Derivative Instruments And Hedging Activities (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2017		Jun. 30, 2016	Dec. 31, 2016
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	$ 2		$ 8		$ 0		$ 28
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	1		3		3		6
Fair values of derivative assets reduced (increased) by net credit valuation adjustments	2		7		2		7
Total derivatives, Notional amount	6,314				6,314			$ 6,209
Cash collateral pledged for derivative liabilities	45				45
Additional collateral that would be required to be pledge if credit rating was downgraded by one notch	1				1
Derivative Instrument, Noninterest Income (Expense)	7		6		11		8
Derivatives Designated As Hedging Instrument Offset To Interest Expense	0		0		0		0
Derivative Credit Risk Valuation Adjustment, Derivative Liabilities	1				1			0
Derivatives Designated As Hedging Instruments [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	2		8		0		28
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	1	[1]	3	[1]	3	[1]	6
Total derivatives, Notional amount	1,388				1,388			1,388
Derivatives Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Total derivatives, Notional amount	4,926				4,926			4,821
Derivatives Not Designated As Hedging Instruments [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Total derivatives, Notional amount	196				196			235
Derivative Instrument, Noninterest Income (Expense)	0		2		0		2
Derivatives Not Designated As Hedging Instruments [Member] | Interest Rate Swaps For Customers [Member]
Derivative [Line Items]
Total derivatives, Notional amount	4,412				4,412			4,162
Derivative Instrument, Noninterest Income (Expense)	3		1		4		1
Derivatives Not Designated As Hedging Instruments [Member] | Foreign Exchange [Member]
Derivative [Line Items]
Total derivatives, Notional amount	318				318			424
Derivative Instrument, Noninterest Income (Expense)	4		$ 3		7		$ 5
Other Liabilities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	38				38			59
Other Liabilities [Member] | Derivatives Designated As Hedging Instruments [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0				0			1
Other Liabilities [Member] | Derivatives Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	38				38			58
Other Liabilities [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0				0			0
Other Liabilities [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Interest Rate Swaps For Customers [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	32				32			49
Other Liabilities [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Foreign Exchange [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	6				6			9
Other Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member]
Derivative [Line Items]
Gross amounts recognized	$ 38				$ 38			$ 59

[1] Amounts recognized in OCI and reclassified from AOCI represent the effective portion of the derivative gain (loss). For the 12 months following June 30, 2017, we estimate that no significant amount will be reclassified from AOCI into interest income.