Equity Method Investments (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2016	May 31, 2016
Schedule of Equity Method Investments [Line Items]
Investments in equity interests	$ 2,398				$ 2,535				$ 2,398	$ 2,535
(Loss) earnings from equity interests	15	$ 11	$ (10)	$ 22	1	$ 1	$ (3)	$ (22)	38	(23)	$ (76)
Equity Method Investee | H3C
Schedule of Equity Method Investments [Line Items]
Sales to related party									1,300	1,200	500
Purchases from related party									273	331	169
Payable to H3C	43				64				43	64
H3C
Schedule of Equity Method Investments [Line Items]
Investments in equity interests	$ 2,400				$ 2,500				$ 2,400	2,500
Ownership	49.00%								49.00%
Cash dividend									$ 164	98
Basis difference												$ 2,534
Equity method goodwill												1,674
Intangible assets												749
In-process research and development												188
Deferred tax liabilities												(152)
Other												$ 75
Weighted-average useful life									5 years
(Loss) earnings from equity interests									$ 38	(23)	(76)
Investment's earnings									192	127	32
Amortization of difference in basis									151	155	93
Elimination of intra-entity sales									$ 3	$ 5	$ 15