Acquisitions, Disposals, and Related Items Acquisitions, Disposals, and Related Items (Details) $ in Millions, £ in Billions, R$ in Billions						12 Months Ended
	Aug. 18, 2018 USD ($)	Apr. 30, 2018 GBP (£)	Apr. 04, 2017 USD ($)	Sep. 09, 2016 USD ($)	Jun. 01, 2016 USD ($)	Jan. 31, 2019 USD ($)	Jan. 31, 2018 USD ($)	Jan. 31, 2017 USD ($)	Aug. 01, 2018 USD ($)	Aug. 01, 2018 BRL (R$)	Sep. 19, 2016 USD ($)
Business Acquisition [Line Items]
Gain (Loss) on Disposition of Business						$ (4,850)	$ 0	$ 0
Goodwill						31,181	18,242	17,037
Finite-Lived Intangible Asset, Useful Life	3 years
Proceeds from the disposal of certain operations						876	1,046	662
Payments to Acquire Available-for-sale Securities						0	0	1,901
Payments to Acquire Businesses, Net of Cash Acquired						14,656	375	2,463
Flipkart [Member]
Business Acquisition [Line Items]
Aggregate Ownership, Percent	81.00%
Diluted Ownership, Percent	77.00%
Payments to Acquire Businesses, Gross	$ 16,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	24,100
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	2,200
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other	2,800
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	5,000
Goodwill	13,600
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets	4,700
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	300
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	3,700
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities	1,800
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities	1,800
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value	$ 4,300
Jet.com [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill											$ 600
Goodwill											1,700
Payments to Acquire Businesses, Net of Cash Acquired				$ 2,400
Additional compensation as part of transaction											$ 800
Walmart Brazil [Member]
Business Acquisition [Line Items]
Ownership Sold, Percent									80.00%	80.00%
Disposal Group, Including Discontinued Operation, Consideration									$ 250
Disposal Group, Including Discontinued Operation, Assets									3,300
Disposal Group, Including Discontinued Operation, Liabilities									1,300
Disposal Group, Including Discontinued Operation, Accounts Payable and Accrued Liabilities, Current									700
Disposal Group, Including Discontinued Operation, Other Liabilities, Current									100
Disposal Group, Including Discontinued Operation, Deferred Tax Liabilities									500
Disposal Group, Including Discontinued Operation, Foreign Currency Translation Gains (Losses)						2,000
Gain (Loss) on Disposition of Business						$ (4,800)
Guarantor Obligations, Current Carrying Value									$ 800
Guarantor Obligations, Maximum Exposure, Undiscounted | R$										R$ 2.3
Equity Method Investment, Ownership Percentage									20.00%	20.00%
Suburbia [Member]
Business Acquisition [Line Items]
Gain (Loss) on Disposition of Business							$ 400
Proceeds from the disposal of certain operations			$ 1,000
Gain (Loss) on Disposition of Business, Including Deferred Portion			$ 700
Gain Deferral Period			20 years
Yihaodian [Member]
Business Acquisition [Line Items]
Noncash or Part Noncash Divestiture, Type of Consideration Received					Class A ordinary shares
Noncash or Part Noncash Divestiture, Amount of Consideration Received					$ 1,500
Available for Sale Securities, Percent					5.00%
Gain (Loss) on Disposition of Assets								$ 535
Asda [Member]
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage		42.00%
Proceeds from the disposal of certain operations | £		£ 3
JD.com [Member]
Business Acquisition [Line Items]
Diluted Ownership, Percent								10.00%
Payments to Acquire Available-for-sale Securities								$ 1,900
Noncash or Part Noncash Acquisition, Interest Acquired								5.00%