Condensed Consolidated Statements of Income and Comprehensive Income - USD ($) $ 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	$ 111,547	$ 108,942	$ 220,256	$ 211,680
Cost of sales	22,835	23,177	46,982	45,758
Gross profit	88,712	85,765	173,274	165,922
Sales and marketing	51,529	50,471	101,797	99,003
General and administrative	22,268	20,409	41,752	38,691
Research and development	7,891	6,887	14,828	14,311
Operating income	7,024	7,998	14,897	13,917
Interest income (expense), net	(251)	76	(434)	121
Other income (expense), net	(4,752)	585	(1,840)	(3,763)
Income before income taxes	2,021	8,659	12,623	10,275
Income tax expense	(1,088)	(3,924)	(6,461)	(7,848)
Net income from continuing operations	933	4,735	6,162	2,427
Discontinued operations (Note 6)
Loss from discontinued operations		(1,300)	(3)	(1,827)
Income tax benefit (expense)	(8)	418	(8)	599
Net loss from discontinued operations	(8)	(882)	(11)	(1,228)
Net income	$ 925	$ 3,853	$ 6,151	$ 1,199
Net income (loss) per common share—basic
Net income from continuing operations	$ 0.05	$ 0.26	$ 0.33	$ 0.13
Net loss from discontinued operations		(0.05)		(0.06)
Net income per common share—basic	0.05	0.21	0.33	0.07
Net income (loss) per common share—diluted
Net income from continuing operations	0.05	0.26	0.32	0.13
Net loss from discontinued operations		(0.05)		(0.06)
Net income per common share—diluted	$ 0.05	$ 0.21	$ 0.32	$ 0.07
Weighted average number of common shares:
Basic	18,413,756	18,050,551	18,409,331	18,015,308
Diluted	18,835,560	18,343,038	18,811,356	18,288,050
Other comprehensive income, before tax
Unrealized gain (loss) on debt securities	$ 1,960		$ 1,960	$ (3,220)
Reclassification adjustment for loss on debt securities in net income				5,585
Currency translation adjustment	(1,175)	$ 2,648	(478)	2,882
Other comprehensive income before tax	785	2,648	1,482	5,247
Income tax related to items of other comprehensive income	(432)		(432)	(900)
Other comprehensive income, net of tax	353	2,648	1,050	4,347
Comprehensive income	$ 1,278	$ 6,501	$ 7,201	$ 5,546