LOANS RECEIVABLE, NET - Summary of changes in allowance for loan losses by class of loans (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Allowance for loan losses
Beginning balance	$ 14,425	$ 16,959	$ 14,500
Charge-offs	(16)	(59)
(Recovery of) provision for loan losses	0	0
(Recovery of) provision for loan losses	(2,518)	2,518
Total ending allowance balance	14,425	16,959
Residential Portfolio Segment \| Residential one-to-four family
Allowance for loan losses
Beginning balance	2,822	3,579	3,446
Charge-offs	0	(49)
(Recovery of) provision for loan losses	0	0
(Recovery of) provision for loan losses	(757)	182
Total ending allowance balance	2,822	3,579
Residential Portfolio Segment \| Multifamily
Allowance for loan losses
Beginning balance	5,263	5,460	4,256
Charge-offs	0	0
(Recovery of) provision for loan losses	0	0
(Recovery of) provision for loan losses	(197)	1,204
Total ending allowance balance	5,263	5,460
Non-residential \| Non-residential
Allowance for loan losses
Beginning balance	2,846	3,244	2,548
Charge-offs	0	0
(Recovery of) provision for loan losses	0	0
(Recovery of) provision for loan losses	(398)	696
Total ending allowance balance	2,846	3,244
Construction and land \| Construction and land
Allowance for loan losses
Beginning balance	2,678	3,655	3,028
Charge-offs	0	0
(Recovery of) provision for loan losses	0	0
(Recovery of) provision for loan losses	(977)	627
Total ending allowance balance	2,678	3,655
Junior liens \| Junior liens
Allowance for loan losses
Beginning balance	636	916	1,002
Charge-offs	0	0
(Recovery of) provision for loan losses	0	0
(Recovery of) provision for loan losses	(280)	(86)
Total ending allowance balance	636	916
Commercial and industrial (including PPP) \| Commercial and industrial (including PPP)
Allowance for loan losses
Beginning balance	51	2	0
Charge-offs	0	0
(Recovery of) provision for loan losses	0	0
(Recovery of) provision for loan losses	49	2
Total ending allowance balance	51	2
Consumer and other \| Consumer and other
Allowance for loan losses
Beginning balance	38	48	56
Charge-offs	(16)	(10)
(Recovery of) provision for loan losses	0	0
(Recovery of) provision for loan losses	6	2
Total ending allowance balance	38	48
Unallocated Financing Receivables
Allowance for loan losses
Beginning balance	91	55	$ 164
Charge-offs	0	0
(Recovery of) provision for loan losses	0	0
(Recovery of) provision for loan losses	36	(109)
Total ending allowance balance	$ 91	$ 55

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

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