v3.26.3
REVENUES: (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers $ 614,841 $ 526,424 $ 1,466,707 $ 1,386,879
Alternative revenue programs and other revenues (7,804) (2,875) 11,765 18,294
Retail revenues        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 554,167 477,870 1,349,252 1,233,369
Idaho fixed cost adjustment mechanism        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers [1] 7,869 4,195 (8,811) 9,344
Alternative revenue programs and other revenues (7,869) (4,195) 8,811 (9,344)
Wholesale energy sales        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 16,957 10,520 25,328 45,443
Transmission Service Agreement        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 18,476 17,856 51,347 53,624
Energy efficiency program revenues        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 8,011 7,460 20,293 18,808
Other revenues        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 9,361 8,523 29,298 26,291
Derivative revenues        
Disaggregation of Revenue [Line Items]        
Alternative revenue programs and other revenues 65 1,320 2,954 27,638
Residential Retail Revenue | Retail revenues        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers [1] 235,900 195,445 608,260 535,505
Residential Retail Revenue | Idaho fixed cost adjustment mechanism        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers (7,811) (4,125) 8,674 (9,194)
Commercial Retail Revenue | Retail revenues        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers [1] 123,946 111,510 319,374 304,014
Commercial Retail Revenue | Idaho fixed cost adjustment mechanism        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers (58) (70) 137 (150)
Industrial Retail Revenue | Retail revenues        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 91,278 72,079 236,963 205,526
Irrigation Retail Revenue | Retail revenues        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 115,648 101,690 214,895 195,172
Deferred revenue-AFUDC | Retail revenues        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers [2] (12,605) (2,854) (30,240) (6,848)
IPUC authorized AFUDC Collection HCC Relicensing - Gross | Idaho Power Company | Hells Canyon Complex        
Disaggregation of Revenue [Line Items]        
Regulatory liabilities $ (38,500) $ (8,800) $ (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.