Derivative Financial Instruments Netting of Financial Instruments - Derivatives (Details) - USD ($) $ in Millions		Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		$ 3,278	$ 3,904
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		3,278	3,904
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		2,656	3,102
Derivative Asset	[1]	622	802
Derivative, Collateral, Obligation to Return Securities		14	28
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		608	774
Derivative Liability, Fair Value, Gross Liability		3,829	4,442
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		3,829	4,442
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		3,131	4,034
Derivative Liability	[2]	698	408
Derivative, Collateral, Right to Reclaim Securities		58	27
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		640	381
Derivatives Subject to Master Netting Arrangement or Similar Arrangement [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		2,940	3,491
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		2,525	2,923
Derivative Asset		415	568
Derivative, Collateral, Obligation to Return Securities		14	28
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		401	540
Derivative Liability, Fair Value, Gross Liability		3,587	4,128
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		3,000	3,855
Derivative Liability		587	273
Derivative, Collateral, Right to Reclaim Securities		58	27
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		529	246
Derivatives Not Subject to Master Netting Arrangement or Similar Arrangement [Member] [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		14	18
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		0	0
Derivative Asset		14	18
Derivative, Collateral, Obligation to Return Securities		0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		14	18
Derivative Liability, Fair Value, Gross Liability		111	130
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		0	0
Derivative Liability		111	130
Derivative, Collateral, Right to Reclaim Securities		0	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		111	130
Exchange Traded [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		324	395
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		131	179
Derivative Asset		193	216
Derivative, Collateral, Obligation to Return Securities		0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		193	216
Derivative Liability, Fair Value, Gross Liability		131	184
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		131	179
Derivative Liability		0	5
Derivative, Collateral, Right to Reclaim Securities		0	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		$ 0	$ 5

[1] At September 30, 2018, $622 million, net of $471 million offsetting cash collateral, is recognized in Trading assets and derivative instruments within the Company's Consolidated Balance Sheets. At December 31, 2017, $802 million, net of $371 million offsetting cash collateral, is recognized in Trading assets and derivative instruments within the Company's Consolidated Balance Sheets.

[2] At September 30, 2018, $698 million, net of $946 million offsetting cash collateral, is recognized in Trading liabilities and derivative instruments within the Company's Consolidated Balance Sheets. At December 31, 2017, $408 million, net of $1.3 billion offsetting cash collateral, is recognized in Trading liabilities and derivative instruments within the Company's Consolidated Balance Sheets.