BENEFIT PLANS: Level 4 (Details) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended
		Apr. 30, 2022	Mar. 31, 2022	Mar. 31, 2021
Defined Benefit Plan Disclosure
Service cost			$ 13,730	$ 13,964
Interest cost			11,584	10,620
Expected return on plan assets			(18,628)	(16,622)
Amortization of prior service cost			71	88
Amortization of net loss			4,594	6,724
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)			11,351	14,774
Regulatory deferral of net periodic benefit cost	[1]		(8,373)	(11,695)
IPUC Authorized recovered pension cost	[1]		4,288	4,288
Net periodic benefit cost recognized for financial reporting	[1],[2]		7,266	7,367
Net Periodic Benefit cost recognize in Other operations and maintenance			4,900	4,800
Net Periodic Benefit cost recognized in other expense, net			2,400	2,600
Pension Plan
Defined Benefit Plan Disclosure
Service cost			13,164	13,408
Interest cost			10,084	9,203
Expected return on plan assets			(18,037)	(16,021)
Amortization of prior service cost			2	2
Amortization of net loss			3,548	5,673
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)			8,761	12,265
Regulatory deferral of net periodic benefit cost	[1]		(8,373)	(11,695)
IPUC Authorized recovered pension cost	[1]		4,288	4,288
Net periodic benefit cost recognized for financial reporting	[1],[2]		4,676	4,858
Pension Plan | Idaho Power Company [Member]
Defined Benefit Plan Disclosure
Defined Benefit Plan, Contributions by Employer			0
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year			30,000
Pension Plan | Subsequent Event | Idaho Power Company [Member]
Defined Benefit Plan Disclosure
Defined Benefit Plan, Contributions by Employer		$ 10,000
Senior Management Security Plan
Defined Benefit Plan Disclosure
Service cost			296	203
Interest cost			974	889
Expected return on plan assets			0	0
Amortization of prior service cost			70	74
Amortization of net loss			1,057	1,051
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)			2,397	2,217
Net periodic benefit cost recognized for financial reporting			2,397	2,217
Postretirement Benefits Plan
Defined Benefit Plan Disclosure
Service cost			270	353
Interest cost			526	528
Expected return on plan assets			(591)	(601)
Amortization of prior service cost			(1)	12
Amortization of net loss			(11)	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)			193	292
Net periodic benefit cost recognized for financial reporting			$ 193	$ 292

[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, $4.9 million and $4.8 million, respectively, were recognized in "Other operations and maintenance" and $2.4 million and $2.6 million, respectively, were recognized in "Other income, net" on the condensed consolidated statements of income of the companies for the three months ended March 31, 2022 and 2021.