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Accounting For Income Taxes (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended | 24 Months Ended
--- | --- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2019
Components of Income Tax Expense (Benefit) [Line Items] |  |  |  |
Federal statutory tax rate | 21.00% | 21.00% | 35.00% | 21.00%
Avista Utilities [Member] |  |  |  |
Components of Income Tax Expense (Benefit) [Line Items] |  |  |  |
Tax Cuts and Jobs Act Period to Return Plant Related Excess Deferred Income Taxes | 36 years |  |  |
Alaska Electric Light & Power [Member] |  |  |  |
Components of Income Tax Expense (Benefit) [Line Items] |  |  |  |
Tax Cuts and Jobs Act Period to Return Plant Related Excess Deferred Income Taxes | 40 years |  |  |
Excess Deferred Income Taxes Plant Related |  |  |  |
Components of Income Tax Expense (Benefit) [Line Items] |  |  |  |
Regulatory Liability For Excess Deferred Income Taxes | $ 416.7 | $ 436.7 |  | $ 416.7

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