Loans And Allowance For Credit Losses (Summary Of Major Portfolio Segment And Specific Loan Class) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at end of period	$ 620,013	$ 736,953	$ 604,663	$ 746,291
Loans held for sale	128,946		132,504
Commercial and industrial	13,264,092		13,162,955
Leasing	407,137		408,974
Owner occupied	7,309,639		7,351,548
Municipal	555,122		520,887
Total commercial	21,535,990		21,444,364
Construction and land development	2,044,641		1,986,408
Term	8,088,430		8,126,600
Total commercial real estate	10,133,071		10,113,008
Home equity credit line	2,314,806		2,321,150
1-4 family residential	5,212,963		5,200,882
Construction and other consumer real estate	373,335		370,542
Bankcard and other revolving plans	406,723		401,352
Other	203,226		212,360
Total consumer	8,511,053		8,506,286
Total loans	40,180,114		40,063,658
Provision for loan losses	1,494	610
Change In Allowance Covered By F D I C Indemnification	38	817
Allowance for Loan and Lease Losses, Write-offs	(20,188)	(20,795)
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	37,070	12,884
Net loan and lease charge-offs	16,882	(7,911)
Reserve for unfunded lending commitments	82,287	88,693	81,076	89,705
Provision for Unfunded Lending Commitments	1,211	1,012
Total allowance for credit losses	702,300	825,646
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at end of period	46,326	51,103	47,140	61,066
Home equity credit line	2,314,806		2,321,150
1-4 family residential	5,212,963		5,200,882
Construction and other consumer real estate	373,335		370,542
Bankcard and other revolving plans	406,723		401,352
Other	203,226		212,360
Total consumer	8,511,053		8,506,286
Total loans	8,511,053		8,506,286
Provision for loan losses	(459)	8,979
Change In Allowance Covered By F D I C Indemnification		36
Allowance for Loan and Lease Losses, Write-offs	(3,611)	(3,145)
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	2,338	2,197
Net loan and lease charge-offs	(1,273)	(948)
Reserve for unfunded lending commitments	575	3,550	628	3,875
Provision for Unfunded Lending Commitments	53	(325)
Total allowance for credit losses	46,901	54,653
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at end of period	131,615	208,149	145,009	216,012
Term	8,088,430		8,126,600
Total commercial real estate	10,133,071		10,113,008
Total loans	10,133,071		10,113,008
Provision for loan losses	(26,887)	2,891
Change In Allowance Covered By F D I C Indemnification		0
Allowance for Loan and Lease Losses, Write-offs	(626)	(7,854)
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	14,119	2,882
Net loan and lease charge-offs	13,493	(4,972)
Reserve for unfunded lending commitments	18,937	35,273	21,517	37,485
Provision for Unfunded Lending Commitments	2,580	2,212
Total allowance for credit losses	150,552	243,422
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at end of period	442,072	477,701	412,514	469,213
Commercial and industrial	13,264,092		13,162,955
Leasing	407,137		408,974
Owner occupied	7,309,639		7,351,548
Municipal	555,122		520,887
Total commercial	21,535,990		21,444,364
Total loans	21,535,990		21,444,364
Provision for loan losses	(24,934)	(11,260)
Change In Allowance Covered By F D I C Indemnification	38	781
Allowance for Loan and Lease Losses, Write-offs	(15,951)	(9,796)
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	20,613	7,805
Net loan and lease charge-offs	4,662	(1,991)
Reserve for unfunded lending commitments	62,775	49,870	58,931	48,345
Provision for Unfunded Lending Commitments	3,844	1,525
Total allowance for credit losses	$ 504,847	$ 527,571