LOANS AND ALLOWANCE FOR CREDIT LOSSES - TDR MODIFICATIONS (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($) loan	Mar. 31, 2019 USD ($) loan	Dec. 31, 2019 USD ($) loan
Troubled Debt Restructurings disclosures
Number of Loans | loan	2,323		1,828
Recorded Investment	$ 27,736,000		$ 30,781,000
Commitments to lend any additional material amounts to existing TDR relationships	$ 0		$ 0
Residential Real Estate
Troubled Debt Restructurings disclosures
Number of Loans | loan	189		194
Recorded Investment	$ 18,342,000		$ 19,770,000
Residential Real Estate | Interest only payments
Troubled Debt Restructurings disclosures
Number of Loans | loan	1		1
Recorded Investment	$ 883,000		$ 904,000
Residential Real Estate | Rate reduction
Troubled Debt Restructurings disclosures
Number of Loans | loan	118		123
Recorded Investment	$ 12,915,000		$ 14,199,000
Residential Real Estate | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	9		10
Recorded Investment	$ 1,009,000		$ 1,024,000
Residential Real Estate | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	61		60
Recorded Investment	$ 3,535,000		$ 3,643,000
Commercial Real Estate and Commercial Construction
Troubled Debt Restructurings disclosures
Number of Loans | loan	17		21
Recorded Investment	$ 8,762,000		$ 10,425,000
Commercial Real Estate and Commercial Construction | Interest only payments
Troubled Debt Restructurings disclosures
Number of Loans | loan	3		3
Recorded Investment	$ 1,547,000		$ 1,568,000
Commercial Real Estate and Commercial Construction | Rate reduction
Troubled Debt Restructurings disclosures
Number of Loans | loan	4		4
Recorded Investment	$ 1,198,000		$ 1,252,000
Commercial Real Estate and Commercial Construction | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	8		12
Recorded Investment	$ 5,153,000		$ 6,578,000
Commercial Real Estate and Commercial Construction | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	2		2
Recorded Investment	$ 864,000		$ 1,027,000
Consumer and other
Troubled Debt Restructurings disclosures
Number of Loans | loan	2,117		1,613
Recorded Investment	$ 632,000		$ 586,000
Consumer and other | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	2,115		1,612
Recorded Investment	$ 614,000		$ 577,000
Consumer and other | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan			1
Recorded Investment			$ 9,000
Consumer
Troubled Debt Restructurings disclosures
Number of Loans | loan	2,117		1,613
Recorded Investment	$ 632,000		$ 586,000
Consumer loans | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	2
Recorded Investment	$ 18,000
Modified During The Period
Troubled Debt Restructurings disclosures
Number of Loans | loan	2,116	13
Recorded Investment	$ 462,000	$ 352,000
Modified During The Period | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan		1
Recorded Investment		$ 18,000
Modified During The Period | Residential Real Estate
Troubled Debt Restructurings disclosures
Number of Loans | loan	4	10
Recorded Investment	$ 128,000	$ 286,000
Modified During The Period | Residential Real Estate | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan		2
Recorded Investment		$ 44,000
Modified During The Period | Residential Real Estate | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	4	8
Recorded Investment	$ 128,000	$ 242,000
Modified During The Period | Commercial Real Estate and Commercial Construction
Troubled Debt Restructurings disclosures
Number of Loans | loan	1	2
Recorded Investment	$ 24,000	$ 48,000
Modified During The Period | Commercial Real Estate and Commercial Construction | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	1	2
Recorded Investment	$ 24,000	$ 48,000
Modified During The Period | Consumer loans
Troubled Debt Restructurings disclosures
Number of Loans | loan	2,111	1
Recorded Investment	$ 310,000	$ 18,000
Modified During The Period | Consumer loans | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	2,111
Recorded Investment	$ 310,000
Performing Financing Receivable
Troubled Debt Restructurings disclosures
Number of Loans | loan	2,306		1,811
Recorded Investment	$ 25,781,000		$ 28,138,000
Percentage of troubled debt restructurings performing as per terms of modifications	93.00%		91.00%
Specific reserve allocations made to customers	$ 2,000,000		$ 2,000,000
Percentage of Bank's TDRs that occurred during period, which were performing according to their modified terms	100.00%	68.00%
Specific reserve allocations made to customers whose loan terms were modified in TDRs during period	$ 93,000	$ 52,000
Performing Financing Receivable | Residential Real Estate
Troubled Debt Restructurings disclosures
Number of Loans | loan	176		181
Recorded Investment	$ 17,396,000		$ 18,796,000
Performing Financing Receivable | Residential Real Estate | Interest only payments
Troubled Debt Restructurings disclosures
Number of Loans | loan	1		1
Recorded Investment	$ 883,000		$ 904,000
Performing Financing Receivable | Residential Real Estate | Rate reduction
Troubled Debt Restructurings disclosures
Number of Loans | loan	113		118
Recorded Investment	$ 12,615,000		$ 13,847,000
Performing Financing Receivable | Residential Real Estate | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	8		8
Recorded Investment	$ 846,000		$ 845,000
Performing Financing Receivable | Residential Real Estate | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	54		54
Recorded Investment	$ 3,052,000		$ 3,200,000
Performing Financing Receivable | Commercial Real Estate and Commercial Construction
