Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
OPERATING ACTIVITIES:
Net income	$ 14,800	$ 16,423	$ 22,186
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	14,498	15,044	13,781
Amortization of deferred financing costs	46	46	45
Deferred income taxes	1,793	2,131	3,654
Loss on sale of property, plant and equipment	86	145	96
Stock-based compensation	934	1,082	848
Changes in operating assets and liabilities:
Trade receivables, net	455	1,043	(1,756)
Inventories	439	(3,363)	(164)
Prepaid expenses and other current assets	(249)	392	18
Other assets	4	4	5
Accounts payable and accrued expenses	637	(1,086)	(294)
Other liabilities	89	(174)	88
Net cash provided by operating activities	33,532	31,687	38,507
INVESTING ACTIVITIES:
Purchase of property, plant and equipment	(8,921)	(8,292)	(9,413)
Proceeds from sale of property, plant and equipment	255	42	128
Net cash used in investing activities	(8,666)	(8,250)	(9,285)
FINANCING ACTIVITIES:
Repayments of term loans	(5,000)	(6,250)	(3,750)
Proceeds from exercise of stock options	34	75
Purchase of treasury shares	(212)	(40,847)	(8,323)
Net cash used in financing activities	(5,178)	(47,022)	(12,073)
Net increase (decrease) in cash and cash equivalents	19,688	(23,585)	17,149
Cash and cash equivalents at beginning of year	29,787	53,372	36,223
Cash and cash equivalents at end of year	$ 49,475	$ 29,787	$ 53,372