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LONG-TERM DEBT: Long-term debt narrative Level 4 (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended 12 Months Ended
Sep. 30, 2023
Jun. 30, 2023
Dec. 31, 2023
Sep. 11, 2023
Apr. 01, 2023
Mar. 14, 2023
Mar. 08, 2023
Dec. 31, 2022
Dec. 22, 2022
Mar. 04, 2022
Aug. 01, 2020
Jun. 05, 2020
First mortgage bonds 5.80 Series due 2054 | First Mortgage                        
Debt Instrument [Line Items]                        
Debt Instrument, Interest Rate, Stated Percentage       5.80%                
Debt Instrument, Face Amount       $ 350,000                
First Mortgage Bonds 2.50 Series due 2023                        
Debt Instrument [Line Items]                        
First mortgage bonds     $ 0         $ 75,000        
Debt Instrument, Interest Rate, Stated Percentage     2.50%   2.50%     2.50%        
Debt Instrument, Repurchased Face Amount         $ 75,000              
First mortgage bonds 5.50 Series due 2053 | First Mortgage                        
Debt Instrument [Line Items]                        
Debt Instrument, Interest Rate, Stated Percentage           5.50%            
Debt Instrument, Face Amount           $ 400,000            
First Mortgage Bonds 5.06 Series Due 2043                        
Debt Instrument [Line Items]                        
First mortgage bonds     $ 60,000         $ 0        
Debt Instrument, Interest Rate, Stated Percentage     5.06%                  
First Mortgage Bonds 5.06 Series Due 2043 | Private Placement                        
Debt Instrument [Line Items]                        
Debt Instrument, Interest Rate, Stated Percentage             5.06%          
Debt Instrument, Face Amount             $ 60,000          
Term Loan Facility                        
Debt Instrument [Line Items]                        
Long-Term Line of Credit, Noncurrent                   $ 150,000    
Repayments of Lines of Credit $ 50,000 $ 100,000                    
Term Loan Facility | Unsecured Debt                        
Debt Instrument [Line Items]                        
Line of Credit, Current     $ 0                  
Idaho Power Company                        
Debt Instrument [Line Items]                        
Debt Instrument, Interest Rate, Effective Percentage     4.98%         4.60%        
Debt instrument interest rate limit     8.00%                  
Indenture, Unused Borrowing Capacity, Amount     $ 1,900,000                  
Percent of Operating Revenues Required to be Spent or Appropriated     15.00%                  
Time Period Expenditures or Appropriations can be Made Up     5 years                  
Earnings test does not apply to refunding bonds that mature in less than this period of time     2 years                  
Debt Instrument, Unused Borrowing Capacity, Amount     $ 700,000                  
Principal amount of debt securities and first mortgage bonds authorized     1,200,000                  
Idaho Power Company | Public Utility Commisions - Idaho, Oregon, and Washington                        
Debt Instrument [Line Items]                        
Indenture, Unused Borrowing Capacity, Amount     $ 280,000                  
Idaho Power Company | First Mortgage Bonds 5.06 Series Due 2043                        
Debt Instrument [Line Items]                        
First mortgage bonds             $ 60,000          
Idaho Power Company | Bond Purchase Agreement Series N                        
Debt Instrument [Line Items]                        
Bond Purchase Agreement Series N Commitment Amount                 $ 170,000      
Idaho Power Company | First mortgage bonds 3.40 Series due 2020                        
Debt Instrument [Line Items]                        
Debt Instrument, Repurchased Face Amount                     $ 4,360  
Idaho Power Company | Principal amount of debt securities in Selling Agreement                        
Debt Instrument [Line Items]                        
Debt Instrument, Unused Borrowing Capacity, Amount                       $ 3,500,000