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LONG-TERM DEBT: Long-term Debt Level 4 (Details) - USD ($)
$ in Thousands
Dec. 31, 2025
Dec. 31, 2024
Debt Instrument [Line Items]    
Total first mortgage bonds $ 3,345,000 $ 2,945,000
Total pollution control revenue bonds 116,300 116,300
American Falls bond guarantee 0 19,885
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net (13,962) (7,523)
Debt, Long-Term and Short-Term, Combined Amount [1] 3,447,338 3,073,662
Current maturities of long-term debt (116,300) (19,885)
Long-Term Debt $ 3,331,038 $ 3,053,777
Idaho Power Company    
Debt Instrument [Line Items]    
Effective cost of outstanding debt 5.13% 5.03%
First Mortgage Bonds 1.90 Series L Due July 15 2030    
Debt Instrument [Line Items]    
First mortgage bonds $ 80,000 $ 80,000
Debt Instrument, Interest Rate, Stated Percentage 1.90% 1.90%
First mortgage bonds 6.00 Series due 2032    
Debt Instrument [Line Items]    
First mortgage bonds $ 100,000 $ 100,000
Debt Instrument, Interest Rate, Stated Percentage 6.00% 6.00%
First Mortgage Bonds 4.99 Series Due 2032    
Debt Instrument [Line Items]    
First mortgage bonds $ 23,000 $ 23,000
Debt Instrument, Interest Rate, Stated Percentage 4.99% 4.99%
First mortgage bonds 5.50 Series due 2033    
Debt Instrument [Line Items]    
First mortgage bonds $ 70,000 $ 70,000
Debt Instrument, Interest Rate, Stated Percentage 5.50% 5.50%
First mortgage bonds 5.50 Series due 2034    
Debt Instrument [Line Items]    
First mortgage bonds $ 50,000 $ 50,000
Debt Instrument, Interest Rate, Stated Percentage 5.50% 5.50%
First mortgage bonds 5.875 Series due 2034    
Debt Instrument [Line Items]    
First mortgage bonds $ 55,000 $ 55,000
Debt Instrument, Interest Rate, Stated Percentage 5.875% 5.875%
First Mortgage Bonds 5.20 Series M Due 2034    
Debt Instrument [Line Items]    
First mortgage bonds $ 300,000 $ 300,000
Debt Instrument, Interest Rate, Stated Percentage 5.20% 5.20%
First mortgage bonds 5.30 Series due 2035    
Debt Instrument [Line Items]    
First mortgage bonds $ 60,000 $ 60,000
Debt Instrument, Interest Rate, Stated Percentage 5.30% 5.30%
First mortgage bonds 6.30 Series due 2037    
Debt Instrument [Line Items]    
First mortgage bonds $ 140,000 $ 140,000
Debt Instrument, Interest Rate, Stated Percentage 6.30% 6.30%
First mortgage bonds 6.25 Series due 2037    
Debt Instrument [Line Items]    
First mortgage bonds $ 100,000 $ 100,000
Debt Instrument, Interest Rate, Stated Percentage 6.25% 6.25%
First mortgage bonds 4.85 Series due 2040    
Debt Instrument [Line Items]    
First mortgage bonds $ 100,000 $ 100,000
Debt Instrument, Interest Rate, Stated Percentage 4.85% 4.85%
First Mortgage Bonds 4.30 Series Due 2042    
Debt Instrument [Line Items]    
First mortgage bonds $ 75,000 $ 75,000
Debt Instrument, Interest Rate, Stated Percentage 4.30% 4.30%
First Mortgage Bonds 5.06 Series Due 2042    
Debt Instrument [Line Items]    
First mortgage bonds $ 25,000 $ 25,000
Debt Instrument, Interest Rate, Stated Percentage 5.06% 5.06%
First Mortgage Bonds 5.06 Series Due 2043    
Debt Instrument [Line Items]    
First mortgage bonds $ 60,000 $ 60,000
Debt Instrument, Interest Rate, Stated Percentage 5.06% 5.06%
First Mortgage Bonds 4.00 Series due 2043    
Debt Instrument [Line Items]    
First mortgage bonds $ 75,000 $ 75,000
Debt Instrument, Interest Rate, Stated Percentage 4.00% 4.00%
First mortgage bonds 3.65% Series due 2045    
Debt Instrument [Line Items]    
First mortgage bonds $ 250,000 $ 250,000
Debt Instrument, Interest Rate, Stated Percentage 3.65% 3.65%
First mortgage bonds 4.05 Series due 2046    
Debt Instrument [Line Items]    
First mortgage bonds $ 120,000 $ 120,000
Debt Instrument, Interest Rate, Stated Percentage 4.05% 4.05%
First Mortgage Bonds 4.20 K Series due 2048    
Debt Instrument [Line Items]    
First mortgage bonds $ 450,000 $ 450,000
Debt Instrument, Interest Rate, Stated Percentage 4.20% 4.20%
First Mortgage Bonds 5.20 Series Due 2053    
Debt Instrument [Line Items]    
First mortgage bonds $ 62,000 $ 62,000
Debt Instrument, Interest Rate, Stated Percentage 5.20% 5.20%
First Mortgage Bonds 5.5% Series K Due 2053 [Member]    
Debt Instrument [Line Items]    
First mortgage bonds $ 400,000 $ 400,000
Debt Instrument, Interest Rate, Stated Percentage 5.50% 5.50%
First Mortgage Bonds 5.8% Series K Due 2054    
Debt Instrument [Line Items]    
First mortgage bonds $ 350,000 $ 350,000
Debt Instrument, Interest Rate, Stated Percentage 5.80% 5.80%
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%
Pollution Control Bond 1.70 due 2026    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Stated Percentage 1.70% 1.70%
Pollution control revenue bonds 5.25 Series due 2026 [2] $ 116,300 $ 116,300
Secured debt including Humboldt County and Sweetwater County pollution control revenue bonds    
Debt Instrument [Line Items]    
Total first mortgage bonds $ 3,461,000  
[1] At December 31, 2025 and 2024, the overall effective cost rate of Idaho Power's outstanding debt was 5.13 percent and 5.03 percent, respectively.
[2] Sweetwater County Pollution Control Revenue Bonds are secured by the first mortgage bonds, bringing the total first mortgage bonds outstanding at December 31, 2025, to $3.461 billion