Accumulated Other Comprehensive Loss (Composition of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	12 Months Ended
Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances - beginning of period	$ (10,181)	$ (14,232)	$ (11,597)
Adoption of new accounting standard, effect of adoption, AOCI	(1,436)
Other comprehensive income (loss) before reclassifications	(2,067)	3,960	(2,670)
Amounts reclassified from accumulated other comprehensive income (loss)	2,142	91	35
Balances - end of period	(11,542)	(10,181)	(14,232)
Currency translation and other
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances - beginning of period	(12,136)	(14,507)	(11,690)
Adoption of new accounting standard, effect of adoption, AOCI	89
Other comprehensive income (loss) before reclassifications	(2,093)	2,345	(2,817)
Amounts reclassified from accumulated other comprehensive income (loss)	2,055	26	0
Balances - end of period	(12,085)	(12,136)	(14,507)
Net investment hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances - beginning of period	1,030	1,435	1,022
Adoption of new accounting standard, effect of adoption, AOCI	93
Other comprehensive income (loss) before reclassifications	272	(405)	413
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0
Balances - end of period	1,395	1,030	1,435
Unrealized gain on available-for-sale securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances - beginning of period	1,646	145	0
Adoption of new accounting standard, effect of adoption, AOCI	(1,646)
Other comprehensive income (loss) before reclassifications	0	1,501	145
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0
Balances - end of period	0	1,646	145
Cash flow hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances - beginning of period	122	(315)	(336)
Adoption of new accounting standard, effect of adoption, AOCI	28
Other comprehensive income (loss) before reclassifications	(339)	436	(22)
Amounts reclassified from accumulated other comprehensive income (loss)	49	1	43
Balances - end of period	(140)	122	(315)
Minimum pension liability
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances - beginning of period	(843)	(990)	(593)
Adoption of new accounting standard, effect of adoption, AOCI	0
Other comprehensive income (loss) before reclassifications	93	83	(389)
Amounts reclassified from accumulated other comprehensive income (loss)	38	64	(8)
Balances - end of period	(712)	$ (843)	$ (990)
Walmart Brazil [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Disposal Group, Including Discontinued Operation, Foreign Currency Translation Gains (Losses)	$ 2,000

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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Amount of foreign currency translation gain (loss) in the disposal group, including discontinued operation, recognized in the statement of income as a result of the sale or complete or substantially complete liquidation of an investment in a foreign entity.

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Amount after tax, before reclassification adjustments of other comprehensive income (loss).

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Amount after tax of reclassification adjustments of other comprehensive income (loss).

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Adoption of new accounting standard, AOCI

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