Pension and Other Postretirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Defined Benefit Plan Deferred Pension And Other Postretirement Benefit Plan Costs Recovered [Abstract]
Deferred (recognized) pension and OPEB costs	$ (100)	$ (1,200)	$ (700)	$ (2,600)
Pension Benefits [Member]
Components of net periodic benefit cost:
Service cost	655	780	1,306	1,539
Interest cost	4,313	4,315	8,569	8,559
Expected return on assets	(7,246)	(7,148)	(14,507)	(14,299)
Amortization of:
Actuarial (gain) loss	102	313	150	429
Net periodic benefit (credit) cost	(2,176)	(1,740)	(4,482)	(3,772)
Postretirement Benefits [Member]
Components of net periodic benefit cost:
Service cost	188	217	371	428
Interest cost	754	779	1,514	1,576
Expected return on assets	(634)	(693)	(1,358)	(1,384)
Amortization of:
Transition obligation	0	0	1	1
Prior service credit	0	(4)	0	(8)
Actuarial (gain) loss	(173)	(129)	(321)	(206)
Net periodic benefit (credit) cost	$ 135	$ 170	$ 207	$ 407