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Commitments (Details) - USD ($) $ in Billions | 12 Months Ended
--- | ---
Jan. 31, 2018 | Jan. 31, 2017 | Jan. 31, 2016
Commitments Disclosure [Abstract] |  |  |
Operating leases, rent expense | $ 2.9 | $ 2.6 | $ 2.5

X
- Definition Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line. + References No definition available. + Details
Name: | us-gaap_LeaseAndRentalExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Commitments Disclosure [Abstract] + References No definition available. + Details
Name: | wmt_CommitmentsDisclosureAbstract
Namespace Prefix: | wmt_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration