FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Financial Impact of Derivative Energy Contracts) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Derivative Instruments, Gain (Loss) [Line Items]
Percent of long-term trading contract gains shared with customers (percentage)			10.00%
Operating Revenues	$ 407,244	$ 429,546	$ 772,980	$ 882,302
Energy Derivative Contracts | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Net Gain (Loss)	23,000	6,000	20,000	(8,000)
Operating Revenues	$ 0	$ 0	$ 21,000	$ 27,000