Financing Receivables and Operating Leases - Allowance for Doubtful Accounts for Financing Receivables (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Apr. 30, 2018	Oct. 31, 2017
Allowance for doubtful accounts
Balance at beginning of period	$ 86	$ 89
Provision for doubtful accounts	16	23
Write-offs, net of recoveries	(5)	(26)
Balance at end of period	$ 97	$ 86