Pension Plan and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Pension Plan
Pension Plan and Other Postretirement Benefits
Employer cash contributions	$ 5,100	$ 9,400
Estimated cash contributions in the current fiscal year	16,100
Components of the pension plans and other postretirement benefits
Service cost	9,235	9,010
Interest cost	6,329	5,319
Expected return on plan assets	(11,307)	(9,866)
Amortization of prior service cost	242	253
Recognized net actuarial loss	999	1,924
Net periodic benefit cost	5,498	6,640
Other Benefits
Pension Plan and Other Postretirement Benefits
Employer cash contributions	100	1,200
Estimated cash contributions in the current fiscal year	700
Components of the pension plans and other postretirement benefits
Service cost	1,683	1,611
Interest cost	1,008	805
Expected return on plan assets	(2,482)	(2,192)
Amortization of prior service cost	39	49
Recognized net actuarial loss	(228)	(110)
Net periodic benefit cost	$ 20	$ 163