Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 53,372	$ 36,223
Trade receivables, net	15,595	13,839
Inventories	10,764	10,600
Prepaid expenses and other current assets	1,207	1,225
Total current assets	80,938	61,887
Property, plant and equipment:
Mineral reserves and land	17,001	16,727
Proved natural gas properties, successful-efforts method	18,220	17,295
Buildings and building and leasehold improvements	3,477	3,392
Machinery and equipment	195,443	189,273
Furniture and fixtures	909	851
Automotive equipment	1,690	1,661
Property, plant and equipment, at cost	236,740	229,199
Less accumulated depreciation and depletion	(115,422)	(102,962)
Property, plant and equipment, net	121,318	126,237
Other assets, net	302	374
Total assets	202,558	188,498
Current liabilities:
Current installments of debt	6,250	5,000
Accounts payable	5,392	4,545
Accrued expenses	4,376	6,166
Total current liabilities	16,018	15,711
Debt, excluding current installments	26,667	31,666
Deferred tax liabilities, net	12,497	8,933
Other liabilities	4,363	3,894
Total liabilities	59,545	60,204
Commitments and contingencies
Stockholders' equity:
Preferred stock, $5.00 par value; authorized 500,000 shares; none issued or outstanding
Common stock, $0.10 par value; authorized 15,000,000 shares; 6,450,718 and 6,421,424 shares issued at December 31, 2011 and 2010, respectively	645	642
Additional paid-in capital	17,199	16,354
Accumulated other comprehensive loss	(3,001)	(3,009)
Retained earnings	136,910	114,724
Less treasury stock at cost, 215,279 and 11,024 shares at December 31, 2011 and 2010, respectively	(8,740)	(417)
Total stockholders' equity	143,013	128,294
Total liabilities and stockholders' equity	$ 202,558	$ 188,498