Fair Value of Financial Instruments - Additional Information (Detail) - USD ($) $ in Billions	Jul. 31, 2017	Jan. 31, 2017	Jul. 31, 2016	Jan. 31, 2016
Debt Disclosure [Abstract]
The total carrying value of short-term borrowings and long-term debt	$ 1.1	$ 1.1	$ 1.1	$ 1.1
Total fair value of short-term borrowings and long-term debt	$ 1.1		$ 1.1

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13433-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13476-108611

Name:	us-gaap_DebtInstrumentFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant