CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating Activities:
Net income	$ 2,757	$ 4,624
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	3,729	3,640
Amortization of deferred financing costs	12	11
Deferred income taxes	9	500
(Gain) loss on sale of property, plant and equipment	(25)	10
Stock-based compensation	231	262
Changes in operating assets and liabilities:
Trade receivables, net	(2,224)	(1,523)
Inventories	438	(206)
Prepaid expenses and other current assets	(331)	37
Other assets	1	5
Accounts payable and accrued expenses	579	(74)
Other liabilities	214	(167)
Net cash provided by operating activities	5,390	7,119
Investing Activities:
Purchase of property, plant and equipment	(1,519)	(2,299)
Proceeds from sale of property, plant and equipment	42	4
Net cash used in investing activities	(1,477)	(2,295)
Financing Activities:
Repayments of term loans		(1,250)
Proceeds from exercise of stock options		73
Purchase of treasury shares	(212)	(40,733)
Net cash used in financing activities	(212)	(41,910)
Net increase (decrease) in cash and cash equivalents	3,701	(37,086)
Cash and cash equivalents at beginning of period	29,787	53,372
Cash and cash equivalents at end of period	$ 33,488	$ 16,286