Fair Value Disclosures - Narrative (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Credit Risk Valuation Adjustment, Derivative Assets and Liabilities	$ 200,000	$ 0
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets and Liabilities, Fair Value Disclosure	$ 5,500,000,000	$ 6,800,000,000
Fair Value, Assets and Liabilities Fair Value as Percent of Total Assets	38.00%	51.00%
Fair Value, Assets and Liabilities, Fair Value as Percent of Total Financial Instruments Measured at Fair Value	73.00%	73.00%