Segments and Disaggregated Revenue Revenue from Contract with Customer Excluding Assessed Tax, International (Details) - Walmart International - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jul. 31, 2018	Jul. 31, 2018
Mexico and Central America [Member]
Revenue from External Customer [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 7,510	$ 15,194
United Kingdom
Revenue from External Customer [Line Items]
Revenue from contract with customer, excluding assessed tax	7,650	15,165
Canada [Member]
Revenue from External Customer [Line Items]
Revenue from contract with customer, excluding assessed tax	4,703	8,957
China [Member]
Revenue from External Customer [Line Items]
Revenue from contract with customer, excluding assessed tax	2,480	5,685
Other [Member]
Revenue from External Customer [Line Items]
Revenue from contract with customer, excluding assessed tax	7,111	14,713
Geographical, Total [Member]
Revenue from External Customer [Line Items]
Revenue from contract with customer, excluding assessed tax	29,454	59,714
eCommerceMember
Revenue from External Customer [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 1,000	$ 1,900