Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Current assets
Cash and cash equivalents	$ 371,124	$ 278,031
Trade receivables, net	47,933	43,982
Inventories	30,908	27,686
Prepaid expenses and other current assets	5,351	5,083
Total current assets	455,316	354,782
Property, plant and equipment
Mineral reserves and land	67,817	60,952
Proved natural gas properties, successful-efforts method	15,934	15,934
Buildings and building and leasehold improvements	13,527	13,246
Machinery and equipment	447,545	393,312
Furniture and fixtures	1,422	1,409
Automotive equipment	8,367	8,393
Property, plant, and equipment	554,612	493,246
Less accumulated depreciation and depletion	(333,191)	(310,355)
Property, plant, and equipment, net	221,421	182,891
Operating lease right-of-use assets	3,864	4,855
Other assets, net	443	635
Total assets	681,044	543,163
Current liabilities
Accounts payable	14,516	8,819
Current portion of operating lease liabilities	1,643	1,602
Accrued expenses	7,473	6,541
Total current liabilities	23,632	16,962
Deferred tax liabilities, net	22,999	23,659
Operating lease liabilities, excluding current portion	2,370	3,437
Other liabilities	1,283	1,364
Total liabilities	50,284	45,422
Commitments and contingencies (Note 8)
Stockholders' equity
Preferred stock, $5.00 par value; authorized 500,000 shares; none issued
Common stock, $0.10 par value; 45,000,000 shares authorized at December 31, 2025 and 2024; 29,742,653 and 29,671,768 shares issued at December 31, 2025 and 2024, respectively	2,975	2,968
Additional paid-in capital	48,839	40,549
Retained earnings	643,025	515,622
Less treasury stock, 1,074,460 and 1,051,931 shares at December 31, 2025 and 2024, respectively, at cost	(64,079)	(61,398)
Total stockholders' equity	630,760	497,741
Total liabilities and stockholders' equity	$ 681,044	$ 543,163