Operating Income by Segment, Interest, Net, and Unrealized (Gains) and Losses (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2018	Jul. 31, 2017
Segment Reporting Information [Line Items]
Nonoperating Income (Expense)	$ 4,849	$ 0	$ 6,694	$ 0
Operating income (loss):	5,750	5,969	10,904	11,206
Interest, net	503	575	990	1,138
Income before income taxes	398	4,606	3,220	9,280
Walmart U.S.
Segment Reporting Information [Line Items]
Operating income (loss):	4,479	4,417	8,406	8,469
Walmart International
Segment Reporting Information [Line Items]
Operating income (loss):	1,269	1,568	2,534	2,707
Sam's Club
Segment Reporting Information [Line Items]
Operating income (loss):	402	391	727	790
Corporate and support
Segment Reporting Information [Line Items]
Operating income (loss):	$ (400)	$ (407)	$ (763)	$ (760)

Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h)(1)(i))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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The net amount of operating interest income (expense).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.10)
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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The aggregate amount of income or expense from ancillary business-related activities (that is to say, excluding major activities considered part of the normal operations of the business).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.7)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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The net result for the period of deducting operating expenses from operating revenues.

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No definition available.

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