Troubled Debt Restructurings disclosures
Number of Loans | loan	13		17
Recorded Investment	$ 7,753,000		$ 8,756,000
Performing Financing Receivable | Commercial Real Estate and Commercial Construction | Interest only payments
Troubled Debt Restructurings disclosures
Number of Loans | loan	3		3
Recorded Investment	$ 1,547,000		$ 1,568,000
Performing Financing Receivable | Commercial Real Estate and Commercial Construction | Rate reduction
Troubled Debt Restructurings disclosures
Number of Loans | loan	3		3
Recorded Investment	$ 1,153,000		$ 1,207,000
Performing Financing Receivable | Commercial Real Estate and Commercial Construction | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	7		11
Recorded Investment	$ 5,053,000		$ 5,981,000
Performing Financing Receivable | Consumer and other
Troubled Debt Restructurings disclosures
Number of Loans | loan	2,117		1,613
Recorded Investment	$ 632,000		$ 586,000
Performing Financing Receivable | Consumer and other | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	2,115		1,612
Recorded Investment	$ 614,000		$ 577,000
Performing Financing Receivable | Consumer and other | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan			1
Recorded Investment			$ 9,000
Performing Financing Receivable | Consumer loans | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	2
Recorded Investment	$ 18,000
Performing Financing Receivable | Modified During The Period
Troubled Debt Restructurings disclosures
Number of Loans | loan	2,116	9
Recorded Investment	$ 462,000	$ 240,000
Performing Financing Receivable | Modified During The Period | Residential Real Estate
Troubled Debt Restructurings disclosures
Number of Loans | loan	4	7
Recorded Investment	$ 128,000	$ 192,000
Performing Financing Receivable | Modified During The Period | Residential Real Estate | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan		1
Recorded Investment		$ 33,000
Performing Financing Receivable | Modified During The Period | Residential Real Estate | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	4	6
Recorded Investment	$ 128,000	$ 159,000
Performing Financing Receivable | Modified During The Period | Commercial Real Estate and Commercial Construction
Troubled Debt Restructurings disclosures
Number of Loans | loan	1	2
Recorded Investment	$ 24,000	$ 48,000
Performing Financing Receivable | Modified During The Period | Commercial Real Estate and Commercial Construction | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	1	2
Recorded Investment	$ 24,000	$ 48,000
Performing Financing Receivable | Modified During The Period | Consumer loans
Troubled Debt Restructurings disclosures
Number of Loans | loan	2,111
Recorded Investment	$ 310,000
Performing Financing Receivable | Modified During The Period | Consumer loans | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	2,111
Recorded Investment	$ 310,000
Nonperforming Financing Receivable
Troubled Debt Restructurings disclosures
Number of Loans | loan	17		17
Recorded Investment	$ 1,955,000		$ 2,643,000
Nonperforming Financing Receivable | Residential Real Estate
Troubled Debt Restructurings disclosures
Number of Loans | loan	13		13
Recorded Investment	$ 946,000		$ 974,000
Nonperforming Financing Receivable | Residential Real Estate | Rate reduction
Troubled Debt Restructurings disclosures
Number of Loans | loan	5		5
Recorded Investment	$ 300,000		$ 352,000
Nonperforming Financing Receivable | Residential Real Estate | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	1		2
Recorded Investment	$ 163,000		$ 179,000
Nonperforming Financing Receivable | Residential Real Estate | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	7		6
Recorded Investment	$ 483,000		$ 443,000
Nonperforming Financing Receivable | Commercial Real Estate and Commercial Construction
Troubled Debt Restructurings disclosures
Number of Loans | loan	4		4
Recorded Investment	$ 1,009,000		$ 1,669,000
Nonperforming Financing Receivable | Commercial Real Estate and Commercial Construction | Rate reduction
Troubled Debt Restructurings disclosures
Number of Loans | loan	1		1
Recorded Investment	$ 45,000		$ 45,000
Nonperforming Financing Receivable | Commercial Real Estate and Commercial Construction | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan	1		1
Recorded Investment	$ 100,000		$ 597,000
Nonperforming Financing Receivable | Commercial Real Estate and Commercial Construction | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan	2		2
Recorded Investment	$ 864,000		$ 1,027,000
Nonperforming Financing Receivable | Modified During The Period
Troubled Debt Restructurings disclosures
Number of Loans | loan		4
Recorded Investment		$ 112,000
Nonperforming Financing Receivable | Modified During The Period | Legal modifications
Troubled Debt Restructurings disclosures
Number of Loans | loan		1
Recorded Investment		$ 18,000
Nonperforming Financing Receivable | Modified During The Period | Residential Real Estate
Troubled Debt Restructurings disclosures
Number of Loans | loan		3
Recorded Investment		$ 94,000
Nonperforming Financing Receivable | Modified During The Period | Residential Real Estate | Principal deferral
Troubled Debt Restructurings disclosures
Number of Loans | loan		1
Recorded Investment		$ 11,000
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 | Consumer loans
Troubled Debt Restructurings disclosures
Number of Loans | loan		1
Recorded Investment		$ 18,000