v3.26.3
REGULATORY MATTERS (Regulatory Assets) (Details) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Regulatory Assets [Line Items]    
Remaining Recovery Period (years) 1 year  
Total Regulatory Assets $ 305,000 $ 294,000
Less Current Portion 115,223 126,836
Total Noncurrent Regulatory Assets 189,805 167,108
Pension and Other Postretirement Benefits (Note 8)    
Regulatory Assets [Line Items]    
Total Regulatory Assets 88,000 91,000
Roadrunner Reserve I Accounting Order    
Regulatory Assets [Line Items]    
Total Regulatory Assets $ 44,000 16,000
Lost Fixed Cost Recovery    
Regulatory Assets [Line Items]    
Remaining Recovery Period (years) 1 year  
Total Regulatory Assets $ 41,000 33,000
Early Generation Retirement Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets $ 35,000 36,000
Property Tax Deferrals    
Regulatory Assets [Line Items]    
Remaining Recovery Period (years) 1 year  
Total Regulatory Assets $ 33,000 32,000
Transmission Revenue Requirement Balancing Account    
Regulatory Assets [Line Items]    
Remaining Recovery Period (years) 2 years  
Total Regulatory Assets $ 20,000 32,000
Derivatives (Note 9)    
Regulatory Assets [Line Items]    
Remaining Recovery Period (years) 3 years  
Total Regulatory Assets $ 15,000 23,000
Transportation Electrification and Electric Vehicle Infrastructure    
Regulatory Assets [Line Items]    
Total Regulatory Assets $ 10,000 8,000
Self-Insured Medical & Short-Term Disability    
Regulatory Assets [Line Items]    
Remaining Recovery Period (years) 1 year  
Total Regulatory Assets $ 7,000 7,000
Income Taxes Recoverable through Future Rates    
Regulatory Assets [Line Items]    
Total Regulatory Assets 4,000 4,000
Other Regulatory Assets    
Regulatory Assets [Line Items]    
Total Regulatory Assets $ 8,000 $ 12,000