ALLOWANCE FOR LOAN AND LEASE LOSSES AND CREDIT QUALITY INFORMATION - Additional Information (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020 USD ($) loan	Sep. 30, 2019 USD ($) loan	Sep. 30, 2020 USD ($) SecurityLoan loan	Sep. 30, 2019 USD ($) loan	Dec. 31, 2019 USD ($) SecurityLoan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	$ 500,000		$ 800,000
Interest income on impaired loans		$ 200,000		$ 600,000
Loan workout and other credit costs	1,422,000	846,000	6,462,000	2,537,000
Troubled debt restructuring related reserves	200,000		$ 200,000		$ 600,000
Usual sustained repayment performance period			6 months
Increase (decrease) in allowance for loan losses (less than)	100,000	100,000	$ 100,000	200,000
Troubled debt restructurings charged off	$ 0	$ 0	$ 0	$ 0
TRD defaulted | loan	0	2	0	6
Subsequent default, loan amount, less than		$ 200,000		$ 1,500,000
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of residential loans in the process of foreclosure | SecurityLoan			24		33
Total loans outstanding, residential loans			$ 1,700,000		$ 3,200,000
Gross loans	$ 857,494,000		$ 857,494,000		$ 1,016,500,000
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of residential loans in the process of foreclosure | SecurityLoan			24		29
Total loans outstanding, residential loans			$ 13,100,000		$ 9,500,000
Commercial | Paycheck Protection Program, CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	954,200,000		954,200,000
Residential and Consumer Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan workout and other credit costs	$ 600,000	$ 600,000	$ 2,400,000	$ 1,800,000
Impairment loans, charge off period			90 days