Consolidated Statements of Changes in Shareholders’ Equity - USD ($) $ in Thousands	Total	Charitable Foundation	Unallocated Common Stock Held by ESOP	Common Stock	Common Stock Charitable Foundation	Additional Paid-In Capital	Additional Paid-In Capital Charitable Foundation	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)
Balance at beginning of period (in shares) at Dec. 31, 2020				100,000
Balance at beginning of period at Dec. 31, 2020	$ 205,600		$ 0	$ 10		$ 822		$ 205,799		$ (1,031)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(36,342)							(36,342)
Other comprehensive income	659									659
Proceeds of stock offering and issuance of common shares, net of issuance costs, and Issuance of common shares donated to Blue Foundry Charitable Foundation (in shares)				27,672,500	750,000
Proceeds of stock offering and issuance of common shares, net of issuance costs, and Issuance of common shares donated to Blue Foundry Charitable Foundation	273,598	$ 7,500		$ 268	$ 7	273,330	$ 7,493
Purchase of common shares by the ESOP	(22,818)		(22,818)
ESOP shares committed to be released (91,272 shares)	$ 1,274		913			361
Balance at end of period (in shares) at Dec. 31, 2021	28,522,500			28,522,500
Balance at end of period at Dec. 31, 2021	$ 429,471		(21,905)	$ 285		282,006		169,457		(372)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	2,396							2,396
Other comprehensive income	(24,347)									(24,347)
Purchase of common shares by the ESOP	0
Purchase of treasury stock (in shares)				(1,298,762)
Purchase of Treasury stock	(15,618)								$ (15,618)
Treasury stock allocated to restricted stock plan (in shares)				299,481
Treasury stock allocated to restricted stock plan	0					(3,456)		(90)	3,546
Compensation cost for stock options and restricted stock	664					664
ESOP shares committed to be released (91,272 shares)	$ 1,152		912			240
Balance at end of period (in shares) at Dec. 31, 2022	27,523,219			27,523,219
Balance at end of period at Dec. 31, 2022	$ 393,718		$ (20,993)	$ 285		$ 279,454		$ 171,763	$ (12,072)	$ (24,719)