Fair Value Option - Additional Information (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonaccrual Loans	$ 1,360,000,000	$ 1,629,000,000
Accruing Loans Contractually Past Due 90 days or More	46,000,000	80,000,000
Loans Receivable [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonaccrual Loans	$ 0