LOANS RECEIVABLE - Summary of loans receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 1,550,983		$ 1,560,730
Less: Allowance for credit losses	13,012	$ 13,027	14,154	$ 13,872	$ 14,413	$ 13,400
Loans receivable, net	1,537,971		1,546,576
Residential Portfolio Segment | Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	516,754		550,929
Less: Allowance for credit losses	1,842	1,825	1,968	1,966	1,994	2,264
Residential Portfolio Segment | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	666,304		682,564
Less: Allowance for credit losses	6,593	6,677	7,046	6,823	7,017	5,491
Commercial Real Estate Portfolio Segment | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	241,711		232,505
Less: Allowance for credit losses	3,660	3,696	3,748	3,728	3,813	3,357
Construction and Land Portfolio Segment | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	80,081		60,414
Less: Allowance for credit losses	650	636	1,222	1,167	1,428	1,697
Junior Lien Portfolio Segment | Junior liens
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	24,174		22,503
Less: Allowance for credit losses	88	84	76	54	50	451
Commercial Portfolio Segment | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	14,228		11,768
Less: Allowance for credit losses	153	108	94	134	111	47
Consumer and Other Portfolio Segment | Consumer and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	7,731		47
Less: Allowance for credit losses	$ 26	$ 1	$ 0	$ 0	$ 0	$ 0