CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Statement [Abstract]
Revenues	$ 214,794	$ 241,719
Cost of sales	200,203	173,877
Gross profit	14,591	67,842
Earnings of unconsolidated operations	49,994	57,250
Contract termination settlement	0	14,000
Operating expenses
Selling, general and administrative expenses	65,616	63,911
Amortization of intangible assets	2,998	3,719
Loss (gain) on sale of assets	221	(2,463)
Long-lived asset impairment charge	65,887	3,939
Operating expenses	134,722	69,106
Operating (loss) profit	(70,137)	69,986
Other (income) expense
Interest expense	2,460	2,034
Interest income	(6,081)	(1,449)
Closed mine obligations	3,585	1,179
(Gain) loss on equity securities	(1,958)	283
Other contract termination settlements	0	(16,882)
Other, net	(3,985)	(2,902)
Other (income) expense	(5,979)	(17,737)
(Loss) income before income tax (benefit) provision	(64,158)	87,723
Income tax (benefit) provision	(24,571)	13,565
Net (loss) income	$ (39,587)	$ 74,158
(Loss) earnings per share:
Basic loss earnings per share (in dollars per share)	$ (5.29)	$ 10.14
Diluted loss earnings per share (in dollars per share)	$ (5.29)	$ 10.06
Basic weighted average shares outstanding (in shares)	7,478	7,312
Diluted weighted average shares outstanding (in shares)	7,478	7,373