Segments and Disaggregated Revenue (Revenue, Sam's Club) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2021	Jul. 31, 2020	Jul. 31, 2021	Jul. 31, 2020
Revenue from External Customer [Line Items]
Net sales	$ 139,871	$ 136,824	$ 277,030	$ 270,496
Sam's Club
Revenue from External Customer [Line Items]
Net sales	18,644	16,375	35,336	31,538
Sam's Club | eCommerceMember
Revenue from External Customer [Line Items]
Net sales	1,600	1,300	3,200	2,300
Sam's Club | Grocery and consumables
Revenue from External Customer [Line Items]
Net sales	12,014	10,715	22,683	21,076
Sam's Club | Fuel, tobacco and other categories
Revenue from External Customer [Line Items]
Net sales	2,816	2,068	5,115	4,081
Sam's Club | Home and apparel
Revenue from External Customer [Line Items]
Net sales	2,194	1,953	4,276	3,233
Sam's Club | Health and wellness
Revenue from External Customer [Line Items]
Net sales	956	931	1,897	1,832
Sam's Club | Technology, office and entertainment
Revenue from External Customer [Line Items]
Net sales	$ 664	$ 708	$ 1,365	$ 1,316