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Regulatory Matters - Schedule of Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands | Sep. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | $ 17,041 | $ 24,999
Regulatory assets, long-term | 89,491 | 94,655
Regulatory liabilities, current | 32,285 | 17,300
Regulatory liabilities, long -term | 275,809 | 244,497
Deferred Income Taxes |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory liabilities, current | 0 | 0
Regulatory liabilities, long -term | 128,886 | 131,480
Plant Removal Obligations |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory liabilities, current | 8,456 | 8,509
Regulatory liabilities, long -term | 117,359 | 105,733
Fuel Clause Adjustments |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory liabilities, current | 12,217 | 365
Regulatory liabilities, long -term | $ 0 | 0
Regulatory liabilities - Remaining Recovery/Refund Period | 1 year |
Alternative Revenue Program Riders |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory liabilities, current | $ 8,426 | 2,504
Regulatory liabilities, long -term | $ 0 | 0
Regulatory liabilities - Remaining Recovery/Refund Period | 1 year |
North Dakota PTC Refunds |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory liabilities, current | $ 0 | 0
Regulatory liabilities, long -term | 10,281 | 7,136
Pension and Other Postretirement Benefit Plans |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory liabilities, current | 2,279 | 5,589
Regulatory liabilities, long -term | 19,026 | 0
Other |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory liabilities, current | 907 | 333
Regulatory liabilities, long -term | 257 | 148
Pension and Other Postretirement Benefit Plans |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | 0 | 0
Regulatory assets, long-term | 86,286 | 88,354
Alternative Revenue Program Riders |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | 5,780 | 5,679
Regulatory assets, long-term | $ 118 | 2,508
Regulatory assets - Remaining Recovery/Refund Period | 2 years |
Asset Retirement Obligations |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | $ 0 | 0
Regulatory assets, long-term | 0 | 1,467
Deferred Income Taxes |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | 0 | 0
Regulatory assets, long-term | 931 | 0
ISO Cost Recovery Trackers |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | 144 | 575
Regulatory assets, long-term | $ 260 | 314
Regulatory assets - Remaining Recovery/Refund Period | 2 years |
Unrecovered Project Costs |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | $ 349 | 320
Regulatory assets, long-term | $ 962 | 990
Regulatory assets - Remaining Recovery/Refund Period | 4 years |
Deferred Rate Case Expenses |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | $ 377 | 377
Regulatory assets, long-term | $ 471 | 754
Regulatory assets - Remaining Recovery/Refund Period | 3 years |
Fuel Clause Adjustments |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | $ 9,141 | 10,893
Regulatory assets, long-term | $ 0 | 0
Regulatory assets - Remaining Recovery/Refund Period | 1 year |
Derivative Instruments |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | $ 1,225 | 7,130
Regulatory assets, long-term | $ 228 | 0
Regulatory assets - Remaining Recovery/Refund Period | 2 years |
Other |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | $ 25 | 25
Regulatory assets, long-term | $ 235 | $ 268

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- Definition Amortization period for the recovery of regulatory asset, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 980 -SubTopic 340 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481878/980-340-50-1 + Details
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