LOANS RECEIVABLE - Aging analysis (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Total	$ 1,581,745	$ 1,545,127
Total Past Due
Financing Receivable, Past Due [Line Items]
Total	6,764	7,913
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	330	845
90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total	6,434	7,068
Current
Financing Receivable, Past Due [Line Items]
Total	1,574,981	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
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	580,396	597,254
Residential Portfolio Segment | Residential one-to-four family | Total Past Due
Financing Receivable, Past Due [Line Items]
Total	6,648	7,583
Residential Portfolio Segment | Residential one-to-four family | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Residential Portfolio Segment | Residential one-to-four family | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	330	845
Residential Portfolio Segment | Residential one-to-four family | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total	6,318	6,738
Residential Portfolio Segment | Residential one-to-four family | Current
Financing Receivable, Past Due [Line Items]
Total	573,748	589,671
Residential Portfolio Segment | Multifamily
Financing Receivable, Past Due [Line Items]
Total	696,956	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	696,956	690,508
Nonresidential Portfolio Segment | Non-residential
Financing Receivable, Past Due [Line Items]
Total	237,247	216,061
Nonresidential Portfolio Segment | Non-residential | Total Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Nonresidential Portfolio Segment | Non-residential | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	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	237,247	216,061
Construction and Land Portfolio Segment | Construction
Financing Receivable, Past Due [Line Items]
Total	36,032	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	36,032	17,799
Junior Lien Portfolio Segment | Junior liens
Financing Receivable, Past Due [Line Items]
Total	21,338	18,631
Junior Lien Portfolio Segment | Junior liens | Total Past Due
Financing Receivable, Past Due [Line Items]
Total	51	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	51	52
Junior Lien Portfolio Segment | Junior liens | Current
Financing Receivable, Past Due [Line Items]
Total	21,287	18,579
Commercial Portfolio Segment | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total	9,743	4,653
Commercial Portfolio Segment | Commercial and industrial | Total Past Due
Financing Receivable, Past Due [Line Items]
Total	65	96
Commercial Portfolio Segment | Commercial and industrial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial Portfolio Segment | Commercial and industrial | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total	0	0
Commercial Portfolio Segment | Commercial and industrial | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total	65	96
Commercial Portfolio Segment | Commercial and industrial | Current
Financing Receivable, Past Due [Line Items]
Total	9,678	4,557
Consumer and Other Portfolio Segment | Consumer and other
Financing Receivable, Past Due [Line Items]
Total	33	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	$ 33	$ 39