Derivative Financial Instruments Netting of Financial Instruments - Derivatives (Additional Information) (Details) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Derivative Assets	[1]	$ 898	$ 984
Derivative Asset, Collateral, Obligation to Return Cash, Offset		303	291
Derivative Liabilities	[2]	377	398
Derivative Liability, Collateral, Right to Reclaim Cash, Offset		1,420	1,265
Trading Securities [Member]
Derivative [Line Items]
Derivative Assets		898	984
Trading Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities		$ 377	$ 398

[1] At September 30, 2017, $898 million, net of $303 million offsetting cash collateral, is recognized in trading assets and derivative instruments within the Company's Consolidated Balance Sheets. At December 31, 2016, $984 million, net of $291 million offsetting cash collateral, is recognized in trading assets and derivative instruments within the Company's Consolidated Balance Sheets.

[2] At September 30, 2017, $377 million, net of $1.4 billion offsetting cash collateral, is recognized in trading liabilities and derivative instruments within the Company's Consolidated Balance Sheets. At December 31, 2016, $398 million, net of $1.3 billion offsetting cash collateral, is recognized in trading liabilities and derivative instruments within the Company's Consolidated Balance Sheets.