OTHER COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Commitments to grant loans
OTHER COMMITMENTS AND CONTINGENCIES
Financial instruments committed contract amount	$ 581,524	$ 98,866
Unadvanced funds on home equity lines of credit
OTHER COMMITMENTS AND CONTINGENCIES
Financial instruments committed contract amount	170,671	157,867
Unadvanced funds on revolving lines of credit
OTHER COMMITMENTS AND CONTINGENCIES
Financial instruments committed contract amount	150,958	147,047
Unadvanced funds on construction loans
OTHER COMMITMENTS AND CONTINGENCIES
Financial instruments committed contract amount	$ 129,745	$ 112,158