Regulatory matters - Schedule of Bank's Capital Amounts and Ratios (Details) $ in Thousands	Sep. 30, 2025 USD ($)	Dec. 31, 2024 USD ($)
Company
Common equity Tier 1 capital to risk-weighted assets
Common equity Tier 1 capital to risk-weighted assets, Actual Amount	$ 433,211	$ 399,461
Common equity Tier 1 capital to risk-weighted assets, Actual Ratio	11.01	10.16
Common equity Tier 1 capital to risk-weighted assets, Minimum For Capital Adequacy Purposes Amount	$ 177,062	$ 176,971
Common equity Tier 1 capital to risk-weighted assets, Minimum For Capital Adequacy Purposes Ratio	4.5	4.5
Tier 1 capital to risk-weighted assets
Tier 1 capital to risk-weighted assets, Actual Amount	$ 443,211	$ 409,461
Tier 1 capital to risk-weighted assets, Actual Ratio	11.26	10.41
Tier 1 capital to risk-weighted assets, Minimum For Capital Adequacy Purposes Amount	$ 236,169	$ 235,962
Tier 1 capital to risk-weighted assets, Minimum For Capital Adequacy Purposes Ratio	6	6
Total capital to risk-weighted assets
Total capital to risk-weighted assets, Actual Amount	$ 564,792	$ 485,117
Total capital to risk-weighted assets, Actual Ratio	14.35	12.34
Total capital to risk-weighted assets, Minimum For Capital Adequacy Purposes Amount	$ 314,867	$ 314,616
Total capital to risk-weighted assets, Minimum For Capital Adequacy Purposes Ratio	8	8
Tier 1 capital to average assets
Tier 1 capital to average assets, Actual Amount	$ 443,211	$ 409,461
Tier 1 capital to average assets, Actual Ratio	8.87	7.97
Tier 1 capital to average assets, Minimum For Capital Adequacy Purposes Amount	$ 199,870	$ 205,493
Tier 1 capital to average assets, Minimum For Capital Adequacy Purposes Ratio	4	4
Bank
Common equity Tier 1 capital to risk-weighted assets
Common equity Tier 1 capital to risk-weighted assets, Actual Amount	$ 514,266	$ 429,958
Common equity Tier 1 capital to risk-weighted assets, Actual Ratio	13.09	10.95
Common equity Tier 1 capital to risk-weighted assets, Minimum For Capital Adequacy Purposes Amount	$ 176,791	$ 176,640
Common equity Tier 1 capital to risk-weighted assets, Minimum For Capital Adequacy Purposes Ratio	4.5	4.5
Common equity Tier 1 capital to risk-weighted assets, Minimum to be Well Capitalized under Prompt Corrective Action Provisions Amount	$ 255,365	$ 255,147
Common equity Tier 1 capital to risk-weighted assets, Minimum to be Well Capitalized under Prompt Corrective Action Provisions Ratio	6.5	6.5
Tier 1 capital to risk-weighted assets
Tier 1 capital to risk-weighted assets, Actual Amount	$ 514,266	$ 429,958
Tier 1 capital to risk-weighted assets, Actual Ratio	13.09	10.95
Tier 1 capital to risk-weighted assets, Minimum For Capital Adequacy Purposes Amount	$ 235,722	$ 235,520
Tier 1 capital to risk-weighted assets, Minimum For Capital Adequacy Purposes Ratio	6	6
Tier 1 capital to risk-weighted assets, Minimum to be Well Capitalized under Prompt Corrective Action Provisions Amount	$ 314,295	$ 314,027
Tier 1 capital to risk-weighted assets, Minimum to be Well Capitalized under Prompt Corrective Action Provisions Ratio	8	8
Total capital to risk-weighted assets
Total capital to risk-weighted assets, Actual Amount	$ 552,736	$ 472,614
Total capital to risk-weighted assets, Actual Ratio	14.07	12.04
Total capital to risk-weighted assets, Minimum For Capital Adequacy Purposes Amount	$ 314,278	$ 314,027
Total capital to risk-weighted assets, Minimum For Capital Adequacy Purposes Ratio	8	8
Total capital to risk-weighted assets, Minimum to be Well Capitalized under Prompt Corrective Action Provisions Amount	$ 392,847	$ 392,534
Total capital to risk-weighted assets, Minimum to be Well Capitalized under Prompt Corrective Action Provisions Ratio	10	10
Tier 1 capital to average assets
Tier 1 capital to average assets, Actual Amount	$ 514,266	$ 429,958
Tier 1 capital to average assets, Actual Ratio	10.31	8.37
Tier 1 capital to average assets, Minimum For Capital Adequacy Purposes Amount	$ 199,521	$ 205,431
Tier 1 capital to average assets, Minimum For Capital Adequacy Purposes Ratio	4	4
Tier 1 capital to average assets, Minimum to be Well Capitalized under Prompt Corrective Action Provisions Amount	$ 249,402	$ 256,788
Tier 1 capital to average assets, Minimum to be Well Capitalized under Prompt Corrective Action Provisions Ratio	5	5

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Tier 1 Common Equity Risk Based Capital as defined in the regulations.

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The Tier One minimum Common Equity Capital Ratio ( Tier one Common Equity capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The Tier 1 Common Equity capital ratio (Tier 1 Common Equity capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action.

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Amount of total capital as defined by regulatory framework.

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Amount of minimum total risk-based capital required for capital adequacy as defined by regulatory framework.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1B

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Amount of Tier 1 leverage capital as defined by regulatory framework.

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Amount of minimum Tier 1 leverage capital required for capital adequacy as defined by regulatory framework.

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