v3.25.1
REGULATORY MATTERS (Regulatory Liabilities) (Details) - USD ($)
$ in Thousands
Mar. 31, 2025
Dec. 31, 2024
Regulatory Liabilities [Line Items]    
Remaining Recovery Period (years) 1 year  
Total Regulatory Liabilities $ 517,000 $ 506,000
Less Current Portion 144,761 142,844
Total Noncurrent Regulatory Liabilities 371,951 362,859
Income Taxes Payable through Future Rates    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 212,000 209,000
Net Cost of Removal    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 102,000 110,000
Renewable Energy Standard    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities $ 90,000 88,000
Over-Recovered Fuel and Purchased Energy Costs    
Regulatory Liabilities [Line Items]    
Remaining Recovery Period (years) 1 year  
Total Regulatory Liabilities $ 48,000 49,000
Deferred Investment Tax Credits    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities $ 24,000 4,000
Derivatives (Note 10)    
Regulatory Liabilities [Line Items]    
Remaining Recovery Period (years) 5 years  
Total Regulatory Liabilities $ 18,000 22,000
Pension and Other Postretirement Benefits (Note 9)    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities $ 18,000 19,000
Demand Side Management    
Regulatory Liabilities [Line Items]    
Remaining Recovery Period (years) 1 year  
Total Regulatory Liabilities $ 5,000 $ 5,000