ALLOWANCE FOR CREDIT LOSSES - Summary of allowance for credit lost by portfolio segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 13,400	$ 14,425
Charge-offs	(5)	(10)
Recoveries	1	2
Provision for (recovery of) credit loss on loans	89	(952)
Balance at end of period	14,153	13,465
Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	668	0
Balance at end of period	660
Residential Portfolio Segment | Multifamily
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	5,491	5,263
Charge-offs	0	0
Recoveries	0	0
Provision for (recovery of) credit loss on loans	(357)	(487)
Balance at end of period	7,191	4,776
Residential Portfolio Segment | Multifamily | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	2,057
Residential Portfolio Segment | Residential one-to-four family
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	2,264	2,822
Charge-offs	0	0
Recoveries	0	0
Provision for (recovery of) credit loss on loans	(25)	(212)
Balance at end of period	2,056	2,610
Residential Portfolio Segment | Residential one-to-four family | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	(183)
Nonresidential Portfolio Segment | Non-residential
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	3,357	2,846
Charge-offs	0	0
Recoveries	0	0
Provision for (recovery of) credit loss on loans	67	619
Balance at end of period	3,570	3,465
Nonresidential Portfolio Segment | Non-residential | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	146
Commercial Portfolio Segment | Construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	1,697	2,678
Charge-offs	0	0
Recoveries	0	0
Provision for (recovery of) credit loss on loans	325	(773)
Balance at end of period	1,190	1,905
Commercial Portfolio Segment | Construction | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	(832)
Commercial and industrial (including PPP) | Commercial and industrial (including PPP)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	47	51
Charge-offs	0	0
Recoveries	0	0
Provision for (recovery of) credit loss on loans	76	20
Balance at end of period	100	71
Commercial and industrial (including PPP) | Commercial and industrial (including PPP) | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	(23)
Junior Lien Portfolio Segment | Junior liens
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	451	636
Charge-offs	0	0
Recoveries	0	0
Provision for (recovery of) credit loss on loans	0	(87)
Balance at end of period	46	549
Junior Lien Portfolio Segment | Junior liens | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	(405)
Consumer Portfolio Segment | Consumer and other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	0	38
Charge-offs	(5)	(10)
Recoveries	1	2
Provision for (recovery of) credit loss on loans	3	(30)
Balance at end of period	0	0
Consumer Portfolio Segment | Consumer and other | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	1
Unallocated Financing Receivables
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	93	91
Charge-offs	0	0
Recoveries	0	0
Provision for (recovery of) credit loss on loans	0	(2)
Balance at end of period	0	$ 89
Unallocated Financing Receivables | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ (93)