LOANS RECEIVABLE, NET - Aging analysis (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	$ 1,287,609	$ 1,284,073
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	567	6,151
90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	9,615	11,036
Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	10,182	17,187
Current
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	1,277,427	1,266,886
Residential Portfolio Segment | Residential one-to-four family
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	566,483	616,248
Residential Portfolio Segment | Residential one-to-four family | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	457	3,151
Residential Portfolio Segment | Residential one-to-four family | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	8,936	10,075
Residential Portfolio Segment | Residential one-to-four family | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	9,393	13,226
Residential Portfolio Segment | Residential one-to-four family | Current
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	557,090	603,022
Residential Portfolio Segment | Multifamily
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	516,568	429,095
Residential Portfolio Segment | Multifamily | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	0
Residential Portfolio Segment | Multifamily | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	156
Residential Portfolio Segment | Multifamily | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	156
Residential Portfolio Segment | Multifamily | Current
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	516,568	428,939
Non-residential | Non-residential
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	141,534	128,217
Non-residential | Non-residential | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	0
Non-residential | Non-residential | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	381	805
Non-residential | Non-residential | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	381	805
Non-residential | Non-residential | Current
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	141,153	127,412
Construction and land | Construction and land
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	23,420	33,630
Construction and land | Construction and land | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	3,000
Construction and land | Construction and land | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	0
Construction and land | Construction and land | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	3,000
Construction and land | Construction and land | Current
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	23,420	30,630
Junior liens | Junior liens
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	18,550	23,918
Junior liens | Junior liens | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	53	0
Junior liens | Junior liens | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	182	0
Junior liens | Junior liens | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	235	0
Junior liens | Junior liens | Current
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	18,315	23,918
Commercial and industrial (including PPP) | Commercial and industrial (including PPP)
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	20,966	52,867
Commercial and industrial (including PPP) | Commercial and industrial (including PPP) | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	57	0
Commercial and industrial (including PPP) | Commercial and industrial (including PPP) | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	116	0
Commercial and industrial (including PPP) | Commercial and industrial (including PPP) | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	173	0
Commercial and industrial (including PPP) | Commercial and industrial (including PPP) | Current
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	20,793	52,867
Consumer and other | Consumer and other
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	88	98
Consumer and other | Consumer and other | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	0
Consumer and other | Consumer and other | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	0
Consumer and other | Consumer and other | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	0
Consumer and other | Consumer and other | Current
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	$ 88	$ 98