Retirement plans - Schedule of Pension Costs (Income) (Details) - Retirement Plans - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Defined Benefit Plan Disclosure [Line Items]
Interest cost on benefit obligation	$ 5,463	$ 5,697	$ 10,888	$ 11,372
Expected return on plan assets	(5,935)	(5,533)	(10,360)	(11,033)
Amortization of prior service cost (credit)	(67)	20	(117)	45
Amortization of actuarial loss	1,530	1,475	2,955	2,950
Expense for company-sponsored retirement plans	$ 991	$ 1,659	$ 3,366	$ 3,334