LOANS AND ALLOWANCE FOR LOAN AND LEASE LOSSES - TDR MODIFICATIONS (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($) loan	Mar. 31, 2018 USD ($) loan	Dec. 31, 2018 USD ($) loan
Troubled Debt Restructurings disclosures
Number of Loans | loan	468		495
Recorded Investment	$ 30,522,000		$ 32,863,000
Commitments to lend any additional material amounts to existing TDR relationships	$ 0		$ 0
Residential Real Estate
Troubled Debt Restructurings disclosures
Number of Loans | loan	214		216
Recorded Investment	$ 22,918,000		$ 23,610,000
Residential Real Estate | Interest only payments
Troubled Debt Restructurings disclosures
Number of Loans | loan	1		1
Recorded Investment	$ 970,000		$ 970,000
Residential Real Estate | Rate reduction
Troubled Debt Restructurings disclosures
Number of Loans | loan	151		157
Recorded Investment	$ 17,134,000		$ 17,870,000
Residential Real Estate | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	16		15
Recorded Investment	$ 2,997,000		$ 3,042,000
Residential Real Estate | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	46		43
Recorded Investment	$ 1,817,000		$ 1,728,000
Commercial Real Estate and Commercial Construction
Troubled Debt Restructurings disclosures
Number of Loans | loan	21		23
Recorded Investment	$ 7,185,000		$ 8,818,000
Commercial Real Estate and Commercial Construction | Interest only payments
Troubled Debt Restructurings disclosures
Number of Loans | loan	2		2
Recorded Investment	$ 735,000		$ 752,000
Commercial Real Estate and Commercial Construction | Rate reduction
Troubled Debt Restructurings disclosures
Number of Loans | loan	4		8
Recorded Investment	$ 1,403,000		$ 2,962,000
Commercial Real Estate and Commercial Construction | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	14		12
Recorded Investment	$ 5,019,000		$ 5,076,000
Commercial Real Estate and Commercial Construction | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	1		1
Recorded Investment	$ 28,000		$ 28,000
Consumer and other
Troubled Debt Restructurings disclosures
Number of Loans | loan	233		256
Recorded Investment	$ 419,000		$ 435,000
Consumer and other | Rate reduction
Troubled Debt Restructurings disclosures
Number of Loans | loan	1		1
Recorded Investment	$ 18,000		$ 16,000
Consumer and other | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	232		255
Recorded Investment	$ 401,000		$ 419,000
Consumer
Troubled Debt Restructurings disclosures
Number of Loans | loan	233		256
Recorded Investment	$ 419,000		$ 435,000
Modified During The Period
Troubled Debt Restructurings disclosures
Number of Loans | loan	13	7
Recorded Investment	$ 352,000	$ 1,889,000
Modified During The Period | Residential Real Estate
Troubled Debt Restructurings disclosures
Number of Loans | loan	10	3
Recorded Investment	$ 286,000	$ 1,811,000
Modified During The Period | Residential Real Estate | Rate reduction
Troubled Debt Restructurings disclosures
Number of Loans | loan		1
Recorded Investment		$ 85,000
Modified During The Period | Residential Real Estate | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	2	2
Recorded Investment	$ 44,000	$ 1,726,000
Modified During The Period | Residential Real Estate | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	8
Recorded Investment	$ 242,000
Modified During The Period | Commercial Real Estate and Commercial Construction
Troubled Debt Restructurings disclosures
Number of Loans | loan	2	3
Recorded Investment	$ 48,000	$ 17,000
Modified During The Period | Commercial Real Estate and Commercial Construction | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	2	3
Recorded Investment	$ 48,000	$ 17,000
Modified During The Period | Consumer and other
Troubled Debt Restructurings disclosures
Number of Loans | loan	1
Recorded Investment	$ 18,000
Modified During The Period | Consumer and other | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	1
Recorded Investment	$ 18,000
Modified During The Period | Consumer loans
Troubled Debt Restructurings disclosures
Number of Loans | loan		1
Recorded Investment		$ 61,000
Modified During The Period | Consumer loans | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan		1
Recorded Investment		$ 61,000
Performing Financing Receivable
Troubled Debt Restructurings disclosures
Number of Loans | loan	443		469
Recorded Investment	$ 26,682,000		$ 28,788,000
Percentage of troubled debt restructurings performing as per terms of modifications	87.00%		88.00%
Specific reserve allocations made to customers	$ 3,000,000		$ 3,000,000
Percentage of Bank's TDRs that occurred during period, which were performing according to their modified terms	68.00%	67.00%
Specific reserve allocations made to customers whose loan terms were modified in TDRs during period	$ 52,000	$ 127,000
Performing Financing Receivable | Residential Real Estate
Troubled Debt Restructurings disclosures
Number of Loans | loan	191		191
Recorded Investment	$ 19,124,000		$ 19,563,000
Performing Financing Receivable | Residential Real Estate | Rate reduction
Troubled Debt Restructurings disclosures
Number of Loans | loan	142		145
Recorded Investment	$ 16,318,000		$ 16,892,000
Performing Financing Receivable | Residential Real Estate | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	11		11
Recorded Investment	$ 1,185,000		$ 1,171,000
Performing Financing Receivable | Residential Real Estate | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	38		35
Recorded Investment	$ 1,621,000		$ 1,500,000
Performing Financing Receivable | Commercial Real Estate and Commercial Construction
Troubled Debt Restructurings disclosures
Number of Loans | loan	20		22
Recorded Investment	$ 7,157,000		$ 8,790,000
Performing Financing Receivable | Commercial Real Estate and Commercial Construction | Interest only payments
Troubled Debt Restructurings disclosures
Number of Loans | loan	2		2
Recorded Investment	$ 735,000		$ 752,000
