Derivative Financial Instruments Netting of Financial Instruments - Derivatives (Additional Information) (Details) - USD ($) $ in Millions		Jun. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative Asset	[1]	$ 1,457	$ 639
Derivative Asset, Collateral, Obligation to Return Cash, Offset		328	338
Derivative Liability	[2]	206	410
Derivative Liability, Collateral, Right to Reclaim Cash, Offset		918	652
Trading Assets [Member]
Derivative [Line Items]
Derivative Asset		1,500	639
Trading Liabilities [Member]
Derivative [Line Items]
Derivative Liability		$ 206	$ 410

[1] At June 30, 2019, $1.5 billion, net of $328 million offsetting cash collateral, is recognized in Trading assets and derivative instruments within the Company's Consolidated Balance Sheets. At December 31, 2018, $639 million, net of $338 million offsetting cash collateral, is recognized in Trading assets and derivative instruments within the Company's Consolidated Balance Sheets.

[2] At June 30, 2019, $206 million, net of $918 million offsetting cash collateral, is recognized in Trading liabilities and derivative instruments within the Company's Consolidated Balance Sheets. At December 31, 2018, $410 million, net of $652 million offsetting cash collateral, is recognized in Trading liabilities and derivative instruments within the Company's Consolidated Balance Sheets.