Segments and Disaggregated Revenue Revenue from Contract with Customer Excluding Assessed Tax, Walmart US (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 31, 2018
Revenue from External Customer [Line Items]
Net sales	$ 129,388	$ 127,059	$ 252,337	$ 248,689
Walmart U.S.
Revenue from External Customer [Line Items]
Net sales	85,200	82,815	165,544	160,563
Walmart U.S. | Grocery
Revenue from External Customer [Line Items]
Net sales	47,687	45,991	93,091	89,851
Walmart U.S. | General merchandise
Revenue from External Customer [Line Items]
Net sales	27,466	27,305	52,073	51,479
Walmart U.S. | Health and wellness
Revenue from External Customer [Line Items]
Net sales	9,238	8,837	18,756	17,965
Walmart U.S. | Other categories
Revenue from External Customer [Line Items]
Net sales	$ 809	$ 682	$ 1,624	$ 1,268