LOANS RECEIVABLE, NET - Summary of changes in allowance for loan losses by class of loans (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Allowance for loan losses
Beginning balance	$ 13,465	$ 16,150	$ 14,425	$ 16,959
Charge-offs	(10)	(1)
Recoveries	2	0
(Recovery of) provision for loan losses	(952)	(808)
Total ending allowance balance	13,465	16,150
Residential Portfolio Segment \| Residential one-to-four family
Allowance for loan losses
Beginning balance	2,610	3,342	2,822	3,579
Charge-offs	0	0
Recoveries	0	0
(Recovery of) provision for loan losses	(212)	(237)
Total ending allowance balance	2,610	3,342
Residential Portfolio Segment \| Multifamily
Allowance for loan losses
Beginning balance	4,776	5,748	5,263	5,460
Charge-offs	0	0
Recoveries	0	0
(Recovery of) provision for loan losses	(487)	288
Total ending allowance balance	4,776	5,748
Nonresidential Portfolio Segment \| Non-residential
Allowance for loan losses
Beginning balance	3,465	3,145	2,846	3,244
Charge-offs	0	0
Recoveries	0	0
(Recovery of) provision for loan losses	619	(99)
Total ending allowance balance	3,465	3,145
Construction and Land Portfolio Segment \| Construction
Allowance for loan losses
Beginning balance	1,905	2,928	2,678	3,655
Charge-offs	0	0
Recoveries	0	0
(Recovery of) provision for loan losses	(773)	(727)
Total ending allowance balance	1,905	2,928
Junior Lien Portfolio Segment \| Junior liens
Allowance for loan losses
Beginning balance	549	813	636	916
Charge-offs	0	0
Recoveries	0	0
(Recovery of) provision for loan losses	(87)	(103)
Total ending allowance balance	549	813
Commercial Portfolio Segment \| Commercial and industrial (including PPP)
Allowance for loan losses
Beginning balance	71	7	51	2
Charge-offs	0	0
Recoveries	0	0
(Recovery of) provision for loan losses	20	5
Total ending allowance balance	71	7
Consumer and Other Portfolio Segment \| Consumer and other
Allowance for loan losses
Beginning balance	0	44	38	48
Charge-offs	(10)	(1)
Recoveries	2	0
(Recovery of) provision for loan losses	(30)	(3)
Total ending allowance balance	0	44
Unallocated Financing Receivables
Allowance for loan losses
Beginning balance	89	123	$ 91	$ 55
Charge-offs	0	0
Recoveries	0	0
(Recovery of) provision for loan losses	(2)	68
Total ending allowance balance	$ 89	$ 123

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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