v3.26.1
REVENUES: (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Disaggregation of Revenue [Line Items]    
Revenue from contracts with customers $ 383,615 $ 411,142
Alternative revenue programs and other revenues 19,147 20,810
Retail revenues    
Disaggregation of Revenue [Line Items]    
Revenue from contracts with customers 362,683 356,213
Idaho fixed cost adjustment mechanism    
Disaggregation of Revenue [Line Items]    
Revenue from contracts with customers [1] (16,843) 2,236
Alternative revenue programs and other revenues 16,843 (2,236)
Wholesale energy sales    
Disaggregation of Revenue [Line Items]    
Revenue from contracts with customers 4,812 19,548
Transmission Service Agreement    
Disaggregation of Revenue [Line Items]    
Revenue from contracts with customers 17,324 19,442
Energy efficiency program revenues    
Disaggregation of Revenue [Line Items]    
Revenue from contracts with customers 6,171 5,232
Other revenues    
Disaggregation of Revenue [Line Items]    
Revenue from contracts with customers 9,468 8,471
Derivative revenues    
Disaggregation of Revenue [Line Items]    
Alternative revenue programs and other revenues 2,304 23,046
Residential Retail Revenue | Retail revenues    
Disaggregation of Revenue [Line Items]    
Revenue from contracts with customers [1] 203,597 190,705
Residential Retail Revenue | Idaho fixed cost adjustment mechanism    
Disaggregation of Revenue [Line Items]    
Revenue from contracts with customers 16,637 (2,193)
Commercial Retail Revenue | Retail revenues    
Disaggregation of Revenue [Line Items]    
Revenue from contracts with customers [1] 96,655 97,852
Commercial Retail Revenue | Idaho fixed cost adjustment mechanism    
Disaggregation of Revenue [Line Items]    
Revenue from contracts with customers 206 (43)
Industrial Retail Revenue | Retail revenues    
Disaggregation of Revenue [Line Items]    
Revenue from contracts with customers 69,603 68,607
Irrigation Retail Revenue | Retail revenues    
Disaggregation of Revenue [Line Items]    
Revenue from contracts with customers 1,942 1,113
Deferred revenue-AFUDC | Retail revenues    
Disaggregation of Revenue [Line Items]    
Revenue from contracts with customers [2] (9,114) (2,064)
IPUC authorized AFUDC Collection HCC Relicensing - Gross | Idaho Power Company | Hells Canyon Complex    
Disaggregation of Revenue [Line Items]    
Regulatory liabilities $ (38,500) $ (8,800)
[1] The FCA mechanism is an alternative revenue program in the Idaho jurisdiction and does not represent revenue from contracts with customers.
[2] The IPUC allows Idaho Power to recover a portion of the AFUDC on construction work in progress related to the HCC relicensing process in its Idaho jurisdiction, even though the relicensing process is not yet complete and the costs have not been moved to utility plant in service. Effective October 1, 2025, Idaho Power began collecting $38.5 million annually. Prior to October 1, 2025, Idaho Power collected $8.8 million annually. For more information refer to Note 3 - "Regulatory Matters" to the consolidated financial statements included in the 2025 Annual Report. Amounts collected in the Idaho jurisdiction are recognized as deferred revenue until the license is issued and the accumulated license costs approved for recovery are placed in service.