Pension and Other Postretirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Defined Benefit Plan Deferred Pension And Other Postretirement Benefit Plan Costs Recovered [Abstract]
Deferred (recognized) pension and OPEB costs	$ (1,200)	$ 400	$ (2,600)	$ 800
Amortization of:
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Amortization of Prior Service Cost (Credit), Statement of Income or Comprehensive Income [Extensible Enumeration]			Nonoperating Income (Expense)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]			Nonoperating Income (Expense)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			Nonoperating Income (Expense)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			Nonoperating Income (Expense)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Transition Asset (Obligation), Statement of Income or Comprehensive Income [Extensible Enumeration]			Nonoperating Income (Expense)
Pension Benefits [Member]
Components of net periodic benefit cost:
Service cost	780	694	$ 1,539	1,446
Interest cost	4,315	4,337	8,559	8,659
Expected return on assets	(7,148)	(6,302)	(14,299)	(12,624)
Amortization of:
Actuarial (gain) loss	313	492	429	880
Net periodic benefit (credit) cost	(1,740)	(779)	(3,772)	(1,639)
Postretirement Benefits [Member]
Components of net periodic benefit cost:
Service cost	217	190	428	390
Interest cost	779	835	1,576	1,654
Expected return on assets	(693)	(646)	(1,384)	(1,297)
Amortization of:
Transition obligation	0	0	1	1
Prior service credit	(4)	0	(8)	0
Actuarial (gain) loss	(129)	(65)	(206)	(95)
Net periodic benefit (credit) cost	$ 170	$ 314	$ 407	$ 653