Segments and Disaggregated Revenue (Revenue, Walmart US) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2020	Jul. 31, 2019
Revenue from External Customer [Line Items]
Net sales	$ 136,824	$ 129,388	$ 270,496	$ 252,337
Walmart U.S.
Revenue from External Customer [Line Items]
Net sales	93,282	85,200	182,025	165,544
Walmart U.S. | Grocery
Revenue from External Customer [Line Items]
Net sales	51,545	48,196	104,466	94,395
Walmart U.S. | General merchandise
Revenue from External Customer [Line Items]
Net sales	31,682	27,246	57,148	51,637
Walmart U.S. | Health and wellness
Revenue from External Customer [Line Items]
Net sales	9,154	8,949	18,754	17,888
Walmart U.S. | Other categories
Revenue from External Customer [Line Items]
Net sales	$ 901	$ 809	$ 1,657	$ 1,624