Fair Value Measurements - Level 3 Reconciliation (Details) - Guarantees [Member] - USD ($) $ in Millions	12 Months Ended
	Oct. 31, 2018	Oct. 31, 2017
Fair Value Assets And Liablities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset (Liability) Beginning Value	$ (21)	$ (23)
Transfers out of Level 3	0	0
Issuances	(7)	(2)
Settlements	4	4
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset (Liability) Ending Value	(24)	(21)
Change in unrealized gains on assets and liabilities still held	$ 0	$ 0