Employee benefit plans - Summary of Pension and Postretirement Life Insurance Plans (Details) - Pension Benefits - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Change in benefit obligation:
Benefit obligation, beginning	$ 13,845	$ 13,792
Interest cost	634	655	$ 456
Change in experience gain	77	2
Change in actuarial assumptions	(867)	306
Benefits paid	(945)	(910)
Benefit obligation, ending	12,744	13,845	13,792
Change in plan assets:
Fair value of plan assets, beginning	17,609	16,106
Actual return on plan assets	1,868	2,413
Benefits paid	(945)	(910)
Fair value of plan assets, ending	18,532	17,609	$ 16,106
Funded status at end of year	$ 5,788	$ 3,764

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Defined Benefit Plan Change In Experience Gain Loss

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Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

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Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

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Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status.

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Amount of cost recognized for passage of time related to defined benefit plan.

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Amount of payment to participant under defined benefit plan which decreases plan assets. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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