Pension Plan and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Pension Plan
Pension Plan and Other Postretirement Benefits
Employer cash contributions			$ 400	$ 2,900
Estimated cash contributions in the current fiscal year	$ 700		700
Components of the pension plans and other postretirement benefits
Service cost	5,648	$ 6,046	16,944	18,137
Interest cost	8,880	8,746	26,642	26,238
Expected return on plan assets	(13,234)	(13,421)	(39,706)	(40,263)
Amortization of prior service cost	131	131	393	394
Recognized net actuarial (gain) loss	189	(637)	567	(1,911)
Net periodic benefit cost (credit)	1,614	865	4,840	2,595
Other Benefits
Pension Plan and Other Postretirement Benefits
Employer cash contributions			0	200
Estimated cash contributions in the current fiscal year	200		200
Components of the pension plans and other postretirement benefits
Service cost	1,521	1,126	4,561	3,379
Interest cost	1,684	1,297	5,052	3,892
Expected return on plan assets	(2,988)	(2,636)	(8,962)	(7,907)
Amortization of prior service cost	38	39	116	116
Recognized net actuarial (gain) loss	(196)	(581)	(592)	(1,744)
Net periodic benefit cost (credit)	$ 59	$ (755)	$ 175	$ (2,264)