Allowance for Credit Losses - Schedule of Allowance Aging Analysis (Details) - USD ($) $ in Millions	Apr. 30, 2021	Oct. 31, 2020
Financing Receivable, Past Due [Line Items]
Current, and up to 30 days past due	$ 1,588	$ 1,582
30-90 days past due	42	45
Total	1,652	1,647
Over 90 days past due
Financing Receivable, Past Due [Line Items]
Over 90 days past due	22	20
Retail portfolio
Financing Receivable, Past Due [Line Items]
Current, and up to 30 days past due	579	558
30-90 days past due	42	44
Total	643	622
Retail portfolio | Over 90 days past due
Financing Receivable, Past Due [Line Items]
Over 90 days past due	22	20
Wholesale portfolio
Financing Receivable, Past Due [Line Items]
Current, and up to 30 days past due	1,009	1,024
30-90 days past due	0	1
Total	1,009	1,025
Wholesale portfolio | Over 90 days past due
Financing Receivable, Past Due [Line Items]
Over 90 days past due	$ 0	$ 0