Segments and Disaggregated Revenue (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
Apr. 30, 2019	Apr. 30, 2018
Revenue from External Customer [Line Items]
Net sales	$ 122,949	$ 121,630
Walmart U.S.
Revenue from External Customer [Line Items]
Net sales	80,344	77,748
Walmart International
Revenue from External Customer [Line Items]
Net sales	28,775	30,260
Sam's Club
Revenue from External Customer [Line Items]
Net sales	13,830	13,622
eCommerceMember \| Walmart U.S.
Revenue from External Customer [Line Items]
Net sales	4,300	3,200
eCommerceMember \| Walmart International
Revenue from External Customer [Line Items]
Net sales	2,500	1,000
eCommerceMember \| Sam's Club
Revenue from External Customer [Line Items]
Net sales	$ 700	$ 600

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

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