LOANS AND ALLOWANCE FOR LOAN LOSSES - Receivables Past Due (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	$ 14,028	$ 12,043
Loans Past Due 90 Days or More and Still Accruing	21	13
Aging of the recorded investment in loans past due [Abstract]
Past Due	14,800	17,873
Loans Not Past Due	1,276,629	1,184,191
Total recorded investment in loans	1,292,261	1,203,482
30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	7,979	4,969
60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,159	6,383
90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	5,662	6,521
Loans acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	832	1,418
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	832	1,418
Commercial and agricultural:
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	189,303	177,027
Commercial and agricultural: | Loans acquired with deteriorated credit quality
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	0	0
Commercial Mortgages
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	639,501	570,156
Commercial Mortgages | Loans acquired with deteriorated credit quality
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	832	1,323
Commercial Mortgages | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	159	19
Loans Past Due 90 Days or More and Still Accruing	0	0
Aging of the recorded investment in loans past due [Abstract]
Past Due	0	1,177
Loans Not Past Due	57,861	45,333
Total recorded investment in loans	57,861	46,510
Commercial Mortgages | Construction | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	0	0
Commercial Mortgages | Construction | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	0	1,177
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 | Construction | Loans acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	0	0
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	0	0
Commercial Mortgages | Commercial mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	8,473	5,454
Loans Past Due 90 Days or More and Still Accruing	0	0
Aging of the recorded investment in loans past due [Abstract]
Past Due	6,790	7,524
Loans Not Past Due	574,018	514,799
Total recorded investment in loans	581,640	523,646
Commercial Mortgages | Commercial mortgages | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	4,218	652
Commercial Mortgages | Commercial mortgages | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	0	4,460
Commercial Mortgages | Commercial mortgages | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	2,572	2,412
Commercial Mortgages | Commercial mortgages | Loans acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	832	1,323
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	832	1,323
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	3,210	4,201
Loans Past Due 90 Days or More and Still Accruing	0	0
Aging of the recorded investment in loans past due [Abstract]
Past Due	3,531	4,919
Loans Not Past Due	194,170	193,951
Total recorded investment in loans	197,701	198,965
Residential mortgages | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,122	2,100
Residential mortgages | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	695	436
Residential mortgages | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,714	2,383
Residential mortgages | Loans acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	0	95
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	0	95
Consumer loans:
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	265,756	257,334
Consumer loans: | Loans acquired with deteriorated credit quality
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	0	0
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	19	11
Aging of the recorded investment in loans past due [Abstract]
Past Due	27	23
Loans Not Past Due	1,417	1,453
Total recorded investment in loans	1,444	1,476
Consumer loans: | Credit cards | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	6	3
Consumer loans: | Credit cards | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	2	9
Consumer loans: | Credit cards | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	19	11
Consumer loans: | Credit cards | Loans acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	0	0
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	0	0
Consumer loans: | Home equity lines and loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	1,178	1,670
Loans Past Due 90 Days or More and Still Accruing	0	0
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,165	1,376
Loans Not Past Due	97,598	97,477
Total recorded investment in loans	98,763	98,853
Consumer loans: | Home equity lines and loans | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	220	227
Consumer loans: | Home equity lines and loans | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	99	0
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	846	1,149
Consumer loans: | Home equity lines and loans | Loans acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	0	0
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	0	0
Consumer loans: | Indirect consumer loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	837	654
Loans Past Due 90 Days or More and Still Accruing	0	0
Aging of the recorded investment in loans past due [Abstract]
Past Due	2,910	2,602
Loans Not Past Due	144,880	137,391
Total recorded investment in loans	147,790	139,993
Consumer loans: | Indirect consumer loans | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	2,084	1,773
Consumer loans: | Indirect consumer loans | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	325	287
Consumer loans: | Indirect consumer loans | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	501	542
Consumer loans: | Indirect consumer loans | Loans acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	0	0
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	0	0
Consumer loans: | Direct consumer loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	21	45
Loans Past Due 90 Days or More and Still Accruing	0	0
Aging of the recorded investment in loans past due [Abstract]
Past Due	141	83
Loans Not Past Due	17,618	16,929
Total recorded investment in loans	17,759	17,012
Consumer loans: | Direct consumer loans | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	112	54
Consumer loans: | Direct consumer loans | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	21	7
Consumer loans: | Direct consumer loans | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	8	22
Consumer loans: | Direct consumer loans | Loans acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	0	0
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	0	0
Commercial and industrial | Commercial and agricultural:
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	150	0
Loans Past Due 90 Days or More and Still Accruing	2	2
Aging of the recorded investment in loans past due [Abstract]
Past Due	236	169
Loans Not Past Due	188,617	176,497
Total recorded investment in loans	188,853	176,666
Commercial and industrial | Commercial and agricultural: | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	217	160
Commercial and industrial | Commercial and agricultural: | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	17	7
Commercial and industrial | Commercial and agricultural: | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	2	2
Commercial and industrial | Commercial and agricultural: | Loans acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	0	0
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	0	0
Agricultural | Commercial and agricultural:
Aging of the recorded investment in loans past due [Abstract]
Past Due	0	0
Loans Not Past Due	450	361
Total recorded investment in loans	450	361
Agricultural | Commercial and agricultural: | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	0	0
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
Agricultural | Commercial and agricultural: | Loans acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	0	0
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	$ 0	$ 0