Segments and Disaggregated Revenue (Revenue, Walmart US) (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 30, 2021	Apr. 30, 2020
Revenue from External Customer [Line Items]
Net sales	$ 137,159	$ 133,672
Walmart U.S.
Revenue from External Customer [Line Items]
Net sales	93,167	88,743
Walmart U.S. | Grocery
Revenue from External Customer [Line Items]
Net sales	51,391	52,921
Walmart U.S. | General merchandise
Revenue from External Customer [Line Items]
Net sales	30,607	25,466
Walmart U.S. | Health and wellness
Revenue from External Customer [Line Items]
Net sales	9,970	9,600
Walmart U.S. | Other categories
Revenue from External Customer [Line Items]
Net sales	$ 1,199	$ 756