Employee Benefit Plans - Schedule of Net Periodic Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Components of Net Periodic Benefits Cost:
Regulatory adjustments - deferred			$ (70,875)	$ (8,404)
Pension Benefits
Components of Net Periodic Benefits Cost:
Service cost	$ 846	$ 1,342	1,692	2,822
Interest cost	2,513	1,856	5,026	3,700
Expected return on plan assets	(2,623)	(3,290)	(5,246)	(6,582)
Amortization of prior service cost	108	109	216	218
Amortization of actuarial (gain) loss	0	0	0	0
Net periodic benefits costs under accounting standards	844	17	1,688	158
Regulatory adjustments - deferred	(92)	0	(184)	0
Total expense (benefit) recognized, before surcharges and allocation to overhead pool	752	17	1,504	158
Other Postretirement Benefits
Components of Net Periodic Benefits Cost:
Service cost	33	33	66	66
Interest cost	26	16	51	32
Expected return on plan assets	(119)	(147)	(239)	(294)
Amortization of prior service cost	0	0	0	0
Amortization of actuarial (gain) loss	(242)	(412)	(482)	(824)
Net periodic benefits costs under accounting standards	(302)	(510)	(604)	(1,020)
Regulatory adjustments - deferred	0	0	0	0
Total expense (benefit) recognized, before surcharges and allocation to overhead pool	(302)	(510)	(604)	(1,020)
SERP
Components of Net Periodic Benefits Cost:
Service cost	312	298	624	596
Interest cost	411	256	822	512
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	0	0	0	0
Amortization of actuarial (gain) loss	(8)	145	(16)	290
Net periodic benefits costs under accounting standards	715	699	1,430	1,398
Regulatory adjustments - deferred	0	0	0	0
Total expense (benefit) recognized, before surcharges and allocation to overhead pool	$ 715	$ 699	$ 1,430	$ 1,398