| Pay vs Performance Disclosure | 12 Months Ended |
| Dec. 31, 2022 USD ($) item | Dec. 31, 2021 USD ($) item | Dec. 31, 2020 USD ($) item |
| Pay vs Performance Disclosure [Table] | | | |
| Pay vs Performance [Table Text Block] | (in whole dollars, unless otherwise noted) Investment Based on: Average Summary Summary Summary Average Peer Group Compensation Compensation Compensation Compensation Compensation Compensation Total Total Tangible Table Total Table Total Actually Paid Actually Paid Table Total for Actually Paid to Shareholder Shareholder Net Income Book Value Year for First PEO for Second PEO to First PEO to Second PEO Non-PEO NEOs Non-PEO NEOs Return Return (in thousands) Per Share (a) (b.1) (1) (b.2) (2) (c.1) (1) (c.2) (2) (d) (3) (e) (3) (f) (4) (g) (5) (h) (i) (6) 2022 $ 1,456,401 $ 2,648,731 $ 1,467,492 $ 1,873,309 $ 665,848 $ 649,588 $ 132.19 $ 99.14 $ 45,589 $ 11.13 2021 $ 3,080,857 $ N/A $ 3,093,059 $ N/A $ 947,669 $ 1,181,004 $ 137.83 $ 121.96 $ 58,517 $ 11.57 2020 $ 2,143,883 $ N/A $ 1,785,584 $ N/A $ 1,010,159 $ 1,135,032 $ 99.80 $ 95.30 $ 44,792 $ 10.88 (1) Includes amounts from the Summary Compensation Table and Compensation Actually Paid to James W. Blake , former Chief Executive Officer of HarborOne Bank, for the years ended December 31, 2020, 2021, and 2022. (2) Includes amounts from the Summary Compensation Table and Compensation Actually Paid to Joseph F. Casey for the year ended December 31, 2022. (3) The non-principal executive officer (PEO) named executive officers (NEOs) reflected in columns (d) and € represent the following individuals; for 2022: Linda H. Simmons, H. Scott Sanborn, Brenda C. Diepold, and David B. Reilly, for 2021: Joseph F. Casey, Linda H. Simmons, H. Scott Sanborn and Inez H. Friedman-Boyce; and for 2020: Joseph F. Casey and Linda H. Simmons. (4) Reflects the cumulative total shareholder return of HarborOne Bank over the three-year period. The reporting is based on a theoretical $100 invested as of the last day of 2019 and valued as of the last trading day of 2020, 2021, and 2022. (5) Reflects the cumulative total shareholder return of the S&P 600 Thrifts & Mortgage Finance Index (“S&P 600”). S&P 600 is the peer group used by HarborOne Bank for purposes of Item 201(e) of Regulation S-K under the Exchange Act in our Annual Report on Form 10-K for the year ended December 31, 2022. (6) Tangible Book Value per Share is a non-GAAP ratio that is calculated by dividing total stockholders’ equity less goodwill and intangible assets by common stock outstanding. | | |
| Company Selected Measure Name | Tangible Book Value per Share | | |
| Named Executive Officers, Footnote [Text Block] | (1) Includes amounts from the Summary Compensation Table and Compensation Actually Paid to James W. Blake , former Chief Executive Officer of HarborOne Bank, for the years ended December 31, 2020, 2021, and 2022. (3) The non-principal executive officer (PEO) named executive officers (NEOs) reflected in columns (d) and € represent the following individuals; for 2022: Linda H. Simmons, H. Scott Sanborn, Brenda C. Diepold, and David B. Reilly, for 2021: Joseph F. Casey, Linda H. Simmons, H. Scott Sanborn and Inez H. Friedman-Boyce; and for 2020: Joseph F. Casey and Linda H. Simmons. | | |
| Peer Group Issuers, Footnote [Text Block] | (5) Reflects the cumulative total shareholder return of the S&P 600 Thrifts & Mortgage Finance Index (“S&P 600”). S&P 600 is the peer group used by HarborOne Bank for purposes of Item 201(e) of Regulation S-K under the Exchange Act in our Annual Report on Form 10-K for the year ended December 31, 2022. | | |
| Adjustment To PEO Compensation, Footnote [Text Block] | Calculation of Compensation Actually Paid To calculate the CAP amounts in the table above, the following adjustments were made to Total Compensation as reported in the Summary Compensation Table for each covered year: 2022 2021 2020 Average Average Average First PEO Second PEO Non-PEO NEOs First PEO Non-PEO NEOs First PEO Non-PEO NEOs Total Compensation from Summary Compensation Table $ 1,456,401 $ 2,648,731 $ 665,848 $ 3,080,857 $ 947,669 $ 2,143,883 $ 1,010,159 Amount deducted for aggregate change in actuarial present value from SCT — (1,004,270) — (800,591) (97,153) — — Amount deducted for grant date values in the SCT (445,954) (391,896) (112,807) (492,722) (150,905) (468,468) (194,733) Amount included for service costs related to the SERP — 