Derivative And Credit-Related Financial Instruments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair value of securities pledged as collateral for derivative liabilities	$ 0
Cash received as collateral for derivative assets	12
Fair value of securities pledged as collateral for derivative assets	23
Cash posted as collateral for derivative liabilities	15
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
Allowance for credit losses on lending-related commitments	31	$ 30
Allowance for credit losses on lending-related commitments, unused commitments to extend credit	$ 25	24
Final year of expiration for outstanding letters of credit	2028
Risk participation agreements covering standby and commercial letters of credit	$ 161	136
Standby and commercial letters of credit outstanding	3,300	3,300
Carrying value of standby and commercial letters of credit included in accrued expenses and other liabilities	32	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	6	6
Notional Amount of Derivative Credit Risk Participation Agreements	786	703
Maximum estimated exposure to credit risk participation agreements assuming 100% default	$ 20	$ 7
Weighted average remaining maturity of credit risk participation agreements, in years	3 years 4 months 24 days