LOANS AND ALLOWANCE FOR LOAN LOSSES - Loan individually evaluated for impairment by class of loans - (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loans individually evaluated for impairment and average balance of impaired loans
Performing troubled debt restructurings excluded as allowed	$ 228	$ 1,925	$ 2,760
Unpaid Principal Balance
With an allowance recorded	8,263	6,272	4,146
With no related allowance recorded	13,553	17,236	15,230
Total impaired loans	21,816	23,508	19,376
Recorded Investment
With an allowance recorded	7,956	6,141	3,981
With no related allowance recorded	10,627	13,131	12,248
Total impaired loans	18,583	19,272	16,229
Allowance for Loan Losses Allocated
With an allowance recorded	3,461	1,800	1,429
Total impaired loans	3,461	1,800	1,429
Interest Income Recognized
Interest income recognized, no recorded allowance	343	365	342
Interest Income Recognized	343	365	342
Cash Basis Income Recognized
Cash basis interest recognized, no recorded allowance	343	365	342
Cash Basis Income Recognized	343	365	342
Commercial
Allowance for Loan Losses Allocated
With an allowance recorded	2,457	898
Commercial | Commercial and industrial
Unpaid Principal Balance
With an allowance recorded	1,936	719	150
With no related allowance recorded	453	1,028	676
Recorded Investment
With an allowance recorded	1,902	689	150
With no related allowance recorded	25	322	655
Allowance for Loan Losses Allocated
With an allowance recorded	1,632	429	92
Interest Income Recognized
Interest income recognized, no recorded allowance		53	34
Interest Income Recognized	172
Cash Basis Income Recognized
Cash basis interest recognized, no recorded allowance	172	53	34
Commercial | Agricultural
Unpaid Principal Balance
With an allowance recorded	1,438	1,441
With no related allowance recorded	96	254	7
Recorded Investment
With an allowance recorded	1,438	1,441
With no related allowance recorded	96	253	7
Allowance for Loan Losses Allocated
With an allowance recorded	825	469
Commercial real estate
Allowance for Loan Losses Allocated
With an allowance recorded	862	755
Commercial real estate | Farm
Unpaid Principal Balance
With an allowance recorded	709	1,106
With no related allowance recorded	426	506	496
Recorded Investment
With an allowance recorded	708	1,105
With no related allowance recorded	153	241	309
Allowance for Loan Losses Allocated
With an allowance recorded	433	360
Interest Income Recognized
Interest income recognized, no recorded allowance			12
Cash Basis Income Recognized
Cash basis interest recognized, no recorded allowance			12
Commercial real estate | Hotel
Unpaid Principal Balance
With no related allowance recorded		64
Recorded Investment
With no related allowance recorded		64
Commercial real estate | Construction and development
Unpaid Principal Balance
With no related allowance recorded	37	239	189
Recorded Investment
With no related allowance recorded	37	162	186
Interest Income Recognized
Interest income recognized, no recorded allowance			47
Cash Basis Income Recognized
Cash basis interest recognized, no recorded allowance			47
Commercial real estate | Other
Unpaid Principal Balance
With an allowance recorded	3,031	1,900	2,480
With no related allowance recorded	2,193	3,558	4,429
Recorded Investment
With an allowance recorded	2,802	1,755	2,363
With no related allowance recorded	1,809	2,652	3,291
Allowance for Loan Losses Allocated
With an allowance recorded	429	395	1,166
Interest Income Recognized
Interest income recognized, no recorded allowance	102	200	160
Cash Basis Income Recognized
Cash basis interest recognized, no recorded allowance	102	200	160
Residential
Allowance for Loan Losses Allocated
With an allowance recorded	142	147
Residential | 1-4 family
Unpaid Principal Balance
With an allowance recorded	1,052	1,091	1,357
With no related allowance recorded	7,893	9,215	6,718
Recorded Investment
With an allowance recorded	1,009	1,046	1,309
With no related allowance recorded	6,381	7,432	5,391
Allowance for Loan Losses Allocated
With an allowance recorded	141	146	167
Interest Income Recognized
Interest income recognized, no recorded allowance	46	53	49
Cash Basis Income Recognized
Cash basis interest recognized, no recorded allowance	46	53	49
Residential | Home equity
Unpaid Principal Balance
With an allowance recorded	97	15	159
With no related allowance recorded	1,376	2,233	2,589
Recorded Investment
With an allowance recorded	97	105	159
With no related allowance recorded	1,153	1,875	2,296
Allowance for Loan Losses Allocated
With an allowance recorded	1	1	4
Interest Income Recognized
Interest income recognized, no recorded allowance	19	47	17
Cash Basis Income Recognized
Cash basis interest recognized, no recorded allowance	19	47	17
Consumer | Direct
Unpaid Principal Balance
With no related allowance recorded	1,079	139	126
Recorded Investment
With no related allowance recorded	973	130	113
Interest Income Recognized
Interest income recognized, no recorded allowance	4	12	18
Cash Basis Income Recognized
Cash basis interest recognized, no recorded allowance	$ 4	$ 12	18
Consumer | Indirect
Interest Income Recognized
Interest income recognized, no recorded allowance			5
Cash Basis Income Recognized
Cash basis interest recognized, no recorded allowance			$ 5