Segments (Segment Reporting Information) (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]
Net sales	$ 135,150	$ 122,136	$ 121,949	$ 116,526	$ 129,750	$ 117,176	$ 119,405	$ 114,986	$ 495,761	$ 481,317	$ 478,614
Operating income (loss)									20,437	22,764	24,105
Interest, net									(2,178)	(2,267)	(2,467)
Gain (loss) on extinguishment of debt									(3,136)	0	0
Income before income taxes									15,123	20,497	21,638
Total assets	204,522				198,825				204,522	198,825	199,581
Depreciation and amortization									10,529	10,080	9,454
Capital expenditures									10,051	10,619	11,477
Walmart U.S.
Segment Reporting Information [Line Items]
Net sales									318,477	307,833	298,378
Operating income (loss)									17,869	17,745	19,087
Total assets	104,347				104,262				104,347	104,262	103,109
Depreciation and amortization									3,655	3,298	2,800
Capital expenditures									5,680	6,090	6,728
Walmart International
Segment Reporting Information [Line Items]
Net sales									118,068	116,119	123,408
Operating income (loss)									5,352	5,758	5,346
Total assets	81,549				74,508				81,549	74,508	73,720
Depreciation and amortization									2,601	2,629	2,549
Capital expenditures									2,607	2,697	2,930
Sam's Club
Segment Reporting Information [Line Items]
Net sales									59,216	57,365	56,828
Operating income (loss)									982	1,671	1,820
Total assets	13,418				14,125				13,418	14,125	13,998
Depreciation and amortization									466	487	472
Capital expenditures									626	639	695
Corporate and support
Segment Reporting Information [Line Items]
Net sales									0	0	0
Operating income (loss)									(3,766)	(2,410)	(2,148)
Total assets	$ 5,208				$ 5,930				5,208	5,930	8,754
Depreciation and amortization									3,807	3,666	3,633
Capital expenditures									$ 1,138	$ 1,193	$ 1,124