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LOANS AND ALLOWANCE FOR LOAN LOSSES - Allowances (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Sep. 30, 2018	Dec. 31, 2017
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance	$ 19,645	$ 15,104	$ 21,161	$ 14,253	$ 14,253
Charge-offs	(440)	(816)	(5,315)	(1,708)
Recoveries	130	117	418	399
Net recoveries (charge-offs)	(310)	(699)	(4,897)	(1,309)
Provision	300	1,289	3,371	2,750
Ending balance	19,635	15,694	19,635	15,694	21,161
Ending allowance balance attributable to loans [Abstract]
Individually evaluated for impairment						$ 2,209	$ 5,937
Collectively evaluated for impairment						17,426	15,195
Total ending allowance balance	19,645	15,104	21,161	14,253	14,253	19,635	21,161
Loans [Abstract]
Loans individually evaluated for impairment						9,221	13,926
Loans collectively evaluated for impairment						1,315,301	1,300,864
Total recorded investment in loans						1,324,522	1,315,582
Loans acquired with deteriorated credit quality
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance			29
Ending balance					29
Ending allowance balance attributable to loans [Abstract]
Total ending allowance balance			29		29		29
Loans [Abstract]
Total recorded investment in loans						0	792
Commercial and Agricultural
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance	4,969	1,883	6,976	1,589	1,589
Charge-offs	0	(89)	(3,644)	(96)
Recoveries	13	34	34	95
Net recoveries (charge-offs)	13	(55)	(3,610)	(1)
Provision	285	99	1,901	339
Ending balance	5,267	1,927	5,267	1,927	6,976
Ending allowance balance attributable to loans [Abstract]
Individually evaluated for impairment						1,713	5,135
Collectively evaluated for impairment						3,554	1,841
Total ending allowance balance	4,969	1,883	6,976	1,589	1,589	5,267	6,976
Loans [Abstract]
Loans individually evaluated for impairment						2,181	6,133
Loans collectively evaluated for impairment						190,777	193,443
Total recorded investment in loans						192,958	199,576
Commercial and Agricultural | Loans acquired with deteriorated credit quality
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance			0
Ending balance					0
Ending allowance balance attributable to loans [Abstract]
Total ending allowance balance			0		0		0
Loans [Abstract]
Total recorded investment in loans							0
Commercial Mortgages
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance	8,740	7,778	8,514	7,270	7,270
Charge-offs	0	(154)	(145)	(154)
Recoveries	0	1	2	4
Net recoveries (charge-offs)	0	(153)	(143)	(150)
Provision	(91)	758	278	1,263
Ending balance	8,649	8,383	8,649	8,383	8,514
Ending allowance balance attributable to loans [Abstract]
Individually evaluated for impairment						496	802
Collectively evaluated for impairment						8,153	7,683
Total ending allowance balance	8,740	7,778	8,514	7,270	7,270	8,649	8,514
Loans [Abstract]
Loans individually evaluated for impairment						6,572	7,302
Loans collectively evaluated for impairment						661,003	638,080
Total recorded investment in loans						667,575	646,174
Commercial Mortgages | Loans acquired with deteriorated credit quality
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance			29
Ending balance					29
Ending allowance balance attributable to loans [Abstract]
Total ending allowance balance			29		29		29
Loans [Abstract]
Total recorded investment in loans							792
Residential mortgages
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance	1,445	1,517	1,316	1,523	1,523
Charge-offs	(60)	(133)	(225)	(193)
Recoveries	0	0	5	30
Net recoveries (charge-offs)	(60)	(133)	(220)	(163)
Provision	11	12	300	36
Ending balance	1,396	1,396	1,396	1,396	1,316
Ending allowance balance attributable to loans [Abstract]
Individually evaluated for impairment						0	0
Collectively evaluated for impairment						1,396	1,316
Total ending allowance balance	1,445	1,517	1,316	1,523	1,523	1,396	1,316
Loans [Abstract]
Loans individually evaluated for impairment						410	427
Loans collectively evaluated for impairment						188,751	194,510
Total recorded investment in loans						189,161	194,937
Residential mortgages | Loans acquired with deteriorated credit quality
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance			0
Ending balance					0
Ending allowance balance attributable to loans [Abstract]
Total ending allowance balance			0		0		0
Loans [Abstract]
Total recorded investment in loans						0	0
Consumer Loans
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance	4,491	3,926	4,355	3,871	3,871
Charge-offs	(380)	(440)	(1,301)	(1,265)
Recoveries	117	82	377	270
Net recoveries (charge-offs)	(263)	(358)	(924)	(995)
Provision	95	420	892	1,112
Ending balance	4,323	3,988	4,323	3,988	4,355
Ending allowance balance attributable to loans [Abstract]
Individually evaluated for impairment						0	0
Collectively evaluated for impairment						4,323	4,355
Total ending allowance balance	$ 4,491	$ 3,926	4,355	$ 3,871	3,871	4,323	4,355
Loans [Abstract]
Loans individually evaluated for impairment						58	64
Loans collectively evaluated for impairment						274,770	274,831
Total recorded investment in loans						$ 274,828	274,895
Consumer Loans | Loans acquired with deteriorated credit quality
Allowance for loan losses, by portfolio segment [Roll Forward]
Beginning balance			0
Ending balance					0
Ending allowance balance attributable to loans [Abstract]
Total ending allowance balance			$ 0		$ 0		0
Loans [Abstract]
Total recorded investment in loans							$ 0

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