Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Net sales	$ 24,165	$ 24,822	$ 77,179	$ 74,714
Cost of sales	6,910	7,245	22,458	22,269
Gross profit	17,255	17,577	54,721	52,445
Sales and marketing	6,622	6,201	20,504	19,754
General and administrative	3,983	4,562	13,227	12,857
Research and development	2,037	1,761	5,850	5,053
Gain on divestiture			(5,876)
Total operating expenses	12,642	12,524	33,705	37,664
Income from operations	4,613	5,053	21,016	14,781
Other income (expense):
Interest income	192	48	452	100
Foreign currency gain (loss)	(75)	(28)	(275)	(103)
Income before income taxes	4,730	5,073	21,193	14,778
Provision for income taxes	416	31	4,275	1,885
Net income	$ 4,314	$ 5,042	$ 16,918	$ 12,893
Earnings per share of common stock:
Basic	$ 0.22	$ 0.26	$ 0.87	$ 0.69
Diluted	$ 0.21	$ 0.25	$ 0.84	$ 0.65
Weighted-average shares outstanding:
Basic	19,503	19,124	19,369	18,589
Diluted	20,293	20,147	20,258	19,970
Cash dividends declared per common share	$ 0.070	$ 0.055	$ 0.210	$ 0.165