CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
OPERATING ACTIVITIES:
Net income	$ 21,063	$ 15,454
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	12,646	13,011
Amortization of deferred financing costs	7	23
Deferred income taxes	3,999	1,119
Loss on disposition of property, plant and equipment	628	466
Stock-based compensation	1,104	1,144
Changes in operating assets and liabilities:
Trade receivables, net	(3,578)	(1,900)
Inventories, net	(391)	358
Prepaid expenses and other current assets	32	670
Other assets	85	118
Accounts payable and accrued expenses	681	1,566
Other liabilities	(96)	(191)
Net cash provided by operating activities	36,180	31,838
INVESTING ACTIVITIES:
Purchase of property, plant and equipment	(20,423)	(31,687)
Proceeds from sale of property, plant and equipment	195	460
Net cash used in investing activities	(20,228)	(31,227)
FINANCING ACTIVITIES:
Cash dividends paid	(2,273)	(2,267)
Proceeds from exercise of stock options	75	73
Purchase of treasury shares	(241)	(251)
Net cash used in financing activities	(2,439)	(2,445)
Net increase (decrease) in cash and cash equivalents	13,513	(1,834)
Cash and cash equivalents at beginning of period	67,218	85,000
Cash and cash equivalents at end of period	$ 80,731	$ 83,166