CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 255,022	$ 187,964
Trade receivables, net	52,905	38,052
Inventories	27,783	24,313
Prepaid expenses and other current assets	2,749	4,640
Total current assets	338,459	254,969
Property, plant and equipment	483,108	469,598
Less accumulated depreciation and depletion	(305,318)	(289,803)
Property, plant and equipment, net	177,790	179,795
Operating lease right-of-use assets	4,964	5,273
Other assets, net	546	565
Total assets	521,759	440,602
Current liabilities:
Accounts payable	8,496	7,404
Current portion of operating lease liabilities	1,531	1,582
Accrued expenses	8,671	8,505
Total current liabilities	18,698	17,491
Deferred tax liabilities, net	23,834	24,659
Operating lease liabilities, excluding current portion	3,633	3,919
Other liabilities	1,380	1,429
Total liabilities	47,545	47,498
Stockholders' equity:
Common stock, $0.10 par value; 45,000,000 and 30,000,000 shares authorized at September 30, 2024 and December 31, 2023, respectively; 28,594,207 and 28,522,780 shares outstanding at September 30, 2024 and December 31, 2023, respectively	2,963	2,955
Additional paid-in capital	39,251	35,539
Retained earnings	490,061	412,499
Less treasury stock, at cost	(58,061)	(57,889)
Total stockholders' equity	474,214	393,104
Total liabilities and stockholders' equity	$ 521,759	$ 440,602