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Loans Receivable and the Allowance for Credit Losses - Summary of composition of loans (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Mar. 31, 2026	Dec. 31, 2025	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024
Loans Receivable and the Allowance for Credit Losses
Loans receivable	$ 1,919,908		$ 1,860,066
Deferred loan (fees) costs, net	(149)		268
Allowance for credit losses	(4,752)	$ (4,592)	(4,731)	$ (4,724)	$ (5,127)	$ (4,830)
Net loans	1,915,007		1,855,603
Residential real estate
Loans Receivable and the Allowance for Credit Losses
Loans receivable	329,671		334,819
Allowance for credit losses	(1,547)	(1,520)	(1,646)	(1,979)	(2,224)	(1,900)
Residential real estate \| One-to-four family
Loans Receivable and the Allowance for Credit Losses
Loans receivable	3,046		3,114
Residential real estate \| Multi-family
Loans Receivable and the Allowance for Credit Losses
Loans receivable	301,628		306,508
Residential real estate \| Mixed-use
Loans Receivable and the Allowance for Credit Losses
Loans receivable	24,997		25,197
Non-residential real estate
Loans Receivable and the Allowance for Credit Losses
Loans receivable	36,247		38,463
Allowance for credit losses	(238)	(264)	(249)	(229)	(271)	(308)
Construction
Loans Receivable and the Allowance for Credit Losses
Loans receivable	1,403,562		1,336,329
Allowance for credit losses	(2,188)	(2,015)	(2,035)	(1,792)	(1,716)	(1,937)
Commercial and industrial
Loans Receivable and the Allowance for Credit Losses
Loans receivable	150,394		150,397
Allowance for credit losses	(745)	(756)	(743)	(677)	(606)	(520)
Consumer
Loans Receivable and the Allowance for Credit Losses
Loans receivable	34		58
Allowance for credit losses	$ (34)	$ (37)	$ (58)	$ (47)	$ (310)	$ (165)