Regulatory Assets and Liabilities - Regulatory Assets (Details-1) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Regulatory Asset [Line Items]
Regulatory Asset	$ 102,568	$ 113,441
Asset Retirement Obligation [Member]
Regulatory Asset [Line Items]
Regulatory Asset	17,003	14,721
Deferred Bad Debt Expense [Member]
Regulatory Asset [Line Items]
Regulatory Asset	9,150	7,650
Debt Related Costs [Member]
Regulatory Asset [Line Items]
Regulatory Asset	7,014	7,580
Derivatives [Member]
Regulatory Asset [Line Items]
Regulatory Asset	5,226	5,094
Deferred Fuel Costs [Member]
Regulatory Asset [Line Items]
Regulatory Asset	6,713	12,067
Leases [Member]
Regulatory Asset [Line Items]
Regulatory Asset	4,130	3,656
Deferred Pension And Other Postretirement Costs [Member]
Regulatory Asset [Line Items]
Regulatory Asset	4,948	0
Tax Recovery Related to AFUDC Equity [Member]
Regulatory Asset [Line Items]
Regulatory Asset	12,140	10,851
Electric Transmission Costs [Member]
Regulatory Asset [Line Items]
Regulatory Asset	1,998	0
Unfunded Pension and Other Postretirement Plans Costs [Member]
Regulatory Asset [Line Items]
Regulatory Asset	31,374	50,072
Other Regulatory Asset [Member]
Regulatory Asset [Line Items]
Regulatory Asset	$ 2,872	$ 1,750