Pension Plan and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Pension Plan
Pension Plan and Other Postretirement Benefits
Employer cash contributions			$ 3,300	$ 200
Estimated cash contributions in the current fiscal year	$ 5,200		5,200
Components of the pension plans and other postretirement benefits
Service cost	5,207	$ 5,648	10,414	11,296
Interest cost	9,553	8,881	19,106	17,762
Expected return on plan assets	(12,793)	(13,236)	(25,586)	(26,472)
Amortization of prior service cost	131	131	262	262
Recognized net actuarial loss (gain)	194	189	388	378
Net periodic benefit cost (credit)	2,292	1,613	4,584	3,226
Other Benefits
Pension Plan and Other Postretirement Benefits
Employer cash contributions			0	0
Estimated cash contributions in the current fiscal year	0		0
Components of the pension plans and other postretirement benefits
Service cost	1,408	1,520	2,816	3,040
Interest cost	1,773	1,684	3,546	3,368
Expected return on plan assets	(3,197)	(2,987)	(6,394)	(5,974)
Amortization of prior service cost	39	39	78	78
Recognized net actuarial loss (gain)	(522)	(198)	(1,044)	(396)
Net periodic benefit cost (credit)	$ (499)	$ 58	$ (998)	$ 116