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REGULATORY MATTERS: Idaho Base Rate Changes (Details) - USD ($) $ in Thousands			12 Months Ended
		Oct. 15, 2024	Dec. 31, 2026	Sep. 30, 2026	Dec. 31, 2025	Oct. 15, 2025	Dec. 31, 2024	Dec. 31, 2023	Jan. 01, 2026	Jan. 01, 2024
Idaho Base Rate Changes [Line Items]
Regulatory Assets					$ 1,564,458		$ 1,507,372
Wildfire Mitigation Plan Deferral
Idaho Base Rate Changes [Line Items]
Regulatory Assets	[1]				91,670		63,966
2023 Rate Case | Benefit Obligations [Member]
Idaho Base Rate Changes [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount							18,000
Settlement Stipulation - Investment Tax Credits and Idaho Sharing Mechanism
Idaho Base Rate Changes [Line Items]
Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Amount					40,300
Settlement Stipulation - Investment Tax Credits and Idaho Sharing Mechanism | ADITC
Idaho Base Rate Changes [Line Items]
Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Amount					167,800
2025 Rate Case | Idaho Power Cost Adjustment [Member] | Subsequent Event
Idaho Base Rate Changes [Line Items]
Approved Rate Increase (Decrease), Amount			$ 13,100
IDAHO | 2024 Limited Rate Case
Idaho Base Rate Changes [Line Items]
Approved Rate Increase (Decrease), Amount					50,600
IDAHO | 2023 Rate Case | Idaho Power Company
Idaho Base Rate Changes [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount							3,500
IDAHO | Wildfire Mitigation Plan Deferral
Idaho Base Rate Changes [Line Items]
Regulatory Assets					$ 88,200
IDAHO | Hells Canyon Complex | Subsequent Event
Idaho Base Rate Changes [Line Items]
Approved Rate Increase (Decrease), Amount				$ 29,700
IDAHO | May 2018 Tax Reform Settlement Stipulation
Idaho Base Rate Changes [Line Items]
Amortization of Regulatory Asset								$ 7,400
IDAHO | May 2018 Tax Reform Settlement Stipulation | Annual recurring
Idaho Base Rate Changes [Line Items]
Approved Rate Increase (Decrease), Amount								$ 18,700
IDAHO | 2023 Rate Case
Idaho Base Rate Changes [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount							$ 54,700
Authorized Return on Equity in Rate Case, Minimum										9.12%
Authorized Return on Equity in Rate Case, Mid-point										9.60%
Approved Return on Equity, Percentage							9.60%
Approved Authorized Rate of Return							7.247%
IDAHO | 2023 Rate Case | Idaho Power Cost Adjustment [Member]
Idaho Base Rate Changes [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount							$ 168,300
IDAHO | Idaho PCA includes power supply and deferral balance.
Idaho Base Rate Changes [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount							$ 484,900
IDAHO | Idaho PCA includes power supply and deferral balance. | Subsequent Event
Idaho Base Rate Changes [Line Items]
Approved Rate Increase (Decrease), Amount			$ 468,800
IDAHO | 2024 Limited Rate Case
Idaho Base Rate Changes [Line Items]
Approved Rate Increase (Decrease), Percentage					3.70%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount					$ 50,100
IDAHO | 2025 Rate Case
Idaho Base Rate Changes [Line Items]
Percentage to be Shared with Customers					80.00%
Percentage to be Shared with Entity					20.00%
IDAHO | 2025 Rate Case | Subsequent Event
Idaho Base Rate Changes [Line Items]
Approved Rate Increase (Decrease), Percentage			7.48%
Authorized Return on Equity in Rate Case, Minimum									9.12%
Approved Rate Increase (Decrease), Amount			$ 110,000
Approved Return on Equity, Percentage			9.60%
Approved Authorized Rate of Return			7.41%
IDAHO | 2025 Rate Case | Idaho Power Cost Adjustment [Member] | Subsequent Event
Idaho Base Rate Changes [Line Items]
Approved Rate Increase (Decrease), Amount			$ (16,100)
IDAHO | 2025 Rate Case | Wildfire Mitigation Plan Deferral
Idaho Base Rate Changes [Line Items]
Regulatory Assets					$ 73,900
OREGON | Subsequent Event
Idaho Base Rate Changes [Line Items]
Approved Rate Increase (Decrease), Percentage			0.90%
Approved Rate Increase (Decrease), Amount			$ (600)
OREGON | Wildfire mitigation plan costs | Subsequent Event
Idaho Base Rate Changes [Line Items]
Approved Rate Increase (Decrease), Amount			700
OREGON | Wildfire Mitigation Plan Deferral
Idaho Base Rate Changes [Line Items]
Regulatory Assets					$ 3,500
OREGON | Valmy Plant | Subsequent Event
Idaho Base Rate Changes [Line Items]
Approved Rate Increase (Decrease), Amount			$ (1,200)
OREGON | 2023 Rate Case
Idaho Base Rate Changes [Line Items]
Approved Rate Increase (Decrease), Percentage						12.14%
Approved Rate Increase (Decrease), Amount						$ 6,700
Approved Return on Equity, Percentage		9.50%
OREGON | 2023 Rate Case | Cost of Capital and Capital Structure
Idaho Base Rate Changes [Line Items]
Authorized Rate of Return in Rate Case		7.302%
Total Retail Rate Base		$ 188,900
OREGON | 2023 Rate Case | Cost of Debt Capital Structure [Domain]
Idaho Base Rate Changes [Line Items]
Approved Rate of Return		5.104%
[1] This item is discussed in more detail in this Note 3 - "Regulatory Matters."

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