LOANS AND ALLOWANCE FOR LOAN LOSSES - Receivables Past Due (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	$ 17,280	$ 17,324
Loans Past Due 90 Days or More and Still Accruing	28	29
Aging of the recorded investment in loans past due [Abstract]
Past Due	13,221	14,076
Loans Not Past Due	1,310,308	1,300,714
Total recorded investment in loans	1,323,529	1,315,582
30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	5,214	7,639
60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	768	2,605
90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	7,239	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	201,037	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	649,413	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	130	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	55,560	45,688
Total recorded investment in loans	55,560	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	6,597	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	1,370	3,262
Loans Not Past Due	592,483	596,432
Total recorded investment in loans	593,853	600,486
Commercial Mortgages | Commercial mortgages | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	442	2,399
Commercial Mortgages | Commercial mortgages | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	0	115
Commercial Mortgages | Commercial mortgages | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	928	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	3,155	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	3,290	3,812
Loans Not Past Due	191,806	191,125
Total recorded investment in loans	195,096	194,937
Residential mortgages | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,719	1,399
Residential mortgages | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	308	939
Residential mortgages | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,263	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	277,983	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	26	24
Aging of the recorded investment in loans past due [Abstract]
Past Due	38	50
Loans Not Past Due	1,380	1,466
Total recorded investment in loans	1,418	1,516
Consumer loans: | Credit cards | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	3	17
Consumer loans: | Credit cards | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	9	9
Consumer loans: | Credit cards | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	26	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	1,302	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	1,370	1,279
Loans Not Past Due	99,532	99,599
Total recorded investment in loans	100,902	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	283	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	231	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	856	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	886	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	2,037	2,887
Loans Not Past Due	155,303	150,645
Total recorded investment in loans	157,340	153,532
Consumer loans: | Indirect consumer loans | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	1,332	1,822
Consumer loans: | Indirect consumer loans | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	216	484
Consumer loans: | Indirect consumer loans | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	489	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	46	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	77	78
Loans Not Past Due	18,246	18,891
Total recorded investment in loans	18,323	18,969
Consumer loans: | Direct consumer loans | 30 - 59 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	38	48
Consumer loans: | Direct consumer loans | 60 - 89 Days Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	4	28
Consumer loans: | Direct consumer loans | 90 Days or More Past Due
Aging of the recorded investment in loans past due [Abstract]
Past Due	35	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	5,164	5,250
Loans Past Due 90 Days or More and Still Accruing	2	5
Aging of the recorded investment in loans past due [Abstract]
Past Due	5,039	2,708
Loans Not Past Due	195,468	196,322
Total recorded investment in loans	200,507	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	1,397	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	3,642	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	530	546
Total recorded investment in loans	530	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