CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 58,272	$ 49,475
Trade receivables, net	19,687	14,097
Inventories	12,859	13,688
Prepaid expenses and other current assets	1,371	1,584
Total current assets	92,189	78,844
Property, plant and equipment	256,298	249,714
Less accumulated depreciation and depletion	(150,653)	(141,227)
Property, plant and equipment, net	105,645	108,487
Other assets, net	161	195
Total assets	197,995	187,526
Current liabilities:
Current installments of debt	5,000	5,000
Accounts payable	4,823	5,812
Accrued expenses	4,083	3,536
Total current liabilities	13,906	14,348
Debt, excluding current installments	12,917	16,667
Deferred tax liabilities, net	18,209	17,799
Other liabilities	1,529	1,907
Total liabilities	46,561	50,721
Stockholders' equity:
Common stock	651	650
Additional paid-in capital	20,141	19,319
Accumulated other comprehensive loss	(1,068)	(1,498)
Retained earnings	181,677	168,133
Less treasury stock, at cost	(49,967)	(49,799)
Total stockholders' equity	151,434	136,805
Total liabilities and stockholders' equity	$ 197,995	$ 187,526