v3.26.1
BENEFIT PLANS: Level 3 (Tables)
 6 Months Ended
Jun. 30, 2026
Retirement Benefits [Abstract]  
Schedule of Defined Benefit Plans Disclosures [Table Text Block] The table below shows the components of net periodic benefit costs for the pension, SMSP, and postretirement benefits plans for the three months ended June 30, 2026 and 2025 (in thousands of dollars).
Pension PlanSMSPPostretirement
Benefits		Total
 20262025202620252026202520262025
Service cost$8,030 $7,858 $240 $293 $143 $167 $8,413 $8,318 
Interest cost14,518 13,867 1,431 1,410 728 744 16,677 16,021 
Expected return on plan assets(18,529)(17,234)— — (452)(443)(18,981)(17,677)
Amortization of prior service cost1 1 55 56 274 343 330 400 
Amortization of net loss— — 240 172 (426)(443)(186)(271)
Net periodic benefit cost4,020 4,492 1,966 1,931 267 368 6,253 6,791 
Regulatory deferral of net periodic benefit cost(1)
(3,841)(4,265)— — — — (3,841)(4,265)
Previously deferred pension costs recognized(1)
8,795 8,795 — — — — 8,795 8,795 
Net periodic benefit cost recognized for financial reporting(1)(2)
$8,974 $9,022 $1,966 $1,931 $267 $368 $11,207 $11,321 
(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 $1.5 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 June 30, 2026 and 2025.
The table below shows the components of net periodic benefit costs for the pension, SMSP, and postretirement benefits plans for the six months ended June 30, 2026 and 2025 (in thousands of dollars).
Pension PlanSMSPPostretirement
Benefits		Total
 20262025202620252026202520262025
Service cost$16,337 $15,715 $480 $586 $331 $336 $17,148 $16,637 
Interest cost29,078 27,734 2,861 2,820 1,472 1,487 33,411 32,041 
Expected return on plan assets(37,078)(34,469)— — (907)(893)(37,985)(35,362)
Amortization of prior service cost3 3 111 111 549 687 663 801 
Amortization of net loss— — 480 345 (844)(883)(364)(538)
Net periodic benefit cost8,340 8,983 3,932 3,862 601 734 12,873 13,579 
Regulatory deferral of net periodic benefit cost(1)
(7,970)(8,562)— — — — (7,970)(8,562)
Previously deferred pension costs recognized(1)
17,591 17,591 — — — — 17,591 17,591 
Net periodic benefit cost recognized for financial reporting(1)(2)
$17,961 $18,012 $3,932 $3,862 $601 $734 $22,494 $22,608 
(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, $19.4 million and $19.6 million, respectively, were recognized in "Other operations and maintenance" and $3.1 million and $3.0 million, respectively, were recognized in "Other income, net" on the condensed consolidated statements of income of the companies for the six months ended June 30, 2026 and 2025.