CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Operating Activities:
Net income	$ 12,171	$ 12,631
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	11,008	11,216
Amortization of deferred financing costs	34	34
Deferred income taxes	1,297	1,861
Loss on sale of property, plant and equipment	53	82
Stock-based compensation	684	822
Changes in operating assets and liabilities:
Trade receivables, net	(3,215)	(734)
Inventories	577	(1,631)
Prepaid expenses and other current assets	(80)	435
Other assets	3	3
Accounts payable and accrued expenses	1,515	435
Other liabilities	120	(267)
Net cash provided by operating activities	24,167	24,887
Investing Activities:
Purchase of property, plant and equipment	(6,690)	(6,489)
Proceeds from sale of property, plant and equipment	78	48
Net cash used in investing activities	(6,612)	(6,441)
Financing Activities:
Repayments of term loans	(3,750)	(3,750)
Purchase of treasury shares	(212)	(40,790)
Proceeds from exercise of stock options	21	75
Net cash used in financing activities	(3,941)	(44,465)
Net increase (decrease) in cash and cash equivalents	13,614	(26,019)
Cash and cash equivalents at beginning of period	29,787	53,372
Cash and cash equivalents at end of period	$ 43,401	$ 27,353