LOANS AND ALLOWANCE FOR LOAN LOSSES - Credit Quality Indicator (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2018	Dec. 31, 2017
Finance receivable by credit quality indicator [Abstract]
Loans		$ 1,323,529,000	$ 1,315,582,000
Deteriorated Loans Transferred in [Abstract]
Allowance for loan and lease loss, recovery of bad debts	$ 0
Loans acquired with deteriorated credit quality
Finance receivable by credit quality indicator [Abstract]
Loans		0	792,000
Not Rated
Finance receivable by credit quality indicator [Abstract]
Loans		467,690,000	464,414,000
Pass
Finance receivable by credit quality indicator [Abstract]
Loans		807,453,000	807,976,000
Special Mention
Finance receivable by credit quality indicator [Abstract]
Loans		20,289,000	14,112,000
Substandard
Finance receivable by credit quality indicator [Abstract]
Loans		21,737,000	25,489,000
Doubtful
Finance receivable by credit quality indicator [Abstract]
Loans		6,360,000	2,799,000
Commercial and agricultural:
Finance receivable by credit quality indicator [Abstract]
Loans		201,037,000	199,576,000
Commercial and agricultural: | Loans acquired with deteriorated credit quality
Finance receivable by credit quality indicator [Abstract]
Loans			0
Commercial Mortgages
Finance receivable by credit quality indicator [Abstract]
Loans		649,413,000	646,174,000
Commercial Mortgages | Loans acquired with deteriorated credit quality
Finance receivable by credit quality indicator [Abstract]
Loans			792,000
Commercial Mortgages | Construction
Finance receivable by credit quality indicator [Abstract]
Loans		55,560,000	45,688,000
Commercial Mortgages | Construction | Loans acquired with deteriorated credit quality
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Commercial Mortgages | Construction | Not Rated
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Commercial Mortgages | Construction | Pass
Finance receivable by credit quality indicator [Abstract]
Loans		55,430,000	45,553,000
Commercial Mortgages | Construction | Special Mention
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Commercial Mortgages | Construction | Substandard
Finance receivable by credit quality indicator [Abstract]
Loans		130,000	135,000
Commercial Mortgages | Construction | Doubtful
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Commercial Mortgages | Commercial mortgages
Finance receivable by credit quality indicator [Abstract]
Loans		593,853,000	600,486,000
Commercial Mortgages | Commercial mortgages | Loans acquired with deteriorated credit quality
Finance receivable by credit quality indicator [Abstract]
Loans		0	792,000
Commercial Mortgages | Commercial mortgages | Not Rated
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Commercial Mortgages | Commercial mortgages | Pass
Finance receivable by credit quality indicator [Abstract]
Loans		567,624,000	575,321,000
Commercial Mortgages | Commercial mortgages | Special Mention
Finance receivable by credit quality indicator [Abstract]
Loans		11,570,000	9,665,000
Commercial Mortgages | Commercial mortgages | Substandard
Finance receivable by credit quality indicator [Abstract]
Loans		13,307,000	13,331,000
Commercial Mortgages | Commercial mortgages | Doubtful
Finance receivable by credit quality indicator [Abstract]
Loans		1,352,000	1,377,000
Residential mortgages
Finance receivable by credit quality indicator [Abstract]
Loans		195,096,000	194,937,000
Residential and consumer finance receivable [Abstract]
Residential and consumer loans receivable		195,096,000	194,937,000
Residential mortgages | Loans acquired with deteriorated credit quality
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Residential mortgages | Performing
Residential and consumer finance receivable [Abstract]
Residential and consumer loans receivable		191,941,000	191,777,000
Residential mortgages | Non-Performing
Residential and consumer finance receivable [Abstract]
Residential and consumer loans receivable		3,155,000	3,160,000
Residential mortgages | Not Rated
Finance receivable by credit quality indicator [Abstract]
Loans		191,941,000	191,777,000
Residential mortgages | Pass
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Residential mortgages | Special Mention
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Residential mortgages | Substandard
Finance receivable by credit quality indicator [Abstract]
Loans		3,155,000	3,160,000
Residential mortgages | Doubtful
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Consumer loans:
Finance receivable by credit quality indicator [Abstract]
Loans		277,983,000	274,895,000
Consumer loans: | Loans acquired with deteriorated credit quality
Finance receivable by credit quality indicator [Abstract]
Loans			0
Consumer loans: | Credit cards
Finance receivable by credit quality indicator [Abstract]
Loans		1,418,000	1,516,000
Residential and consumer finance receivable [Abstract]
Residential and consumer loans receivable		1,418,000	1,516,000
Consumer loans: | Credit cards | Loans acquired with deteriorated credit quality
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Consumer loans: | Credit cards | Performing
Residential and consumer finance receivable [Abstract]
Residential and consumer loans receivable		1,418,000	1,516,000
Consumer loans: | Credit cards | Non-Performing
Residential and consumer finance receivable [Abstract]
Residential and consumer loans receivable		0	0
Consumer loans: | Credit cards | Not Rated
Finance receivable by credit quality indicator [Abstract]
Loans		1,418,000	1,516,000
Consumer loans: | Credit cards | Pass
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Consumer loans: | Credit cards | Special Mention
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Consumer loans: | Credit cards | Substandard
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Consumer loans: | Credit cards | Doubtful
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Consumer loans: | Home equity lines and loans
