Derivative Financial Instruments Netting of Financial Instruments - Derivatives (Details) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		$ 3,812	$ 4,514
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		3,812	4,514
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		2,914	3,530
Derivative Assets	[1]	898	984
Derivative, Collateral, Obligation to Return Securities		35	48
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		863	936
Derivative Liability, Fair Value, Gross Liability		4,408	4,902
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		4,408	4,902
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		4,031	4,504
Derivative Liabilities	[2]	377	398
Derivative, Collateral, Right to Reclaim Securities		54	33
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		323	365
Derivatives Subject to Master Netting Arrangement or Similar Arrangement [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		3,436	4,193
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		2,768	3,384
Derivative Assets		668	809
Derivative, Collateral, Obligation to Return Securities		35	48
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		633	761
Derivative Liability, Fair Value, Gross Liability		4,146	4,649
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		3,885	4,358
Derivative Liabilities		261	291
Derivative, Collateral, Right to Reclaim Securities		54	33
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		207	258
Derivatives Not Subject to Master Netting Arrangement or Similar Arrangement [Member] [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		26	27
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		0	0
Derivative Assets		26	27
Derivative, Collateral, Obligation to Return Securities		0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		26	27
Derivative Liability, Fair Value, Gross Liability		115	105
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		0	0
Derivative Liabilities		115	105
Derivative, Collateral, Right to Reclaim Securities		0	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		115	105
Exchange Traded [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		350	294
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		146	146
Derivative Assets		204	148
Derivative, Collateral, Obligation to Return Securities		0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		204	148
Derivative Liability, Fair Value, Gross Liability		147	148
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		146	146
Derivative Liabilities		1	2
Derivative, Collateral, Right to Reclaim Securities		0	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		$ 1	$ 2

[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.