Loans And Allowance For Credit Losses (Summary Of Changes In The Allowance For Credit Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	$ 495	$ 518
Provision for loan losses	37	39	$ 24
Gross loan and lease charge-offs	(78)	69
Recoveries	41	85
Net loan and lease charge-offs	37	(16)
Balance at end of period	495	495	518
Balance at beginning of period	57	58
Provision charged (credited) to earnings	2	1	7
Balance at end of period	59	57	58
Total allowance for credit losses	554	552
Commercial [Member]
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	331	371
Provision for loan losses	42	62
Gross loan and lease charge-offs	(57)	(46)
Recoveries	25	68
Net loan and lease charge-offs	32	(22)
Balance at end of period	341	331	371
Balance at beginning of period	40	48
Provision charged (credited) to earnings	1	8
Balance at end of period	39	40	48
Total allowance for credit losses	380	371
Commercial Real Estate [Member]
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	110	103
Provision for loan losses	11	(3)
Gross loan and lease charge-offs	(4)	(5)
Recoveries	6	9
Net loan and lease charge-offs	(2)	(4)
Balance at end of period	101	110	103
Balance at beginning of period	17	10
Provision charged (credited) to earnings	3	7
Balance at end of period	20	17	10
Total allowance for credit losses	121	127
Consumer Portfolio Segment [Member]
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	54	44
Provision for loan losses	6	20
Gross loan and lease charge-offs	(17)	(18)
Recoveries	10	8
Net loan and lease charge-offs	7	10
Balance at end of period	53	54	44
Balance at beginning of period	0	0
Provision charged (credited) to earnings	0	0
Balance at end of period	0	0	$ 0
Total allowance for credit losses	$ 53	$ 54