Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Change in Accounting Principle (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Interest receivable	$ (1,189)	$ (1,079)
Other assets	(16,450)	(15,382)
Total Assets	(334,048)	(308,167)
Interest payable	(299)	(254)
Other liabilities	(9,629)	(8,855)
Total liabilities	$ (286,764)	(263,114)
Restatement Adjustment [Member] | Derivative Presentation Changed from Gross Basis to Net Basis [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Interest receivable		356
Other assets		331
Total Assets		687
Interest payable		63
Other liabilities		624
Total liabilities		$ 687