Allowance for Loan and Lease Losses (Summary of Activity In Allowance for Loan and Lease Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Net loans and leases					$ 24,667,150	$ 23,374,932
Loan and Leases Acquired with Deteriorated Credit Quality [Abstract]
Loans and leases acquired with deteriorated credit quality					638,018	762,998	$ 834,167	$ 809,169
Commercial
Loan and Leases Acquired with Deteriorated Credit Quality [Abstract]
Loans and leases acquired with deteriorated credit quality					317,014	393,419
Noncommercial
Loan and Leases Acquired with Deteriorated Credit Quality [Abstract]
Loans and leases acquired with deteriorated credit quality					321,004
Noncommercial | Mortgage
Loan and Leases Acquired with Deteriorated Credit Quality [Abstract]
Loans and leases acquired with deteriorated credit quality						369,579
Non-PCI Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired Financing Receivable, Related Allowance					11,425	9,728
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 212,442	$ 215,302	$ 211,867	$ 205,026
Provision for Loan, Lease, and Other Losses	2,354	8,483	15,883	29,311
Charge-offs	(9,447)	(8,494)	(28,739)	(26,688)
Recoveries	2,939	3,592	9,277	11,234
Ending balance	208,288	218,883	208,288	218,883
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					154,676	155,646
Loans and leases collectively evaluated for impairment					24,093,653	22,678,181
Net loans and leases					24,248,329	22,833,827
ALLL for loans and leases individually evaluated for impairment					11,425	9,728
ALLL for loans and leases collectively evaluated for impairment					196,863	202,139
Total allowance for loan and lease losses	212,442	215,302	211,867	205,026	208,288	211,867	218,883	205,026
Non-PCI Loans | Commercial | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	23,664	33,559	24,470	28,877
Provision for Loan, Lease, and Other Losses	8,702	(5,150)	7,788	(242)
Charge-offs	(35)	(9)	(43)	(499)
Recoveries	136	56	252	320
Ending balance	32,467	28,456	32,467	28,456
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					2,175	788
Loans and leases collectively evaluated for impairment					677,028	668,427
Net loans and leases					679,203	669,215
ALLL for loans and leases individually evaluated for impairment					296	185
ALLL for loans and leases collectively evaluated for impairment					32,171	24,285
Total allowance for loan and lease losses	23,664	33,559	24,470	28,877	32,467	24,470	28,456	28,877
Non-PCI Loans | Commercial | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	44,465	49,746	45,005	48,278
Provision for Loan, Lease, and Other Losses	(2,870)	(71)	(3,369)	574
Charge-offs	(606)	(39)	(1,111)	(311)
Recoveries	99	1,446	563	2,541
Ending balance	41,088	51,082	41,088	51,082
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					63,412	73,655
Loans and leases collectively evaluated for impairment					10,422,960	9,655,367
Net loans and leases					10,486,372	9,729,022
ALLL for loans and leases individually evaluated for impairment					2,983	3,648
ALLL for loans and leases collectively evaluated for impairment					38,105	41,357
Total allowance for loan and lease losses	44,465	49,746	45,005	48,278	41,088	45,005	51,082	48,278
Non-PCI Loans | Commercial | Other commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,823	3,612	4,571	3,269
Provision for Loan, Lease, and Other Losses	(1,219)	891	(2,044)	1,228
Charge-offs	0	0	(69)	(5)
Recoveries	1	8	147	19
Ending balance	2,605	4,511	2,605	4,511
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					929	1,857
Loans and leases collectively evaluated for impairment					470,603	471,576
Net loans and leases					471,532	473,433
ALLL for loans and leases individually evaluated for impairment					46	209
ALLL for loans and leases collectively evaluated for impairment					2,559	4,362
Total allowance for loan and lease losses	3,823	3,612	4,571	3,269	2,605	4,571	4,511	3,269
Non-PCI Loans | Commercial | Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	57,330	51,068	53,697	50,225
Provision for Loan, Lease, and Other Losses	(9,271)	5,621	(4,026)	10,181
Charge-offs	(1,256)	(1,275)	(4,725)	(7,649)
Recoveries	494	433	2,351	3,090
Ending balance	47,297	55,847	47,297	55,847
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					9,048	7,974
Loans and leases collectively evaluated for impairment					3,180,289	2,722,433
Net loans and leases					3,189,337	2,730,407
ALLL for loans and leases individually evaluated for impairment					1,133	665
ALLL for loans and leases collectively evaluated for impairment					46,164	53,032
Total allowance for loan and lease losses	57,330	51,068	53,697	50,225	47,297	53,697	55,847	50,225
Non-PCI Loans | Commercial | Lease financing
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,981	6,404	6,127	5,907
