Pensions and Other Post-retirement Benefits - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,013	$ 2,007	$ 4,026	$ 4,001
Interest cost	5,782	5,979	11,564	11,913
Expected return on plan assets	(12,418)	(12,005)	(24,836)	(24,010)
Amortization of prior service cost	40	32	80	64
Recognized net actuarial losses	205	197	410	394
Settlements	0	(721)	0	(721)
Net periodic benefit (income) cost	(4,378)	(3,069)	(8,756)	(6,917)
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	21	31	42	62
Interest cost	228	276	455	552
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	0	0	0	0
Recognized net actuarial losses	127	163	254	326
Settlements	0	0	0	0
Net periodic benefit (income) cost	$ 376	$ 470	$ 751	$ 940