Segments and Disaggregated Revenue (Revenue from Contract with Customer Excluding Assessed Tax, Sam's Club) (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2019
Revenue from External Customer [Line Items]
Net sales	$ 555,233	$ 519,926	$ 510,329
Sams Club [Member]
Revenue from External Customer [Line Items]
Net sales	63,910	58,792	$ 57,839
Sams Club [Member] | E Commerce [Member]
Revenue from External Customer [Line Items]
Net sales	5,300	3,800
Grocery and consumables [Member] | Sams Club [Member]
Revenue from External Customer [Line Items]
Net sales	42,148	35,043
Fuel, tobacco, and other categories [Member] | Sams Club [Member]
Revenue from External Customer [Line Items]
Net sales	7,838	10,571
Home and apparel [Member] | Sams Club [Member]
Revenue from External Customer [Line Items]
Net sales	7,092	6,744
Health and Wellness [Member] | Sams Club [Member]
Revenue from External Customer [Line Items]
Net sales	3,792	3,372
Technology, offices, and entertainment [Member] | Sams Club [Member]
Revenue from External Customer [Line Items]
Net sales	$ 3,040	$ 3,062