Segments and Disaggregated Revenue (Revenue, Walmart US) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Revenue from External Customer [Line Items]
Net sales	$ 133,752	$ 126,981	$ 404,248	$ 379,318
Walmart U.S.
Revenue from External Customer [Line Items]
Net sales	88,353	83,189	270,378	248,733
Walmart U.S. | Grocery
Revenue from External Customer [Line Items]
Net sales	50,683	48,117	155,149	142,511
Walmart U.S. | General merchandise
Revenue from External Customer [Line Items]
Net sales	26,927	24,964	84,075	76,602
Walmart U.S. | Health and wellness
Revenue from External Customer [Line Items]
Net sales	9,806	9,225	28,560	27,113
Walmart U.S. | Other categories
Revenue from External Customer [Line Items]
Net sales	$ 937	$ 883	$ 2,594	$ 2,507