Investments - Effect of Derivative Instruments Not Designated as Hedging Instruments on Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended
Apr. 30, 2016	Apr. 30, 2015
Derivatives not designated as hedging instruments \| Foreign currency derivative contracts \| Other income (expense)
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) on Derivative Instruments Recognized in Income	$ (1,442)	$ 11,459

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a),(c),(d),(e)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration