Employee Benefit Plans - Schedule of Net Periodic Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Components of Net Periodic Benefits Cost:
Regulatory adjustments - deferred			$ 8,622	$ (86,070)
Pension Benefits
Components of Net Periodic Benefits Cost:
Service cost	$ 792	$ 705	2,492	2,397
Interest cost	2,580	2,581	7,680	7,607
Expected return on plan assets	(3,004)	(2,617)	(9,022)	(7,863)
Amortization of prior service cost	109	110	326	326
Amortization of actuarial (gain) loss	0	0	0	0
Net periodic benefits costs under accounting standards	477	779	1,476	2,467
Regulatory adjustments - deferred	0	(27)	0	(211)
Total expense (benefit) recognized, before surcharges and allocation to overhead pool	477	752	1,476	2,256
Other Postretirement Benefits
Components of Net Periodic Benefits Cost:
Service cost	32	33	96	99
Interest cost	25	26	74	77
Expected return on plan assets	(142)	(119)	(426)	(358)
Amortization of prior service cost	0	0	0	0
Amortization of actuarial (gain) loss	(278)	(242)	(834)	(724)
Net periodic benefits costs under accounting standards	(363)	(302)	(1,090)	(906)
Regulatory adjustments - deferred	0	0	0	0
Total expense (benefit) recognized, before surcharges and allocation to overhead pool	(363)	(302)	(1,090)	(906)
SERP
Components of Net Periodic Benefits Cost:
Service cost	358	312	1,074	936
Interest cost	426	411	1,278	1,233
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	0	0	0	0
Amortization of actuarial (gain) loss	(4)	(8)	(11)	(24)
Net periodic benefits costs under accounting standards	780	715	2,341	2,145
Regulatory adjustments - deferred	0	0	0	0
Total expense (benefit) recognized, before surcharges and allocation to overhead pool	$ 780	$ 715	$ 2,341	$ 2,145