Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net income	$ 41,721	$ 19,707	$ 24,664
Adjustments to reconcile net income to net cash provided from operating activities:
Depreciation, depletion, and amortization	42,721	41,649	37,046
Amortization of deferred financing costs in interest expense	795	679	649
Stock-based compensation expense	5,446	5,741	5,889
Deferred tax (benefit) expense	(5,495)	(2,442)	(2,462)
Changes in assets and liabilities net of acquired assets and liabilities:
Decrease (increase) in accounts receivable	(2,066)	12,116	(4,716)
Decrease (increase) in inventory	(30,412)	(8,241)	(18,880)
Decrease (increase) in prepaid and other current assets	(191)	6,647	483
Increase (decrease) in accounts payable and accrued expenses	6,164	(7,739)	1,472
Increase (decrease) in unearned revenue	4,401	(1,064)	(1,491)
Increase (decrease) in interest and taxes payable	1,161	2,391	(2,324)
Increase (decrease) in long-term liabilities	(7,348)	6,879	(5,053)
Other — net	3,384	(401)	3,343
Net cash provided from operating activities	60,281	75,922	38,620
Cash flows from investing activities:
Payments for purchase of property, plant, and equipment	(29,312)	(27,848)	(34,088)
Payments for mine development	(1,247)	(4,776)	(10,573)
Reimbursement for capital spending under government contract	0	0	991
Payments for purchase of business less cash received	0	0	(3,894)
Proceeds from sale of property, plant, and equipment	3,090	22	0
Other investments — net	(2)	15	4,201
Net cash (used in) investing activities	(27,471)	(32,587)	(43,363)
Cash flows from financing activities:
Proceeds from issuance (repayment) of short-term debt	(6,291)	(13,692)	8,594
Proceeds from issuance of long-term debt	33,332	70,423	32,403
Repayment of long-term debt	(38,945)	(86,036)	(27,986)
Principal payments under capital lease obligations	(666)	(657)	(749)
Cash dividends paid	(6,865)	(6,497)	(4,615)
Deferred financing costs	0	(1,587)	0
Repurchase of common stock	(22,282)	0	(119)
Issuance of common stock under stock option plans	359	1,163	158
Tax benefit from stock compensation realization	477	711	817
Net cash (used in) provided from financing activities	(40,881)	(36,172)	8,503
Effects of exchange rate changes	(1,553)	(445)	41
Net change in cash and cash equivalents	(9,624)	6,718	3,801
Cash and cash equivalents at beginning of period	22,774	16,056	12,255
Cash and cash equivalents at end of period	$ 13,150	$ 22,774	$ 16,056