CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Operating Activities:
Net income	$ 12,631	$ 17,671
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	11,216	10,378
Amortization of deferred financing costs	34	34
Deferred income taxes	1,861	3,489
Loss on disposition of property, plant and equipment	82	102
Stock-based compensation	822	623
Changes in operating assets and liabilities:
Trade receivables	(734)	(4,903)
Inventories	(1,631)	1,097
Prepaid expenses and other current assets	435	116
Other assets	3	9
Accounts payable and accrued expenses	435	101
Other liabilities	(267)	386
Net cash provided by operating activities	24,887	29,103
Investing Activities:
Purchase of property, plant and equipment	(6,489)	(7,075)
Proceeds from sale of property, plant and equipment	48	129
Net cash used in investing activities	(6,441)	(6,946)
Financing Activities:
Repayments of term loans	(3,750)	(3,750)
Purchase of treasury shares	(40,790)	(8,256)
Proceeds from exercise of stock options	75
Net cash used in financing activities	(44,465)	(12,006)
Net (decrease) increase in cash and cash equivalents	(26,019)	10,151
Cash and cash equivalents at beginning of period	53,372	36,223
Cash and cash equivalents at end of period	$ 27,353	$ 46,374