v3.25.1
BENEFIT PLANS: Level 4 (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Defined Benefit Plan Disclosure    
Service cost $ 8,319 $ 8,611
Interest cost 16,020 14,817
Expected return on plan assets (17,685) (17,285)
Amortization of prior service cost 401 504
Amortization of net loss (267) (67)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) 6,788 6,580
Regulatory deferral of net periodic benefit cost [1] (4,297) (4,026)
IPUC Authorized recovered pension cost [1] 8,796 8,796
Net periodic benefit cost recognized for financial reporting [1],[2] 11,287 11,350
Net Periodic Benefit cost recognize in Other operations and maintenance 9,800 9,400
Net Periodic Benefit cost recognized in other expense, net 1,500 2,000
Pension Plan    
Defined Benefit Plan Disclosure    
Service cost 7,857 8,184
Interest cost 13,867 12,793
Expected return on plan assets (17,235) (16,830)
Amortization of prior service cost 2 62
Amortization of net loss 0 0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) 4,491 4,209
Regulatory deferral of net periodic benefit cost [1] (4,297) (4,026)
IPUC Authorized recovered pension cost [1] 8,796 8,796
Net periodic benefit cost recognized for financial reporting [1],[2] 8,990 8,979
Pension Plan | Idaho Power Company    
Defined Benefit Plan Disclosure    
Defined Benefit Plan, Contributions by Employer 0  
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year 30,000  
Senior Management Security Plan    
Defined Benefit Plan Disclosure    
Service cost 293 263
Interest cost 1,410 1,333
Expected return on plan assets 0 0
Amortization of prior service cost 55 55
Amortization of net loss 173 328
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) 1,931 1,979
Net periodic benefit cost recognized for financial reporting 1,931 1,979
Postretirement Benefits Plan    
Defined Benefit Plan Disclosure    
Service cost 169 164
Interest cost 743 691
Expected return on plan assets (450) (455)
Amortization of prior service cost 344 387
Amortization of net loss (440) (395)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) 366 392
Net periodic benefit cost recognized for financial reporting $ 366 $ 392
[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.