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Derivative Instruments - Gains (losses) Associated with Foreign Currency Forward Contracts (Detail) - USD ($)
$ in Thousands
3 Months Ended
Apr. 30, 2018
Apr. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]    
Derivative instruments, gain (loss) expected to be reclassified from accumulated OCI within the next 12 months $ (9,000)  
Other income (expense), net    
Derivative Instruments, Gain (Loss) [Line Items]    
Foreign currency forward contracts not designated as hedges 1,794 $ (6)
Designated as Hedging Instrument | Revenues    
Derivative Instruments, Gain (Loss) [Line Items]    
Gains (losses) reclassified from OCI into income (effective portion) (1,117) 234
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) 2,231 623
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) $ 18,274 $ (975)