v3.26.1
BENEFIT PLANS: Level 4 (Details)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
USD ($)
plan
Mar. 31, 2025
USD ($)
plan
Defined Benefit Plan Disclosure    
Number of plans | plan 2 2
Service cost $ 8,735 $ 8,319
Interest cost 16,734 16,020
Expected return on plan assets (19,004) (17,685)
Amortization of prior service cost 333 401
Amortization of net loss (178) (267)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) 6,620 6,788
Regulatory deferral of net periodic benefit cost [1] (4,129) (4,297)
IPUC Authorized recovered pension cost [1] 8,796 8,796
Net periodic benefit cost recognized for financial reporting [1],[2] 11,287 11,287
Net Periodic Benefit cost recognize in Other operations and maintenance 9,700 9,800
Net Periodic Benefit cost recognized in other expense, net 1,600 1,500
Pension Plan    
Defined Benefit Plan Disclosure    
Service cost 8,307 7,857
Interest cost 14,560 13,867
Expected return on plan assets (18,549) (17,235)
Amortization of prior service cost 2 2
Amortization of net loss 0 0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) 4,320 4,491
Regulatory deferral of net periodic benefit cost [1] (4,129) (4,297)
IPUC Authorized recovered pension cost [1] 8,796 8,796
Net periodic benefit cost recognized for financial reporting [1],[2] 8,987 8,990
Pension Plan | Idaho Power Company    
Defined Benefit Plan Disclosure    
Defined Benefit Plan, Contributions by Employer 0  
Defined Benefit Plan, Expected Future Benefit Payment, Remainder of Fiscal Year 30,000  
Senior Management Security Plan    
Defined Benefit Plan Disclosure    
Service cost 240 293
Interest cost 1,430 1,410
Expected return on plan assets 0 0
Amortization of prior service cost 56 55
Amortization of net loss 240 173
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) 1,966 1,931
Net periodic benefit cost recognized for financial reporting 1,966 1,931
Postretirement Benefits Plan    
Defined Benefit Plan Disclosure    
Service cost 188 169
Interest cost 744 743
Expected return on plan assets (455) (450)
Amortization of prior service cost 275 344
Amortization of net loss (418) (440)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) 334 366
Net periodic benefit cost recognized for financial reporting $ 334 $ 366
[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, $9.7 million and $9.8 million, respectively, were recognized in "Other operations and maintenance" and $1.6 million and $1.5 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, 2026 and 2025.