OTHER COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Commitments to grant residential real estate loans - HarborOne Mortgage
OTHER COMMITMENTS AND CONTINGENCIES
Financial instruments committed contract amount	$ 312,884	$ 485,428
Commitments to grant other loans
OTHER COMMITMENTS AND CONTINGENCIES
Financial instruments committed contract amount	99,976	53,714
Unadvanced funds on home equity lines of credit
OTHER COMMITMENTS AND CONTINGENCIES
Financial instruments committed contract amount	198,700	178,432
Unadvanced funds on revolving lines of credit
OTHER COMMITMENTS AND CONTINGENCIES
Financial instruments committed contract amount	195,880	169,907
Unadvanced funds on construction loans
OTHER COMMITMENTS AND CONTINGENCIES
Financial instruments committed contract amount	$ 131,107	$ 127,776