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LONG-TERM DEBT: Long-term debt narrative Level 4 (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2025
Mar. 13, 2025
Feb. 03, 2025
Dec. 31, 2024
Dec. 02, 2024
Aug. 12, 2024
Oct. 14, 2022
First Mortgage Bonds 5.7% Series K Due 2055              
Debt Instrument [Line Items]              
First mortgage bonds $ 400,000     $ 0      
Debt Instrument, Interest Rate, Stated Percentage 5.70%     5.70%      
First Mortgage Bonds 5.7% Series K Due 2055 | First Mortgage              
Debt Instrument [Line Items]              
Debt Instrument, Face Amount   $ 400,000          
Debt Instrument, Interest Rate, Stated Percentage   5.70%          
Variable Rate American Falls [Domain] | Unsecured Debt              
Debt Instrument [Line Items]              
Debt Instrument, Repurchased Face Amount     $ 19,900        
Humboldt County pollution control revenue bonds | Pollution Control Bonds 5.15 due 2024 [Member]              
Debt Instrument [Line Items]              
Debt Instrument, Repurchased Face Amount         $ 49,800    
Debt Instrument, Interest Rate, Stated Percentage         1.45%    
First mortgage bonds 5.20 Series due 2034 | First Mortgage              
Debt Instrument [Line Items]              
Debt Instrument, Face Amount           $ 300,000  
Debt Instrument, Interest Rate, Stated Percentage           5.20%  
Idaho Power Company              
Debt Instrument [Line Items]              
Principal amount of debt securities and first mortgage bonds authorized $ 1,200,000            
Debt instrument interest rate limit 8.00%            
Indenture, Unused Borrowing Capacity, Amount $ 2,000,000            
Debt Instrument, Unused Borrowing Capacity, Amount $ 2,300,000            
Earnings test does not apply to refunding bonds that mature in less than this period of time 2 years            
Percent of Operating Revenues Required to be Spent or Appropriated 15.00%            
Time Period Expenditures or Appropriations can be Made Up 5 years            
Idaho Power Company | Public Utility Commisions - Idaho, Oregon, and Washington              
Debt Instrument [Line Items]              
Indenture, Unused Borrowing Capacity, Amount $ 500,000            
Idaho Power Company | Principal amount of debt securities in Selling Agreement              
Debt Instrument [Line Items]              
Principal amount of debt securities in Selling Agreement $ 2,100,000            
Debt Instrument, Unused Borrowing Capacity, Amount             $ 5,500,000