LOANS AND ALLOWANCE FOR LOAN LOSSES - Receivables Past Due (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	$ 23,468	$ 12,254
Loans Past Due 90 Days or More and Still Accruing	53	19
Aging of the recorded investment in loans past due [Abstract]
Past Due	13,659	14,367
Loans Not Past Due	1,296,661	1,301,242
Total recorded investment in loans	1,310,320	1,315,609
30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	7,598	10,688
60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,659	1,207
90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	4,402	2,472
Commercial and agricultural
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	227,725	203,412
Commercial Mortgages
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	653,405	662,988
Commercial Mortgages | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	87	109
Loans Past Due 90 Days or More and Still Accruing	0	0
Aging of the recorded investment in loans past due [Abstract]
Past Due	279	0
Loans Not Past Due	48,490	54,626
Total recorded investment in loans	48,769	54,626
Commercial Mortgages | Construction | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	279	0
Commercial Mortgages | Construction | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	0	0
Commercial Mortgages | Construction | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	0	0
Commercial Mortgages | Commercial mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	13,250	5,529
Loans Past Due 90 Days or More and Still Accruing	0	0
Aging of the recorded investment in loans past due [Abstract]
Past Due	4,571	6,600
Loans Not Past Due	600,065	601,762
Total recorded investment in loans	604,636	608,362
Commercial Mortgages | Commercial mortgages | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	2,176	6,273
Commercial Mortgages | Commercial mortgages | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	402	158
Commercial Mortgages | Commercial mortgages | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,993	169
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	2,455	2,655
Loans Past Due 90 Days or More and Still Accruing	0	0
Aging of the recorded investment in loans past due [Abstract]
Past Due	3,838	3,746
Loans Not Past Due	180,731	179,479
Total recorded investment in loans	184,569	183,225
Residential mortgages | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,906	2,204
Residential mortgages | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	674	516
Residential mortgages | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,258	1,026
Consumer Loans
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	244,621	265,984
Consumer Loans | Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	0	0
Loans Past Due 90 Days or More and Still Accruing	0	9
Aging of the recorded investment in loans past due [Abstract]
Past Due		13
Loans Not Past Due		1,437
Total recorded investment in loans		1,450
Consumer Loans | Credit cards | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due		1
Consumer Loans | Credit cards | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due		3
Consumer Loans | Credit cards | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due		9
Consumer Loans | Home equity lines and loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	722	1,183
Loans Past Due 90 Days or More and Still Accruing	0	0
Aging of the recorded investment in loans past due [Abstract]
Past Due	547	1,106
Loans Not Past Due	92,205	97,360
Total recorded investment in loans	92,752	98,466
Consumer Loans | Home equity lines and loans | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	36	279
Consumer Loans | Home equity lines and loans | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	15	97
Consumer Loans | Home equity lines and loans | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	496	730
Consumer Loans | Indirect consumer loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	613	693
Loans Past Due 90 Days or More and Still Accruing	0	0
Aging of the recorded investment in loans past due [Abstract]
Past Due	2,010	2,266
Loans Not Past Due	134,830	147,540
Total recorded investment in loans	136,840	149,806
Consumer Loans | Indirect consumer loans | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,356	1,511
Consumer Loans | Indirect consumer loans | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	305	319
Consumer Loans | Indirect consumer loans | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	349	436
Consumer Loans | Direct consumer loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	6	37
Loans Past Due 90 Days or More and Still Accruing	0	0
Aging of the recorded investment in loans past due [Abstract]
Past Due	81	204
Loans Not Past Due	14,948	16,058
Total recorded investment in loans	15,029	16,262
Consumer Loans | Direct consumer loans | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	63	120
Consumer Loans | Direct consumer loans | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	14	53
Consumer Loans | Direct consumer loans | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	4	31
Commercial and industrial | Commercial and agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	6,335	2,048
Loans Past Due 90 Days or More and Still Accruing	53	10
Aging of the recorded investment in loans past due [Abstract]
Past Due	2,333	416
Loans Not Past Due	225,177	202,667
Total recorded investment in loans	227,510	203,083
Commercial and industrial | Commercial and agricultural | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,782	284
Commercial and industrial | Commercial and agricultural | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	249	61
Commercial and industrial | Commercial and agricultural | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	302	71
Agricultural | Commercial and agricultural
Aging of the recorded investment in loans past due [Abstract]
Past Due	0	16
Loans Not Past Due	215	313
Total recorded investment in loans	215	329
Agricultural | Commercial and agricultural | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	0	16
Agricultural | Commercial and agricultural | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	0	0
Agricultural | Commercial and agricultural | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	$ 0	$ 0