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Long-term Debt Long-term Debt (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended 0 Months Ended
Apr. 30, 2015
Apr. 30, 2014
Apr. 01, 2015
Debt Instrument [Line Items]      
Repayments of Long-term Debt $ 915us-gaap_RepaymentsOfLongTermDebt $ 1,574us-gaap_RepaymentsOfLongTermDebt  
Unsecured Debt [Member] | 2.875% Debt, Due 2015 [Domain]      
Debt Instrument [Line Items]      
Repayments of Long-term Debt     $ 750us-gaap_RepaymentsOfLongTermDebt
/ us-gaap_DebtInstrumentAxis
= wmt_A2.875DebtDue2015Domain
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
Interest Rate     2.875%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= wmt_A2.875DebtDue2015Domain
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember