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Revenue Revenue Utility Related Taxes (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017 | Dec. 31, 2017
Schedule Of Utilities Operating Revenue Expense Taxes [Line Items] |  |  |  |  |
Public Utility Operating Expenses Excise Taxes Collected | $ 12,294 | $ 12,663 | $ 44,447 | $ 47,799 |
Alaska Electric Light & Power [Member] |  |  |  |  |
Schedule Of Utilities Operating Revenue Expense Taxes [Line Items] |  |  |  |  |
Public Utility Operating Expenses Excise Taxes Collected |  |  |  |  | $ 2,000

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