Segments and Disaggregated Revenue Revenue from Contract with Customer Excluding Assessed Tax, International (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 International
Revenue from External Customer [Line Items]
Net sales	29,139	29,454	57,914	59,714
Mexico and Central America | Walmart International
Revenue from External Customer [Line Items]
Net sales	8,014	7,510	15,852	15,194
United Kingdom | Walmart International
Revenue from External Customer [Line Items]
Net sales	7,316	7,650	14,393	15,165
Canada | Walmart International
Revenue from External Customer [Line Items]
Net sales	4,635	4,703	8,758	8,957
China | Walmart International
Revenue from External Customer [Line Items]
Net sales	2,428	2,480	5,491	5,685
Other | Walmart International
Revenue from External Customer [Line Items]
Net sales	$ 6,746	$ 7,111	$ 13,420	$ 14,713