Fair Value Measurements - Level 3 Reconciliation (Details) - Guarantees [Member] - USD ($) $ in Millions	12 Months Ended
	Oct. 31, 2017	Oct. 31, 2016
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	$ (23)	$ (10)
Transfers out of Level 3	0	0
Issuances	(2)	(17)
Settlements	4	4
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset (Liability) Ending Value	(21)	(23)
Change in unrealized gains on assets and liabilities still held	$ 0	$ 0