss) reclassified from accumulated other comprehensive (loss) income into (loss) income (effective portion)	5.3	2.5	6.9	8.6
Designated as hedging instrument | Net revenue
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of gain (loss) reclassified from accumulated other comprehensive (loss) income into (loss) income (effective portion)	2.4	1.0	7.2	8.4
Designated as hedging instrument | Operating expenses
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of gain (loss) reclassified from accumulated other comprehensive (loss) income into (loss) income (effective portion)	2.9	1.5	(0.3)	0.2
Designated as hedging instrument | Interest and other expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of gain (loss) recognized in (loss) income on derivatives (ineffective portion and amount excluded from effectiveness testing)	0.0	(0.1)	(0.1)	(0.5)
Derivatives not designated as hedging instruments | Interest and other expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of gain (loss) recognized in (loss) income on derivatives	$ 0.9	$ (1.4)	$ (7.4)	$ (12.3)