Provision for Loan, Lease, and Other Losses	4,011	884	3,119	1,645
Charge-offs	(850)	(687)	(2,149)	(957)
Recoveries	3	3	48	9
Ending balance	7,145	6,604	7,145	6,604
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					1,042	1,914
Loans and leases collectively evaluated for impairment					615,909	892,887
Net loans and leases					616,951	894,801
ALLL for loans and leases individually evaluated for impairment					135	397
ALLL for loans and leases collectively evaluated for impairment					7,010	5,730
Total allowance for loan and lease losses	3,981	6,404	6,127	5,907	7,145	6,127	6,604	5,907
Non-PCI Loans | Commercial | Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	4,691	3,302	4,689	3,127
Provision for Loan, Lease, and Other Losses	(2,404)	58	(2,403)	299
Charge-offs	(56)	(666)	(98)	(853)
Recoveries	117	123	160	244
Ending balance	2,348	2,817	2,348	2,817
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					241	521
Loans and leases collectively evaluated for impairment					296,747	301,655
Net loans and leases					296,988	302,176
ALLL for loans and leases individually evaluated for impairment					18	0
ALLL for loans and leases collectively evaluated for impairment					2,330	4,689
Total allowance for loan and lease losses	4,691	3,302	4,689	3,127	2,348	4,689	2,817	3,127
Non-PCI Loans | Noncommercial | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	4,027	1,503	3,962	1,596
Provision for Loan, Lease, and Other Losses	(1,203)	92	(1,046)	(1)
Charge-offs	0	0	(219)	0
Recoveries	0	0	127	0
Ending balance	2,824	1,595	2,824	1,595
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					4,236	4,551
Loans and leases collectively evaluated for impairment					237,200	243,738
Net loans and leases					241,436	248,289
ALLL for loans and leases individually evaluated for impairment					501	68
ALLL for loans and leases collectively evaluated for impairment					2,323	3,894
Total allowance for loan and lease losses	4,027	1,503	3,962	1,596	2,824	3,962	1,595	1,596
Non-PCI Loans | Noncommercial | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	17,802	15,843	15,706	14,447
Provision for Loan, Lease, and Other Losses	(1,828)	531	1,176	2,037
Charge-offs	(360)	(604)	(1,455)	(1,076)
Recoveries	128	92	315	454
Ending balance	15,742	15,862	15,742	15,862
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					42,617	37,842
Loans and leases collectively evaluated for impairment					4,030,618	3,485,944
Net loans and leases					4,073,235	3,523,786
ALLL for loans and leases individually evaluated for impairment					2,791	2,733
ALLL for loans and leases collectively evaluated for impairment					12,951	12,973
Total allowance for loan and lease losses	17,802	15,843	15,706	14,447	15,742	15,706	15,862	14,447
Non-PCI Loans | Noncommercial | Revolving mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	21,886	22,465	22,436	21,013
Provision for Loan, Lease, and Other Losses	465	842	1,220	2,446
Charge-offs	(759)	(218)	(2,778)	(1,323)
Recoveries	712	228	1,426	1,181
Ending balance	22,304	23,317	22,304	23,317
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					28,089	23,770
Loans and leases collectively evaluated for impairment					2,542,007	2,677,755
Net loans and leases					2,570,096	2,701,525
ALLL for loans and leases individually evaluated for impairment					2,759	1,085
ALLL for loans and leases collectively evaluated for impairment					19,545	21,351
Total allowance for loan and lease losses	21,886	22,465	22,436	21,013	22,304	22,436	23,317	21,013
Non-PCI Loans | Noncommercial | Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	30,773	27,800	31,204	28,287
Provision for Loan, Lease, and Other Losses	7,971	4,785	15,468	11,144
Charge-offs	(5,525)	(4,996)	(16,092)	(14,015)
Recoveries	1,249	1,203	3,888	3,376
Ending balance	34,468	28,792	34,468	28,792
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					2,887	2,774
Loans and leases collectively evaluated for impairment					1,620,292	1,558,399
Net loans and leases					1,623,179	1,561,173
ALLL for loans and leases individually evaluated for impairment					763	738
ALLL for loans and leases collectively evaluated for impairment					33,705	30,466
Total allowance for loan and lease losses	30,773	27,800	31,204	28,287	34,468	31,204	28,792	28,287
PCI Loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	12,423	13,496	10,026	13,769
Provision for Loan, Lease, and Other Losses	(1,514)	(537)	1,000	(810)
Charge-offs	0	0	(117)	0
Recoveries	0	0	0	0
Ending balance	10,909	12,959	10,909	12,959
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Total allowance for loan and lease losses	$ 12,423	$ 13,496	$ 10,026	$ 13,769	10,909	10,026	$ 12,959	$ 13,769
Loan and Leases Acquired with Deteriorated Credit Quality [Abstract]
Loans and leases acquired with deteriorated credit quality					$ 638,018	$ 762,998