Allowance for Loan and Lease Losses (Summary of Activity In Allowance for Loan and Lease Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Net loans and leases					$ 24,313,572	$ 23,374,932
Loan and Leases Acquired with Deteriorated Credit Quality [Abstract]
Loans and leases acquired with deteriorated credit quality					674,269	762,998	$ 894,863	$ 809,169
Allowance for loan and lease losses					224,865	221,893
Commercial
Loan and Leases Acquired with Deteriorated Credit Quality [Abstract]
Loans and leases acquired with deteriorated credit quality					336,109
Noncommercial
Loan and Leases Acquired with Deteriorated Credit Quality [Abstract]
Loans and leases acquired with deteriorated credit quality					338,160
Non-PCI Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Related Allowance					10,001	9,728
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 210,820	$ 210,019	$ 211,867	$ 205,026
Provision for Loan, Lease, and Other Losses	8,277	9,752	13,528	20,828
Charge-offs	(9,678)	(9,423)	(19,291)	(18,194)
Recoveries	3,023	4,954	6,338	7,642
Ending balance	212,442	215,302	212,442	215,302
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					155,228	155,646
Loans and leases collectively evaluated for impairment					23,708,940	22,678,181
Net loans and leases					23,864,168	22,833,827
ALLL for loans and leases individually evaluated for impairment					10,001	9,728
ALLL for loans and leases collectively evaluated for impairment					202,441	202,139
Total allowance for loan and lease losses	210,820	210,019	211,867	205,026	212,442	211,867	215,302	205,026
Non-PCI Loans | Commercial | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	26,718	31,391	24,470	28,877
Provision for Loan, Lease, and Other Losses	(3,139)	2,372	(914)	4,908
Charge-offs	(8)	(413)	(8)	(490)
Recoveries	93	209	116	264
Ending balance	23,664	33,559	23,664	33,559
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					2,098	788
Loans and leases collectively evaluated for impairment					712,913	668,427
Net loans and leases					715,011	669,215
ALLL for loans and leases individually evaluated for impairment					274	185
ALLL for loans and leases collectively evaluated for impairment					23,390	24,285
Total allowance for loan and lease losses	26,718	31,391	24,470	28,877	23,664	24,470	33,559	28,877
Non-PCI Loans | Commercial | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	43,833	48,611	45,005	48,278
Provision for Loan, Lease, and Other Losses	866	639	(499)	645
Charge-offs	(459)	(235)	(505)	(272)
Recoveries	225	731	464	1,095
Ending balance	44,465	49,746	44,465	49,746
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					66,172	73,655
Loans and leases collectively evaluated for impairment					10,212,569	9,655,367
Net loans and leases					10,278,741	9,729,022
ALLL for loans and leases individually evaluated for impairment					3,325	3,648
ALLL for loans and leases collectively evaluated for impairment					41,140	41,357
Total allowance for loan and lease losses	43,833	48,611	45,005	48,278	44,465	45,005	49,746	48,278
Non-PCI Loans | Commercial | Other commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,423	3,572	4,571	3,269
Provision for Loan, Lease, and Other Losses	468	33	(825)	337
Charge-offs	(69)	0	(69)	(5)
Recoveries	1	7	146	11
Ending balance	3,823	3,612	3,823	3,612
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					1,077	1,857
Loans and leases collectively evaluated for impairment					472,375	471,576
Net loans and leases					473,452	473,433
ALLL for loans and leases individually evaluated for impairment					65	209
ALLL for loans and leases collectively evaluated for impairment					3,758	4,362
Total allowance for loan and lease losses	3,423	3,572	4,571	3,269	3,823	4,571	3,612	3,269
Non-PCI Loans | Commercial | Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	53,016	50,829	53,697	50,225
Provision for Loan, Lease, and Other Losses	5,670	968	5,245	4,560
Charge-offs	(1,994)	(3,121)	(3,469)	(6,374)
Recoveries	638	2,392	1,857	2,657
Ending balance	57,330	51,068	57,330	51,068
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					7,652	7,974
Loans and leases collectively evaluated for impairment					3,089,889	2,722,433
Net loans and leases					3,097,541	2,730,407
ALLL for loans and leases individually evaluated for impairment					985	665
ALLL for loans and leases collectively evaluated for impairment					56,345	53,032
Total allowance for loan and lease losses	53,016	50,829	53,697	50,225	57,330	53,697	51,068	50,225
Non-PCI Loans | Commercial | Lease financing
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	6,301	6,315	6,127	5,907
Provision for Loan, Lease, and Other Losses	(1,879)	186	(892)	761
Charge-offs	(445)	(97)	(1,299)	(270)
