LOANS AND ALLOWANCE FOR LOAN LOSSES - Receivables Past Due (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	$ 12,790	$ 17,324
Loans Past Due 90 Days or More and Still Accruing	17	29
Aging of the recorded investment in loans past due [Abstract]
Past Due	10,611	14,076
Loans Not Past Due	1,327,499	1,300,714
Total recorded investment in loans	1,338,110	1,315,582
30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	3,906	7,639
60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,034	2,605
90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	5,671	3,832
Loans acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	0	792
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	0	792
Commercial and agricultural:
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	194,057	199,576
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
Commercial Mortgages
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	668,558	646,174
Commercial Mortgages | Loans acquired with deteriorated credit quality
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans		792
Commercial Mortgages | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	123	135
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	0
Loans Not Past Due	45,671	45,688
Total recorded investment in loans	45,671	45,688
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	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 | 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	6,101	6,520
Loans Past Due 90 Days or More and Still Accruing	0	0
Aging of the recorded investment in loans past due [Abstract]
Past Due	4,424	3,262
Loans Not Past Due	618,463	596,432
Total recorded investment in loans	622,887	600,486
Commercial Mortgages | Commercial mortgages | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	992	2,399
Commercial Mortgages | Commercial mortgages | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	93	115
Commercial Mortgages | Commercial mortgages | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	3,339	748
Commercial Mortgages | Commercial mortgages | Loans acquired with deteriorated credit quality
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	0	792
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	0	792
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	2,981	3,160
Loans Past Due 90 Days or More and Still Accruing	0	0
Aging of the recorded investment in loans past due [Abstract]
Past Due	2,870	3,812
Loans Not Past Due	191,061	191,125
Total recorded investment in loans	193,931	194,937
Residential mortgages | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,117	1,399
Residential mortgages | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	492	939
Residential mortgages | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,261	1,474
Residential mortgages | 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:
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans	281,564	274,895
Consumer loans: | Loans acquired with deteriorated credit quality
Aging of the recorded investment in loans past due [Abstract]
Total recorded investment in loans		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	14	24
Aging of the recorded investment in loans past due [Abstract]
Past Due	36	50
Loans Not Past Due	1,332	1,466
Total recorded investment in loans	1,368	1,516
Consumer loans: | Credit cards | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	11	17
Consumer loans: | Credit cards | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	11	9
Consumer loans: | Credit cards | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	14	24
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	1,359	1,310
Loans Past Due 90 Days or More and Still Accruing	0	0
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,342	1,279
Loans Not Past Due	97,995	99,599
Total recorded investment in loans	99,337	100,878
Consumer loans: | Home equity lines and loans | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	359	265
Consumer loans: | Home equity lines and loans | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	196	31
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	787	983
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	673	935
Loans Past Due 90 Days or More and Still Accruing	0	0
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,428	2,887
Loans Not Past Due	161,778	150,645
Total recorded investment in loans	163,206	153,532
Consumer loans: | Indirect consumer loans | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	979	1,822
Consumer loans: | Indirect consumer loans | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	218	484
Consumer loans: | Indirect consumer loans | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	231	581
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	40	14
Loans Past Due 90 Days or More and Still Accruing	0	0
Aging of the recorded investment in loans past due [Abstract]
Past Due	102	78
Loans Not Past Due	17,551	18,891
Total recorded investment in loans	17,653	18,969
Consumer loans: | Direct consumer loans | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	56	48
Consumer loans: | Direct consumer loans | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	24	28
Consumer loans: | Direct consumer loans | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	22	2
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	1,513	5,250
Loans Past Due 90 Days or More and Still Accruing	3	5
Aging of the recorded investment in loans past due [Abstract]
Past Due	409	2,708
Loans Not Past Due	193,223	196,322
Total recorded investment in loans	193,632	199,030
Commercial and industrial | Commercial and agricultural: | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	392	1,689
Commercial and industrial | Commercial and agricultural: | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	0	999
Commercial and industrial | Commercial and agricultural: | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	17	20
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	425	546
Total recorded investment in loans	425	546
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