Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Oct. 02, 2015
Cash flows from operating activities:
Net income	$ 18,962	$ 25,443
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation, depletion, and amortization	34,379	28,462
Amortization of deferred financing costs in interest expense	417	497
Stock-based compensation expense	2,880	4,518
(Gain) loss on sale of property, plant, and equipment	(601)	310
Deferred income tax (benefit) expense	(676)	3,841
Changes in assets and liabilities net of acquired assets and liabilities:
Decrease (increase) in accounts receivable	(19,781)	(1,583)
Decrease (increase) in inventory	3,294	9,928
Decrease (increase) in prepaid and other current assets	(956)	(1,965)
Increase (decrease) in accounts payable and accrued expenses	(2,207)	(19,299)
Increase (decrease) in unearned revenue	(2,546)	(773)
Increase (decrease) in interest and taxes payable	898	896
Increase (decrease) in long-term liabilities	(9,320)	(5,175)
Other-net	1,611	(256)
Net cash provided by operating activities	26,354	44,844
Cash flows from investing activities:
Payments for purchase of property, plant, and equipment	(20,052)	(24,085)
Payments for mine development	(8,934)	(16,972)
Proceeds from sale of property, plant, and equipment	1,366	43
Net cash used in investing activities	(27,620)	(41,014)
Cash flows from financing activities:
Proceeds from issuance of short-term debt, net	3,777	14,152
Proceeds from issuance of long-term debt	10,000	53,990
Repayment of long-term debt	(10,517)	(46,275)
Principal payments under capital lease obligations	(549)	(582)
Cash dividends paid	(5,601)	(5,331)
Deferred financing costs	(1,000)	0
Repurchase of common stock	(3,798)	(7,129)
Net cash (used in) provided by financing activities	(7,688)	8,825
Effects of exchange rate changes	524	(979)
Net change in cash and cash equivalents	(8,430)	11,676
Cash and cash equivalents at beginning of period	24,236	13,150
Cash and cash equivalents at end of period	$ 15,806	$ 24,826