SEGMENTS OF BUSINESS - Schedule of EBITDA Margin to Income (loss) before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2025	Dec. 31, 2024
SEGMENTS OF BUSINESS
Income (Loss) before Income Taxes		$ 43,704	$ (235,542)
Other operating revenue		(10,074)	(5,184)
Depreciation, depletion and amortization		41,222	65,626
Asset impairment	$ 215,100	0	215,136
Asset retirement obligations accretion		1,764	1,628
Exploration costs		216	260
Gain on disposal or abandonment of assets, net		(2,489)	(50)
Interest income		(602)	(235)
Interest expense		16,896	13,850
Loss on extinguishment of debt		608	2,790
Equity method investment (loss)		450	746
Settlement of litigation			2,750
Corporate - general and administrative		12,319	11,339
Corporate - other operating and maintenance costs			440
Segment EBITDA		104,014	73,554
Electric sales
SEGMENTS OF BUSINESS
Income (Loss) before Income Taxes		43,704
Operating Segment | Electric Operations
SEGMENTS OF BUSINESS
Income (Loss) before Income Taxes			51,367
Other operating revenue		(3,534)	(946)
Depreciation, depletion and amortization		22,681	19,290
Asset retirement obligations accretion		497	457
Interest income		(52)	(36)
Interest expense		9,097	1,875
Segment EBITDA		85,430	72,007
Operating Segment | Electric Operations | Electric sales
SEGMENTS OF BUSINESS
Income (Loss) before Income Taxes		56,741
Operating Segment | Coal Operations
SEGMENTS OF BUSINESS
Income (Loss) before Income Taxes			(274,120)
Other operating revenue		(5,373)	(2,559)
Depreciation, depletion and amortization		18,465	46,245
Asset impairment		0	215,136
Asset retirement obligations accretion		1,267	1,171
Exploration costs		216	260
Gain on disposal or abandonment of assets, net		(2,489)	1,629
Interest income		(235)	(197)
Interest expense		7,799	11,033
Settlement of litigation			2,750
Segment EBITDA		20,130	1,348
Operating Segment | Coal Operations | Electric sales
SEGMENTS OF BUSINESS
Income (Loss) before Income Taxes		480
Corporate and Other and Eliminations
SEGMENTS OF BUSINESS
Income (Loss) before Income Taxes			(12,789)
Other operating revenue		(1,167)	(1,679)
Depreciation, depletion and amortization		76	91
Gain on disposal or abandonment of assets, net			(1,679)
Interest income		(315)	(2)
Interest expense			942
Loss on extinguishment of debt		608	2,790
Equity method investment (loss)		450	746
Corporate - general and administrative		12,319	11,339
Corporate - other operating and maintenance costs			440
Segment EBITDA		(1,546)	$ 199
Corporate and Other and Eliminations | Electric sales
SEGMENTS OF BUSINESS
Income (Loss) before Income Taxes		$ (13,517)