Loans - Narrative (Details)	Mar. 31, 2026 USD ($) loan	Dec. 31, 2025 USD ($) loan	Mar. 31, 2025 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net deferred loan costs	$ 12,669,000	$ 12,737,000	$ 12,570,000
Loans used to collateralize borrowings from the Federal Home Loan Bank of Boston	662,819,000	669,541,000	631,410,000
Loans	$ 2,405,149,000	$ 2,394,109,000	$ 2,383,150,000
Number of mortgage loans in the process of foreclosure \| loan	8	7	4
Mortgage loans in the process of foreclosure	$ 1,788,000	$ 1,754,000	$ 1,208,000
Home Equity Line of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of mortgage loans in the process of foreclosure \| loan	1	1
Mortgage loans in the process of foreclosure	$ 63,000	$ 63,000
Consumer Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of mortgage loans in the process of foreclosure \| loan	1
Mortgage loans in the process of foreclosure	$ 7,000
Commercial Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of mortgage loans in the process of foreclosure \| loan	13	7
Mortgage loans in the process of foreclosure	$ 6,436,000	$ 3,826,000
Asset Pledged as Collateral
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	394,989,000	366,032,000	411,257,000
Residential \| Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	739,446,000	739,188,000	719,348,000
Interest rate swap agreements \| Designated as Hedging Instrument
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value	(502,000)	(910,000)	(1,016,000)
Interest rate swap agreements \| Fair Value Hedging \| Designated as Hedging Instrument
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value	(502,000)	(910,000)	(1,120,000)
Interest rate cap agreements \| Fair Value Hedging \| Designated as Hedging Instrument
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value	1,312,000	154,000	0
Interest rate cap agreements \| Fair Value Hedging \| Designated as Hedging Instrument \| Residential \| Term
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value	$ 164,000	$ (371,000)	$ 0

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Fair value of the assets less the liabilities of a derivative or group of derivatives.

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Amount of the collateral pledged in support of federal home loan bank advances outstanding.

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Amount of fee received for commitment to originate or purchase financing receivable where likelihood of commitment being exercised is remote, to be recognized as service income.

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Recorded investment of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process.

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