Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 28, 2019	Jun. 29, 2018
Cash flows from operating activities:
Net income	$ 32,446	$ 21,708
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation, depletion, and amortization	22,607	18,349
Amortization of deferred financing costs in interest expense	472	514
Stock-based compensation expense (non-cash)	3,541	2,164
Deferred income tax expense (benefit)	4,578	429
Pension curtailment	3,296	0
Changes in assets and liabilities:
Decrease (increase) in accounts receivable	(11,778)	(12,060)
Decrease (increase) in inventory	1,306	10,428
Decrease (increase) in prepaid and other current assets	(588)	4,928
Increase (decrease) in accounts payable and accrued expenses	(18,813)	(14,189)
Increase (Decrease) in Unearned Revenue	(88)	2,132
Increase (decrease) in interest and taxes payable	(1,130)	2,084
Domestic pension plan contributions	(3,000)	(13,000)
Other-net	(2,803)	5,817
Net cash used in operating activities	30,046	29,304
Cash flows from investing activities:
Payments for purchase of property, plant, and equipment	(13,833)	(17,153)
Payments for mine development	(1,591)	(3,425)
Proceeds from sale of property, plant, and equipment	15	27
Net cash used in investing activities	(15,409)	(20,551)
Cash flows from financing activities:
Repayment of long-term debt	(397)	(383)
Principal payments under finance lease obligations	599	425
Cash dividends paid	(4,368)	(4,137)
Repurchase of common stock	(199)	0
Payments of withholding taxes for stock-based compensation awards	(4,763)	(2,765)
Net cash used in financing activities	(10,326)	(7,710)
Effects of exchange rate changes	(100)	8
Net change in cash and cash equivalents	4,211	1,051
Cash and cash equivalents at beginning of period	70,645	41,844
Cash and cash equivalents at end of period	$ 74,856	$ 42,895