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LOANS AND ALLOWANCE FOR LOAN LOSSES - Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Unpaid Principal Balance
Unpaid principal balance, total	$ 18,800		$ 18,800		$ 16,546
Recorded Investment
Recorded investment, total	12,217		12,217		10,589
Allowance for Loan Losses Allocated	3,398		3,398		1,527
Average Recorded Investment
Average recorded investment, total	12,672	$ 16,049	11,464	$ 15,715
Interest Income Recognized
Interest income, accrual method, total	55	23	96	50
Commercial and agricultural: | Commercial and industrial
Unpaid Principal Balance
With no related allowance, unpaid principal balance	995		995		1,960
With related allowance, unpaid principal balance	5,487		5,487		5,228
Recorded Investment
With no related allowance, recorded investment	970		970		1,963
With related allowance, recorded investment	1,612		1,612		1,437
Allowance for Loan Losses Allocated	1,525		1,525		1,401
Average Recorded Investment
With no related allowance, average recorded investment	1,378	1,239	1,645	679
With related allowance, average recorded investment	1,545	5,804	1,511	5,867
Interest Income Recognized
With no related allowance, interest income, accrual method	3	2	3	2
With related allowance, interest income, accrual method	4	2	6	4
Commercial mortgages: | Construction
Unpaid Principal Balance
With no related allowance, unpaid principal balance	143		143		188
Recorded Investment
With no related allowance, recorded investment	143		143		189
Average Recorded Investment
With no related allowance, average recorded investment	151	213	167	226
Interest Income Recognized
With no related allowance, interest income, accrual method	1	2	5	6
Commercial mortgages: | Commercial mortgages, other
Unpaid Principal Balance
With no related allowance, unpaid principal balance	7,312		7,312		6,814
With related allowance, unpaid principal balance	3,554		3,554		258
Recorded Investment
With no related allowance, recorded investment	4,651		4,651		4,760
With related allowance, recorded investment	3,562		3,562		168
Allowance for Loan Losses Allocated	1,800		1,800		74
Average Recorded Investment
With no related allowance, average recorded investment	4,665	4,515	4,743	3,938
With related allowance, average recorded investment	3,644	2,229	1,905	3,645
Interest Income Recognized
With no related allowance, interest income, accrual method	8	0	23	0
With related allowance, interest income, accrual method	25	8	25	16
Residential mortgages
Unpaid Principal Balance
With no related allowance, unpaid principal balance	960		960		1,283
Recorded Investment
With no related allowance, recorded investment	946		946		1,271
Average Recorded Investment
With no related allowance, average recorded investment	950	1,224	1,034	873
Interest Income Recognized
With no related allowance, interest income, accrual method	12	7	29	17
Consumer loans: | Home equity lines and loans
Unpaid Principal Balance
With no related allowance, unpaid principal balance	195		195		645
With related allowance, unpaid principal balance	154		154		170
Recorded Investment
With no related allowance, recorded investment	179		179		631
With related allowance, recorded investment	154		154		170
Allowance for Loan Losses Allocated	73		73		$ 52
Average Recorded Investment
With no related allowance, average recorded investment	184	650	299	399
With related allowance, average recorded investment	155	175	160	88
Interest Income Recognized
With no related allowance, interest income, accrual method	2	2	5	5
With related allowance, interest income, accrual method	$ 0	$ 0	$ 0	$ 0

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