Financial Instruments Effects of Derivative Instruments on Condensed Consolidated Statements of Operations (Details) - Foreign currency contracts - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2017	Jul. 31, 2016
Designated as hedging instrument
Derivative Instruments, Gain (Loss) [Line Items]
Amount of (loss) gain recognized in accumulated other comprehensive (loss) income on derivatives (effective portion)	$ (9.3)	$ 1.5	$ (11.4)	$ (4.9)
Amount and location of gain (loss) reclassified from accumulated other comprehensive (loss) income into (loss) income (effective portion)	2.3	3.0	1.6	6.1
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)	2.8	2.5	4.8	7.4
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)	(0.5)	0.5	(3.2)	(1.3)
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)	0.1	(0.2)	(0.1)	(0.4)
Derivatives not designated as hedging instruments | Interest and other expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of loss recognized in (loss) income on derivatives	$ (6.5)	$ (3.9)	$ (8.3)	$ (10.9)