INCOME TAXES - Effective Income Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Effective income tax reconciliation:
Pretax GAAP income at Federal statutory rate	$ 2,118	$ 0	$ 5,435
Pretax GAAP income at State statutory rate, net of federal benefit	282	0	725
Patronage exclusion	(2,401)	0	(6,159)
Asset retirement and environmental reclamation obligations	(6,302)	16,655	10,917
Deferred revenues and membership withdrawal	(11,216)	(22,759)	18,673
Operating liabilities, net of right-of-use assets	(5,281)	(4,919)	1,165
Valuation Allowance	0	0	0
Net operating loss carryforward	26,955	21,034	(27,539)
Other items, net	(4,690)	(9,445)	(2,531)
Impairment	0	0	0
Regulatory treatment of deferred taxes	539	(815)	(391)
Total deferred income tax expense (benefit)	$ 4	$ (249)	$ 295