LOANS RECEIVABLE - Aging analysis (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Total	$ 1,586,060	$ 1,545,127
Total Past Due
Financing Receivable, Past Due [Line Items]
Total	8,368	7,913
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,877	0
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	65	845
90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total	6,426	7,068
Current
Financing Receivable, Past Due [Line Items]
Total	1,577,692	1,537,214
Residential one-to-four family
Financing Receivable, Past Due [Line Items]
Total		597,254
Multifamily
Financing Receivable, Past Due [Line Items]
Total		690,690
Non-residential
Financing Receivable, Past Due [Line Items]
Total		216,061
Construction
Financing Receivable, Past Due [Line Items]
Total		17,799
Junior liens
Financing Receivable, Past Due [Line Items]
Total		18,631
Commercial and industrial (including PPP)
Financing Receivable, Past Due [Line Items]
Total		4,653
Consumer and other
Financing Receivable, Past Due [Line Items]
Total		39
Residential Portfolio Segment | Residential one-to-four family
Financing Receivable, Past Due [Line Items]
Total	592,809	597,254
Residential Portfolio Segment | Residential one-to-four family | Total Past Due
Financing Receivable, Past Due [Line Items]
Total	8,092	7,583
Residential Portfolio Segment | Residential one-to-four family | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	1,718	0
Residential Portfolio Segment | Residential one-to-four family | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	65	845
Residential Portfolio Segment | Residential one-to-four family | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total	6,309	6,738
Residential Portfolio Segment | Residential one-to-four family | Current
Financing Receivable, Past Due [Line Items]
Total	584,717	589,671
Residential Portfolio Segment | Multifamily
Financing Receivable, Past Due [Line Items]
Total	695,207	690,690
Residential Portfolio Segment | Multifamily | Total Past Due
Financing Receivable, Past Due [Line Items]
Total	0	182
Residential Portfolio Segment | Multifamily | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Residential Portfolio Segment | Multifamily | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Residential Portfolio Segment | Multifamily | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total	0	182
Residential Portfolio Segment | Multifamily | Current
Financing Receivable, Past Due [Line Items]
Total	695,207	690,508
Nonresidential Portfolio Segment | Non-residential
Financing Receivable, Past Due [Line Items]
Total	239,844	216,061
Nonresidential Portfolio Segment | Non-residential | Total Past Due
Financing Receivable, Past Due [Line Items]
Total	159	0
Nonresidential Portfolio Segment | Non-residential | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	159	0
Nonresidential Portfolio Segment | Non-residential | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Nonresidential Portfolio Segment | Non-residential | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Nonresidential Portfolio Segment | Non-residential | Current
Financing Receivable, Past Due [Line Items]
Total	239,685	216,061
Construction and Land Portfolio Segment | Construction
Financing Receivable, Past Due [Line Items]
Total	28,141	17,799
Construction and Land Portfolio Segment | Construction | Total Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Construction and Land Portfolio Segment | Construction | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Construction and Land Portfolio Segment | Construction | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Construction and Land Portfolio Segment | Construction | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Construction and Land Portfolio Segment | Construction | Current
Financing Receivable, Past Due [Line Items]
Total	28,141	17,799
Junior Lien Portfolio Segment | Junior liens
Financing Receivable, Past Due [Line Items]
Total	19,644	18,631
Junior Lien Portfolio Segment | Junior liens | Total Past Due
Financing Receivable, Past Due [Line Items]
Total	52	52
Junior Lien Portfolio Segment | Junior liens | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Junior Lien Portfolio Segment | Junior liens | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Junior Lien Portfolio Segment | Junior liens | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total	52	52
Junior Lien Portfolio Segment | Junior liens | Current
Financing Receivable, Past Due [Line Items]
Total	19,592	18,579
Commercial Portfolio Segment | Commercial and industrial (including PPP)
Financing Receivable, Past Due [Line Items]
Total	10,357	4,653
Commercial Portfolio Segment | Commercial and industrial (including PPP) | Total Past Due
Financing Receivable, Past Due [Line Items]
Total	65	96
Commercial Portfolio Segment | Commercial and industrial (including PPP) | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial Portfolio Segment | Commercial and industrial (including PPP) | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial Portfolio Segment | Commercial and industrial (including PPP) | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total	65	96
Commercial Portfolio Segment | Commercial and industrial (including PPP) | Current
Financing Receivable, Past Due [Line Items]
Total	10,292	4,557
Consumer and Other Portfolio Segment | Consumer and other
Financing Receivable, Past Due [Line Items]
Total	58	39
Consumer and Other Portfolio Segment | Consumer and other | Total Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Consumer and Other Portfolio Segment | Consumer and other | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Consumer and Other Portfolio Segment | Consumer and other | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Consumer and Other Portfolio Segment | Consumer and other | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Consumer and Other Portfolio Segment | Consumer and other | Current
Financing Receivable, Past Due [Line Items]
Total	$ 58	$ 39