Pension Plan and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Pension Plan
Pension Plan and Other Postretirement Benefits
Employer cash contributions			$ 8,800	$ 14,100
Estimated cash contributions in the current fiscal year	$ 16,100		16,100
Components of the pension plans and other postretirement benefits
Service cost	9,235	$ 9,010	18,470	18,020
Interest cost	6,329	5,319	12,658	10,638
Expected return on plan assets	(11,307)	(9,866)	(22,614)	(19,732)
Amortization of prior service cost	242	253	484	506
Recognized net actuarial loss	999	1,924	1,998	3,848
Net periodic benefit cost	5,498	6,640	10,996	13,280
Other Benefits
Pension Plan and Other Postretirement Benefits
Employer cash contributions			300	1,500
Estimated cash contributions in the current fiscal year	700		700
Components of the pension plans and other postretirement benefits
Service cost	1,683	1,611	3,366	3,222
Interest cost	1,008	805	2,016	1,611
Expected return on plan assets	(2,482)	(2,192)	(4,964)	(4,383)
Amortization of prior service cost	39	49	78	97
Recognized net actuarial loss	(228)	(110)	(456)	(220)
Net periodic benefit cost	$ 20	$ 163	$ 40	$ 327