Derivatives - Effect of Derivative Instruments Not Designated as Hedging Instruments on Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 31, 2018
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	$ (35)	$ (10)	$ 1	$ 10

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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959

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