Performing Financing Receivable | Commercial Real Estate and Commercial Construction | Rate reduction
Troubled Debt Restructurings disclosures
Number of Loans | loan	4		8
Recorded Investment	$ 1,403,000		$ 2,962,000
Performing Financing Receivable | Commercial Real Estate and Commercial Construction | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	14		12
Recorded Investment	$ 5,019,000		$ 5,076,000
Performing Financing Receivable | Consumer and other
Troubled Debt Restructurings disclosures
Number of Loans | loan	232		256
Recorded Investment	$ 401,000		$ 435,000
Performing Financing Receivable | Consumer and other | Rate reduction
Troubled Debt Restructurings disclosures
Number of Loans | loan			1
Recorded Investment			$ 16,000
Performing Financing Receivable | Consumer and other | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	232		255
Recorded Investment	$ 401,000		$ 419,000
Performing Financing Receivable | Modified During The Period
Troubled Debt Restructurings disclosures
Number of Loans | loan	9	4
Recorded Investment	$ 240,000	$ 1,268,000
Performing Financing Receivable | Modified During The Period | Residential Real Estate
Troubled Debt Restructurings disclosures
Number of Loans | loan	7	1
Recorded Investment	$ 192,000	$ 1,204,000
Performing Financing Receivable | Modified During The Period | Residential Real Estate | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	1	1
Recorded Investment	$ 33,000	$ 1,204,000
Performing Financing Receivable | Modified During The Period | Residential Real Estate | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	6
Recorded Investment	$ 159,000
Performing Financing Receivable | Modified During The Period | Commercial Real Estate and Commercial Construction
Troubled Debt Restructurings disclosures
Number of Loans | loan	2	2
Recorded Investment	$ 48,000	$ 3,000
Performing Financing Receivable | Modified During The Period | Commercial Real Estate and Commercial Construction | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	2	2
Recorded Investment	$ 48,000	$ 3,000
Performing Financing Receivable | Modified During The Period | Consumer loans
Troubled Debt Restructurings disclosures
Number of Loans | loan		1
Recorded Investment		$ 61,000
Performing Financing Receivable | Modified During The Period | Consumer loans | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan		1
Recorded Investment		$ 61,000
Nonperforming Financing Receivable
Troubled Debt Restructurings disclosures
Number of Loans | loan	25		26
Recorded Investment	$ 3,840,000		$ 4,075,000
Nonperforming Financing Receivable | Residential Real Estate
Troubled Debt Restructurings disclosures
Number of Loans | loan	23		25
Recorded Investment	$ 3,794,000		$ 4,047,000
Nonperforming Financing Receivable | Residential Real Estate | Interest only payments
Troubled Debt Restructurings disclosures
Number of Loans | loan	1		1
Recorded Investment	$ 970,000		$ 970,000
Nonperforming Financing Receivable | Residential Real Estate | Rate reduction
Troubled Debt Restructurings disclosures
Number of Loans | loan	9		12
Recorded Investment	$ 816,000		$ 978,000
Nonperforming Financing Receivable | Residential Real Estate | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	5		4
Recorded Investment	$ 1,812,000		$ 1,871,000
Nonperforming Financing Receivable | Residential Real Estate | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	8		8
Recorded Investment	$ 196,000		$ 228,000
Nonperforming Financing Receivable | Commercial Real Estate and Commercial Construction
Troubled Debt Restructurings disclosures
Number of Loans | loan	1		1
Recorded Investment	$ 28,000		$ 28,000
Nonperforming Financing Receivable | Commercial Real Estate and Commercial Construction | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	1		1
Recorded Investment	$ 28,000		$ 28,000
Nonperforming Financing Receivable | Consumer and other
Troubled Debt Restructurings disclosures
Number of Loans | loan	1
Recorded Investment	$ 18,000
Nonperforming Financing Receivable | Consumer and other | Rate reduction
Troubled Debt Restructurings disclosures
Number of Loans | loan	1
Recorded Investment	$ 18,000
Nonperforming Financing Receivable | Modified During The Period
Troubled Debt Restructurings disclosures
Number of Loans | loan	4	3
Recorded Investment	$ 112,000	$ 621,000
Nonperforming Financing Receivable | Modified During The Period | Residential Real Estate
Troubled Debt Restructurings disclosures
Number of Loans | loan	3	2
Recorded Investment	$ 94,000	$ 607,000
Nonperforming Financing Receivable | Modified During The Period | Residential Real Estate | Rate reduction
Troubled Debt Restructurings disclosures
Number of Loans | loan		1
Recorded Investment		$ 85,000
Nonperforming Financing Receivable | Modified During The Period | Residential Real Estate | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	1	1
Recorded Investment	$ 11,000	$ 522,000
Nonperforming Financing Receivable | Modified During The Period | Residential Real Estate | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	2
Recorded Investment	$ 83,000
Nonperforming Financing Receivable | Modified During The Period | Commercial Real Estate and Commercial Construction
Troubled Debt Restructurings disclosures
Number of Loans | loan		1
Recorded Investment		$ 14,000
Nonperforming Financing Receivable | Modified During The Period | Commercial Real Estate and Commercial Construction | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan		1
Recorded Investment		$ 14,000
Nonperforming Financing Receivable | Modified During The Period | Consumer and other
Troubled Debt Restructurings disclosures
Number of Loans | loan	1
Recorded Investment	$ 18,000
Nonperforming Financing Receivable | Modified During The Period | Consumer and other | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	1
Recorded Investment	$ 18,000