Loans - Repricing Characteristics (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Over 1 But Within 5 Years	$ 21,112
Over 5 Years	19,870
Receivables at predetermined interest rates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Over 1 But Within 5 Years	2,921
Over 5 Years	6,371
Receivables at floating or adjustable rates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Over 1 But Within 5 Years	18,191
Over 5 Years	$ 13,499