Loans Held for Sale - Loans Held for Sale (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	$ 399	$ 1,018
Commercial Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	58	481
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	341	537
Consumer Loans [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	277	472
Consumer Loans [Member] | Other Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale	$ 64	$ 65