Pensions and Other Post-retirement Benefits - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,315	$ 1,884
Interest cost	5,970	5,918
Expected return on plan assets	(10,812)	(9,906)
Amortization of prior service cost (credit)	37	37
Recognized net actuarial losses	282	47
Net periodic benefit (income) cost	(2,208)	(2,020)
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	44	53
Interest cost	248	273
Expected return on plan assets	0	0
Amortization of prior service cost (credit)	(46)	(61)
Recognized net actuarial losses	115	138
Net periodic benefit (income) cost	$ 361	$ 403