Segment Information - Segment Operating Results from Continuing Operations (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2018	Jul. 31, 2017
Segment Reporting Information [Line Items]
Net revenue	$ 7,764	$ 7,501	$ 22,906	$ 21,211
Segment earnings (loss) from continuing operations	516	201	1,174	849
Intersegment net revenue and other
Segment Reporting Information [Line Items]
Net revenue	192	187	537	740
Operating Segment
Segment Reporting Information [Line Items]
Net revenue	7,956	7,688	23,443	21,951
Segment earnings (loss) from continuing operations	801	631	2,195	1,975
Hybrid IT
Segment Reporting Information [Line Items]
Net revenue	6,058	5,898	18,086	16,782
Hybrid IT | Intersegment net revenue and other
Segment Reporting Information [Line Items]
Net revenue	185	182	511	690
Hybrid IT | Operating Segment
Segment Reporting Information [Line Items]
Net revenue	6,243	6,080	18,597	17,472
Segment earnings (loss) from continuing operations	661	482	1,890	1,672
Intelligent Edge
Segment Reporting Information [Line Items]
Net revenue	784	707	2,100	1,864
Intelligent Edge | Intersegment net revenue and other
Segment Reporting Information [Line Items]
Net revenue	1	4	15	23
Intelligent Edge | Operating Segment
Segment Reporting Information [Line Items]
Net revenue	785	711	2,115	1,887
Segment earnings (loss) from continuing operations	91	104	155	166
Financial Services
Segment Reporting Information [Line Items]
Net revenue	922	896	2,721	2,565
Financial Services | Intersegment net revenue and other
Segment Reporting Information [Line Items]
Net revenue	6	1	11	27
Financial Services | Operating Segment
Segment Reporting Information [Line Items]
Net revenue	928	897	2,732	2,592
Segment earnings (loss) from continuing operations	73	69	217	222
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	$ (24)	$ (24)	$ (67)	$ (85)