Segment Information - Segment Operating Results from Continuing Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2019	Apr. 30, 2018
Segment Reporting Information [Line Items]
Net revenue	$ 7,150	$ 7,468	$ 14,703	$ 15,142
Segment earnings (loss) from operations	434	366	890	594
Intersegment net revenue and other
Segment Reporting Information [Line Items]
Net revenue	173	181	313	345
Operating Segment
Segment Reporting Information [Line Items]
Net revenue	7,323	7,649	15,016	15,487
Segment earnings (loss) from operations	713	691	1,446	1,342
Hybrid IT
Segment Reporting Information [Line Items]
Net revenue	5,469	5,721	11,301	11,721
Hybrid IT | Intersegment net revenue and other
Segment Reporting Information [Line Items]
Net revenue	167	172	305	330
Hybrid IT | Operating Segment
Segment Reporting Information [Line Items]
Net revenue	5,636	5,893	11,606	12,051
Segment earnings (loss) from operations	645	591	1,320	1,163
Intelligent Edge
Segment Reporting Information [Line Items]
Net revenue	662	699	1,349	1,351
Intelligent Edge | Intersegment net revenue and other
Segment Reporting Information [Line Items]
Net revenue	4	7	3	11
Intelligent Edge | Operating Segment
Segment Reporting Information [Line Items]
Net revenue	666	706	1,352	1,362
Segment earnings (loss) from operations	20	56	29	90
Financial Services
Segment Reporting Information [Line Items]
Net revenue	894	914	1,810	1,800
Financial Services | Intersegment net revenue and other
Segment Reporting Information [Line Items]
Net revenue	2	2	5	4
Financial Services | Operating Segment
Segment Reporting Information [Line Items]
Net revenue	896	916	1,815	1,804
Segment earnings (loss) from operations	77	72	154	143
Corporate Investments
Segment Reporting Information [Line Items]
Net revenue	125	134	243	270
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	125	134	243	270
Segment earnings (loss) from operations	$ (29)	$ (28)	$ (57)	$ (54)