Pension and Other Postretirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Defined Benefit Plan Deferred Pension And Other Postretirement Benefit Plan Costs Recovered [Abstract]
Deferred (recognized) pension and OPEB costs	$ (500)	$ 1,600	$ (3,100)	$ 2,400
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	769	723	$ 2,308	2,169
Interest cost	4,280	4,330	12,839	12,989
Expected return on assets	(7,149)	(6,312)	(21,448)	(18,936)
Amortization of:
Actuarial (gain) loss	215	440	644	1,320
Net periodic benefit (credit) cost	(1,885)	(819)	(5,657)	(2,458)
Postretirement Benefits [Member]
Components of net periodic benefit cost:
Service cost	214	195	642	585
Interest cost	778	827	2,354	2,481
Expected return on assets	(675)	(649)	(2,059)	(1,946)
Settlement cost	(288)	(0)	(288)	(0)
Amortization of:
Transition obligation	1	1	2	2
Prior service credit	(234)	0	(242)	0
Actuarial (gain) loss	774	(48)	568	(143)
Net periodic benefit (credit) cost	$ 1,146	$ 326	$ 1,553	$ 979