Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Total revenues	$ 191,603	$ 196,129	$ 184,158
Costs and expenses
Cost of sales (excludes amortization of intangible assets of $6,485, $6,341, and $6,283, respectively)	73,414	71,688	74,180
Research and development	38,672	35,514	37,913
Sales and marketing	47,821	47,886	43,076
General and administrative	27,062	29,447	25,811
Amortization of intangible assets from acquired businesses and technology	9,073	8,856	8,828
Impairment loss	0	0	3,558
Total costs and expenses	196,042	193,391	193,366
Operating (loss) income	(4,439)	2,738	(9,208)
Interest expense, net	(11,760)	(12,035)	(1,775)
Loss before benefit for income taxes	(16,199)	(9,297)	(10,983)
Benefit for income taxes	(2,391)	(3,218)	(3,909)
Net loss	$ (13,808)	$ (6,079)	$ (7,074)
Basic and diluted loss per share	$ (0.42)	$ (0.18)	$ (0.21)
Shares used in basic and diluted per share calculation	32,708	34,104	34,451