Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Net sales		$ 75,498	$ 77,029	$ 190,311	$ 190,281
Cost of sales		41,850	38,651	97,792	90,158
Gross profit		33,648	38,378	92,519	100,123
Operating expenses:
Selling and marketing		22,084	23,628	58,847	61,293
General and administrative		6,327	7,315	13,237	14,801
Research and development		4,035	3,586	8,536	7,497
Total operating expenses		32,446	34,529	80,620	83,591
Operating income		1,202	3,849	11,899	16,532
Other income (expense):
Interest income		294	175	566	306
Interest expense		(268)	(412)	(561)	(856)
Other, net		31	110	18	63
Total other income (expense), net		57	(127)	23	(487)
Income from continuing operations before income taxes		1,259	3,722	11,922	16,045
Income tax expense		252	1,156	2,775	5,294
Income from continuing operations		1,007	2,566	9,147	10,751
Discontinued operations:
Loss from discontinued operations before income taxes		(11)	(29)	(28)	(1,655)
Income tax expense (benefit) of discontinued operations		68	48	132	(486)
Loss from discontinued operations		(79)	(77)	(160)	(1,169)
Net income		$ 928	$ 2,489	$ 8,987	$ 9,582
Earnings Per Share, Basic [Abstract]
Basic income per share from continuing operations (in dollars per share)		$ 0.03	$ 0.08	$ 0.30	$ 0.35
Basic loss per share from discontinued operation (in dollars per share)		0	0	(0.01)	(0.04)
Basic net income per share (in dollars per share)	[1]	0.03	0.08	0.30	0.31
Earnings Per Share, Diluted [Abstract]
Diluted income per share from continuing operations (in dollars per share)		0.03	0.08	0.30	0.35
Diluted loss per share from discontinued operation (in dollars per share)		0	0	(0.01)	(0.04)
Diluted net income per share (in dollars per share)		$ 0.03	$ 0.08	$ 0.29	$ 0.31
Shares used in per share calculations:
Basic (in shares)		30,193	30,755	30,253	30,734
Diluted (in shares)		30,476	31,095	30,533	31,110

[1] May not add due to rounding.