Segment Information - Segment Operating Results from Continuing Operations (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 31, 2018
Segment Reporting Information [Line Items]
Net revenue	$ 7,217	$ 7,764	$ 21,920	$ 22,906
Segment earnings (loss) from operations	(76)	490	814	1,084
Intersegment net revenue and other
Segment Reporting Information [Line Items]
Net revenue	(112)	(192)	(425)	(537)
Operating Segment
Segment Reporting Information [Line Items]
Net revenue	7,329	7,956	22,345	23,443
Segment earnings (loss) from operations	793	772	2,239	2,114
Hybrid IT
Segment Reporting Information [Line Items]
Net revenue	5,444	5,925	16,745	17,649
Hybrid IT | Intersegment net revenue and other
Segment Reporting Information [Line Items]
Net revenue	(105)	(184)	(410)	(511)
Hybrid IT | Operating Segment
Segment Reporting Information [Line Items]
Net revenue	5,549	6,109	17,155	18,160
Segment earnings (loss) from operations	704	624	2,024	1,787
Intelligent Edge
Segment Reporting Information [Line Items]
Net revenue	758	783	2,107	2,132
Intelligent Edge | Intersegment net revenue and other
Segment Reporting Information [Line Items]
Net revenue	(4)	(2)	(7)	(15)
Intelligent Edge | Operating Segment
Segment Reporting Information [Line Items]
Net revenue	762	785	2,114	2,147
Segment earnings (loss) from operations	37	101	66	191
Financial Services
Segment Reporting Information [Line Items]
Net revenue	885	922	2,695	2,721
Financial Services | Intersegment net revenue and other
Segment Reporting Information [Line Items]
Net revenue	(3)	(6)	(8)	(11)
Financial Services | Operating Segment
Segment Reporting Information [Line Items]
Net revenue	888	928	2,703	2,732
Segment earnings (loss) from operations	77	72	231	215
Corporate Investments
Segment Reporting Information [Line Items]
Net revenue	130	134	373	404
Corporate Investments | Intersegment net revenue and other
Segment Reporting Information [Line Items]
Net revenue	0	0	0	0
Corporate Investments | Operating Segment
Segment Reporting Information [Line Items]
Net revenue	130	134	373	404
Segment earnings (loss) from operations	$ (25)	$ (25)	$ (82)	$ (79)