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Short-Term Borrowings - Additional Information (Details) - USD ($)
 9 Months Ended
Sep. 30, 2024
Dec. 31, 2023
Avista Utilities [Member]    
Short-term Debt [Line Items]    
Line of credit facility, maximum borrowing capacity $ 500,000,000  
Line of credit facility, expiration date 2028-06  
Line of credit facility additional expiration period 2 years  
Line of credit facility, covenant terms, maximum debt to equity ratio 65.00%  
Average interest rate on borrowings 6.13% 6.46%
Letters of credit outstanding $ 4,700,000 $ 4,700,000
Avista Utilities [Member] | Letter of Credit [Member]    
Short-term Debt [Line Items]    
Principal amount 50,000,000  
Letters of credit outstanding 7,000,000 20,000,000
Alaska Electric Light & Power [Member]    
Short-term Debt [Line Items]    
Line of credit facility, maximum borrowing capacity $ 25,000,000  
Line of credit facility, expiration date 2028-06  
Line of credit facility, covenant terms, maximum debt to equity ratio 67.50%  
Average interest rate on borrowings 7.30%  
Letters of credit outstanding $ 4,300,000 $ 0