Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 29, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net income	$ 21,708	$ 10,363
Adjustments to reconcile net income to net cash provided from (used in) operating activities:
Depreciation, depletion, and amortization	18,349	20,725
Amortization of deferred financing costs in interest expense	514	440
Non-cash compensation expense	5,412	5,816
Deferred income tax expense	429	658
Changes in assets and liabilities net of acquired assets and liabilities:
Decrease (increase) in accounts receivable	(12,060)	(30,882)
Decrease (increase) in inventories	10,428	(6,498)
Decrease (increase) in prepaid and other current assets	4,928	(9,267)
Increase (decrease) in accounts payable and accrued expenses	(14,189)	15,519
Increase (Decrease) in Unearned Revenue	2,132	1,685
Increase (decrease) in interest and taxes payable	2,084	(1,115)
Domestic pension plan contributions	(13,000)	(4,000)
Other-net	2,569	(3,141)
Net cash used in operating activities	29,304	303
Cash flows from investing activities:
Payments for purchase of property, plant, and equipment	(17,153)	(11,252)
Payments for mine development	(3,425)	(509)
Payments for acquisition	0	(16,504)
Proceeds from sale of property, plant, and equipment	27	27
Net cash used in investing activities	(20,551)	(28,238)
Cash flows from financing activities:
Proceeds from issuance of short-term debt	0	2,387
Proceeds from issuance of long-term debt	0	45,000
Repayment of long-term debt	(383)	(25,362)
Principal payments under capital lease obligations	(425)	(383)
Cash dividends paid	(4,137)	(3,899)
Deferred financing costs	0	(300)
Repurchase of common stock	0	(1,086)
Payments of withholding taxes for stock-based compensation awards	(2,765)	(2,302)
Net cash (used in) provided by financing activities	(7,710)	14,055
Effects of exchange rate changes	8	913
Net change in cash and cash equivalents	1,051	(12,967)
Cash and cash equivalents at beginning of period	41,844	31,464
Cash and cash equivalents at end of period	$ 42,895	$ 18,497