Pensions and Other Post-retirement Benefits - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,315	$ 1,884	$ 4,630	$ 3,768
Interest cost	5,970	5,918	11,940	11,836
Expected return on plan assets	(10,812)	(9,906)	(21,624)	(19,812)
Amortization of prior service cost (credit)	37	37	74	74
Recognized net actuarial losses	282	47	564	94
Settlements	1,308	0	1,308	0
Net periodic benefit (income) cost	(900)	(2,020)	(3,108)	(4,040)
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	44	53	88	106
Interest cost	248	273	496	546
Expected return on plan assets	0	0	0	0
Amortization of prior service cost (credit)	(46)	(61)	(92)	(122)
Recognized net actuarial losses	115	138	230	276
Settlements	0	0	0	0
Net periodic benefit (income) cost	$ 361	$ 403	$ 722	$ 806