OTHER COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Commitments to grant loans
OTHER COMMITMENTS AND CONTINGENCIES
Financial instruments committed contract amount	$ 289,623	$ 98,866
Unadvanced funds on home equity lines of credit
OTHER COMMITMENTS AND CONTINGENCIES
Financial instruments committed contract amount	164,169	157,867
Unadvanced funds on revolving lines of credit
OTHER COMMITMENTS AND CONTINGENCIES
Financial instruments committed contract amount	152,251	147,047
Unadvanced funds on construction loans
OTHER COMMITMENTS AND CONTINGENCIES
Financial instruments committed contract amount	$ 98,947	$ 112,158