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Long-Term Debt - Schedule Of Long-Term Debt Instruments (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2024 | Dec. 31, 2023
Debt Instrument [Line Items] |  |
Secured Debt | $ 2,619 | $ 2,619
Secured and Unsecured Debt | 2,634 | 2,634
Unamortized debt discount | (1) | (1)
Unamortized Debt Issuance Expense | (19) | (19)
Total | 2,614 | 2,614
Current portion of long-term debt | 0 | (15)
Non Affiliated Trusts [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | $ 2,614 | 2,515
First Mortgage [Member] |  |
Debt Instrument [Line Items] |  |
Debt Instrument, Interest Rate, Stated Percentage | 8.00% |
Secured Debt [Member] |  |
Debt Instrument [Line Items] |  |
Pollution Control Bonds | $ 0 | (84)
Avista Utilities [Member] |  |
Debt Instrument [Line Items] |  |
Secured Debt | $ 2,544 | 2,544
Avista Utilities [Member] | 2028 [Member] | Secured Debt [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2028 |
Debt Instrument, Interest Rate, Stated Percentage | 6.37% |
Medium-Term Notes, Noncurrent | $ 25 | 25
Avista Utilities [Member] | 2032 [Member] | Secured Debt [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2032 |
Debt Instrument, Interest Rate, Stated Percentage | 3.88% |
Pollution Control Bonds | $ 67 | 67
Avista Utilities [Member] | 2034 [Member] | Secured Debt [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2034 |
Debt Instrument, Interest Rate, Stated Percentage | 3.88% |
Pollution Control Bonds | $ 17 | 17
Avista Utilities [Member] | 2035 [Member] | First Mortgage [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2035 |
Debt Instrument, Interest Rate, Stated Percentage | 6.25% |
Secured Debt | $ 150 | 150
Avista Utilities [Member] | 2037 [Member] | First Mortgage [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2037 |
Debt Instrument, Interest Rate, Stated Percentage | 5.70% |
Secured Debt | $ 150 | 150
Avista Utilities [Member] | 2040 [Member] | First Mortgage [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2040 |
Debt Instrument, Interest Rate, Stated Percentage | 5.55% |
Secured Debt | $ 35 | 35
Avista Utilities [Member] | 2041 [Member] | First Mortgage [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2041 |
Debt Instrument, Interest Rate, Stated Percentage | 4.45% |
Secured Debt | $ 85 | 85
Avista Utilities [Member] | 2044 [Member] | First Mortgage [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2044 |
Debt Instrument, Interest Rate, Stated Percentage | 4.11% |
Secured Debt | $ 60 | 60
Avista Utilities [Member] | 2045 [Member] | First Mortgage [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2045 |
Debt Instrument, Interest Rate, Stated Percentage | 4.37% |
Secured Debt | $ 100 | 100
Avista Utilities [Member] | 2047 [Member] | First Mortgage [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2047 |
Debt Instrument, Interest Rate, Stated Percentage | 4.23% |
Secured Debt | $ 80 | 80
Avista Utilities [Member] | 2047 3.91% [Member] | First Mortgage [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2047 |
Debt Instrument, Interest Rate, Stated Percentage | 3.91% |
Secured Debt | $ 90 | 90
Avista Utilities [Member] | 2048 4.35% [Member] | First Mortgage [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2048 |
Debt Instrument, Interest Rate, Stated Percentage | 4.35% |
Secured Debt | $ 375 | 375
Avista Utilities [Member] | 2049 3.43% [Member] | First Mortgage [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2049 |
Debt Instrument, Interest Rate, Stated Percentage | 3.43% |
Secured Debt | $ 180 | 180
Avista Utilities [Member] | 2050 3.07% [Member] | First Mortgage [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2050 |
Debt Instrument, Interest Rate, Stated Percentage | 3.07% |
Secured Debt | $ 165 | 165
Avista Utilities [Member] | 2051 [Member] | First Mortgage [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2051 |
Debt Instrument, Interest Rate, Stated Percentage | 3.54% |
Secured Debt | $ 175 | 175
Avista Utilities [Member] | 2.90% Due in 2051 [Member] | First Mortgage [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2051 |
Debt Instrument, Interest Rate, Stated Percentage | 2.90% |
Secured Debt | $ 140 | 140
Avista Utilities [Member] | 2052 [Member] | First Mortgage [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2052 |
Debt Instrument, Interest Rate, Stated Percentage | 4.00% |
Secured Debt | $ 400 | 400
Avista Utilities [Member] | 2053 [Member] | First Mortgage [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2053 |
Debt Instrument, Interest Rate, Stated Percentage | 5.66% |
Secured Debt | $ 250 | 250
Alaska Electric Light & Power [Member] | 2044 [Member] | First Mortgage [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2044 |
Debt Instrument, Interest Rate, Stated Percentage | 4.54% |
Secured Debt | $ 75 | 75
Alaska Energy Resources Company [Member] | 2029 [Member] | Unsecured Debt [Member] |  |
Debt Instrument [Line Items] |  |
Maturity Year | 2029 |
Debt Instrument, Interest Rate, Stated Percentage | 5.92% |
Unsecured Debt | $ 15 | $ 15

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