Segments Revenue from Contract with Customer Excluding Assessed Tax, Sam's Club (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017
Revenue from External Customer [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 137,743	$ 123,897	$ 127,059	$ 121,630	$ 135,150	$ 122,136	$ 121,949	$ 116,526	$ 510,329	$ 495,761	$ 481,317
Sam's Club
Revenue from External Customer [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									57,839	$ 59,216	$ 57,365
Sam's Club | eCommerceMember
Revenue from External Customer [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									2,700
Grocery and consumables [Member] | Sam's Club
Revenue from External Customer [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									33,708
Fuel, tobacco, and other categories [Member] | Sam's Club
Revenue from External Customer [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									12,110
Home and apparel [Member] | Sam's Club
Revenue from External Customer [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									5,452
Technology, offices, and entertainment [Member] | Sam's Club
Revenue from External Customer [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									3,388
Health and Wellness [Member] | Sam's Club
Revenue from External Customer [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									$ 3,181