Segments and Disaggregated Revenue Revenue from Contract with Customer Excluding Assessed Tax, Sam's Club (Details) - Sam's Club - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jul. 31, 2018	Jul. 31, 2018
Grocery and consumables [Member]
Revenue from External Customer [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 8,585	$ 16,597
Fuel, tobacco, and other categories [Member]
Revenue from External Customer [Line Items]
Revenue from contract with customer, excluding assessed tax	3,261	6,180
Home and apparel [Member]
Revenue from External Customer [Line Items]
Revenue from contract with customer, excluding assessed tax	1,398	2,600
Health and wellness [Member]
Revenue from External Customer [Line Items]
Revenue from contract with customer, excluding assessed tax	789	1,590
Technology, offices, and entertainment [Member]
Revenue from External Customer [Line Items]
Revenue from contract with customer, excluding assessed tax	757	1,445
Product and services, total [Member]
Revenue from External Customer [Line Items]
Revenue from contract with customer, excluding assessed tax	14,790	28,412
eCommerceMember
Revenue from External Customer [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 700	$ 1,200