Pension Plan and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Pension Plan
Pension Plan and Other Postretirement Benefits
Employer cash contributions			$ 4,300	$ 400
Estimated cash contributions in the current fiscal year	$ 5,200		5,200
Components of the pension plans and other postretirement benefits
Service cost	5,206	$ 5,648	15,620	16,944
Interest cost	9,552	8,880	28,658	26,642
Expected return on plan assets	(12,792)	(13,234)	(38,378)	(39,706)
Amortization of prior service cost	132	131	394	393
Recognized net actuarial loss (gain)	195	189	583	567
Net periodic benefit cost (credit)	2,293	1,614	6,877	4,840
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	1,407	1,521	4,223	4,561
Interest cost	1,774	1,684	5,320	5,052
Expected return on plan assets	(3,197)	(2,988)	(9,591)	(8,962)
Amortization of prior service cost	38	38	116	116
Recognized net actuarial loss (gain)	(522)	(196)	(1,566)	(592)
Net periodic benefit cost (credit)	$ (500)	$ 59	$ (1,498)	$ 175