Loans and Asset Quality Information (Schedule of Nonaccrual Loans) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Company's nonaccrual loans:
Nonaccrual loans	$ 21,849	$ 20,968	$ 25,684
Commercial, financial, and agricultural [Member]
Company's nonaccrual loans:
Nonaccrual loans	801	1,001
Real estate construction, land development & other land loans [Member]
Company's nonaccrual loans:
Nonaccrual loans	1,766	1,822
Real estate mortgage residential (1-4 family) first mortgages [Member]
Company's nonaccrual loans:
Nonaccrual loans	12,073	12,201
Real estate mortgage home equity loans / lines of credit [Member]
Company's nonaccrual loans:
Nonaccrual loans	1,980	2,524
Real estate mortgage commercial and other [Member]
Company's nonaccrual loans:
Nonaccrual loans	5,119	3,345
Installment loans to individuals [Member]
Company's nonaccrual loans:
Nonaccrual loans	$ 110	$ 75