Long-Term Debt - Additional Information (Details)	1 Months Ended	6 Months Ended
	Jul. 31, 2025 USD ($) Contract	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)
Debt Instrument [Line Items]
Proceeds from issuance of long-term debt		$ 0	$ 84,000,000
Avista Utilities [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		500,000,000
Long-term debt line of credit		119,000,000
Alaska Electric Light & Power [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		25,000,000
Long-term debt line of credit		$ 16,000,000
Alaska Electric Light & Power [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Debt instrument interest rate percentage	5.49%
Principal amount	$ 20,000,000
Debt instrument maturity year	July 2030
Long-term debt line of credit	$ 20,000,000
2055 Due 6.18% [Member] | First Mortgage [Member] | Avista Utilities [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Proceeds from issuance of long-term debt	$ 120,000,000
Debt instrument interest rate percentage	6.18%
Debt instrument maturity year	2055
2055 Due 6.18% [Member] | First Mortgage [Member] | Avista Utilities [Member] | Interest Rate Swap [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Number of interest rate swaps settled | Contract	1
Notional amount	$ 10,000,000
Net payments from settlement of derivatives	$ 1,000,000