SEGMENT REPORTING (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($) segment	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Segment Reporting Information
Number of reportable segments | segment			2
Net interest and dividend income	$ 31,350	$ 32,100	$ 61,932	$ 66,498
Provision for credit losses	615	3,283	447	5,149
Net interest and dividend income, after provision for credit losses	30,735	28,817	61,485	61,349
Mortgage banking income:
Gain on sale of mortgage loans	3,143	3,300	5,156	5,524
Changes in mortgage servicing rights fair value	(1,098)	436	(1,044)	(1,256)
Other	2,356	2,312	4,632	4,528
Total mortgage banking income	4,401	6,048	8,744	8,796
Other noninterest income (loss)	7,518	6,614	13,916	12,556
Total noninterest income	11,919	12,662	22,660	21,352
Noninterest expense	33,144	31,725	64,894	63,234
Income (loss) before income taxes	9,510	9,754	19,251	19,467
Provision (benefit) for income taxes	2,214	2,275	4,655	4,691
Net income	7,296	7,479	14,596	14,776
Total assets at period end	5,787,035	5,659,254	5,787,035	5,659,254	$ 5,667,896
Goodwill at period end	59,042	69,802	59,042	69,802	$ 59,042
Operating Segments | HarborOne Bank
Segment Reporting Information
Net interest and dividend income	31,098	32,490	61,583	67,052
Provision for credit losses	615	3,283	447	5,149
Net interest and dividend income, after provision for credit losses	30,483	29,207	61,136	61,903
Mortgage banking income:
Intersegment gain (loss)	(464)	(358)	(700)	(706)
Changes in mortgage servicing rights fair value	(74)	29	(106)	(107)
Other	180	195	360	396
Total mortgage banking income	(358)	(134)	(446)	(417)
Other noninterest income (loss)	7,514	6,614	13,905	12,556
Total noninterest income	7,156	6,480	13,459	12,139
Noninterest expense	27,791	26,193	55,196	52,383
Income (loss) before income taxes	9,848	9,494	19,399	21,659
Provision (benefit) for income taxes	2,310	2,193	4,696	5,308
Net income	7,538	7,301	14,703	16,351
Total assets at period end	5,793,429	5,668,582	5,793,429	5,668,582
Goodwill at period end	59,042	59,042	59,042	59,042
Operating Segments | HarborOne Mortgage.
Segment Reporting Information
Net interest and dividend income	240	120	320	447
Net interest and dividend income, after provision for credit losses	240	120	320	447
Mortgage banking income:
Gain on sale of mortgage loans	3,141	3,300	5,155	5,524
Intersegment gain (loss)	464	90	772	544
Changes in mortgage servicing rights fair value	(1,024)	407	(938)	(1,149)
Other	2,177	2,117	4,273	4,132
Total mortgage banking income	4,758	5,914	9,262	9,051
Other noninterest income (loss)	4		14
Total noninterest income	4,762	5,914	9,276	9,051
Noninterest expense	5,269	5,493	9,580	10,815
Income (loss) before income taxes	(267)	541	16	(1,317)
Provision (benefit) for income taxes	(76)	232	(16)	(333)
Net income	(191)	309	32	(984)
Total assets at period end	$ 120,390	115,782	$ 120,390	115,782
Goodwill at period end		$ 10,760		$ 10,760