257,565 — — 139,232 — 255,401 Amount included for year-end fair value of unvested awards granted in the current year 25,201 377,166 106,533 611,883 213,041 550,602 228,875 Amount included (+ or -) for year-over-year difference of year-end fair values for unvested awards granted in prior years — (17,904) (8,772) 429,408 68,297 (112,109) (28,536) Amount included (+ or -) for difference in fair values between prior year-end fair values and vest date fair values for awards granted in prior years 431,844 3,917 (1,214) 264,224 60,823 (328,324) (136,134) Total Adjustments $ 457,045 $ 620,744 $ 96,547 $ 1,305,515 $ 481,393 $ 110,169 $ 319,606 Compensation Actually Paid (as calculated) $ 1,467,492 $ 1,873,309 $ 649,588 $ 3,093,059 $ 1,181,004 $ 1,785,584 $ 1,135,032 | | |
| Non-PEO NEO Average Total Compensation Amount | $ 665,848 | $ 947,669 | $ 1,010,159 |
| Non-PEO NEO Average Compensation Actually Paid Amount | $ 649,588 | 1,181,004 | 1,135,032 |
| Adjustment to Non-PEO NEO Compensation Footnote [Text Block] | Calculation of Compensation Actually Paid To calculate the CAP amounts in the table above, the following adjustments were made to Total Compensation as reported in the Summary Compensation Table for each covered year: 2022 2021 2020 Average Average Average First PEO Second PEO Non-PEO NEOs First PEO Non-PEO NEOs First PEO Non-PEO NEOs Total Compensation from Summary Compensation Table $ 1,456,401 $ 2,648,731 $ 665,848 $ 3,080,857 $ 947,669 $ 2,143,883 $ 1,010,159 Amount deducted for aggregate change in actuarial present value from SCT — (1,004,270) — (800,591) (97,153) — — Amount deducted for grant date values in the SCT (445,954) (391,896) (112,807) (492,722) (150,905) (468,468) (194,733) Amount included for service costs related to the SERP — 257,565 — — 139,232 — 255,401 Amount included for year-end fair value of unvested awards granted in the current year 25,201 377,166 106,533 611,883 213,041 550,602 228,875 Amount included (+ or -) for year-over-year difference of year-end fair values for unvested awards granted in prior years — (17,904) (8,772) 429,408 68,297 (112,109) (28,536) Amount included (+ or -) for difference in fair values between prior year-end fair values and vest date fair values for awards granted in prior years 431,844 3,917 (1,214) 264,224 60,823 (328,324) (136,134) Total Adjustments $ 457,045 $ 620,744 $ 96,547 $ 1,305,515 $ 481,393 $ 110,169 $ 319,606 Compensation Actually Paid (as calculated) $ 1,467,492 $ 1,873,309 $ 649,588 $ 3,093,059 $ 1,181,004 $ 1,785,584 $ 1,135,032 | | |
| Compensation Actually Paid vs. Total Shareholder Return [Text Block] | | | |
| Compensation Actually Paid vs. Net Income [Text Block] | | | |
| Tabular List [Table Text Block] | Tabular List of Performance Measures The six performance measures listed below represent the most important metrics the Company used to align pay and performance and to determine compensation paid in 2022, as further described in our Compensation Discussion and Analysis (CD&A) within the sections titled “Annual Incentive Plan” and “Long-Term Incentives”: Most Important Performance Measures Application in 2022 Compensation Tangible Book Value Per Share Long-Term Incentive Plan Relative Total Shareholder Return Long-Term Incentive Plan Return On Assets Annual Incentive Plan Earnings Per Share Annual Incentive Plan Core Deposit Growth Annual Incentive Plan Commercial and Small Business Loan Growth Annual Incentive Plan | | |
| Total Shareholder Return Amount | $ 132.19 | 137.83 | 99.80 |
| Peer Group Total Shareholder Return Amount | 99.14 | 121.96 | 95.30 |
| Net Income (Loss) | $ 45,589,000 | $ 58,517,000 | $ 44,792,000 |
| Company Selected Measure Amount | item | 11.13 | 11.57 | 10.88 |
| Measure [Axis]: 1 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Tangible Book Value Per Share | | |
| Non-GAAP Measure Description [Text Block] | (6) Tangible Book Value per Share is a non-GAAP ratio that is calculated by dividing total stockholders’ equity less goodwill and intangible assets by common stock outstanding. | | |
| Measure [Axis]: 2 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Relative Total Shareholder Return | | |
| Measure [Axis]: 3 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Return On Assets | | |
| Measure [Axis]: 4 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Earnings Per Share | | |
| Measure [Axis]: 5 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Core Deposit Growth | | |
