Segments (Segment Revenues and Long-Lived Assets) (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]
Total revenues	$ 138,793	$ 124,894	$ 128,028	$ 122,690	$ 136,267	$ 123,179	$ 123,355	$ 117,542	$ 514,405	$ 500,343	$ 485,873
Long-lived assets	111,395				114,818				111,395	114,818	114,178
United States
Segment Reporting Information [Line Items]
Total revenues									392,265	380,580	367,784
Long-lived assets	81,144				81,478				81,144	81,478	82,746
Walmart International
Segment Reporting Information [Line Items]
Total revenues									122,140	119,763	118,089
Long-lived assets	$ 30,251				$ 33,340				$ 30,251	$ 33,340	$ 31,432