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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Net loans and leases					$ 26,501,654	$ 25,299,564
Loan and Leases Acquired with Deteriorated Credit Quality [Abstract]
Loans and leases acquired with deteriorated credit quality					551,447	606,576	$ 674,269	$ 762,998
Commercial
Loan and Leases Acquired with Deteriorated Credit Quality [Abstract]
Loans and leases acquired with deteriorated credit quality					275,637	296,672
Noncommercial
Loan and Leases Acquired with Deteriorated Credit Quality [Abstract]
Loans and leases acquired with deteriorated credit quality					275,810
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	$ 219,795	$ 210,820	$ 214,568	$ 211,867
Provision for Loan, Lease, and Other Losses	5,835	8,277	17,749	13,528
Charge-offs	(10,602)	(9,678)	(20,756)	(19,291)
Recoveries	3,212	3,023	6,679	6,338
Ending balance	218,240	212,442	218,240	212,442
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					166,673	146,430
Loans and leases collectively evaluated for impairment					26,010,117	24,770,270
Net loans and leases					26,176,790	24,916,700
ALLL for loans and leases individually evaluated for impairment					11,098	9,827
ALLL for loans and leases collectively evaluated for impairment					207,142	204,741
Total allowance for loan and lease losses	219,795	210,820	218,240	211,867	218,240	214,568	212,442	211,867
Non-PCI Loans | Commercial
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					77,330
ALLL for loans and leases individually evaluated for impairment					4,775
Non-PCI Loans | Commercial | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	37,476	26,718	35,270	24,470
Provision for Loan, Lease, and Other Losses	(5,544)	(3,139)	(3,425)	(914)
Charge-offs	(28)	(8)	(72)	(8)
Recoveries	40	93	171	116
Ending balance	31,944	23,664	31,944	23,664
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					2,078	2,175
Loans and leases collectively evaluated for impairment					717,456	755,679
Net loans and leases					719,534	757,854
ALLL for loans and leases individually evaluated for impairment					196	490
ALLL for loans and leases collectively evaluated for impairment					31,748	34,780
Total allowance for loan and lease losses	37,476	26,718	35,270	24,470	31,944	35,270	23,664	24,470
Non-PCI Loans | Commercial | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	45,281	43,833	43,451	45,005
Provision for Loan, Lease, and Other Losses	3,714	866	6,085	(499)
Charge-offs	(89)	(459)	(850)	(505)
Recoveries	56	225	276	464
Ending balance	48,962	44,465	48,962	44,465
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					62,270	55,447
Loans and leases collectively evaluated for impairment					11,274,414	10,661,787
Net loans and leases					11,336,684	10,717,234
ALLL for loans and leases individually evaluated for impairment					3,042	2,671
ALLL for loans and leases collectively evaluated for impairment					45,920	40,780
Total allowance for loan and lease losses	45,281	43,833	48,962	45,005	48,962	43,451	44,465	45,005
Non-PCI Loans | Commercial | Other commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,399	3,423	2,481	4,571
Provision for Loan, Lease, and Other Losses	(57)	468	(140)	(825)
Charge-offs	0	(69)	0	(69)
Recoveries	0	1	1	146
Ending balance	2,342	3,823	2,342	3,823
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					506	860
Loans and leases collectively evaluated for impairment					506,254	426,125
Net loans and leases					506,760	426,985
ALLL for loans and leases individually evaluated for impairment					11	42
ALLL for loans and leases collectively evaluated for impairment					2,331	2,439
Total allowance for loan and lease losses	2,399	3,423	2,481	4,571	2,342	2,481	3,823	4,571
Non-PCI Loans | Commercial | Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	57,025	59,317	55,620	59,824
Provision for Loan, Lease, and Other Losses	2,699	3,791	5,424	4,353
Charge-offs	(3,422)	(2,439)	(5,280)	(4,768)
Recoveries	599	642	1,137	1,902
Ending balance	56,901	61,311	56,901	61,311
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					12,161	9,868
Loans and leases collectively evaluated for impairment					3,968,343	3,928,862
Net loans and leases					3,980,504	3,938,730
ALLL for loans and leases individually evaluated for impairment					1,422	1,137
ALLL for loans and leases collectively evaluated for impairment					55,479	54,483
