Segments (Segment Revenues and Long-Lived Assets) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Segment Reporting Information [Line Items]
Total revenues	$ 136,267	$ 123,179	$ 123,355	$ 117,542	$ 130,936	$ 118,179	$ 120,854	$ 115,904	$ 500,343	$ 485,873	$ 482,130
Long-lived assets	114,818				114,178				114,818	114,178	116,516
United States
Segment Reporting Information [Line Items]
Total revenues									380,580	367,784	357,559
Long-lived assets	81,478				82,746				81,478	82,746	82,475
Walmart International
Segment Reporting Information [Line Items]
Total revenues									119,763	118,089	124,571
Long-lived assets	$ 33,340				$ 31,432				$ 33,340	$ 31,432	$ 34,041