Regulatory Assets and Liabilities - Regulatory Liabilities (Details-2) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Regulatory Liability [Line Items]
Regulatory Liability	$ 171,302	$ 177,612
Non Asset Retirement Obligation Removal Cost [Member]
Regulatory Liability [Line Items]
Regulatory Liability	41,714	42,031
Elm Road [Member]
Regulatory Liability [Line Items]
Regulatory Liability	1,700	1,666
Deferred Fuel Savings [Member]
Regulatory Liability [Line Items]
Regulatory Liability	3,043	7,219
Income Taxes
Regulatory Liability [Line Items]
Regulatory Liability	94,110	107,048
Pension and Other Postretirement Plans Costs [Member]
Regulatory Liability [Line Items]
Regulatory Liability	20,342	17,977
Purchased Gas Adjustment [Member]
Regulatory Liability [Line Items]
Regulatory Liability	1,441	1,340
Renewable project savings
Regulatory Liability [Line Items]
Regulatory Liability	5,222	0
Unfunded/funded pension and other postretirement asset
Regulatory Liability [Line Items]
Regulatory Liability	3,489	0
Other Regulatory Liability [Member]
Regulatory Liability [Line Items]
Regulatory Liability	$ 241	$ 331