Deposits - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Loans and Leases Receivable Disclosure [Line Items]
Demand deposits of $100,000 or more	$ 39,730	$ 55,030
Demand deposit overdrafts	3,240	2,620
Non-U.S.
Loans and Leases Receivable Disclosure [Line Items]
Demand deposits of $100,000 or more	252	$ 214
Wholesale CDs
Loans and Leases Receivable Disclosure [Line Items]
Demand deposits of $100,000 or more	4,750
Customer Deposits
Loans and Leases Receivable Disclosure [Line Items]
Demand deposits of $100,000 or more	$ 34,730