LOANS RECEIVABLE - Credit quality indicators (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
2023	$ 55,682
2022	522,790
2021	315,153
2020	68,134
2019	87,347
Pre-2019	536,937
Revolving Loans	17
Total	1,586,060	$ 1,545,127
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total		1,534,434
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total		2,224
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total		8,469
Doubtful / Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Residential one-to-four family
Financing Receivable, Credit Quality Indicator [Line Items]
Total		597,254
Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Total		690,690
Non-residential
Financing Receivable, Credit Quality Indicator [Line Items]
Total		216,061
Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total		17,799
Junior liens
Financing Receivable, Credit Quality Indicator [Line Items]
Total		18,631
Commercial and industrial (including PPP)
Financing Receivable, Credit Quality Indicator [Line Items]
Total		4,653
Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
Total		39
Residential Portfolio Segment | Residential one-to-four family
Financing Receivable, Credit Quality Indicator [Line Items]
2023	6,646
2022	101,708
2021	121,744
2020	16,046
2019	19,409
Pre-2019	327,256
Revolving Loans	0
Total	592,809	597,254
Residential Portfolio Segment | Residential one-to-four family | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2023	6,646
2022	101,708
2021	121,744
2020	16,046
2019	19,409
Pre-2019	319,827
Revolving Loans	0
Total	585,380	589,137
Residential Portfolio Segment | Residential one-to-four family | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total		247
Residential Portfolio Segment | Residential one-to-four family | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	0
2020	0
2019	0
Pre-2019	7,429
Revolving Loans	0
Total	7,429	7,870
Residential Portfolio Segment | Residential one-to-four family | Doubtful / Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Residential Portfolio Segment | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
2023	10,279
2022	283,488
2021	161,788
2020	36,050
2019	60,244
Pre-2019	143,358
Revolving Loans	0
Total	695,207	690,690
Residential Portfolio Segment | Multifamily | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2023	10,279
2022	283,488
2021	161,788
2020	36,050
2019	60,244
Pre-2019	142,859
Revolving Loans	0
Total	694,708	689,277
Residential Portfolio Segment | Multifamily | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total		897
Residential Portfolio Segment | Multifamily | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	0
2020	0
2019	0
Pre-2019	499
Revolving Loans	0
Total	499	516
Residential Portfolio Segment | Multifamily | Doubtful / Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Nonresidential Portfolio Segment | Non-residential
Financing Receivable, Credit Quality Indicator [Line Items]
2023	25,819
2022	121,004
2021	14,953
2020	15,426
2019	5,531
Pre-2019	57,111
Revolving Loans	0
Total	239,844	216,061
Nonresidential Portfolio Segment | Non-residential | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2023	25,819
2022	121,004
2021	14,953
2020	15,426
2019	5,531
Pre-2019	56,053
Revolving Loans	0
Total	238,786	214,981
Nonresidential Portfolio Segment | Non-residential | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	0
2020	0
2019	0
Pre-2019	1,058
Revolving Loans	0
Total	1,058	1,080
Nonresidential Portfolio Segment | Non-residential | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Nonresidential Portfolio Segment | Non-residential | Doubtful / Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Construction and Land Portfolio Segment | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
2023	4,937
2022	11,279
2021	11,809
2020	0
2019	0
Pre-2019	116
Revolving Loans	0
Total	28,141	17,799
Construction and Land Portfolio Segment | Construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2023	4,937
2022	11,279
2021	11,809
2020	0
2019	0
Pre-2019	116
Revolving Loans	0
Total	28,141	17,799
Construction and Land Portfolio Segment | Construction | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Construction and Land Portfolio Segment | Construction | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Construction and Land Portfolio Segment | Construction | Doubtful / Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Junior Lien Portfolio Segment | Junior liens
Financing Receivable, Credit Quality Indicator [Line Items]
2023	1,403
2022	5,199
2021	1,387
2020	396
2019	2,163
Pre-2019	9,096
Revolving Loans	0
Total	19,644	18,631
Junior Lien Portfolio Segment | Junior liens | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2023	1,403
2022	5,199
2021	1,387
2020	396
2019	2,163
Pre-2019	9,044
Revolving Loans	0
Total	19,592	18,579
Junior Lien Portfolio Segment | Junior liens | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Junior Lien Portfolio Segment | Junior liens | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	0
2020	0
2019	0
Pre-2019	52
Revolving Loans	0
Total	52	52
Junior Lien Portfolio Segment | Junior liens | Doubtful / Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Commercial Portfolio Segment | Commercial and industrial (including PPP)
Financing Receivable, Credit Quality Indicator [Line Items]
2023	6,557
2022	112
2021	3,472
2020	216
2019	0
Pre-2019	0
Revolving Loans	0
Total	10,357	4,653
Commercial Portfolio Segment | Commercial and industrial (including PPP) | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2023	6,557
2022	112
2021	3,407
2020	216
2019	0
Pre-2019	0
Revolving Loans	0
Total	10,292	4,653
Commercial Portfolio Segment | Commercial and industrial (including PPP) | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Commercial Portfolio Segment | Commercial and industrial (including PPP) | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2023	0
2022	0
2021	65
2020	0
2019	0
Pre-2019	0
Revolving Loans	0
Total	65	0
Commercial Portfolio Segment | Commercial and industrial (including PPP) | Doubtful / Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Consumer and Other Portfolio Segment | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2023	41
2022	0
2021	0
2020	0
2019	0
Pre-2019	0
Revolving Loans	17
Total	58	39
Consumer and Other Portfolio Segment | Consumer and other | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2023	41
2022	0
2021	0
2020	0
2019	0
Pre-2019	0
Revolving Loans	17
Total	$ 58	8
Consumer and Other Portfolio Segment | Consumer and other | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Consumer and Other Portfolio Segment | Consumer and other | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total		31
Consumer and Other Portfolio Segment | Consumer and other | Doubtful / Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total		$ 0