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Long-Term Debt- Additional Information (Details) - First Mortgage [Member] $ in Millions | Dec. 31, 2020 USD ($)
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Avista Utilities [Member] |
Debt Instrument [Line Items] |
Amount of First Mortgage Bonds that Could be Issued, Percent | 66.66%
Amount of First Mortgage Bonds that Could be Issued | $ 1,700.0
Alaska Electric Light & Power [Member] |
Debt Instrument [Line Items] |
Amount of First Mortgage Bonds that Could be Issued, Percent | 66.66%
Amount of First Mortgage Bonds that Could be Issued | $ 36.1

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- Definition Amount Of First Mortgage Bonds That Could Be Issued + References No definition available. + Details
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- Definition Amount of First Mortgage Bonds that Could be Issued, Percent + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Details
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Namespace Prefix: |
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Period Type: |

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- Details
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Namespace Prefix: |
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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |