DERIVATIVES - Net gains and losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Derivative disclosures
Loss in OCI on derivatives (effective portion), net of tax	$ 1,456	$ 581	$ 5,687	$ (4,401)
Designated as hedging instruments
Derivative disclosures
Total derivative gain (loss)	10	20	15	11
Loss in OCI on derivatives (effective portion), net of tax	(63)	(711)	(771)	(1,080)
Gain reclassified from OCI into interest income (effective portion)	77	1,264	1,064	2,499
Designated as hedging instruments \| Derivative loan commitments
Derivative disclosures
Total derivative gain (loss)	$ 156	$ (197)	$ 644	$ (1,626)
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest and Dividend Income, Operating	Interest and Dividend Income, Operating	Interest and Dividend Income, Operating	Interest and Dividend Income, Operating
Designated as hedging instruments \| Interest rate swaps
Derivative disclosures
Total derivative gain (loss)	$ (146)	$ 217	$ (629)	$ 1,637
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest and Dividend Income, Operating	Interest and Dividend Income, Operating	Interest and Dividend Income, Operating	Interest and Dividend Income, Operating
Not designated as hedging instruments
Derivative disclosures
Total derivative gain (loss)	$ 238	$ (291)	$ 540	$ (145)
Not designated as hedging instruments \| Derivative loan commitments
Derivative disclosures
Total derivative gain (loss)	$ 122	$ (64)	$ 295	$ (7)
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Mortgage Banking Noninterest Income	Mortgage Banking Noninterest Income	Mortgage Banking Noninterest Income	Mortgage Banking Noninterest Income
Not designated as hedging instruments \| Forward loan sale commitments
Derivative disclosures
Total derivative gain (loss)	$ (233)	$ 53	$ (665)	$ 363
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Mortgage Banking Noninterest Income	Mortgage Banking Noninterest Income	Mortgage Banking Noninterest Income	Mortgage Banking Noninterest Income
Not designated as hedging instruments \| Interest rate futures
Derivative disclosures
Total derivative gain (loss)	$ 349	$ (280)	$ 910	$ (501)
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Mortgage Banking Noninterest Income	Mortgage Banking Noninterest Income	Mortgage Banking Noninterest Income	Mortgage Banking Noninterest Income

HarborOne Bancorp, Inc. 10-Q