Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating Activities
Net income	$ 37,547	$ 27,449	$ 13,986
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	12,312	13,407	11,397
Amortization of bond premiums	790	155	156
Provision for losses on accounts receivable, net of adjustments	141	(83)	(289)
Provision for excess and obsolete inventories	243	63	(50)
Share-based compensation	1,763	1,294	680
Excess tax benefits from stock options exercised and restricted stock awards vested	(843)	(393)	(211)
(Gain) loss on disposition of assets	(22)	4	1,802
Foreign currency transaction gain	67	(27)	(8)
Interest income on note receivable	(40)	(42)	0
Deferred income taxes	(1,594)	(2,028)	10,122
Write-off of note receivable	75	0	0
Changes in assets and liabilities:
Accounts receivable	4,662	(9,646)	6,053
Income tax receivable	464	9,715	(10,016)
Inventories	231	2,271	(1,296)
Prepaid expenses and other	436	(17)	(67)
Accounts payable	(5,197)	2,461	(2,751)
Deferred revenue	615	0	0
Accrued liabilities	1,942	6,584	(3,024)
Net cash provided by operating activities	53,592	51,167	26,484
Investing Activities
Capital expenditures	(9,041)	(14,147)	(35,914)
Proceeds from sale of property, plant and equipment	92	11	482
Investment in certificates of deposits	(9,108)	(6,540)	0
Maturities of certificates of deposits	3,600	1,300	1,503
Purchase of investments held to maturity	(22,275)	(11,654)	0
Maturities of investments	2,005	0	9,364
Proceeds from called investments	3,332	626	0
Principal payments from note receivable	69	69	27
Net cash used in investing activities	(31,326)	(30,335)	(24,538)
Financing Activities
Borrowings under revolving credit facility	8,325	34,847	82,078
Payments under revolving credit facility	(8,325)	(39,422)	(77,503)
Stock options exercised	1,467	1,996	494
Excess tax benefits from stock options exercised and restricted stock awards vested	843	393	211
Repurchase of stock	(8,222)	(6,660)	(3,671)
Cash dividends paid to stockholders	(7,428)	(8,840)	(5,935)
Net cash used in financing activities	(13,340)	(17,686)	(4,326)
Net increase (decrease) in cash and cash equivalents	8,926	3,146	(2,380)
Cash and cash equivalents, beginning of year	3,159	13	2,393
Cash and cash equivalents, end of year	$ 12,085	$ 3,159	$ 13