Segment Information - Segment Operating Results from Continuing Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017
Segment Reporting Information [Line Items]
Net revenue	$ 7,468	$ 6,808	$ 15,142	$ 13,710
Segment earnings (loss) from continuing operations	397	195	658	648
Intersegment net revenue and other
Segment Reporting Information [Line Items]
Net revenue	181	307	345	553
Operating Segment
Segment Reporting Information [Line Items]
Net revenue	7,649	7,115	15,487	14,263
Segment earnings (loss) from continuing operations	717	552	1,394	1,344
Hybrid IT
Segment Reporting Information [Line Items]
Net revenue	5,851	5,348	12,027	10,884
Hybrid IT | Intersegment net revenue and other
Segment Reporting Information [Line Items]
Net revenue	172	289	327	508
Hybrid IT | Operating Segment
Segment Reporting Information [Line Items]
Net revenue	6,023	5,637	12,354	11,392
Segment earnings (loss) from continuing operations	621	457	1,229	1,190
Intelligent Edge
Segment Reporting Information [Line Items]
Net revenue	703	595	1,316	1,157
Intelligent Edge | Intersegment net revenue and other
Segment Reporting Information [Line Items]
Net revenue	7	11	14	19
Intelligent Edge | Operating Segment
Segment Reporting Information [Line Items]
Net revenue	710	606	1,330	1,176
Segment earnings (loss) from continuing operations	46	46	64	62
Financial Services
Segment Reporting Information [Line Items]
Net revenue	914	865	1,800	1,669
Financial Services | Intersegment net revenue and other
Segment Reporting Information [Line Items]
Net revenue	2	7	4	26
Financial Services | Operating Segment
Segment Reporting Information [Line Items]
Net revenue	916	872	1,804	1,695
Segment earnings (loss) from continuing operations	72	77	144	153
Corporate Investments
Segment Reporting Information [Line Items]
Net revenue	0	0	(1)	0
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	0	0	(1)	0
Segment earnings (loss) from continuing operations	$ (22)	$ (28)	$ (43)	$ (61)