Derivative And Credit-Related Financial Instruments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Cash received as collateral for derivative assets	$ 23
Fair value of securities pledged as collateral for derivative assets	12
Cash posted as collateral for derivative liabilities	18
Aggregate fair value of all derivative instruments with credit-risk contingent features that were in a liability position	0
Net gain on open foreign currency positions	0	$ 0
Allowance for credit losses on lending-related commitments	30		$ 30
Allowance for credit losses on lending-related commitments, amount related to unused commitments to extend credit	$ 23		24
Final year of expiration for outstanding letters of credit	2028
Risk participation agreements covering standby and commercial letters of credit	$ 126		136
Standby and commercial letters of credit	3,200		3,300
Carrying value of standby and commercial letters of credit included in accrued expenses and other liabilities	33		34
Deferred fees on standby and commercial letters of credit included in accrued expenses and other liabilities	26		28
Allowance for credit losses on lending-related commitments, amount related to standby and commercial letters of credit	7		6
Notional amount of derivative credit risk participation agreements	674		703
Maximum estimated exposure to credit risk participation agreements assuming 100% default	$ 12		$ 7
Weighted average remaining maturity of credit risk participation agreements, in years	3 years 7 months 6 days