| Measure [Axis]: 6 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Commercial and Small Business Loan Growth | | |
| James W. Blake | | | |
| Pay vs Performance Disclosure [Table] | | | |
| PEO Total Compensation Amount | $ 1,456,401 | $ 3,080,857 | $ 2,143,883 |
| PEO Actually Paid Compensation Amount | $ 1,467,492 | 3,093,059 | 1,785,584 |
| PEO Name | James W. Blake | | |
| Joseph F. Casey | | | |
| Pay vs Performance Disclosure [Table] | | | |
| PEO Total Compensation Amount | $ 2,648,731 | | |
| PEO Actually Paid Compensation Amount | $ 1,873,309 | | |
| PEO Name | Joseph F. Casey | | |
| PEO [Member] | James W. Blake | Amount deducted for aggregate change in actuarial present value from SCT | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | | (800,591) | |
| PEO [Member] | James W. Blake | Amount deducted for grant date values in the SCT | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | $ (445,954) | (492,722) | (468,468) |
| PEO [Member] | James W. Blake | Amount included for year-end fair value of unvested awards granted in the current year | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 25,201 | 611,883 | 550,602 |
| PEO [Member] | James W. Blake | Amount included (+ or -) for year-over-year difference of year-end fair values for unvested awards granted in prior years | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | | 429,408 | (112,109) |
| PEO [Member] | James W. Blake | Amount included (+ or -) for difference in fair values between prior year-end fair values and vest date fair values for awards granted in prior years | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 431,844 | 264,224 | (328,324) |
| PEO [Member] | James W. Blake | Total Adjustments | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 457,045 | 1,305,515 | 110,169 |
| PEO [Member] | Joseph F. Casey | Amount deducted for aggregate change in actuarial present value from SCT | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (1,004,270) | | |
| PEO [Member] | Joseph F. Casey | Amount deducted for grant date values in the SCT | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (391,896) | | |
| PEO [Member] | Joseph F. Casey | Amount included for service costs related to the SERP | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 257,565 | | |
| PEO [Member] | Joseph F. Casey | Amount included for year-end fair value of unvested awards granted in the current year | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 377,166 | | |
| PEO [Member] | Joseph F. Casey | Amount included (+ or -) for year-over-year difference of year-end fair values for unvested awards granted in prior years | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (17,904) | | |
| PEO [Member] | Joseph F. Casey | Amount included (+ or -) for difference in fair values between prior year-end fair values and vest date fair values for awards granted in prior years | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 3,917 | | |
| PEO [Member] | Joseph F. Casey | Total Adjustments | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 620,744 | | |
| Non-PEO NEO [Member] | Amount deducted for aggregate change in actuarial present value from SCT | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | | (97,153) | |
| Non-PEO NEO [Member] | Amount deducted for grant date values in the SCT | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (112,807) | (150,905) | (194,733) |
| Non-PEO NEO [Member] | Amount included for service costs related to the SERP | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | | 139,232 | 255,401 |
| Non-PEO NEO [Member] | Amount included for year-end fair value of unvested awards granted in the current year | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 106,533 | 213,041 | 228,875 |
| Non-PEO NEO [Member] | Amount included (+ or -) for year-over-year difference of year-end fair values for unvested awards granted in prior years | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (8,772) | 68,297 | (28,536) |
| Non-PEO NEO [Member] | Amount included (+ or -) for difference in fair values between prior year-end fair values and vest date fair values for awards granted in prior years | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (1,214) | 60,823 | (136,134) |
| Non-PEO NEO [Member] | Total Adjustments | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | $ 96,547 | $ 481,393 | $ 319,606 |
