Segments and Disaggregated Revenue (Revenue, Walmart US) (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 30, 2020	Apr. 30, 2019
Revenue from External Customer [Line Items]
Net sales	$ 133,672	$ 122,949
Walmart U.S.
Revenue from External Customer [Line Items]
Net sales	88,743	80,344
Walmart U.S. | Grocery
Revenue from External Customer [Line Items]
Net sales	52,835	46,153
Walmart U.S. | General merchandise
Revenue from External Customer [Line Items]
Net sales	25,476	24,406
Walmart U.S. | Health and wellness
Revenue from External Customer [Line Items]
Net sales	9,665	8,970
Walmart U.S. | Other categories
Revenue from External Customer [Line Items]
Net sales	$ 767	$ 815