Acquisitions, Disposals and Related Items Acquisitions, Disposals and Related Items (Details) - USD ($)				3 Months Ended		6 Months Ended
	Apr. 04, 2017	Sep. 09, 2016	Jun. 01, 2016	Jul. 31, 2017	Oct. 31, 2016	Jul. 31, 2017	Jul. 31, 2016	Jan. 31, 2017	Sep. 19, 2016
Significant Acquisitions and Disposals [Line Items]
Business acquisitions, net of cash acquired						$ 363,000,000	$ 0
Goodwill				$ 18,037,000,000		18,037,000,000	16,339,000,000	$ 17,037,000,000
Proceeds from the disposal of certain operations						$ 1,012,000,000	$ 0
JD.com [Member]
Significant Acquisitions and Disposals [Line Items]
Purchase of available for sale securities					$ 1,900,000,000
Noncash or Part Noncash Acquisition, Interest Acquired					5.00%
Aggregate Ownership, Percent				10.00%		10.00%
Suburbia [Member]
Significant Acquisitions and Disposals [Line Items]
Proceeds from the disposal of certain operations	$ 1,000,000,000
Gain (Loss) on Disposition of Business, Including Deferred Portion	746,000,000
Gain (Loss) on Disposition of Business	387,000,000
Gain (Loss) on Disposition of Business, Deferred Portion	$ 300,000,000
Gain Deferral Period				20 years
Yihaodian [Member]
Significant Acquisitions and Disposals [Line Items]
Noncash or Part Noncash Divestiture, Type of Consideration Received			Class A ordinary shares
Available-for-sale Securities, Percent							5.00%
Noncash or Part Noncash Divestiture, Amount of Consideration Received			$ 1,500,000,000
Gain (Loss) on Disposition of Assets			$ 535,000,000
Jet.com [Member]
Significant Acquisitions and Disposals [Line Items]
Business acquisitions, net of cash acquired		$ 2,400,000,000
Goodwill									$ 1,700,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill									600,000,000
Additional compensation over five year period									$ 800,000,000