Restructuring and Other Charges - Narrative (Details) $ in Millions			12 Months Ended
	Sep. 30, 2019 USD ($) employee	Oct. 10, 2016 USD ($) employee	Oct. 31, 2019 USD ($)	Oct. 31, 2018 USD ($)	Oct. 31, 2017 USD ($)
Restructuring Cost and Reserve [Line Items]
Other charges			$ 28	$ 33	$ 135
Fiscal 2020 Plan
Restructuring Cost and Reserve [Line Items]
Estimated pre-tax charges	$ 1,000
Fiscal 2017 Plan
Restructuring Cost and Reserve [Line Items]
Expected number of positions to be eliminated | employee		5,300
Severance | Fiscal 2017 Plan
Restructuring Cost and Reserve [Line Items]
Severance costs		$ 390
Infrastructure and other | Fiscal 2017 Plan
Restructuring Cost and Reserve [Line Items]
Other charges		$ 305
Labor costs related to workforce reductions | Fiscal 2020 Plan
Restructuring Cost and Reserve [Line Items]
Estimated pre-tax charges	$ 900
Minimum | Fiscal 2020 Plan
Restructuring Cost and Reserve [Line Items]
Expected number of positions to be eliminated | employee	7,000
Maximum | Fiscal 2020 Plan
Restructuring Cost and Reserve [Line Items]
Expected number of positions to be eliminated | employee	9,000