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Regulatory Assets and Liabilities - Regulatory Liabilities (Details-2) - USD ($) $ in Thousands | Dec. 31, 2025 | Dec. 31, 2024
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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

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- Definition The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 980 -SubTopic 405 -Name Accounting Standards Codification -Section 25 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477571/980-405-25-1 + Details
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