Retirement plans - Schedule of Assumptions Used (Details) - Retirement Plans	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	5.50%	2.89%	2.54%
Expected return on plan assets	5.75%	3.75%	6.50%