Total allowance for loan and lease losses	57,025	59,317	56,901	61,311	56,901	55,620	61,311	59,824
Non-PCI Loans | Commercial | Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,167	4,842	2,221	4,689
Provision for Loan, Lease, and Other Losses	(174)	(114)	(672)	0
Charge-offs	(31)	(38)	(31)	(41)
Recoveries	221	1	665	43
Ending balance	2,183	4,691	2,183	4,691
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					315	291
Loans and leases collectively evaluated for impairment					301,031	296,133
Net loans and leases					301,346	296,424
ALLL for loans and leases individually evaluated for impairment					104	105
ALLL for loans and leases collectively evaluated for impairment					2,079	2,116
Total allowance for loan and lease losses	2,167	4,842	2,183	4,691	2,183	2,221	4,691	4,689
Non-PCI Loans | Noncommercial
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					89,343
ALLL for loans and leases individually evaluated for impairment					6,323
Non-PCI Loans | Noncommercial | Construction and land development
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,473	3,913	2,350	3,962
Provision for Loan, Lease, and Other Losses	277	50	400	157
Charge-offs	0	(37)	0	(219)
Recoveries	0	101	0	127
Ending balance	2,750	4,027	2,750	4,027
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					3,059	3,749
Loans and leases collectively evaluated for impairment					312,012	253,281
Net loans and leases					315,071	257,030
ALLL for loans and leases individually evaluated for impairment					82	81
ALLL for loans and leases collectively evaluated for impairment					2,668	2,269
Total allowance for loan and lease losses	2,473	3,913	2,350	4,027	2,750	2,350	4,027	3,962
Non-PCI Loans | Noncommercial | Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	16,987	16,489	15,472	15,706
Provision for Loan, Lease, and Other Losses	371	1,492	1,879	3,004
Charge-offs	(478)	(289)	(644)	(1,095)
Recoveries	52	110	225	187
Ending balance	16,932	17,802	16,932	17,802
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					53,137	42,168
Loans and leases collectively evaluated for impairment					4,737,499	4,223,519
Net loans and leases					4,790,636	4,265,687
ALLL for loans and leases individually evaluated for impairment					2,566	1,901
ALLL for loans and leases collectively evaluated for impairment					14,366	13,571
Total allowance for loan and lease losses	16,987	16,489	16,932	17,802	16,932	15,472	17,802	15,706
Non-PCI Loans | Noncommercial | Revolving mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	21,495	22,104	21,862	22,436
Provision for Loan, Lease, and Other Losses	(328)	289	(119)	755
Charge-offs	(493)	(1,027)	(1,456)	(2,019)
Recoveries	447	520	834	714
Ending balance	21,121	21,886	21,121	21,886
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					30,040	28,852
Loans and leases collectively evaluated for impairment					2,440,613	2,514,123
Net loans and leases					2,470,653	2,542,975
ALLL for loans and leases individually evaluated for impairment					2,704	2,515
ALLL for loans and leases collectively evaluated for impairment					18,417	19,347
Total allowance for loan and lease losses	21,495	22,104	21,862	21,886	21,121	21,862	21,886	22,436
Non-PCI Loans | Noncommercial | Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	34,492	30,181	35,841	31,204
Provision for Loan, Lease, and Other Losses	4,877	4,574	8,317	7,497
Charge-offs	(6,061)	(5,312)	(12,423)	(10,567)
Recoveries	1,797	1,330	3,370	2,639
Ending balance	35,105	30,773	35,105	30,773
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Loans and leases individually evaluated for impairment					3,107	3,020
Loans and leases collectively evaluated for impairment					1,752,495	1,710,761
Net loans and leases					1,755,602	1,713,781
ALLL for loans and leases individually evaluated for impairment					971	885
ALLL for loans and leases collectively evaluated for impairment					34,134	34,956
Total allowance for loan and lease losses	34,492	30,181	35,841	30,773	35,105	35,841	30,773	31,204
PCI Loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	8,980	12,296	9,144	10,026
Provision for Loan, Lease, and Other Losses	(637)	161	(801)	2,515
Charge-offs	0	34	0	118
Recoveries	0	0	0	0
Ending balance	8,343	12,423	8,343	12,423
Allowance for Loans and Leases Evaluated for Impairment [Abstract]
Total allowance for loan and lease losses	$ 8,980	$ 12,296	$ 8,343	$ 12,423	$ 8,343	$ 9,144	$ 12,423	$ 10,026