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REGULATORY MATTERS: Idaho Jurisdiction Power Cost Adjustment Mechanism (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2026
May 31, 2026
May 31, 2025
May 31, 2024
Dec. 31, 2025
Jun. 01, 2025
Dec. 31, 2024
Jun. 01, 2024
Jun. 01, 2023
Idaho Power Cost Adjustment Mechanism [Line Items]                  
Regulatory Liabilities         $ 1,052,151   $ 984,326    
Regulatory Assets         1,564,458   1,507,372    
Power supply costs                  
Idaho Power Cost Adjustment Mechanism [Line Items]                  
Regulatory Assets [1]         $ 0   $ 18,507    
Idaho Power Cost Adjustment [Member]                  
Idaho Power Cost Adjustment Mechanism [Line Items]                  
Percentage to be Shared with Customers           95.00%      
Percentage to be Shared with Entity           5.00%      
Approved Rate Increase (Decrease), Amount     $ (35,700) $ 105,100          
Idaho Power Cost Adjustment [Member] | Subsequent Event                  
Idaho Power Cost Adjustment Mechanism [Line Items]                  
Approved Rate Increase (Decrease), Amount   $ (94,800)              
Oregon jurisdiction                  
Idaho Power Cost Adjustment Mechanism [Line Items]                  
Annual Power Cost Update           $ (1,800)   $ (6,900) $ 7,700
IDAHO | Idaho PCA includes power supply and deferral balance. | Subsequent Event                  
Idaho Power Cost Adjustment Mechanism [Line Items]                  
Approved Rate Increase (Decrease), Amount $ 468,800                
OREGON | Subsequent Event                  
Idaho Power Cost Adjustment Mechanism [Line Items]                  
Approved Rate Increase (Decrease), Amount $ (600)                
[1] This item is discussed in more detail in this Note 3 - "Regulatory Matters."