v3.26.3
BENEFIT PLANS: Level 4 (Details)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
USD ($)
plan
Sep. 30, 2025
USD ($)
plan
Sep. 30, 2026
USD ($)
plan
Sep. 30, 2025
USD ($)
plan
Defined Benefit Plan Disclosure        
Number of plans | plan 2 2 2 2
Service cost $ 8,574 $ 8,576 $ 25,722 $ 25,213
Interest cost 16,704 16,532 50,115 48,573
Expected return on plan assets (18,992) (17,676) (56,977) (53,038)
Amortization of prior service cost 332 401 995 1,202
Amortization of net loss (181) (268) (545) (806)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) 6,437 7,565 19,310 21,144
Regulatory deferral of net periodic benefit cost (3,985) [1] (5,058) [1] (11,955) [2] (13,620) [2]
IPUC Authorized recovered pension cost 8,796 [1] 8,796 [1] 26,387 [2] 26,387 [2]
Net periodic benefit cost recognized for financial reporting 11,248 [1],[3] 11,303 [1],[3] 33,742 [2],[4] 33,911 [2],[4]
Net Periodic Benefit cost recognize in Other operations and maintenance 9,800 9,800 29,100 29,400
Net Periodic Benefit cost recognized in other expense, net 1,600 1,500 4,600 4,500
Pension Plan        
Defined Benefit Plan Disclosure        
Service cost 8,168 8,115 24,505 23,830
Interest cost 14,539 14,379 43,617 42,113
Expected return on plan assets (18,539) (17,229) (55,617) (51,698)
Amortization of prior service cost 2 2 5 5
Amortization of net loss 0 0 0 0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) 4,170 5,267 12,510 14,250
Regulatory deferral of net periodic benefit cost (3,985) [1] (5,058) [1] (11,955) [2] (13,620) [2]
IPUC Authorized recovered pension cost 8,796 [1] 8,796 [1] 26,387 [2] 26,387 [2]
Net periodic benefit cost recognized for financial reporting 8,981 [1],[3] 9,005 [1],[3] 26,942 [2],[4] 27,017 [2],[4]
Pension Plan | Idaho Power Company        
Defined Benefit Plan Disclosure        
Defined Benefit Plan, Contributions by Employer 20,000   20,000  
Senior Management Security Plan        
Defined Benefit Plan Disclosure        
Service cost 240 293 720 879
Interest cost 1,430 1,410 4,291 4,230
Expected return on plan assets 0 0 0 0
Amortization of prior service cost 55 55 166 166
Amortization of net loss 241 173 721 518
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) 1,966 1,931 5,898 5,793
Net periodic benefit cost recognized for financial reporting 1,966 1,931 5,898 5,793
Postretirement Benefits Plan        
Defined Benefit Plan Disclosure        
Service cost 166 168 497 504
Interest cost 735 743 2,207 2,230
Expected return on plan assets (453) (447) (1,360) (1,340)
Amortization of prior service cost 275 344 824 1,031
Amortization of net loss (422) (441) (1,266) (1,324)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) 301 367 902 1,101
Net periodic benefit cost recognized for financial reporting $ 301 $ 367 $ 902 $ 1,101
[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] 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.
[3] Of total net periodic benefit cost recognized for financial reporting, $9.8 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 September 30, 2026 and 2025.
[4] Of total net periodic benefit cost recognized for financial reporting, $29.1 million and $29.4 million, respectively, were recognized in "Other operations and maintenance" and $4.6 million and $4.5 million, respectively, were recognized in "Other income, net" on the condensed consolidated statements of income of the companies for the nine months ended September 30, 2026 and 2025.