Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock, at Cost	Accumulated Other Comprehensive Income (Loss)	Unearned Compensation - ESOP	Total
Balance at beginning of period at Dec. 31, 2016	$ 321	$ 144,420	$ 197,211		$ (1,290)	$ (11,278)	$ 329,384
Balance, beginning of period (in shares) at Dec. 31, 2016	57,670,838
Comprehensive income (loss)			10,379		762		11,141
ESOP shares committed to be released (in shares)		550				593	1,143
Restricted stock awards granted, net of awards forfeited	$ 6	(6)
Restricted stock awards granted, net of awards forfeited (in shares)	972,074
Share-based compensation expense		2,096					2,096
Treasury stock purchased				$ (280)			(280)
Treasury stock purchased (in shares)	(26,752)
Balance at end of year at Dec. 31, 2017	$ 327	147,060	207,590	(280)	(528)	(10,685)	343,484
Balance, end of period (in shares) at Dec. 31, 2017	58,616,160
Comprehensive income (loss)			11,394		(1,726)		9,668
Reclassification of stranded effect of tax rate change			104		(104)
ESOP shares committed to be released (in shares)		503				594	1,097
Restricted stock awards granted, net of awards forfeited (in shares)	30,763
Share-based compensation expense		4,593					4,593
Treasury stock purchased				(1,268)			(1,268)
Treasury stock purchased (in shares)	(119,892)
Balance at end of year at Dec. 31, 2018	$ 327	152,156	219,088	(1,548)	(2,358)	(10,091)	$ 357,574
Balance, end of period (in shares) at Dec. 31, 2018	58,465,505						58,465,505
Comprehensive income (loss)			18,268		3,838		$ 22,106
Conversion of HarborOne Bancorp, Inc.	$ 257	303,804					304,061
Conversion of HarborOne Bancorp, Inc. (in shares)	8,760
Purchase of shares by the ESOP						(24,829)	(24,829)
Treasury stock retired		(1,548)		1,548
Contribution of HarborOne Bancorp Mutual Bancshares		99					99
ESOP shares committed to be released (in shares)		872				1,783	2,655
Restricted stock awards granted, net of awards forfeited (in shares)	14,957
Share-based compensation expense		4,849					4,849
Treasury stock purchased				(721)			(721)
Treasury stock purchased (in shares)	(71,201)
Balance at end of year at Dec. 31, 2019	$ 584	$ 460,232	$ 237,356	$ (721)	$ 1,480	$ (33,137)	$ 665,794
Balance, end of period (in shares) at Dec. 31, 2019	58,418,021						58,418,021