BENEFIT PLANS: Level 4 (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Defined Benefit Plan Disclosure
Service cost		$ 8,631	$ 8,382	$ 17,242	$ 16,791
Interest cost		14,848	14,702	29,665	29,460
Expected return on plan assets		(17,291)	(15,841)	(34,576)	(31,694)
Amortization of prior service cost		504	473	1,008	946
Amortization of net loss		(25)	(203)	(92)	(333)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		6,667	7,513	13,247	15,170
Regulatory deferral of net periodic benefit cost	[1]	(4,025)	(5,061)	(8,051)	(10,121)
IPUC Authorized recovered pension cost	[1]	8,795	4,289	17,591	8,577
Net periodic benefit cost recognized for financial reporting	[1],[2]	11,437	6,741	22,787	13,626
Net Periodic Benefit cost recognize in Other operations and maintenance		9,500	5,100	18,800	10,400
Net Periodic Benefit cost recognized in other expense, net		1,900	1,600	4,000	3,200
Pension Plan
Defined Benefit Plan Disclosure
Service cost		8,183	8,078	16,367	16,156
Interest cost		12,794	12,655	25,587	25,309
Expected return on plan assets		(16,830)	(15,434)	(33,660)	(30,868)
Amortization of prior service cost		62	1	124	3
Amortization of net loss		0	0	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		4,209	5,300	8,418	10,600
Regulatory deferral of net periodic benefit cost	[1]	(4,025)	(5,061)	(8,051)	(10,121)
IPUC Authorized recovered pension cost	[1]	8,795	4,289	17,591	8,577
Net periodic benefit cost recognized for financial reporting	[1],[2]	8,979	4,528	17,958	9,056
Pension Plan | Idaho Power Company
Defined Benefit Plan Disclosure
Defined Benefit Plan, Contributions by Employer				0
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year		30,000		30,000
Senior Management Security Plan
Defined Benefit Plan Disclosure
Service cost		263	153	526	306
Interest cost		1,333	1,330	2,666	2,661
Expected return on plan assets		0	0	0	0
Amortization of prior service cost		55	55	110	110
Amortization of net loss		327	143	655	285
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		1,978	1,681	3,957	3,362
Net periodic benefit cost recognized for financial reporting		1,978	1,681	3,957	3,362
Postretirement Benefits Plan
Defined Benefit Plan Disclosure
Service cost		185	151	349	329
Interest cost		721	717	1,412	1,490
Expected return on plan assets		(461)	(407)	(916)	(826)
Amortization of prior service cost		387	417	774	833
Amortization of net loss		(352)	(346)	(747)	(618)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		480	532	872	1,208
Net periodic benefit cost recognized for financial reporting		$ 480	$ 532	$ 872	$ 1,208

[1] Net periodic benefit costs for the pension plan are recognized for financial reporting based upon the authorization of each regulatory jurisdiction in which Idaho Power operates. Under IPUC order, the Idaho portion of net periodic benefit cost is recorded as a regulatory asset and is recognized in the income statement as those costs are recovered through rates.

[2] Of total net periodic benefit cost recognized for financial reporting, $9.5 million and $5.1 million, respectively, were recognized in "Other operations and maintenance" and $1.9 million and $1.6 million, respectively, were recognized in "Other income, net" on the condensed consolidated statements of income of the companies for the three months ended June 30, 2024 and 2023.