Loans and Asset Quality Information (Schedule of Recorded Investment in Loans by Credit Quality Indicators) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Recorded investment in loans by credit quality indicators:
Total	$ 4,114,036	$ 4,043,355
Unamortized net deferred loan costs	(251)	(986)	$ (704)
Total loans	4,113,785	4,042,369	$ 3,289,355
Pass [Member]
Recorded investment in loans by credit quality indicators:
Total	3,976,168	3,891,038
Special Mention Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	57,869	72,915
Classified Accruing Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	58,150	58,434
Classified Nonaccrual Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	21,849	20,968
Commercial, financial, and agricultural [Member]
Recorded investment in loans by credit quality indicators:
Total	411,248	380,482
Commercial, financial, and agricultural [Member] | Pass [Member]
Recorded investment in loans by credit quality indicators:
Total	405,159	368,658
Commercial, financial, and agricultural [Member] | Special Mention Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	4,546	9,901
Commercial, financial, and agricultural [Member] | Classified Accruing Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	742	922
Commercial, financial, and agricultural [Member] | Classified Nonaccrual Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	801	1,001
Real estate construction, land development & other land loans [Member]
Recorded investment in loans by credit quality indicators:
Total	542,560	538,613
Real estate construction, land development & other land loans [Member] | Pass [Member]
Recorded investment in loans by credit quality indicators:
Total	527,835	523,642
Real estate construction, land development & other land loans [Member] | Special Mention Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	7,538	7,129
Real estate construction, land development & other land loans [Member] | Classified Accruing Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	5,421	6,020
Real estate construction, land development & other land loans [Member] | Classified Nonaccrual Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	1,766	1,822
Real estate - mortgage - residential (1-4 family) first mortgages [Member]
Recorded investment in loans by credit quality indicators:
Total	987,333	963,913
Real estate - mortgage - residential (1-4 family) first mortgages [Member] | Pass [Member]
Recorded investment in loans by credit quality indicators:
Total	932,840	905,111
Real estate - mortgage - residential (1-4 family) first mortgages [Member] | Special Mention Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	16,243	16,235
Real estate - mortgage - residential (1-4 family) first mortgages [Member] | Classified Accruing Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	26,177	30,366
Real estate - mortgage - residential (1-4 family) first mortgages [Member] | Classified Nonaccrual Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	12,073	12,201
Real estate mortgage home equity loans / lines of credit [Member]
Recorded investment in loans by credit quality indicators:
Total	373,524	379,695
Real estate mortgage home equity loans / lines of credit [Member] | Pass [Member]
Recorded investment in loans by credit quality indicators:
Total	360,194	365,982
Real estate mortgage home equity loans / lines of credit [Member] | Special Mention Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	1,884	3,784
Real estate mortgage home equity loans / lines of credit [Member] | Classified Accruing Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	9,466	7,405
Real estate mortgage home equity loans / lines of credit [Member] | Classified Nonaccrual Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	1,980	2,524
Real estate mortgage commercial and other [Member]
Recorded investment in loans by credit quality indicators:
Total	1,706,382	1,683,595
Real estate mortgage commercial and other [Member] | Pass [Member]
Recorded investment in loans by credit quality indicators:
Total	1,673,395	1,647,725
Real estate mortgage commercial and other [Member] | Special Mention Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	20,277	23,355
Real estate mortgage commercial and other [Member] | Classified Accruing Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	7,591	9,190
Real estate mortgage commercial and other [Member] | Classified Nonaccrual Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	5,119	3,345
Installment loans to individuals [Member]
Recorded investment in loans by credit quality indicators:
Total	70,842	73,892
Installment loans to individuals [Member] | Pass [Member]
Recorded investment in loans by credit quality indicators:
Total	70,286	73,379
Installment loans to individuals [Member] | Special Mention Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	219	222
Installment loans to individuals [Member] | Classified Accruing Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	227	216
Installment loans to individuals [Member] | Classified Nonaccrual Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	110	75
Purchased credit impaired [Member]
Recorded investment in loans by credit quality indicators:
Total	22,147	23,165
Purchased credit impaired [Member] | Pass [Member]
Recorded investment in loans by credit quality indicators:
Total	6,459	6,541
Purchased credit impaired [Member] | Special Mention Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	7,162	12,309
Purchased credit impaired [Member] | Classified Accruing Loans [Member]
Recorded investment in loans by credit quality indicators:
Total	8,526	4,315
Purchased credit impaired [Member] | Classified Nonaccrual Loans [Member]
Recorded investment in loans by credit quality indicators:
Total