Employee benefit plans - Summary of Pension and Postretirement Life Insurance Plans (Details) - Pension Benefits - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Change in benefit obligation:
Benefit obligation, beginning	$ 18,066	$ 19,113
Interest cost	456	419	$ 544
Change in experience gain	26	(49)
Change in actuarial assumptions loss	(3,899)	(603)
Benefits paid	(857)	(814)
Benefit obligation, ending	13,792	18,066	19,113
Change in plan assets:
Fair value of plan assets, beginning	19,257	17,628
Actual return on plan assets	(2,294)	2,443
Benefits paid	(857)	(814)
Fair value of plan assets, ending	16,106	19,257	$ 17,628
Funded status at end of year	$ 2,314	$ 1,191