LOANS RECEIVABLE, NET - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	$ 1,254,223	$ 1,284,073
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	1,235,306	1,253,057
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	4,966	16,802
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	13,951	14,214
Doubtful/Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	0	0
Residential Portfolio Segment | Residential one-to-four family
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	526,831	616,248
Residential Portfolio Segment | Residential one-to-four family | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	515,423	604,167
Residential Portfolio Segment | Residential one-to-four family | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	0	0
Residential Portfolio Segment | Residential one-to-four family | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	11,408	12,081
Residential Portfolio Segment | Residential one-to-four family | Doubtful/Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	0	0
Residential Portfolio Segment | Multifamily
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	512,879	429,095
Residential Portfolio Segment | Multifamily | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	507,027	411,369
Residential Portfolio Segment | Multifamily | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	4,820	16,648
Residential Portfolio Segment | Multifamily | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	1,032	1,078
Residential Portfolio Segment | Multifamily | Doubtful/Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	0	0
Nonresidential Portfolio Segment | Non-residential
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	130,850	128,217
Nonresidential Portfolio Segment | Non-residential | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	129,306	127,089
Nonresidential Portfolio Segment | Non-residential | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	146	154
Nonresidential Portfolio Segment | Non-residential | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	1,398	974
Nonresidential Portfolio Segment | Non-residential | Doubtful/Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	0	0
Construction and Land Portfolio Segment | Construction and land
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	21,290	33,630
Construction and Land Portfolio Segment | Construction and land | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	21,290	33,630
Construction and Land Portfolio Segment | Construction and land | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	0	0
Construction and Land Portfolio Segment | Construction and land | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	0	0
Construction and Land Portfolio Segment | Construction and land | Doubtful/Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	0	0
Junior Lien Portfolio Segment | Junior liens
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	19,632	23,918
Junior Lien Portfolio Segment | Junior liens | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	19,519	23,837
Junior Lien Portfolio Segment | Junior liens | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	0	0
Junior Lien Portfolio Segment | Junior liens | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	113	81
Junior Lien Portfolio Segment | Junior liens | Doubtful/Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	0	0
Commercial Portfolio Segment | Commercial and industrial (including PPP)
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	42,661	52,867
Commercial Portfolio Segment | Commercial and industrial (including PPP) | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	42,661	52,867
Commercial Portfolio Segment | Commercial and industrial (including PPP) | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	0	0
Commercial Portfolio Segment | Commercial and industrial (including PPP) | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	0	0
Commercial Portfolio Segment | Commercial and industrial (including PPP) | Doubtful/Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable		0
Consumer and Other Portfolio Segment | Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	80	98
Consumer and Other Portfolio Segment | Consumer and other | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	80	98
Consumer and Other Portfolio Segment | Consumer and other | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	0	0
Consumer and Other Portfolio Segment | Consumer and other | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	0	0
Consumer and Other Portfolio Segment | Consumer and other | Doubtful/Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans Receivable	$ 0	$ 0