LOAN CREDIT QUALITY AND RELATED ALLOWANCE FOR LOAN LOSSES - Allowance Activity (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016
Changes in allowance
Balance at the beginning of the period				$ 12,896				$ 12,044	$ 12,896	$ 12,044	$ 10,579
Charge-offs									(1,045)	(530)	(1,361)
Recoveries									277	186	526
Provision for loan losses	$ 125	$ 60	$ 215	330	$ 330	$ 258	$ 258	350	730	1,196	2,300
Balance at the end of the period	12,858				12,896				12,858	12,896	12,044
Allowance for Loan Losses:
Individually evaluated for impairment												$ 2,184	$ 2,179
Collectively evaluated for impairment												10,674	10,717
Total ending allowance balance	12,858			12,896	12,896			12,044	12,896	12,044	10,579	12,858	12,896
Loans:
Individually evaluated for impairment												14,446	15,976
Collectively evaluated for impairment												1,231,896	1,078,962
Total												1,246,342	1,094,938
Commercial, Financial, and Agricultural
Changes in allowance
Balance at the beginning of the period				1,554				1,532	1,554	1,532	1,124
Charge-offs									(106)	(167)	(283)
Recoveries									135	62	176
Provision for loan losses									(406)	127	515
Balance at the end of the period	1,177				1,554				1,177	1,554	1,532
Allowance for Loan Losses:
Individually evaluated for impairment												96	74
Collectively evaluated for impairment												1,081	1,480
Total ending allowance balance	1,177			1,554	1,554			1,532	1,554	1,532	1,124	1,177	1,554
Loans:
Individually evaluated for impairment												1,268	241
Collectively evaluated for impairment												177,617	145,869
Total												178,885	146,110
Residential Real Estate Mortgage
Changes in allowance
Balance at the beginning of the period				5,383				5,116	5,383	5,116	3,755
Charge-offs									(578)	(39)	(49)
Recoveries									55	15	81
Provision for loan losses									819	291	1,329
Balance at the end of the period	5,679				5,383				5,679	5,383	5,116
Allowance for Loan Losses:
Individually evaluated for impairment												367	437
Collectively evaluated for impairment												5,312	4,946
Total ending allowance balance	5,679			5,383	5,383			5,116	$ 5,383	$ 5,116	3,755	5,679	5,383
Loans:
Individually evaluated for impairment												3,732	3,477
Collectively evaluated for impairment												593,345	561,263
Total												597,077	564,740
Residential Real Estate Mortgage | Financing receivable | Owners of rental properties
Changes in allowance
Concentration of loans (as a percent)									15.16%	16.10%
Commercial Real Estate Mortgage
Changes in allowance
Balance at the beginning of the period				4,975				4,217	$ 4,975	$ 4,217	4,205
Charge-offs									(58)	(93)	(743)
Recoveries									1	8	182
Provision for loan losses									(641)	843	573
Balance at the end of the period	4,277				4,975				4,277	4,975	4,217
Allowance for Loan Losses:
Individually evaluated for impairment												1,721	1,668
Collectively evaluated for impairment												2,556	3,307
Total ending allowance balance	4,277			4,975	4,975			4,217	$ 4,975	$ 4,217	4,205	4,277	4,975
Loans:
Individually evaluated for impairment												9,446	12,258
Collectively evaluated for impairment												322,573	293,924
Total												332,019	306,182
Commercial Real Estate Mortgage | Financing receivable | Owners of rental properties
Changes in allowance
Concentration of loans (as a percent)									13.57%	14.18%
Construction Real Estate Mortgage
Changes in allowance
Balance at the beginning of the period				178				160	$ 178	$ 160	786
Charge-offs									0	(2)	(46)
Recoveries									9	9	23
Provision for loan losses									(32)	11	(603)
Balance at the end of the period	155				178				155	178	160
Allowance for Loan Losses:
Individually evaluated for impairment												0	0
Collectively evaluated for impairment												155	178
Total ending allowance balance	155			178	178			160	178	160	786	155	178
Loans:
Individually evaluated for impairment												0	0
Collectively evaluated for impairment												31,683	34,650
Total												31,683	34,650
Installment Loans to Individuals
Changes in allowance
Balance at the beginning of the period				416				243	416	243	245
Charge-offs									(303)	(229)	(240)
Recoveries									77	92	64
Provision for loan losses									885	310	174
Balance at the end of the period	1,075				416				1,075	416	243
Allowance for Loan Losses:
Individually evaluated for impairment												0	0
Collectively evaluated for impairment												1,075	416
Total ending allowance balance	1,075			416	416			243	416	243	245	1,075	416
Loans:
Individually evaluated for impairment												0	0
Collectively evaluated for impairment												106,678	43,256
Total												106,678	43,256
Unallocated
Changes in allowance
Balance at the beginning of the period				390				776	390	776	464
Charge-offs									0	0	0
Recoveries									0	0	0
Provision for loan losses									105	(386)	312
Balance at the end of the period	495				390				495	390	776
Allowance for Loan Losses:
Individually evaluated for impairment												0	0
Collectively evaluated for impairment												495	390
Total ending allowance balance	$ 495			$ 390	$ 390			$ 776	$ 390	$ 776	$ 464	$ 495	$ 390