Quarterly Results of Operations (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 39,232	$ 38,231	$ 39,479	$ 36,671	$ 38,847	$ 37,150	$ 38,327	$ 33,264	$ 153,612	$ 147,588	$ 132,257
Gross Profit	23,717	27,036	24,132	26,906	29,408	23,577	28,507	24,295	51,821	41,801	32,750
Operating expenses	45,483	36,370	36,282	36,569	40,539	32,504	32,279	29,611	154,704	134,933	109,875
Net loss	$ (15,293)	$ (10,917)	$ (13,001)	$ (11,213)	$ (14,782)	$ (13,938)	$ (8,993)	$ 5,295	$ (50,424)	$ (32,418)	$ (16,068)
Basic loss per share (in USD per share)	$ (0.22)	$ (0.16)	$ (0.19)	$ (0.17)	$ (0.22)	$ (0.21)	$ (0.14)	$ 0.08
Diluted loss per share (in USD per share)	$ (0.22)	$ (0.16)	$ (0.19)	$ (0.17)	$ (0.22)	$ (0.21)	$ (0.14)	$ 0.08