Derivative Financial Instruments Netting of Financial Instruments - Derivatives (Details) - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		$ 3,128	$ 2,631
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		3,128	2,631
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		2,100	1,992
Derivative Asset	[1]	1,028	639
Derivative, Collateral, Obligation to Return Securities		13	12
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		1,015	627
Derivative Liability, Fair Value, Gross Liability		2,804	2,716
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		2,804	2,716
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		2,540	2,306
Derivative Liability	[2]	264	410
Derivative, Collateral, Right to Reclaim Securities		30	14
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		234	396
Derivatives Subject to Master Netting Arrangement or Similar Arrangement [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		2,720	2,425
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		1,976	1,873
Derivative Asset		744	552
Derivative, Collateral, Obligation to Return Securities		13	12
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		731	540
Derivative Liability, Fair Value, Gross Liability		2,599	2,521
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		2,416	2,187
Derivative Liability		183	334
Derivative, Collateral, Right to Reclaim Securities		30	14
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		153	320
Derivatives Not Subject to Master Netting Arrangement or Similar Arrangement [Member] [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		24	20
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		0	0
Derivative Asset		24	20
Derivative, Collateral, Obligation to Return Securities		0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		24	20
Derivative Liability, Fair Value, Gross Liability		81	76
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		0	0
Derivative Liability		81	76
Derivative, Collateral, Right to Reclaim Securities		0	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		81	76
Exchange Traded [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		384	186
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		124	119
Derivative Asset		260	67
Derivative, Collateral, Obligation to Return Securities		0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		260	67
Derivative Liability, Fair Value, Gross Liability		124	119
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		124	119
Derivative Liability		0	0
Derivative, Collateral, Right to Reclaim Securities		0	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		$ 0	$ 0

[1] At March 31, 2019, $1.0 billion, net of $391 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 March 31, 2019, $264 million, net of $831 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.