Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	[1]
Income Statement [Abstract]
Net sales	$ 91,057	$ 88,132	$ 281,368	$ 278,413
Cost of sales	52,551	46,817	150,343	136,975
Gross profit	38,506	41,315	131,025	141,438
Operating expenses:
Selling and marketing	20,635	18,028	79,482	79,321
General and administrative	7,503	6,305	20,740	21,106
Research and development	4,208	3,617	12,744	11,114
Total operating expenses	32,346	27,950	112,966	111,541
Operating income	6,160	13,365	18,059	29,897
Other income (expense):
Interest income	269	170	835	476
Interest expense	(244)	(377)	(805)	(1,233)
Other, net	188	46	206	109
Total other income (expense), net	213	(161)	236	(648)
Income from continuing operations before income taxes	6,373	13,204	18,295	29,249
Income tax expense	1,870	4,862	4,645	10,156
Income from continuing operations	4,503	8,342	13,650	19,093
Discontinued operations:
Loss from discontinued operations before income taxes	(159)	(40)	(187)	(1,695)
Income tax expense (benefit) of discontinued operations	35	61	167	(425)
Loss from discontinued operations	(194)	(101)	(354)	(1,270)
Net income	$ 4,309	$ 8,241	$ 13,296	$ 17,823	[2]
Earnings Per Share, Basic [Abstract]
Basic income per share from continuing operations (in dollars per share)	$ 0.15	$ 0.27	$ 0.45	$ 0.62
Basic loss per share from discontinued operation (in dollars per share)	(0.01)	0	(0.01)	(0.04)
Basic net income per share (in dollars per share)	0.14	0.27	0.44	0.58
Earnings Per Share, Diluted [Abstract]
Diluted income per share from continuing operations (in dollars per share)	0.15	0.27	0.45	0.61
Diluted loss per share from discontinued operation (in dollars per share)	(0.01)	0	(0.01)	(0.04)
Diluted net income per share (in dollars per share)	$ 0.14	$ 0.27	$ 0.44	$ 0.57
Shares used in per share calculations:
Basic (in shares)	30,185	30,749	30,230	30,739
Diluted (in shares)	30,433	31,075	30,500	31,098

[1] See Note 2.

[2] See Note 2.