Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jul. 31, 2017	Jul. 31, 2017
Foreign currency forward contracts [Member]
Foreign Currency Fair Value Hedge Derivative [Line Items]
Foreign currency losses recognized	$ 2.2	$ 2.8

Amount of gain (loss) from the increase (decrease) in fair value of foreign currency derivatives and nonderivative instruments designated as fair value hedging instruments which were recognized in earnings, net of offsets by the gain (loss) on the hedged item to the extent that the fair value hedge was determined to be effective.

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=84234895&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)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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