Derivative Financial Instruments Netting of Financial Instruments - Derivatives (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Document Period End Date		Sep. 30, 2019
Derivative Asset, Fair Value, Gross Asset		$ 3,878	$ 2,631
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		3,878	2,631
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		2,108	1,992
Derivative Asset	[1]	1,770	639
Derivative, Collateral, Obligation to Return Securities		16	12
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		1,754	627
Derivative Liability, Fair Value, Gross Liability		3,031	2,716
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		3,031	2,716
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		2,757	2,306
Derivative Liability	[2]	274	410
Derivative, Collateral, Right to Reclaim Securities		31	14
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		243	396
Derivatives Subject to Master Netting Arrangement or Similar Arrangement [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		3,269	2,425
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		1,973	1,873
Derivative Asset		1,296	552
Derivative, Collateral, Obligation to Return Securities		15	12
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		1,281	540
Derivative Liability, Fair Value, Gross Liability		2,787	2,521
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		2,622	2,187
Derivative Liability		165	334
Derivative, Collateral, Right to Reclaim Securities		18	14
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		147	320
Derivatives Not Subject to Master Netting Arrangement or Similar Arrangement [Member] [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		143	20
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		0	0
Derivative Asset		143	20
Derivative, Collateral, Obligation to Return Securities		1	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		142	20
Derivative Liability, Fair Value, Gross Liability		109	76
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		0	0
Derivative Liability		109	76
Derivative, Collateral, Right to Reclaim Securities		13	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		96	76
Exchange Traded [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		466	186
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		135	119
Derivative Asset		331	67
Derivative, Collateral, Obligation to Return Securities		0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		331	67
Derivative Liability, Fair Value, Gross Liability		135	119
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		135	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 September 30, 2019, $1.8 billion, net of $358 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 September 30, 2019, $274 million, net of $1.0 billion 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.