Pension and Other Postretirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Defined Benefit Plan Deferred Pension And Other Postretirement Benefit Plan Costs Recovered [Abstract]
Deferred (recognized) pension and OPEB costs	$ (200)	$ (300)	$ (800)	$ (3,900)
Deferred savings from current year employee benefit plan costs	300	2,800	1,100	5,400
Returned savings from prior year employee benefit costs	1,000		3,100
Pension Benefits [Member]
Components of net periodic benefit cost:
Service cost	1,266	1,432	3,798	4,296
Interest cost	2,791	2,280	8,371	6,840
Expected return on assets	(7,848)	(7,372)	(23,543)	(22,115)
Amortization of:
Prior service credit	(5)	(31)	(15)	(93)
Actuarial loss	604	1,662	1,812	4,985
Net periodic benefit (credit) cost	(3,192)	(2,029)	(9,577)	(6,087)
Postretirement Benefits [Member]
Components of net periodic benefit cost:
Service cost	323	362	970	1,086
Interest cost	485	387	1,455	1,161
Expected return on assets	(842)	(819)	(2,524)	(2,457)
Amortization of:
Transition obligation	1	1	2	2
Prior service credit	(74)	(379)	(223)	(1,138)
Actuarial loss	37	123	109	370
Net periodic benefit (credit) cost	$ (70)	$ (325)	$ (211)	$ (976)