Supplementary Financial Information - Disaggregation of revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2020	Apr. 30, 2019
Disaggregation of Revenue [Line Items]
Total net revenue	$ 12,469	$ 14,036	$ 27,087	$ 28,746
Americas
Disaggregation of Revenue [Line Items]
Total net revenue	5,205	5,785	11,164	11,817
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total net revenue	4,654	5,110	9,886	10,468
Asia-Pacific and Japan
Disaggregation of Revenue [Line Items]
Total net revenue	$ 2,610	$ 3,141	$ 6,037	$ 6,461