Derivative Financial Instruments Netting of Financial Instruments - Derivatives (Details) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		$ 3,887	$ 4,514
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		3,887	4,514
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		3,024	3,530
Derivative Assets	[1]	863	984
Collateral Held by The Company Against Derivative Asset Positions		47	48
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		816	936
Derivative Liability, Fair Value, Gross Liability		4,487	4,902
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		4,487	4,902
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		4,126	4,504
Derivative Liabilities	[2]	361	398
Derivative, Collateral, Right to Reclaim Securities		41	33
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		320	365
Derivatives Subject to Master Netting Arrangement or Similar Arrangement [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		3,570	4,193
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		2,899	3,384
Derivative Assets		671	809
Collateral Held by The Company Against Derivative Asset Positions		47	48
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		624	761
Derivative Liability, Fair Value, Gross Liability		4,262	4,649
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		4,001	4,358
Derivative Liabilities		261	291
Derivative, Collateral, Right to Reclaim Securities		41	33
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		220	258
Derivatives Not Subject to Master Netting Arrangement or Similar Arrangement [Member] [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		32	27
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		0	0
Derivative Assets		32	27
Collateral Held by The Company Against Derivative Asset Positions		0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		32	27
Derivative Liability, Fair Value, Gross Liability		98	105
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		0	0
Derivative Liabilities		98	105
Derivative, Collateral, Right to Reclaim Securities		0	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		98	105
Exchange Traded [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		285	294
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		125	146
Derivative Assets		160	148
Collateral Held by The Company Against Derivative Asset Positions		0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		160	148
Derivative Liability, Fair Value, Gross Liability		127	148
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		125	146
Derivative Liabilities		2	2
Derivative, Collateral, Right to Reclaim Securities		0	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		$ 2	$ 2

[1] At March 31, 2017, $863 million, net of $277 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 March 31, 2017, $361 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.