Financial Instruments - Fair Value of Derivative Instruments (Detail) - USD ($) $ in Millions	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Derivatives, Fair Value [Line Items]
Notional amount of foreign currency forward contracts not designated as cash flow hedges	$ 619.9	$ 369.4
Net loss expected to be recognized into earnings	(256.0)	733.6	$ 1,619.6	$ 2,219.2
Derivative asset, net	8.2	13.3
Derivative liability, net	26.6	10.5
Net Unrealized Gains (Losses) on Derivative Instruments
Derivatives, Fair Value [Line Items]
Net loss expected to be recognized into earnings	(16.6)	14.6	$ 15.7
Foreign Exchange Contracts
Derivatives, Fair Value [Line Items]
Notional amount of foreign currency forward contracts not designated as cash flow hedges	329.6	270.6
Designated as Hedging Instrument | Foreign Exchange Contracts | Prepaid expenses and other current assets
Derivatives, Fair Value [Line Items]
Derivative asset, net	6.2	10.1
Designated as Hedging Instrument | Foreign Exchange Contracts | Other Accrued Liabilities
Derivatives, Fair Value [Line Items]
Derivative liability, net	18.7	4.5
Not Designated as Hedging Instrument | Other assets
Derivatives, Fair Value [Line Items]
Derivative asset, net	2.0	3.2
Not Designated as Hedging Instrument | Other Accrued Liabilities
Derivatives, Fair Value [Line Items]
Derivative liability, net	$ 7.9	$ 6.0