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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Net loans and leases					$ 26,969,686	$ 25,299,564
Loan and Leases Acquired with Deteriorated Credit Quality [Abstract]
Loans and leases acquired with deteriorated credit quality					513,589	606,576	$ 638,018	$ 762,998
Commercial
Loan and Leases Acquired with Deteriorated Credit Quality [Abstract]
Loans and leases acquired with deteriorated credit quality					252,828	296,672
Noncommercial
Loan and Leases Acquired with Deteriorated Credit Quality [Abstract]
Loans and leases acquired with deteriorated credit quality					260,761
Noncommercial | Mortgage
Loan and Leases Acquired with Deteriorated Credit Quality [Abstract]
Loans and leases acquired with deteriorated credit quality						309,904
Non-PCI Loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 218,240	$ 212,442	$ 214,568	$ 211,867
Provision for Loan, Lease, and Other Losses	8,242	2,354	25,991	15,883
Charge-offs	(9,647)	(9,447)	(30,403)	(28,739)
Recoveries	3,123	2,939	9,802	9,277
Ending balance	219,958	208,288	219,958	208,288
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					173,124	146,430
Loans and leases collectively evaluated for impairment					26,509,798	24,770,270
Net loans and leases					26,682,922	24,916,700
ALLL for loans and leases individually evaluated for impairment					10,895	9,827
ALLL for loans and leases collectively evaluated for impairment					209,063	204,741
Total allowance for loan and lease losses	218,240	212,442	219,958	208,288	219,958	214,568	208,288	211,867
Non-PCI Loans | Commercial
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					83,787	68,641
ALLL for loans and leases individually evaluated for impairment					4,423	4,445
Non-PCI Loans | Commercial | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	31,944	23,664	35,270	24,470
Provision for Loan, Lease, and Other Losses	208	8,702	(3,217)	7,788
Charge-offs	(116)	(35)	(188)	(43)
Recoveries	52	136	223	252
Ending balance	32,088	32,467	32,088	32,467
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					5,713	2,175
Loans and leases collectively evaluated for impairment					938,034	755,679
Net loans and leases					943,747	757,854
ALLL for loans and leases individually evaluated for impairment					311	490
ALLL for loans and leases collectively evaluated for impairment					31,777	34,780
Total allowance for loan and lease losses	31,944	23,664	32,088	24,470	32,088	35,270	32,467	24,470
Non-PCI Loans | Commercial | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	48,962	44,465	43,451	45,005
Provision for Loan, Lease, and Other Losses	(1,337)	(2,870)	4,748	(3,369)
Charge-offs	(1)	(606)	(851)	(1,111)
Recoveries	226	99	502	563
Ending balance	47,850	41,088	47,850	41,088
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					64,380	55,447
Loans and leases collectively evaluated for impairment					11,388,973	10,661,787
Net loans and leases					11,453,353	10,717,234
ALLL for loans and leases individually evaluated for impairment					2,850	2,671
ALLL for loans and leases collectively evaluated for impairment					45,000	40,780
Total allowance for loan and lease losses	48,962	44,465	47,850	41,088	47,850	43,451	41,088	45,005
Non-PCI Loans | Commercial | Other commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,342	3,823	2,481	4,571
Provision for Loan, Lease, and Other Losses	(90)	(1,219)	(230)	(2,044)
Charge-offs	0	0	0	(69)
Recoveries	0	1	1	147
Ending balance	2,252	2,605	2,252	2,605
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					1,171	860
Loans and leases collectively evaluated for impairment					489,892	426,125
Net loans and leases					491,063	426,985
ALLL for loans and leases individually evaluated for impairment					12	42
ALLL for loans and leases collectively evaluated for impairment					2,240	2,439
Total allowance for loan and lease losses	2,342	3,823	2,481	4,571	2,252	2,481	2,605	4,571
Non-PCI Loans | Commercial | Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	56,901	61,311	55,620	59,824
Provision for Loan, Lease, and Other Losses	4,714	(5,260)	10,138	(907)
Charge-offs	(3,047)	(2,106)	(8,327)	(6,874)
Recoveries	611	497	1,748	2,399
Ending balance	59,179	54,442	59,179	54,442
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					12,262	9,868
Loans and leases collectively evaluated for impairment					4,117,122	3,928,862
Net loans and leases					4,129,384	3,938,730
ALLL for loans and leases individually evaluated for impairment					1,191	1,137
