Derivative And Credit-Related Financial Instruments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Cash received as collateral for derivative assets	$ 17		$ 17
Fair value of securities pledged as collateral for derivative assets	40		40
Cash posted as collateral for derivative liabilities	544		544
Net cash flow hedge gains included in interest and fees on loans	24	$ 19	48	$ 22
Interest rate swap agreements maturity	300		300
Net gain on open foreign currency positions	0	$ 0	0	$ 0
Allowance for credit losses on lending-related commitments	31		31		$ 44
Allowance for credit losses on lending-related commitments, amount related to unused commitments to extend credit	28		$ 28		37
Final year of expiration for outstanding letters of credit			2028
Standby and commercial letters of credit	3,500		$ 3,500		3,300
Risk participation agreements covering standby and commercial letters of credit	144		144		150
Carrying value of standby and commercial letters of credit included in accrued expenses and other liabilities	31		31		37
Deferred fees on standby and commercial letters of credit included in accrued expenses and other liabilities	28		28		30
Allowance for credit losses on lending-related commitments, amount related to standby and commercial letters of credit	3		3		7
Notional amount of derivative credit risk participation agreements	1,000		1,000		1,100
Fair Value Amount of Derivative Credit Risk Participation Agreements	1		1		3
Maximum estimated exposure to credit risk participation agreements assuming 100% default	$ 41		$ 41		$ 62
Weighted average remaining maturity of credit risk participation agreements, in years			4 years 3 months