REVENUES: (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		$ 385,666	$ 318,182
Alternative revenue programs and other revenues		43,672	25,739
Retail revenues
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		330,724	295,843
Idaho fixed cost adjustment mechanism
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	[1]	(9,185)	(10,376)
Alternative revenue programs and other revenues		9,185	10,376
Wholesale energy sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		30,195	3,035
Transmission Service Agreement
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		21,585	16,466
Energy efficiency program revenues
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		5,215	6,589
Other revenues
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		7,132	6,625
Derivative revenues
Disaggregation of Revenue [Line Items]
Alternative revenue programs and other revenues		34,487	15,363
Residential Retail Revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	[1]	188,536	169,295
Residential Retail Revenue | Idaho fixed cost adjustment mechanism
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		8,909	10,093
Commercial Retail Revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	[1]	87,830	78,566
Commercial Retail Revenue | Idaho fixed cost adjustment mechanism
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		276	283
Industrial Retail Revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		55,544	49,060
Irrigation Retail Revenue | Retail revenues
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		933	1,041
Deferred revenue-AFUDC | Retail revenues
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	[2]	(2,119)	(2,119)
IPUC authorized AFUDC Collection HCC Relicensing - Gross | Idaho Power Company [Member] | Hells Canyon Complex
Disaggregation of Revenue [Line Items]
Regulatory liabilities		$ (8,800)	$ (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 allowance for funds used during construction (AFUDC) on construction work in progress related to the Hells Canyon Complex (HCC) relicensing process, even though the relicensing process is not yet complete and the costs have not been moved to electric plant in service. Idaho Power is collecting $8.8 million annually in the Idaho jurisdiction but is deferring revenue recognition of the amounts collected until the license is issued and the accumulated license costs approved for recovery are placed in service.