Financial Instruments (Fair Value of Derivative Instruments) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018	Jan. 31, 2019
Derivatives, Fair Value [Line Items]
Derivative assets	$ 6.4		$ 6.4		$ 8.5
Derivative liabilities	7.2		7.2		7.4
Foreign currency contracts | Designated as hedging instrument
Derivatives, Fair Value [Line Items]
Amount of (loss) gain recognized in accumulated other comprehensive loss on derivatives (effective portion)	(0.4)		2.7
Amount of (loss) gain recognized in accumulated other comprehensive loss on derivatives (effective portion)		$ 6.8		$ 20.1
Amount of gain (loss) reclassified from accumulated other comprehensive loss into income (loss) (effective portion)	2.9		7.0
Amount of gain (loss) reclassified from accumulated other comprehensive loss into income (loss) (effective portion)		(4.7)		(9.0)
Foreign currency contracts | Designated as hedging instrument | Prepaid expenses and other current assets
Derivatives, Fair Value [Line Items]
Derivative assets	2.4		2.4		4.3
Foreign currency contracts | Designated as hedging instrument | Other accrued liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	3.0		3.0		3.3
Foreign currency contracts | Derivatives not designated as hedging instruments | Prepaid expenses and other current assets
Derivatives, Fair Value [Line Items]
Derivative assets	4.0		4.0		4.2
Foreign currency contracts | Derivatives not designated as hedging instruments | Other accrued liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	4.2		4.2		$ 4.1
Net revenue | Foreign currency contracts | Designated as hedging instrument
Derivatives, Fair Value [Line Items]
Amount of gain (loss) reclassified from accumulated other comprehensive loss into income (loss) (effective portion)	4.9		13.4
Amount of gain (loss) reclassified from accumulated other comprehensive loss into income (loss) (effective portion)		(2.5)		(8.5)
Cost of revenue | Foreign currency contracts | Designated as hedging instrument
Derivatives, Fair Value [Line Items]
Amount of gain (loss) reclassified from accumulated other comprehensive loss into income (loss) (effective portion)	(0.4)		(0.7)
Amount of gain (loss) reclassified from accumulated other comprehensive loss into income (loss) (effective portion)		0.0		0.0
Operating expenses | Foreign currency contracts | Designated as hedging instrument
Derivatives, Fair Value [Line Items]
Amount of gain (loss) reclassified from accumulated other comprehensive loss into income (loss) (effective portion)	(1.6)		(5.7)
Amount of gain (loss) reclassified from accumulated other comprehensive loss into income (loss) (effective portion)		(2.2)		(0.5)
Interest and other expense, net | Foreign currency contracts | Designated as hedging instrument
Derivatives, Fair Value [Line Items]
Amount of (loss) gain recognized in (loss) income on derivatives (ineffective portion and amount excluded from effectiveness testing)	1.5		2.8
Amount of (loss) gain recognized in (loss) income on derivatives (ineffective portion and amount excluded from effectiveness testing)		0.9		1.4
Interest and other expense, net | Foreign currency contracts | Derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Amount and location of gain recognized on derivatives in net (loss) income	$ 1.5	$ 4.7	$ 3.2	$ 10.7