v3.26.1
REVENUES: (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers $ 468,250 $ 449,313 $ 851,865 $ 860,456
Alternative revenue programs and other revenues 423 359 19,570 21,169
Retail revenues        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 432,403 399,287 795,085 755,499
Idaho fixed cost adjustment mechanism        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers [1] 163 2,912 (16,680) 5,149
Alternative revenue programs and other revenues (163) (2,912) 16,680 (5,149)
Wholesale energy sales        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 3,559 15,376 8,371 34,924
Transmission Service Agreement        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 15,547 16,325 32,871 35,768
Energy efficiency program revenues        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 6,110 6,115 12,282 11,348
Other revenues        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 10,468 9,298 19,936 17,768
Derivative revenues        
Disaggregation of Revenue [Line Items]        
Alternative revenue programs and other revenues 586 3,271 2,890 26,318
Residential Retail Revenue | Retail revenues        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers [1] 168,764 149,355 372,360 340,060
Residential Retail Revenue | Idaho fixed cost adjustment mechanism        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers (153) (2,876) 16,484 (5,069)
Commercial Retail Revenue | Retail revenues        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers [1] 98,773 94,652 195,429 192,504
Commercial Retail Revenue | Idaho fixed cost adjustment mechanism        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers (10) (36) 196 (80)
Industrial Retail Revenue | Retail revenues        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 76,081 64,840 145,684 133,446
Irrigation Retail Revenue | Retail revenues        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 97,306 92,370 99,247 93,482
Deferred revenue-AFUDC | Retail revenues        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers [2] (8,521) (1,930) (17,635) (3,993)
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.