Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Activities:
Net income	$ 12,886	$ 19,367	$ 14,800
Adjustments to reconcile net income to net cash provided by operations:
Depreciation, depletion and amortization	16,033	14,903	14,498
Amortization of deferred financing costs	29	34	46
Deferred income taxes	(227)	1,059	1,793
Loss on sale of property, plant and equipment	39	78	86
Stock-based compensation	1,199	1,102	934
Changes in operating assets and liabilities:
Trade receivables, net	1,555	(3,347)	455
Inventories, net	(1,292)	252	439
Prepaid expenses and other current assets	698	(882)	(249)
Other assets	(47)	16	4
Accounts payable and accrued expenses	198	(952)	637
Other liabilities	1,423	344	89
Net cash provided by operating activities	32,494	31,974	33,532
Investing Activities:
Purchase of property, plant and equipment	(11,459)	(11,672)	(8,921)
Acquisition of assets of a business	(50)	(3,705)
Proceeds from sale of property, plant and equipment	449	316	255
Net cash used in investing activities	(11,060)	(15,061)	(8,666)
Financing Activities:
Repayment of term loans	(16,667)	(5,000)	(5,000)
Cash dividends paid	(2,798)	(2,790)
Proceeds from exercise of stock options	28		34
Purchase of treasury shares	(403)	(266)	(212)
Net cash used in financing activities	(19,840)	(8,056)	(5,178)
Net increase in cash and cash equivalents	1,594	8,857	19,688
Cash and cash equivalents at beginning of year	58,332	49,475	29,787
Cash and cash equivalents at end of year	$ 59,926	$ 58,332	$ 49,475