Pension Plan and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Pension Plan
Pension Plan and Other Postretirement Benefits
Employer cash contributions			$ 200	$ 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	11,296	12,092
Interest cost	8,881	8,746	17,762	17,492
Expected return on plan assets	(13,236)	(13,421)	(26,472)	(26,842)
Amortization of prior service cost	131	131	262	262
Recognized net actuarial (gain) loss	189	(637)	378	(1,274)
Net periodic benefit cost (credit)	1,613	865	3,226	1,730
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	1,520	1,126	3,040	2,252
Interest cost	1,684	1,297	3,368	2,595
Expected return on plan assets	(2,987)	(2,636)	(5,974)	(5,271)
Amortization of prior service cost	39	39	78	77
Recognized net actuarial (gain) loss	(198)	(581)	(396)	(1,163)
Net periodic benefit cost (credit)	$ 58	$ (755)	$ 116	$ (1,510)