v3.26.3
FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Schedule of Financial Impact of Energy Contracts) (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Derivative Instruments, Gain (Loss) [Line Items]        
Percent of long-term trading contract gains shared with customers (percentage)     10.00%  
Operating Revenues $ 565,841 $ 544,515 $ 1,337,227 $ 1,317,495
Energy Derivative Contracts | Not Designated as Hedging Instrument        
Derivative Instruments, Gain (Loss) [Line Items]        
Unrealized Net Gain (Loss) 4,000 (21,000) 3,000 (1,000)
Operating Revenues $ 6,000 $ 2,000 $ 21,000 $ 23,000