Segments and Disaggregated Revenue (Operating Income by Segment, Interest, Net, and Unrealized (Gains) and Losses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Segment Reporting Information [Line Items]
Operating income	$ 5,778	$ 4,718	$ 17,061	$ 15,246
Interest, net	516	589	1,700	1,799
Other (gains) and losses	(1,853)	(244)	(5,796)	(996)
Income before income taxes	7,115	4,373	21,157	14,443
Walmart U.S.
Segment Reporting Information [Line Items]
Operating income	4,589	4,176	13,948	12,977
Walmart International
Segment Reporting Information [Line Items]
Operating income	1,078	634	2,696	2,265
Sam's Club
Segment Reporting Information [Line Items]
Operating income	431	327	1,517	1,258
Corporate and support
Segment Reporting Information [Line Items]
Operating income	$ (320)	$ (419)	$ (1,100)	$ (1,254)