CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Operating Activities:
Net income	$ 4,624	$ 4,813
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	3,640	3,414
Amortization of deferred financing costs	11	11
Deferred income taxes	500	581
Loss (gain) on sale of property, plant and equipment	10	(7)
Stock-based compensation	262	205
Changes in operating assets and liabilities:
Trade receivables	(1,523)	(4,563)
Inventories	(206)	299
Prepaid expenses and other current assets	37	153
Other assets	5	2
Accounts payable and accrued expenses	(74)	482
Other liabilities	(167)	31
Net cash provided by operating activities	7,119	5,421
Investing Activities:
Purchase of property, plant and equipment	(2,299)	(1,741)
Proceeds from sale of property, plant and equipment	4	13
Net cash used in investing activities	(2,295)	(1,728)
Financing Activities:
Repayments of term loans	(1,250)	(1,250)
Proceeds from exercise of stock options	73
Purchase of treasury shares	(40,733)	(80)
Net cash used in financing activities	(41,910)	(1,330)
Net (decrease) increase in cash and cash equivalents	(37,086)	2,363
Cash and cash equivalents at beginning of period	53,372	36,223
Cash and cash equivalents at end of period	$ 16,286	$ 38,586