Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Cash flows from operating activities:
Income from continuing operations		$ 15,110		$ 27,625	[1],[2]	$ 35,101	[1],[2]
Loss from discontinued operations		(452)		(1,358)	[1],[2]	(923)	[1],[2]
Net income		14,658		26,267	[1],[2]	34,178	[1],[2]
Adjustments to reconcile net income to net cash provided by operating activities:
Asset impairment charge		0		8,800	[1],[2]	0	[1],[2]
Depreciation and amortization		8,942		8,643	[2]	7,874	[2]
Bad debt expense		27		311	[2]	289	[2]
Inventory lower-of-cost-or-market/NRV adjustments		558		1,067	[2]	245	[2]
Stock-based compensation expense		1,981		1,856	[2]	2,613	[2]
Loss on asset disposals		32		56	[2]	147	[2]
Deferred income taxes, net of valuation allowances		3,229		(8,556)	[2]	9,510	[2]
Excess tax benefit related to stock-based awards		0		0	[2]	(1,857)	[2]
Other		133		(117)	[2]	5	[2]
Changes in operating assets and liabilities:
Trade receivables		(3,030)		2,516	[2]	(694)	[2]
Inventories		(15,634)		(7,526)	[2]	(3,110)	[2]
Prepaids and other current assets		(495)		1,080	[2]	(1,415)	[2]
Income taxes receivable		(5,636)		3,214	[2]	(2,792)	[2]
Trade payables		19,312		449	[2]	6,464	[2]
Accrued liabilities, including warranty obligations		(2,826)		(3,044)	[2]	(5,606)	[2]
Net cash provided by operating activities		21,251		35,016	[2]	45,851	[2]
Cash flows from investing activities:
Acquisition of business, net of cash acquired		(2,750)		0	[2]	(3,468)	[2]
Purchases of property, plant and equipment and intangible assets		(10,380)		(3,792)	[2]	(4,656)	[2]
Purchases of available-for-sale-securities		(29,522)		(88,413)	[2]	(34,739)	[2]
Proceeds from maturities of available-for-sale securities		61,365		62,939	[2]	32,923	[2]
Proceeds from sales of available-for-sale securities		0		0	[2]	71	[2]
Net cash provided by (used in) investing activities		18,713		(29,266)	[2]	(9,869)	[2]
Cash flows from financing activities:
Payments on long-term debt		16,000		16,000	[2]	16,000	[2]
Proceeds from employee stock purchases		444		487	[2]	381	[2]
Tax payments related to stock award issuances		366		560	[2]	356	[2]
Excess tax benefit related to stock-based awards		(396)		(741)	[2]	(239)	[2]
Excess tax benefit related to stock-based awards		0		0	[2]	1,857	[2]
Payments for stock repurchases		(12,996)		(11,055)	[2]	(5,390)	[2]
Net cash used in financing activities		(28,582)		(26,749)	[2]	(19,035)	[2]
Effect of exchange rate changes on cash and cash equivalents		(1,150)		1,018	[2]	149	[2]
Increase (decrease) in cash and cash equivalents		10,232		(19,981)	[2]	17,096	[2]
Beginning of year	[2]	27,893	[3]	47,874		30,778
End of year		38,125		27,893	[2],[3]	47,874	[2]
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net		8,885		11,630	[2]	11,511	[2]
Cash paid for interest		1,044		1,545	[2]	1,920	[2]
Capital expenditures incurred but not yet paid		$ 1,220		$ 404	[2]	$ 210	[2]

[1] See Note 4.

[2] See Note 4.

[3] See Note 4.