Segments and Disaggregated Revenue Revenue from Contract with Customer Excluding Assessed Tax, Walmart US (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Revenue from External Customer [Line Items]
Net sales	$ 126,981	$ 123,897	$ 379,318	$ 372,586
Walmart U.S.
Revenue from External Customer [Line Items]
Net sales	83,189	80,583	248,733	241,146
Walmart U.S. | Grocery
Revenue from External Customer [Line Items]
Net sales	47,845	46,183	140,936	136,034
Walmart U.S. | General merchandise
Revenue from External Customer [Line Items]
Net sales	25,196	24,838	77,269	76,317
Walmart U.S. | Health and wellness
Revenue from External Customer [Line Items]
Net sales	9,262	8,869	28,018	26,834
Walmart U.S. | Other categories
Revenue from External Customer [Line Items]
Net sales	$ 886	$ 693	$ 2,510	$ 1,961