Loans and Asset Quality Information (Schedule of Analysis of Payment Status of Loans) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Analysis of the payment status of loans
Nonaccrual loans	$ 25,494	$ 20,968	$ 22,795
Total loans	4,149,390	4,042,369	3,375,976
Unamortized net deferred loan fees	(69)	(986)	(808)
Total loans	4,149,390	4,042,369	$ 3,375,976
Commercial, financial, and agricultural [Member]
Analysis of the payment status of loans
Nonaccrual loans	3,407	1,001
Real estate construction, land development & other land loans [Member]
Analysis of the payment status of loans
Nonaccrual loans	1,374	1,822
Real estate mortgage residential (1-4 family) first mortgages [Member]
Analysis of the payment status of loans
Nonaccrual loans	11,513	12,201
Real estate mortgage home equity loans / lines of credit [Member]
Analysis of the payment status of loans
Nonaccrual loans	1,765	2,524
Real estate mortgage commercial and other [Member]
Analysis of the payment status of loans
Nonaccrual loans	7,292	3,345
Installment loans to individuals [Member]
Analysis of the payment status of loans
Nonaccrual loans	143	75
All Total Loans [Member]
Analysis of the payment status of loans
Nonaccrual loans	25,494	20,968
Current	4,109,921	4,007,515
Total loans	4,149,459	4,043,355
Unamortized net deferred loan fees	(69)	(986)
Total loans	4,149,390	4,042,369
All Total Loans [Member] | 30-59 Days past due [Member]
Analysis of the payment status of loans
Financing receivable, past due	11,543	11,903
All Total Loans [Member] | 60-89 Days past due [Member]
Analysis of the payment status of loans
Financing receivable, past due	2,038	2,368
All Total Loans [Member] | 90 Days or More Past Due [Member]
Analysis of the payment status of loans
Financing receivable, past due	463	601
All Total Loans [Member] | Commercial, financial, and agricultural [Member]
Analysis of the payment status of loans
Nonaccrual loans	3,407	1,001
Current	412,264	379,241
Total loans	417,097	380,482
All Total Loans [Member] | Commercial, financial, and agricultural [Member] | 30-59 Days past due [Member]
Analysis of the payment status of loans
Financing receivable, past due	1,398	89
All Total Loans [Member] | Commercial, financial, and agricultural [Member] | 60-89 Days past due [Member]
Analysis of the payment status of loans
Financing receivable, past due	28	151
All Total Loans [Member] | Commercial, financial, and agricultural [Member] | 90 Days or More Past Due [Member]
Analysis of the payment status of loans
Financing receivable, past due
All Total Loans [Member] | Real estate construction, land development & other land loans [Member]
Analysis of the payment status of loans
Nonaccrual loans	1,374	1,822
Current	597,143	535,423
Total loans	599,706	538,613
All Total Loans [Member] | Real estate construction, land development & other land loans [Member] | 30-59 Days past due [Member]
Analysis of the payment status of loans
Financing receivable, past due	913	1,154
All Total Loans [Member] | Real estate construction, land development & other land loans [Member] | 60-89 Days past due [Member]
Analysis of the payment status of loans
Financing receivable, past due	276	214
All Total Loans [Member] | Real estate construction, land development & other land loans [Member] | 90 Days or More Past Due [Member]
Analysis of the payment status of loans
Financing receivable, past due
All Total Loans [Member] | Real estate mortgage residential (1-4 family) first mortgages [Member]
Analysis of the payment status of loans
Nonaccrual loans	11,513	12,201
Current	975,883	943,565
Total loans	992,796	963,913
All Total Loans [Member] | Real estate mortgage residential (1-4 family) first mortgages [Member] | 30-59 Days past due [Member]
Analysis of the payment status of loans
Financing receivable, past due	4,708	6,777
All Total Loans [Member] | Real estate mortgage residential (1-4 family) first mortgages [Member] | 60-89 Days past due [Member]
Analysis of the payment status of loans
Financing receivable, past due	692	1,370
All Total Loans [Member] | Real estate mortgage residential (1-4 family) first mortgages [Member] | 90 Days or More Past Due [Member]
Analysis of the payment status of loans
Financing receivable, past due
All Total Loans [Member] | Real estate mortgage home equity loans / lines of credit [Member]
Analysis of the payment status of loans
Nonaccrual loans	1,765	2,524
Current	366,377	375,814
Total loans	369,502	379,695
All Total Loans [Member] | Real estate mortgage home equity loans / lines of credit [Member] | 30-59 Days past due [Member]
Analysis of the payment status of loans
Financing receivable, past due	1,189	1,347
All Total Loans [Member] | Real estate mortgage home equity loans / lines of credit [Member] | 60-89 Days past due [Member]
Analysis of the payment status of loans
Financing receivable, past due	171	10
All Total Loans [Member] | Real estate mortgage home equity loans / lines of credit [Member] | 90 Days or More Past Due [Member]
Analysis of the payment status of loans
Financing receivable, past due
All Total Loans [Member] | Real estate mortgage commercial and other [Member]
Analysis of the payment status of loans
Nonaccrual loans	7,292	3,345
Current	1,667,577	1,678,529
Total loans	1,678,033	1,683,595
All Total Loans [Member] | Real estate mortgage commercial and other [Member] | 30-59 Days past due [Member]
Analysis of the payment status of loans
Financing receivable, past due	2,604	1,270
All Total Loans [Member] | Real estate mortgage commercial and other [Member] | 60-89 Days past due [Member]
Analysis of the payment status of loans
Financing receivable, past due	560	451
All Total Loans [Member] | Real estate mortgage commercial and other [Member] | 90 Days or More Past Due [Member]
Analysis of the payment status of loans
Financing receivable, past due
All Total Loans [Member] | Installment loans to individuals [Member]
Analysis of the payment status of loans
Nonaccrual loans	143	75
Current	70,923	73,277
Total loans	71,493	73,892
All Total Loans [Member] | Installment loans to individuals [Member] | 30-59 Days past due [Member]
Analysis of the payment status of loans
Financing receivable, past due	279	445
All Total Loans [Member] | Installment loans to individuals [Member] | 60-89 Days past due [Member]
Analysis of the payment status of loans
Financing receivable, past due	148	95
All Total Loans [Member] | Installment loans to individuals [Member] | 90 Days or More Past Due [Member]
Analysis of the payment status of loans
Financing receivable, past due
All Total Loans [Member] | Purchased credit impaired [Member]
Analysis of the payment status of loans
Nonaccrual loans
Current	19,754	21,666
Total loans	20,832	23,165
All Total Loans [Member] | Purchased credit impaired [Member] | 30-59 Days past due [Member]
Analysis of the payment status of loans
Financing receivable, past due	452	821
All Total Loans [Member] | Purchased credit impaired [Member] | 60-89 Days past due [Member]
Analysis of the payment status of loans
Financing receivable, past due	163	77
All Total Loans [Member] | Purchased credit impaired [Member] | 90 Days or More Past Due [Member]
Analysis of the payment status of loans
Financing receivable, past due	$ 463	$ 601