Loans And Allowance For Loan Losses (Schedule Of Allowances For Loan Losses And Recorded Investment In Loans) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				$ 251,758				$ 252,496	$ 251,758	$ 252,496	$ 261,317
Allowance for loan losses of sold Memphis loans											0
Charge-offs									(90,419)	(57,960)	(57,339)
Recoveries									20,744	29,222	29,508
Provision for loan losses	$ 8,565	$ 39,686	$ 10,260	8,674	$ 6,259	$ 5,671	$ 6,693	9,377	67,185	28,000	19,010
Ending balance	249,268				251,758				249,268	251,758	252,496
Ending balance: individually evaluated for impairment	14,908				18,111				14,908	18,111	30,435
Ending balance: collectively evaluated for impairment	234,360				233,647				234,360	233,647	222,061
Ending balance: total loans	24,812,795				23,882,382				24,812,795	23,882,382	22,459,664
Ending balance: individually evaluated for impairment	200,286				249,496				200,286	249,496	301,800
Ending balance: collectively evaluated for impairment	24,612,509				23,632,886				24,612,509	23,632,886	22,157,864
Deferred fees and costs, net	25,331				25,991				25,331	25,991	30,100
Total commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				81,816				87,133	81,816	87,133	101,471
Allowance for loan losses of sold Memphis loans											0
Charge-offs									(12,193)	(18,216)	(13,998)
Recoveries									8,026	15,226	13,644
Provision for loan losses									(2,651)	(2,327)	(13,984)
Ending balance	74,998				81,816				74,998	81,816	87,133
Ending balance: individually evaluated for impairment	4,240				7,916				4,240	7,916	18,969
Ending balance: collectively evaluated for impairment	70,758				73,900				70,758	73,900	68,164
Ending balance: total loans	6,935,288				7,374,112				6,935,288	7,374,112	7,394,768
Ending balance: individually evaluated for impairment	56,896				91,410				56,896	91,410	157,958
Ending balance: collectively evaluated for impairment	6,878,392				7,282,702				6,878,392	7,282,702	7,236,810
Total commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				125,778				122,989	125,778	122,989	118,110
Allowance for loan losses of sold Memphis loans											0
Charge-offs									(49,244)	(25,039)	(22,583)
Recoveries									6,685	9,071	8,611
Provision for loan losses									43,584	18,757	18,851
Ending balance	126,803				125,778				126,803	125,778	122,989
Ending balance: individually evaluated for impairment	9,515				8,384				9,515	8,384	10,477
Ending balance: collectively evaluated for impairment	117,288				117,394				117,288	117,394	112,512
Ending balance: total loans	12,023,650				11,543,806				12,023,650	11,543,806	10,772,130
Ending balance: individually evaluated for impairment	111,334				120,560				111,334	120,560	105,599
Ending balance: collectively evaluated for impairment	11,912,316				11,423,246				11,912,316	11,423,246	10,666,531
Total consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				$ 44,164				$ 42,374	44,164	42,374	41,736
Allowance for loan losses of sold Memphis loans											0
Charge-offs									(28,982)	(14,705)	(20,758)
Recoveries									6,033	4,925	7,253
Provision for loan losses									26,252	11,570	14,143
Ending balance	47,467				44,164				47,467	44,164	42,374
Ending balance: individually evaluated for impairment	1,153				1,811				1,153	1,811	989
Ending balance: collectively evaluated for impairment	46,314				42,353				46,314	42,353	41,385
Ending balance: total loans	5,853,857				4,964,464				5,853,857	4,964,464	4,292,766
Ending balance: individually evaluated for impairment	32,056				37,526				32,056	37,526	38,243
Ending balance: collectively evaluated for impairment	$ 5,821,801				$ 4,926,938				$ 5,821,801	$ 4,926,938	$ 4,254,523