Supplementary Financial Information - Disaggregation of revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2020	Jul. 31, 2019
Disaggregation of Revenue [Line Items]
Total net revenue	$ 14,294	$ 14,603	$ 41,381	$ 43,349
Americas
Disaggregation of Revenue [Line Items]
Total net revenue	6,229	6,574	17,393	18,391
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total net revenue	4,725	4,746	14,611	15,214
Asia-Pacific and Japan
Disaggregation of Revenue [Line Items]
Total net revenue	$ 3,340	$ 3,283	$ 9,377	$ 9,744