Pension Plans and Other Postretirement Benefit Plans - Change in Benefit Obligation and Plan Assets (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Other current liabilities		$ (15,625)	$ (13,582)
Non-current liabilities		(93,901)	(153,467)
Accumulated other comprehensive loss for unfunded benefit obligation for pensions and other postretirement benefit plans		(2,058)	(11,039)
Pension Plan And SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year		799,042	826,915
Service cost	[1]	23,877	25,306	$ 22,392
Interest cost		$ 26,536	$ 26,160	27,853
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]		Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses	Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses
Actuarial (gain)/loss		$ (204,775)	$ (13,997)
Plan change		3,302
Settlement		60,206
Benefits paid		(30,067)	(65,342)
Benefit obligation as of end of year		557,709	799,042	826,915
Fair value of plan assets as of beginning of year		750,963	722,024
Actual return on plan assets		(163,866)	50,370
Employer contributions		42,000	42,000
Settlement		(60,206)
Benefits paid		(28,188)	(63,431)
Fair value of plan assets as of end of year		540,703	750,963	722,024
Funded status		(17,006)	(48,079)
Other non-current assets		13,382
Other current liabilities		(1,934)	(1,951)
Non-current liabilities		(28,454)	(46,128)
Net amount recognized		(17,006)	(48,079)
Accumulated pension benefit obligation		495,654	685,493
Unrecognized prior service cost (credit)		4,105	1,699
Unrecognized net actuarial loss		83,794	94,109
Total		87,899	95,808
Less regulatory asset		(85,198)	(85,550)
Accumulated other comprehensive loss for unfunded benefit obligation for pensions and other postretirement benefit plans		$ 2,701	$ 10,258
Discount rate for benefit obligation		6.10%	3.39%
Discount rate for annual expense		3.39%	3.25%
Expected long-term return on plan assets		5.80%	5.40%
Rate of compensation increase		4.69%	4.66%
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year		$ 167,598	$ 161,233
Service cost	[1]	4,369	4,114	3,902
Interest cost		$ 5,503	5,139	6,042
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]		Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses
Actuarial (gain)/loss		$ (54,120)	2,808
Benefits paid		(7,715)	(5,696)
Benefit obligation as of end of year		115,635	167,598	161,233
Fair value of plan assets as of beginning of year		59,544	52,173
Actual return on plan assets		(10,072)	7,371
Fair value of plan assets as of end of year		49,472	59,544	$ 52,173
Funded status		(66,163)	(108,054)
Other current liabilities		(706)	(684)
Non-current liabilities		(65,457)	(107,370)
Net amount recognized		(66,163)	(108,054)
Unrecognized prior service cost (credit)		(1,911)	(2,741)
Unrecognized net actuarial loss		13,643	48,872
Total		11,732	46,131
Less regulatory asset		(12,375)	(45,350)
Accumulated other comprehensive loss for unfunded benefit obligation for pensions and other postretirement benefit plans		$ (643)	$ 781
Discount rate for benefit obligation		6.10%	3.40%
Discount rate for annual expense		3.40%	3.27%
Expected long-term return on plan assets		4.70%	4.60%
Other Postretirement Benefits [Member] | Pre-Age 65 [Member]
Defined Benefit Plan Disclosure [Line Items]
Medical cost trend – initial		6.25%	6.00%
Medical cost trend – ultimate		5.00%	5.00%
Ultimate medical cost trend year		2028	2026
Other Postretirement Benefits [Member] | Post-Age 65 [Member]
Defined Benefit Plan Disclosure [Line Items]
Medical cost trend – initial		6.25%	6.00%
Medical cost trend – ultimate		5.00%	5.00%
Ultimate medical cost trend year		2028	2026
Other Postretirement Benefits [Member] | Retirees [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year		$ 78,347
Benefit obligation as of end of year		61,984	$ 78,347
Other Postretirement Benefits [Member] | Fully eligible employees [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year		32,144
Benefit obligation as of end of year		19,731	32,144
Other Postretirement Benefits [Member] | Other participants [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year		57,107
Benefit obligation as of end of year		$ 33,920	$ 57,107

[1] Total service costs in the table above are recorded to the same accounts as labor expense. Labor and benefits expense is recorded to various projects based on whether the work is a capital project or an operating expense. Approximately 40 percent of all labor and benefits is capitalized to utility property and 60 percent is expensed to utility other operating expenses.