Derivative Financial Instruments Netting of Financial Instruments - Derivatives (Additional Information) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Derivative [Line Items]
Derivative Assets	$ 1,475	[1]	$ 1,307	[1]
Derivative Liabilities	552	[2]	462	[2]
Trading Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities	552		462
Derivative Liability, Fair Value of Collateral	1,114		1,032
Trading Account Assets [Member]
Derivative [Line Items]
Derivative Assets	1,500		1,300
Derivative Asset, Fair Value of Collateral	$ 530		$ 449

[1] At March 31, 2015, $1.5 billion, net of $530 million offsetting cash collateral, is recognized in trading assets and derivative instruments within the Company's Consolidated Balance Sheets. At December 31, 2014, $1.3 billion, net of $449 million offsetting cash collateral, is recognized in trading assets and derivative instruments within the Company's Consolidated Balance Sheets.

[2] At March 31, 2015, $552 million, net of $1.1 billion offsetting cash collateral, is recognized in trading liabilities and derivative instruments within the Company's Consolidated Balance Sheets. At December 31, 2014, $462 million, net of $1.0 billion offsetting cash collateral, is recognized in trading liabilities and derivative instruments within the Company's Consolidated Balance Sheets.