UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Income Statement [Abstract]
Revenues	$ 53,289	$ 50,141
Cost of sales	46,271	46,784
Gross profit	7,018	3,357
Earnings of unconsolidated operations	13,307	13,824
Operating expenses
Selling, general and administrative expenses	15,453	14,876
Amortization of intangible assets	126	727
Gain on sale of assets	(11)	(236)
Operating expenses	15,568	15,367
Operating profit	4,757	1,814
Other (income) expense
Interest expense	1,111	545
Interest income	(1,127)	(1,155)
Closed mine obligations	455	409
Gain on equity securities	(1,041)	(628)
Other, net	(214)	(1,725)
Other (income) expense	(816)	(2,554)
Income before income tax provision (benefit)	5,573	4,368
Income tax provision (benefit)	1,003	(1,324)
Net income	$ 4,570	$ 5,692
Earnings per share:
Basic earnings per share (in dollars per share)	$ 0.61	$ 0.77
Diluted earnings per share (in dollars per share)	$ 0.61	$ 0.76
Basic weighted average shares outstanding (in shares)	7,452	7,428
Diluted weighted average shares outstanding (in shares)	7,515	7,515