Derivative Financial Instruments Netting of Financial Instruments - Derivatives (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		$ 4,514	$ 4,465
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement		4,514	4,465
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		3,530	3,313
Derivative Assets	[1]	984	1,152
Collateral Held by The Company Against Derivative Asset Positions		48	66
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		936	1,086
Derivative Liability, Fair Value, Gross Liability		4,902	4,428
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		4,902	4,428
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		4,504	3,964
Derivative Liabilities	[2]	398	464
Derivative, Collateral, Right to Reclaim Securities		33	19
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		365	445
Derivatives Subject to Master Netting Arrangement or Similar Arrangement [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		4,193	4,184
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		3,384	3,156
Derivative Assets		809	1,028
Collateral Held by The Company Against Derivative Asset Positions		48	66
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		761	962
Derivative Liability, Fair Value, Gross Liability		4,649	4,162
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		4,358	3,807
Derivative Liabilities		291	355
Derivative, Collateral, Right to Reclaim Securities		33	19
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		258	336
Derivatives Not Subject to Master Netting Arrangement or Similar Arrangement [Member] [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		27	21
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		0	0
Derivative Assets		27	21
Collateral Held by The Company Against Derivative Asset Positions		0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		27	21
Derivative Liability, Not Subject to Master Netting Arrangement		105	105
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		0	0
Derivative Liabilities		105	105
Derivative, Collateral, Right to Reclaim Securities		0	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		105	105
Exchange Traded [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		294	260
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		146	157
Derivative Assets		148	103
Collateral Held by The Company Against Derivative Asset Positions		0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		148	103
Derivative Liability, Fair Value, Gross Liability		148	161
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		146	157
Derivative Liabilities		2	4
Derivative, Collateral, Right to Reclaim Securities		0	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral		2	4
Other Income [Member] | Loans [Member]
Derivative [Line Items]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments		$ (1)	$ (1)

[1] 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. At December 31, 2015, $1.2 billion, net of $397 million offsetting cash collateral, is recognized in trading assets and derivative instruments within the Company's Consolidated Balance Sheets.

[2] 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. At December 31, 2015, $464 million, net of $1.0 billion offsetting cash collateral, is recognized in trading liabilities and derivative instruments within the Company's Consolidated Balance Sheets.