Goodwill and Intangible Assets (Details 2)	3 Months Ended								12 Months Ended
	Oct. 31, 2018 USD ($)	Jul. 31, 2018 USD ($)	Apr. 30, 2018 USD ($)	Jan. 31, 2018 USD ($)	Oct. 31, 2017 USD ($)	Jul. 31, 2017 USD ($)	Apr. 30, 2017 USD ($)	Jan. 31, 2017 USD ($)	Oct. 31, 2018 USD ($) segment	Oct. 31, 2017 USD ($)	Oct. 31, 2016 USD ($)	Nov. 01, 2017 segment
Intangible assets
Number of reportable segments | segment									4
Number of reportable segments after realignment | segment												2
Goodwill impairment loss									$ 88,000,000
Goodwill	$ 17,537,000,000				$ 17,516,000,000				17,537,000,000	$ 17,516,000,000	$ 16,090,000,000
Intangible assets, gross	1,498,000,000				1,563,000,000				1,498,000,000	1,563,000,000
Amortizable intangible assets, accumulated amortization	(709,000,000)				(521,000,000)				(709,000,000)	(521,000,000)
Amortizable intangible assets, net	771,000,000								771,000,000
Total Intangible Assets- Net	789,000,000				1,042,000,000				789,000,000	1,042,000,000
Gross intangible assets acquired									41,000,000	688,000,000
Amount of fully amortized intangible assets									106,000,000	384,000,000
Amortization of intangible assets	72,000,000	$ 72,000,000	$ 72,000,000	$ 78,000,000	86,000,000	$ 97,000,000	$ 72,000,000	$ 66,000,000	294,000,000	321,000,000	272,000,000
In-process research and development
Intangible assets
Amortizable intangible assets, gross	18,000,000				75,000,000				18,000,000	75,000,000
Amortizable intangible assets, net	18,000,000				75,000,000				18,000,000	75,000,000
Customer contracts, customer lists and distribution agreements
Intangible assets
Amortizable intangible assets, gross	272,000,000				268,000,000				272,000,000	268,000,000
Amortizable intangible assets, accumulated amortization	(142,000,000)				(71,000,000)				(142,000,000)	(71,000,000)
Amortizable intangible assets, net	130,000,000				197,000,000				$ 130,000,000	197,000,000
Weighted-Average Remaining Useful Lives									4 years
Developed and core technology and patents
Intangible assets
Amortizable intangible assets, gross	1,121,000,000				1,133,000,000				$ 1,121,000,000	1,133,000,000
Amortizable intangible assets, accumulated amortization	(525,000,000)				(427,000,000)				(525,000,000)	(427,000,000)
Amortizable intangible assets, net	596,000,000				706,000,000				$ 596,000,000	706,000,000
Weighted-Average Remaining Useful Lives									4 years
Developed and core technology and patents | In-process research and development
Intangible assets
Reclassified	57,000,000				10,000,000				$ 57,000,000	10,000,000
Trade name and trade marks
Intangible assets
Amortizable intangible assets, gross	87,000,000				87,000,000				87,000,000	87,000,000
Amortizable intangible assets, accumulated amortization	(42,000,000)				(23,000,000)				(42,000,000)	(23,000,000)
Amortizable intangible assets, net	45,000,000				64,000,000				$ 45,000,000	64,000,000
Weighted-Average Remaining Useful Lives									4 years
Hybrid IT
Intangible assets
Goodwill impairment loss									$ 88,000,000
Goodwill	15,472,000,000				$ 15,454,000,000				15,472,000,000	15,454,000,000	14,045,000,000
CMS Reporting Unit [Member]
Intangible assets
Goodwill impairment loss									88,000,000	$ 0	$ 0
Goodwill	$ 0								$ 0