LOAN CREDIT QUALITY AND RELATED ALLOWANCE FOR LOAN LOSSES - Aging Category of Loans, by Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Aging categories of loans by segment
Current	$ 1,229,330	$ 1,071,656
Past Due 30 To 89 Days	9,744	11,656
Past Due 90 Days Or More & Still Accruing	509	870
Non-Accrual	6,759	10,756
Total	1,246,342	1,094,938
Net deferred loan fees and discounts	272	(1,257)
Allowance for loan losses	(12,858)	(12,896)	$ (12,044)	$ (10,579)
Current loans, net	1,216,744	1,057,503
Loans, net	1,233,756	1,080,785
Commercial, Financial, and Agricultural
Aging categories of loans by segment
Current	178,022	145,179
Past Due 30 To 89 Days	663	785
Past Due 90 Days Or More & Still Accruing	86	14
Non-Accrual	114	132
Total	178,885	146,110
Allowance for loan losses	(1,177)	(1,554)	(1,532)	(1,124)
Residential Real Estate Mortgage
Aging categories of loans by segment
Current	588,278	553,053
Past Due 30 To 89 Days	6,853	9,112
Past Due 90 Days Or More & Still Accruing	318	587
Non-Accrual	1,628	1,988
Total	597,077	564,740
Allowance for loan losses	(5,679)	(5,383)	(5,116)	(3,755)
Commercial Real Estate Mortgage
Aging categories of loans by segment
Current	325,148	296,537
Past Due 30 To 89 Days	1,823	786
Past Due 90 Days Or More & Still Accruing	80	268
Non-Accrual	4,968	8,591
Total	332,019	306,182
Allowance for loan losses	(4,277)	(4,975)	(4,217)	(4,205)
Construction Real Estate Mortgage
Aging categories of loans by segment
Current	31,547	33,879
Past Due 30 To 89 Days	116	771
Past Due 90 Days Or More & Still Accruing	20	0
Non-Accrual	0	0
Total	31,683	34,650
Allowance for loan losses	(155)	(178)	(160)	(786)
Installment Loans to Individuals
Aging categories of loans by segment
Current	106,335	43,008
Past Due 30 To 89 Days	289	202
Past Due 90 Days Or More & Still Accruing	5	1
Non-Accrual	49	45
Total	106,678	43,256
Allowance for loan losses	$ (1,075)	$ (416)	$ (243)	$ (245)