Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Net sales	$ 113,499	$ 111,708	$ 338,461	$ 331,964
Cost of sales	24,896	24,020	74,416	71,002
Gross profit	88,603	87,688	264,045	260,962
Sales and marketing	54,805	49,898	165,363	151,695
General and administrative	21,090	22,276	63,497	63,658
Research and development	7,982	9,598	26,191	24,426
Acquisition-related amortization and remeasurement (Note 12)	23,608	2,009	31,873	3,491
Operating income (loss)	(18,882)	3,907	(22,879)	17,692
Interest income (expense), net	186	(181)	386	(615)
Other expense, net	(8,146)	(5,054)	(8,786)	(5,785)
Income (loss) before income taxes	(26,842)	(1,328)	(31,279)	11,292
Income tax benefit (expense)	(13,656)	117	(8,869)	(6,352)
Net income (loss)	$ (40,498)	$ (1,211)	$ (40,148)	$ 4,940
Net income (loss) per common share:
Basic	$ (2.14)	$ (0.07)	$ (2.13)	$ 0.26
Diluted	$ (2.14)	$ (0.07)	$ (2.13)	$ 0.26
Weighted average number of common shares:
Basic	18,957,876	18,562,204	18,847,728	18,460,848
Diluted	18,957,876	18,562,204	18,847,728	18,864,169
Other comprehensive income (loss), before tax
Unrealized gain (loss) on debt security		$ 1,240	$ (2,593)	$ 3,200
Reclassification adjustment for amortization of historical unrealized gains on debt security	$ (345)		(1,034)
Reclassification adjustment for other-than-temporary impairment on debt security	(5,193)		(5,193)
Currency translation adjustment	(1,893)	(844)	(2,195)	(1,322)
Other comprehensive income (loss) before tax	(7,431)	396	(11,015)	1,878
Income tax related to other comprehensive income (loss)	1,388	(366)	2,200	(798)
Other comprehensive income (loss), net of tax	(6,043)	30	(8,815)	1,080
Comprehensive income (loss)	$ (46,541)	$ (1,181)	$ (48,963)	$ 6,020