Long-Term Debt (Tables)

12 Months Ended

Dec. 31, 2023

Long-Term Debt, Unclassified [Abstract]

Schedule of Long-term Debt Instruments

Maturity Year	Description	Interest Rate	2023			2022
Avista Corp. Secured Long-Term Debt
2023	Secured Medium-Term Notes	7.18%-7.54%		—			13,500
2028	Secured Medium-Term Notes	6.37%		25,000			25,000
2032	Secured Pollution Control Bonds (1)	(1)		66,700			66,700
2034	Secured Pollution Control Bonds (1)	(1)		17,000			17,000
2035	First Mortgage Bonds	6.25%		150,000			150,000
2037	First Mortgage Bonds	5.70%		150,000			150,000
2040	First Mortgage Bonds	5.55%		35,000			35,000
2041	First Mortgage Bonds	4.45%		85,000			85,000
2044	First Mortgage Bonds	4.11%		60,000			60,000
2045	First Mortgage Bonds	4.37%		100,000			100,000
2047	First Mortgage Bonds	4.23%		80,000			80,000
2047	First Mortgage Bonds	3.91%		90,000			90,000
2048	First Mortgage Bonds	4.35%		375,000			375,000
2049	First Mortgage Bonds	3.43%		180,000			180,000
2050	First Mortgage Bonds	3.07%		165,000			165,000
2051	First Mortgage Bonds	3.54%		175,000			175,000
2051	First Mortgage Bonds	2.90%		140,000			140,000
2052	First Mortgage Bonds	4.00%		400,000			400,000
2053	First Mortgage Bonds (2)	5.66%		250,000			—
	Total Avista Corp. secured long-term debt			2,543,700			2,307,200
Alaska Electric Light and Power Company Secured Long-Term Debt
2044	First Mortgage Bonds	4.54%		75,000			75,000
	Total secured long-term debt			2,618,700			2,382,200
Alaska Energy and Resources Company Unsecured Long-Term Debt
2024	Unsecured Term Loan	3.44%		15,000			15,000
	Total secured and unsecured long-term debt			2,633,700			2,397,200
Other Long-Term Debt Components
	Unamortized debt discount			(689	)		(726	)
	Unamortized long-term debt issuance costs			(18,953	)		(18,261	)
	Total			2,614,058			2,378,213
	Secured Pollution Control Bonds held by Avista    Corporation (1)			(83,700	)		(83,700	)
	Current portion of long-term debt			(15,000	)		(13,500	)
	Total long-term debt		$	2,515,358		$	2,281,013

(1)In December 2010, $66.7 million and $17.0 million of the City of Forsyth, Montana Pollution Control Revenue Refunding Bonds (Avista Corporation Colstrip Project) due in 2032 and 2034, respectively, which had been held by Avista Corp. since 2008 and 2009, respectively, were refunded by new variable rate bond issues. The new bonds were not offered to the public and were purchased by Avista Corp. due to market conditions. The Company can remarket these bonds to unaffiliated investors at a later date, subject to market conditions. So long as Avista Corp. is the holder of these bonds, the bonds are not reflected as an asset or a liability on the Consolidated Balance Sheets.

(2)In March 2023, the Company issued and sold $250.0 million of 5.66 percent first mortgage bonds due in 2053 with institutional investors in the private placement market. A portion of the net proceeds from the sale of these bonds was used for the construction or improvement of utility facilities, and a portion was used to refinance existing indebtedness, including the repayment of Avista Corp.'s $150.0 million term loan. In connection with the pricing of the first mortgage bonds in March 2023, the Company cash settled four interest rate swap derivatives (notional

aggregate amount of $40.0 million) and received a net amount of $7.5 million. See Note 8 for a discussion of interest rate swap derivatives.

Schedule of Maturities of Long-term Debt

	2024		2025		2026		2027		2028		Thereafter		Total
Debt maturities	$	15,000	$	—	$	—	$	—	$	25,000	$	2,561,547	$	2,601,547