Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Net sales	$ 115,850	$ 111,547	$ 224,962	$ 220,256
Cost of sales	25,812	22,835	49,520	46,982
Gross profit	90,038	88,712	175,442	173,274
Sales and marketing	56,864	51,529	110,558	101,797
General and administrative	21,935	21,958	42,407	41,382
Research and development	8,980	7,891	18,209	14,828
Acquisition-related amortization and remeasurement (Note 13)	1,808	1,419	8,265	1,482
Operating income (loss)	451	5,915	(3,997)	13,785
Interest income (expense), net	457	(251)	200	(434)
Other expense, net	(236)	(3,643)	(640)	(731)
Income (loss) before income taxes	672	2,021	(4,437)	12,620
Income tax benefit (expense)	(1,219)	(1,096)	4,787	(6,469)
Net income (loss)	$ (547)	$ 925	$ 350	$ 6,151
Net income (loss) per common share:
Basic	$ (0.03)	$ 0.05	$ 0.02	$ 0.33
Diluted	$ (0.03)	$ 0.05	$ 0.02	$ 0.32
Weighted average number of common shares:
Basic	18,834,886	18,413,756	18,790,612	18,409,331
Diluted	18,834,886	18,835,560	19,179,057	18,811,356
Other comprehensive income (loss), before tax
Unrealized gain (loss) on debt security		$ 1,960	$ (2,593)	$ 1,960
Reclassification adjustment for amortization of historical unrealized gains on debt security	$ (689)		(689)
Currency translation adjustment	147	(1,175)	(302)	(478)
Other comprehensive income (loss) before tax	(542)	785	(3,584)	1,482
Income tax related to other comprehensive income (loss)	171	(432)	812	(432)
Other comprehensive income (loss), net of tax	(371)	353	(2,772)	1,050
Comprehensive income (loss)	$ (918)	$ 1,278	$ (2,422)	$ 7,201