Loans - Repricing Characteristics (Details) $ in Millions	Dec. 31, 2016 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Due Over 1 But Within 5 Years	$ 33,445
Loans Due Over 5 Years	19,205
Receivables at predetermined interest rates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Due Over 1 But Within 5 Years	4,047
Loans Due Over 5 Years	4,777
Receivables at floating or adjustable rates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Due Over 1 But Within 5 Years	29,398
Loans Due Over 5 Years	$ 14,428