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Regulatory Matters - Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands | 3 Months Ended |
--- | --- | ---
Mar. 31, 2021 | Dec. 31, 2020
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | $ 21,419 | $ 21,900
Regulatory assets, long-term | 167,556 | 168,395
Regulatory liabilities, current | 12,517 | 16,663
Regulatory liabilities, long -term | 234,986 | 233,973
Deferred Income Taxes |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory liabilities, current | 0 | 0
Regulatory liabilities, long -term | 133,306 | 134,719
Plant Removal Obligations |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory liabilities, current | 0 | 0
Regulatory liabilities, long -term | 100,616 | 98,707
Fuel Clause Adjustments |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory liabilities, current | 7,072 | 10,947
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 | $ 3,306 | 3,581
Regulatory liabilities, long -term | 837 | 470
Pension and Other Postretirement Benefit Plans |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory liabilities, current | 1,959 | 1,959
Regulatory liabilities, long -term | $ 0 | 0
Regulatory Liabilities - Remaining Recovery/Refund Period | 1 year |
Other |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory liabilities, current | $ 180 | 176
Regulatory liabilities, long -term | 227 | 77
Pension and Other Postretirement Benefit Plans |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | 11,037 | 11,037
Regulatory assets, long-term | 143,996 | 146,071
Alternative Revenue Program Riders |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | 6,891 | 8,871
Regulatory assets, long-term | $ 10,418 | 9,373
Regulatory Assets - Remaining Recovery/Refund Period | 3 years |
Asset Retirement Obligations |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | $ 0 | 0
Regulatory assets, long-term | 8,539 | 8,462
ISO Cost Recovery Trackers |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | 809 | 1,079
Regulatory assets, long-term | $ 703 | 867
Regulatory Assets - Remaining Recovery/Refund Period | 2 years |
Unrecovered Project Costs |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | $ 1,556 | 361
Regulatory assets, long-term | $ 2,937 | 2,989
Regulatory Assets - Remaining Recovery/Refund Period | 3 years |
Deferred Rate Case Expenses |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | $ 493 | 360
Regulatory assets, long-term | 165 | 230
Debt Reacquisition Premiums |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | 180 | 192
Regulatory assets, long-term | $ 302 | 341
Regulatory Assets - Remaining Recovery/Refund Period | 12 years |
Other |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |
Regulatory assets - current | $ 453 | 0
Regulatory assets, long-term | $ 496 | $ 62

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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 -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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