Segments and Disaggregated Revenue Revenue from Contract with Customer Excluding Assessed Tax, Walmart US (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 30, 2019	Apr. 30, 2018
Revenue from External Customer [Line Items]
Net sales	$ 122,949	$ 121,630
Walmart U.S.
Revenue from External Customer [Line Items]
Net sales	80,344	77,748
Walmart U.S. | Grocery
Revenue from External Customer [Line Items]
Net sales	45,404	43,860
Walmart U.S. | General merchandise
Revenue from External Customer [Line Items]
Net sales	24,607	24,174
Walmart U.S. | Health and wellness
Revenue from External Customer [Line Items]
Net sales	9,518	9,128
Walmart U.S. | Other categories
Revenue from External Customer [Line Items]
Net sales	815	586
eCommerceMember | Walmart U.S.
Revenue from External Customer [Line Items]
Net sales	$ 4,300	$ 3,200