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BENEFIT PLANS:
 3 Months Ended
Mar. 31, 2025
Retirement Benefits, Description [Abstract]  
Benefit Plans BENEFIT PLANS
Idaho Power has a noncontributory defined benefit pension plan (pension plan) and two nonqualified defined benefit plans for certain senior management employees called the SMSP. Idaho Power also has a nonqualified defined benefit pension plan for directors that was frozen in 2002. Remaining vested benefits from that plan are included with the SMSP in the disclosures below. The benefits under the pension plan are based on years of service and the employee’s final average earnings. Idaho Power also maintains a defined benefit postretirement benefit plan (consisting of health care and death benefits) that covers all employees who were enrolled in the active-employee group plan at the time of retirement as well as their spouses and qualifying dependents. The table below shows the components of net periodic benefit costs for the pension, SMSP, and postretirement benefits plans for the three months ended March 31, 2025 and 2024 (in thousands).
Pension PlanSMSPPostretirement
Benefits		Total
 20252024202520242025202420252024
Service cost$7,857 $8,184 $293 $263 $169 $164 $8,319 $8,611 
Interest cost13,867 12,793 1,410 1,333 743 691 16,020 14,817 
Expected return on plan assets(17,235)(16,830)— — (450)(455)(17,685)(17,285)
Amortization of prior service cost2 62 55 55 344 387 401 504 
Amortization of net loss— — 173 328 (440)(395)(267)(67)
Net periodic benefit cost4,491 4,209 1,931 1,979 366 392 6,788 6,580 
Regulatory deferral of net periodic benefit cost(1)
(4,297)(4,026)— — — — (4,297)(4,026)
Previously deferred pension costs recognized(1)
8,796 8,796 — — — — 8,796 8,796 
Net periodic benefit cost recognized for financial reporting(1)(2)
$8,990 $8,979 $1,931 $1,979 $366 $392 $11,287 $11,350 
(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, $9.8 million and $9.4 million, respectively, were recognized in "Other operations and maintenance" and $1.5 million and $2.0 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, 2025 and 2024.
Idaho Power has no minimum contribution requirement to its defined benefit pension plan in 2025, and during the three months ended March 31, 2025, Idaho Power made no contributions. Idaho Power is considering contributing up to $30 million during 2025 in a continued effort to balance the regulatory collection of these expenditures with the amount and timing of contributions, as well as to mitigate the cost of being in an underfunded position. The primary impact of pension contributions is on the timing of cash flows, as the timing of cost recovery lags behind contributions.

Idaho Power also has an Employee Savings Plan that complies with Section 401(k) of the Internal Revenue Code and covers substantially all employees. Idaho Power matches specified percentages of employee contributions to the Employee Savings Plan.