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

Long-Term Debt, Before Current Portion And Bonds Held by Company

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Secured and Unsecured Debt

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Contractual interest rate for funds borrowed, under the debt agreement.

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Description of the maturity date of the debt instrument including whether the debt matures serially and, if so, a brief description of the serial maturities.

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Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt classified as current. Excludes lease obligation.

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Noncurrent portion of a debt security issued by a state, certain agencies or authorities, a local government, or development corporation to finance the construction of air- or water-pollution control facilities or sewage or solid waste disposal facilities pursuant to federal law. The bonds are backed by the credit of the beneficiary of the financing rather than the credit of the issuer.

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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