Recoveries	4	0	45	6
Ending balance	3,981	6,404	3,981	6,404
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					1,176	1,914
Loans and leases collectively evaluated for impairment					612,201	892,887
Net loans and leases					613,377	894,801
ALLL for loans and leases individually evaluated for impairment					107	397
ALLL for loans and leases collectively evaluated for impairment					3,874	5,730
Total allowance for loan and lease losses	6,301	6,315	6,127	5,907	3,981	6,127	6,404	5,907
Non-PCI Loans | Commercial | Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	4,842	3,534	4,689	3,127
Provision for Loan, Lease, and Other Losses	(114)	(214)	0	241
Charge-offs	(38)	(64)	(41)	(187)
Recoveries	1	46	43	121
Ending balance	4,691	3,302	4,691	3,302
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					97	521
Loans and leases collectively evaluated for impairment					296,517	301,655
Net loans and leases					296,614	302,176
ALLL for loans and leases individually evaluated for impairment					20	0
ALLL for loans and leases collectively evaluated for impairment					4,671	4,689
Total allowance for loan and lease losses	4,842	3,534	4,689	3,127	4,691	4,689	3,302	3,127
Non-PCI Loans | Noncommercial | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,913	1,513	3,962	1,596
Provision for Loan, Lease, and Other Losses	50	(10)	157	(93)
Charge-offs	(37)	0	(219)	0
Recoveries	101	0	127	0
Ending balance	4,027	1,503	4,027	1,503
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					2,911	4,551
Loans and leases collectively evaluated for impairment					247,793	243,738
Net loans and leases					250,704	248,289
ALLL for loans and leases individually evaluated for impairment					66	68
ALLL for loans and leases collectively evaluated for impairment					3,961	3,894
Total allowance for loan and lease losses	3,913	1,513	3,962	1,596	4,027	3,962	1,503	1,596
Non-PCI Loans | Noncommercial | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	16,489	15,835	15,706	14,447
Provision for Loan, Lease, and Other Losses	1,492	155	3,004	1,506
Charge-offs	(289)	(222)	(1,095)	(472)
Recoveries	110	75	187	362
Ending balance	17,802	15,843	17,802	15,843
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					43,953	37,842
Loans and leases collectively evaluated for impairment					3,936,892	3,485,944
Net loans and leases					3,980,845	3,523,786
ALLL for loans and leases individually evaluated for impairment					3,343	2,733
ALLL for loans and leases collectively evaluated for impairment					14,459	12,973
Total allowance for loan and lease losses	16,489	15,835	15,706	14,447	17,802	15,706	15,843	14,447
Non-PCI Loans | Noncommercial | Revolving mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	22,104	21,290	22,436	21,013
Provision for Loan, Lease, and Other Losses	289	1,054	755	1,604
Charge-offs	(1,027)	(280)	(2,019)	(1,105)
Recoveries	520	401	714	953
Ending balance	21,886	22,465	21,886	22,465
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					27,407	23,770
Loans and leases collectively evaluated for impairment					2,577,548	2,677,755
Net loans and leases					2,604,955	2,701,525
ALLL for loans and leases individually evaluated for impairment					1,112	1,085
ALLL for loans and leases collectively evaluated for impairment					20,774	21,351
Total allowance for loan and lease losses	22,104	21,290	22,436	21,013	21,886	22,436	22,465	21,013
Non-PCI Loans | Noncommercial | Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	30,181	27,129	31,204	28,287
Provision for Loan, Lease, and Other Losses	4,574	4,569	7,497	6,359
Charge-offs	(5,312)	(4,991)	(10,567)	(9,019)
Recoveries	1,330	1,093	2,639	2,173
Ending balance	30,773	27,800	30,773	27,800
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					2,685	2,774
Loans and leases collectively evaluated for impairment					1,550,243	1,558,399
Net loans and leases					1,552,928	1,561,173
ALLL for loans and leases individually evaluated for impairment					704	738
ALLL for loans and leases collectively evaluated for impairment					30,069	30,466
Total allowance for loan and lease losses	30,181	27,129	31,204	28,287	30,773	31,204	27,800	28,287
PCI Loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	12,296	10,924	10,026	13,769
Provision for Loan, Lease, and Other Losses	161	2,572	2,515	(273)
Charge-offs	(34)	0	(118)	0
Recoveries	0	0	0	0
Ending balance	12,423	13,496	12,423	13,496
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Total allowance for loan and lease losses	$ 12,296	$ 10,924	$ 10,026	$ 13,769	12,423	10,026	$ 13,496	$ 13,769
Loan and Leases Acquired with Deteriorated Credit Quality [Abstract]
Loans and leases acquired with deteriorated credit quality					$ 674,269	$ 762,998