Segment Information - Segment Assets (Details) - USD ($) $ in Millions	Jan. 31, 2018	Oct. 31, 2017
Segment Reporting Information [Line Items]
Assets	$ 61,619	$ 61,406
Operating Segment | Hybrid IT
Segment Reporting Information [Line Items]
Assets	26,085	25,923
Operating Segment | Intelligent Edge
Segment Reporting Information [Line Items]
Assets	2,986	3,002
Operating Segment | Financial Services
Segment Reporting Information [Line Items]
Assets	13,712	13,470
Operating Segment | Corporate Investments
Segment Reporting Information [Line Items]
Assets	152	161
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Assets	$ 18,684	$ 18,850