LOANS RECEIVABLE, NET - Aging Analysis (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	$ 1,254,223	$ 1,284,073
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	784	6,151
90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	10,696	11,036
Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	11,480	17,187
Current
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	1,242,743	1,266,886
Residential Portfolio Segment | Residential one-to-four family
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	526,831	616,248
Residential Portfolio Segment | Residential one-to-four family | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	542	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	9,233	10,075
Residential Portfolio Segment | Residential one-to-four family | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	9,775	13,226
Residential Portfolio Segment | Residential one-to-four family | Current
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	517,056	603,022
Residential Portfolio Segment | Multifamily
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	512,879	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	145	156
Residential Portfolio Segment | Multifamily | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	145	156
Residential Portfolio Segment | Multifamily | Current
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	512,734	428,939
Nonresidential Portfolio Segment | Non-residential
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	130,850	128,217
Nonresidential Portfolio Segment | Non-residential | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	191	0
Nonresidential Portfolio Segment | Non-residential | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	1,262	805
Nonresidential Portfolio Segment | Non-residential | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	1,453	805
Nonresidential Portfolio Segment | Non-residential | Current
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	129,397	127,412
Construction and Land Portfolio Segment | Construction and land
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	21,290	33,630
Construction and Land Portfolio Segment | Construction and land | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	3,000
Construction and Land Portfolio Segment | Construction and land | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	0
Construction and Land Portfolio Segment | Construction and land | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	3,000
Construction and Land Portfolio Segment | Construction and land | Current
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	21,290	30,630
Junior Lien Portfolio Segment | Junior liens
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	19,632	23,918
Junior Lien Portfolio Segment | Junior liens | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	51	0
Junior Lien Portfolio Segment | Junior liens | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	56	0
Junior Lien Portfolio Segment | Junior liens | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	107	0
Junior Lien Portfolio Segment | Junior liens | Current
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	19,525	23,918
Commercial Portfolio Segment | Commercial and industrial (including PPP)
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	42,661	52,867
Commercial Portfolio Segment | Commercial and industrial (including PPP) | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	0
Commercial Portfolio Segment | Commercial and industrial (including PPP) | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	0
Commercial Portfolio Segment | Commercial and industrial (including PPP) | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	0
Commercial Portfolio Segment | Commercial and industrial (including PPP) | Current
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	42,661	52,867
Consumer and Other Portfolio Segment | Consumer and other
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	80	98
Consumer and Other Portfolio Segment | Consumer and other | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	0
Consumer and Other Portfolio Segment | Consumer and other | 90 Days and Greater Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	0
Consumer and Other Portfolio Segment | Consumer and other | Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	0	0
Consumer and Other Portfolio Segment | Consumer and other | Current
Financing Receivable, Past Due [Line Items]
Total Loans Receivable	$ 80	$ 98