Derivative And Credit-Related Financial Instruments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Cash received as collateral for derivative assets	$ 427
Fair value of securities pledged as collateral for derivative assets	59
Cash posted as collateral for derivative liabilities	26
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	62		$ 31
Allowance for credit losses on lending-related commitments, amount related to unused commitments to extend credit	$ 51		25
Final year of expiration for outstanding letters of credit	2028
Risk participation agreements covering standby and commercial letters of credit	$ 160		161
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		32
Deferred fees on standby and commercial letters of credit included in accrued expenses and other liabilities	23		26
Allowance for credit losses on lending-related commitments, amount related to standby and commercial letters of credit	10		6
Notional amount of derivative credit risk participation agreements	807		786
Maximum estimated exposure to credit risk participation agreements assuming 100% default	$ 50		$ 20
Weighted average remaining maturity of credit risk participation agreements, in years	3 years 4 months 24 days