CONDENSED FINANCIAL STATEMENTS OF PARENT COMPANY - Condensed Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Expenses:
Contribution to Blue Foundry Charitable Foundation		$ 9,000	$ 0
Goodwill impairment		0	15,460
Income tax (benefit) expense		9,618	(7,866)
Net loss	$ (36,342)	(36,342)	(31,506)
Parent Company
Income:
Interest on ESOP loan receivable		343	0
Other income		23	16
Total income		366	16
Expenses:
Contribution to Blue Foundry Charitable Foundation		9,000	0
Goodwill impairment		0	13,100
Other expenses		719	66
Costs and Expenses, Total		9,719	13,166
Loss before income tax (benefit) expense		(9,353)	(13,150)
Income tax (benefit) expense		(59)	98
Loss before undistributed earnings of subsidiary		(9,294)	(13,248)
Equity in undistributed earnings of banking subsidiary		(27,048)	(18,258)
Net loss		$ (36,342)	$ (31,506)