Segments (Segment Reporting Information) (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
Segment Reporting Information [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
Walmart U.S.
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									331,666	318,477	307,833
Walmart International
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									120,824	118,068	116,119
Sam's Club
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									57,839	59,216	57,365
Corporate and support
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									0	$ 0	$ 0
Mexico and Central America [Member] | Walmart International
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									31,790
United Kingdom | Walmart International
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									30,547
CANADA | Walmart International
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									18,613
CHINA | Walmart International
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									10,702
Other [Member] | Walmart International
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									29,172
eCommerceMember | Walmart U.S.
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									15,700
eCommerceMember | Walmart International
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									6,700
eCommerceMember | Sam's Club
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									$ 2,700