Derivative Instruments - Gains (losses) Associated with Foreign Currency Forward Contracts (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reclassified from OCI into income (effective portion)	$ 16,375	$ 6,693	$ 50,712	$ (17,912)
Derivative instruments, gain (loss) expected to be reclassified from accumulated OCI within the next 12 months			400
Other income (expense), net
Derivative Instruments, Gain (Loss) [Line Items]
Foreign currency forward contracts not designated as hedges	2,488	829	6,166	(1,796)
Designated as Hedging Instrument \| Revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reclassified from OCI into income (effective portion)	(2,373)	679	(5,450)	1,386
Designated as Hedging Instrument \| Other income (expense), net
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in income (amount excluded from effectiveness testing and ineffective portion)	2,700	350	8,958	1,740
Designated as Hedging Instrument \| Net change in market value of effective foreign currency forward exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in OCI (effective portion)	$ 16,341	$ 7,372	$ 52,506	$ (16,526)

The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

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Amount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of foreign currency derivatives not designated as hedging instruments.

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Amount, after tax and reclassification, of gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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