ALLL for loans and leases collectively evaluated for impairment					57,988	54,483
Total allowance for loan and lease losses	56,901	61,311	59,179	54,442	59,179	55,620	54,442	59,824
Non-PCI Loans | Commercial | Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,183	4,691	2,221	4,689
Provision for Loan, Lease, and Other Losses	54	(2,404)	(618)	(2,403)
Charge-offs	(42)	(56)	(73)	(98)
Recoveries	20	117	685	160
Ending balance	2,215	2,348	2,215	2,348
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					261	291
Loans and leases collectively evaluated for impairment					301,530	296,133
Net loans and leases					301,791	296,424
ALLL for loans and leases individually evaluated for impairment					59	105
ALLL for loans and leases collectively evaluated for impairment					2,156	2,116
Total allowance for loan and lease losses	2,183	4,691	2,215	4,689	2,215	2,221	2,348	4,689
Non-PCI Loans | Noncommercial
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					89,337	77,789
ALLL for loans and leases individually evaluated for impairment					6,472	5,382
Non-PCI Loans | Noncommercial | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,750	4,027	2,350	3,962
Provision for Loan, Lease, and Other Losses	148	(1,203)	548	(1,046)
Charge-offs	0	0	0	(219)
Recoveries	0	0	0	127
Ending balance	2,898	2,824	2,898	2,824
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					3,088	3,749
Loans and leases collectively evaluated for impairment					318,815	253,281
Net loans and leases					321,903	257,030
ALLL for loans and leases individually evaluated for impairment					88	81
ALLL for loans and leases collectively evaluated for impairment					2,810	2,269
Total allowance for loan and lease losses	2,750	4,027	2,898	2,824	2,898	2,350	2,824	3,962
Non-PCI Loans | Noncommercial | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	16,932	17,802	15,472	15,706
Provision for Loan, Lease, and Other Losses	1,024	(1,828)	2,903	1,176
Charge-offs	(313)	(360)	(957)	(1,455)
Recoveries	68	128	293	315
Ending balance	17,711	15,742	17,711	15,742
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					54,311	42,168
Loans and leases collectively evaluated for impairment					4,815,251	4,223,519
Net loans and leases					4,869,562	4,265,687
ALLL for loans and leases individually evaluated for impairment					2,761	1,901
ALLL for loans and leases collectively evaluated for impairment					14,950	13,571
Total allowance for loan and lease losses	16,932	17,802	17,711	15,742	17,711	15,472	15,742	15,706
Non-PCI Loans | Noncommercial | Revolving mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	21,121	21,886	21,862	22,436
Provision for Loan, Lease, and Other Losses	(153)	465	(272)	1,220
Charge-offs	(534)	(759)	(1,990)	(2,778)
Recoveries	201	712	1,035	1,426
Ending balance	20,635	22,304	20,635	22,304
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					28,730	28,852
Loans and leases collectively evaluated for impairment					2,386,154	2,514,123
Net loans and leases					2,414,884	2,542,975
ALLL for loans and leases individually evaluated for impairment					2,559	2,515
ALLL for loans and leases collectively evaluated for impairment					18,076	19,347
Total allowance for loan and lease losses	21,121	21,886	20,635	22,304	20,635	21,862	22,304	22,436
Non-PCI Loans | Noncommercial | Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	35,105	30,773	35,841	31,204
Provision for Loan, Lease, and Other Losses	3,674	7,971	11,991	15,468
Charge-offs	(5,594)	(5,525)	(18,017)	(16,092)
Recoveries	1,945	1,249	5,315	3,888
Ending balance	35,130	34,468	35,130	34,468
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					3,208	3,020
Loans and leases collectively evaluated for impairment					1,754,027	1,710,761
Net loans and leases					1,757,235	1,713,781
ALLL for loans and leases individually evaluated for impairment					1,064	885
ALLL for loans and leases collectively evaluated for impairment					34,066	34,956
Total allowance for loan and lease losses	35,105	30,773	35,130	34,468	35,130	35,841	34,468	31,204
PCI Loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	8,343	12,423	9,144	10,026
Provision for Loan, Lease, and Other Losses	(1,476)	(1,514)	(2,277)	1,000
Charge-offs	0	0	0	(117)
Recoveries	0	0	0	0
Ending balance	6,867	10,909	6,867	10,909
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Total allowance for loan and lease losses	$ 8,343	$ 12,423	$ 6,867	$ 10,909	$ 6,867	$ 9,144	$ 10,909	$ 10,026