FINANCIAL INSTRUMENTS WITH OFF-BALANCE SHEET RISK (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Variable rate
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	$ 85,156	$ 60,473
Fixed rate
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	61,196	63,747
Total commitments to originate new loans
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	146,352	124,220
Unadvanced portion of loans and unused lines of credit
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	1,676,779	1,468,782
Standby letters of credit
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	87,718	49,117
Forward commitments to sell loans
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	$ 33,488	$ 11,850