Pension and Other Postretirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Defined Benefit Plan Deferred Pension And Other Postretirement Benefit Plan Costs Recovered [Abstract]
Deferred (recognized) pension and OPEB costs	$ (300)	$ (3,400)
Returned Savings From Prior Year Employee Benefit Costs	1,000
Pension Benefits [Member]
Components of net periodic benefit cost:
Service cost	1,337	1,422
Interest cost	2,796	2,272
Expected return on assets	(7,851)	(7,375)
Amortization of:
Prior service credit	(5)	(31)
Actuarial loss	724	1,580
Net periodic benefit (credit) cost	(2,999)	(2,132)
Postretirement Benefits [Member]
Components of net periodic benefit cost:
Service cost	333	351
Interest cost	491	384
Expected return on assets	(843)	(817)
Amortization of:
Transition obligation	1	1
Prior service credit	(74)	(380)
Actuarial loss	48	109
Net periodic benefit (credit) cost	$ (44)	$ (352)