Regulatory Assets and Liabilities - Regulatory Liabilities (Details-2) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Regulatory Liability [Line Items]
Regulatory Liability	$ 208,862	$ 171,302
Non Asset Retirement Obligation Removal Cost [Member]
Regulatory Liability [Line Items]
Regulatory Liability	46,022	41,714
Elm Road [Member]
Regulatory Liability [Line Items]
Regulatory Liability	1,444	1,700
Deferred Fuel Savings [Member]
Regulatory Liability [Line Items]
Regulatory Liability	7,140	3,043
Income Taxes
Regulatory Liability [Line Items]
Regulatory Liability	90,963	94,110
Deferred Pension And Other Postretirement Costs [Member]
Regulatory Liability [Line Items]
Regulatory Liability	4,919	0
Pension and Other Postretirement Plans Costs [Member]
Regulatory Liability [Line Items]
Regulatory Liability	23,115	20,342
Purchased Gas Adjustment [Member]
Regulatory Liability [Line Items]
Regulatory Liability	4,736	1,441
Renewable project savings
Regulatory Liability [Line Items]
Regulatory Liability	5,407	5,222
Unfunded/funded pension and other postretirement asset
Regulatory Liability [Line Items]
Regulatory Liability	24,019	3,489
Other Regulatory Liability [Member]
Regulatory Liability [Line Items]
Regulatory Liability	$ 1,097	$ 241