Finance receivable by credit quality indicator [Abstract]
Loans		100,902,000	100,878,000
Residential and consumer finance receivable [Abstract]
Residential and consumer loans receivable		100,902,000	100,878,000
Consumer loans: | Home equity lines and loans | Loans acquired with deteriorated credit quality
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Consumer loans: | Home equity lines and loans | Performing
Residential and consumer finance receivable [Abstract]
Residential and consumer loans receivable		99,600,000	99,568,000
Consumer loans: | Home equity lines and loans | Non-Performing
Residential and consumer finance receivable [Abstract]
Residential and consumer loans receivable		1,302,000	1,310,000
Consumer loans: | Home equity lines and loans | Not Rated
Finance receivable by credit quality indicator [Abstract]
Loans		99,600,000	99,568,000
Consumer loans: | Home equity lines and loans | Pass
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Consumer loans: | Home equity lines and loans | Special Mention
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Consumer loans: | Home equity lines and loans | Substandard
Finance receivable by credit quality indicator [Abstract]
Loans		1,302,000	1,310,000
Consumer loans: | Home equity lines and loans | Doubtful
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Consumer loans: | Indirect consumer loans
Finance receivable by credit quality indicator [Abstract]
Loans		157,340,000	153,532,000
Residential and consumer finance receivable [Abstract]
Residential and consumer loans receivable		157,340,000	153,532,000
Consumer loans: | Indirect consumer loans | Loans acquired with deteriorated credit quality
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Consumer loans: | Indirect consumer loans | Performing
Residential and consumer finance receivable [Abstract]
Residential and consumer loans receivable		156,454,000	152,598,000
Consumer loans: | Indirect consumer loans | Non-Performing
Residential and consumer finance receivable [Abstract]
Residential and consumer loans receivable		886,000	934,000
Consumer loans: | Indirect consumer loans | Not Rated
Finance receivable by credit quality indicator [Abstract]
Loans		156,454,000	152,598,000
Consumer loans: | Indirect consumer loans | Pass
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Consumer loans: | Indirect consumer loans | Special Mention
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Consumer loans: | Indirect consumer loans | Substandard
Finance receivable by credit quality indicator [Abstract]
Loans		886,000	934,000
Consumer loans: | Indirect consumer loans | Doubtful
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Consumer loans: | Direct consumer loans
Finance receivable by credit quality indicator [Abstract]
Loans		18,323,000	18,969,000
Residential and consumer finance receivable [Abstract]
Residential and consumer loans receivable		18,323,000	18,969,000
Consumer loans: | Direct consumer loans | Loans acquired with deteriorated credit quality
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Consumer loans: | Direct consumer loans | Performing
Residential and consumer finance receivable [Abstract]
Residential and consumer loans receivable		18,277,000	18,955,000
Consumer loans: | Direct consumer loans | Non-Performing
Residential and consumer finance receivable [Abstract]
Residential and consumer loans receivable		46,000	14,000
Consumer loans: | Direct consumer loans | Not Rated
Finance receivable by credit quality indicator [Abstract]
Loans		18,277,000	18,955,000
Consumer loans: | Direct consumer loans | Pass
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Consumer loans: | Direct consumer loans | Special Mention
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Consumer loans: | Direct consumer loans | Substandard
Finance receivable by credit quality indicator [Abstract]
Loans		46,000	14,000
Consumer loans: | Direct consumer loans | Doubtful
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Commercial and industrial | Commercial and agricultural:
Finance receivable by credit quality indicator [Abstract]
Loans		200,507,000	199,030,000
Commercial and industrial | Commercial and agricultural: | Loans acquired with deteriorated credit quality
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Commercial and industrial | Commercial and agricultural: | Not Rated
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Commercial and industrial | Commercial and agricultural: | Pass
Finance receivable by credit quality indicator [Abstract]
Loans		183,869,000	186,556,000
Commercial and industrial | Commercial and agricultural: | Special Mention
Finance receivable by credit quality indicator [Abstract]
Loans		8,719,000	4,447,000
Commercial and industrial | Commercial and agricultural: | Substandard
Finance receivable by credit quality indicator [Abstract]
Loans		2,911,000	6,605,000
Commercial and industrial | Commercial and agricultural: | Doubtful
Finance receivable by credit quality indicator [Abstract]
Loans		5,008,000	1,422,000
Agricultural | Commercial and agricultural:
Finance receivable by credit quality indicator [Abstract]
Loans		530,000	546,000
Agricultural | Commercial and agricultural: | Loans acquired with deteriorated credit quality
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Agricultural | Commercial and agricultural: | Not Rated
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Agricultural | Commercial and agricultural: | Pass
Finance receivable by credit quality indicator [Abstract]
Loans		530,000	546,000
Agricultural | Commercial and agricultural: | Special Mention
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Agricultural | Commercial and agricultural: | Substandard
Finance receivable by credit quality indicator [Abstract]
Loans		0	0
Agricultural | Commercial and agricultural: | Doubtful
Finance receivable by credit quality indicator [Abstract]
Loans		$ 0	$ 0