Derivative And Credit-Related Financial Instruments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair value of securities received as collateral for derivative assets	$ 3
Cash received as collateral for derivative assets	1
Fair value of securities pledged as collateral for derivative liabilities	25
Cash posted as collateral for derivative liabilities	40
Aggregate fair value of all derivative instruments with credit-risk contingent features that were in a liability position	0
Net interest income generated by risk management fair value interest rate swaps	32	$ 60
Net (loss) gain on interest rate fair value hedge ineffectiveness	1	(2)
Gain (loss) on foreign currency derivatives used as economic hedges	0	0
Net gain on open foreign currency positions	0	1
Allowance for credit losses on lending-related commitments	42	41
Allowance for credit losses on lending-related commitments, unused commitments to extend credit	$ 27	29
Final year of expiration for outstanding letters of credit	2023
Risk participation agreements covering standby and commercial letters of credit	$ 127	255
Standby and commercial letters of credit outstanding	3,300	3,700
Carrying value of standby and commercial letters of credit included in accrued expenses and other liabilities	40	44
Deferred fees on standby and commercial letters of credit included in accrued expenses and other liabilities	25	32
Allowance for credit losses on lending-related commitments, amount related to standby and commercial letters of credit	15	12
Notional Amount of Derivative Credit Risk Participation Agreements	549	458
Maximum estimated exposure to credit risk participation agreements assuming 100% default	$ 0	$ 3
Weighted average remaining maturity of credit risk participation agreements, in years	2 years 6 months 18 days