Segment Net Sales (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Segment Reporting Information [Line Items]
Net sales	$ 122,136	$ 117,176	$ 360,611	$ 351,567
Walmart U.S.
Segment Reporting Information [Line Items]
Net sales	77,724	74,550	231,898	224,086
Walmart International
Segment Reporting Information [Line Items]
Net sales	29,548	28,390	84,976	85,094
Sam's Club
Segment Reporting Information [Line Items]
Net sales	$ 14,864	$ 14,236	$ 43,737	$ 42,387