LOAN CREDIT QUALITY AND RELATED ALLOWANCE FOR LOAN LOSSES - Average Recorded Investment in Impaired Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Investment in Impaired Loans	$ 15,516	$ 16,896	$ 21,995
Interest Income Recognized on an Accrual Basis on Impaired Loans	302	292	436
Interest Income Recognized on a Cash Basis on Impaired Loans	332	212	190
Commercial, Financial, and Agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Investment in Impaired Loans	727	400	1,031
Interest Income Recognized on an Accrual Basis on Impaired Loans	41	16	21
Interest Income Recognized on a Cash Basis on Impaired Loans	7	1	10
Residential Real Estate Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Investment in Impaired Loans	3,233	3,471	2,570
Interest Income Recognized on an Accrual Basis on Impaired Loans	75	89	72
Interest Income Recognized on a Cash Basis on Impaired Loans	91	101	47
Commercial Real Estate Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Investment in Impaired Loans	11,551	12,887	17,529
Interest Income Recognized on an Accrual Basis on Impaired Loans	186	187	342
Interest Income Recognized on a Cash Basis on Impaired Loans	233	110	80
Construction Real Estate Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Investment in Impaired Loans	0	138	865
Interest Income Recognized on an Accrual Basis on Impaired Loans	0	0	1
Interest Income Recognized on a Cash Basis on Impaired Loans	0	$ 0	$ 53
Installment loans to individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Investment in Impaired Loans	5
Interest Income Recognized on an Accrual Basis on Impaired Loans	0
Interest Income Recognized on a Cash Basis on Impaired Loans	$ 1