Quarterly Results of Operations (unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 38,847	$ 37,150	$ 38,327	$ 33,264	$ 35,249	$ 33,260	$ 33,964	$ 29,784	$ 147,588	$ 132,257	$ 105,946
Gross Profit	29,408	23,577	28,507	24,295	26,077	25,898	25,004	22,528	41,801	32,750	25,282
Operating expenses	40,539	32,504	32,279	29,611	27,217	28,116	27,524	27,018	134,933	109,875	102,555
Net loss	$ (14,782)	$ (13,938)	$ (8,993)	$ 5,295	$ (3,412)	$ (8,990)	$ 5,670	$ (9,335)	$ (32,418)	$ (16,068)	$ (35,774)
Basic loss per share (in USD per share)	$ (0.22)	$ (0.21)	$ (0.14)	$ 0.08	$ (0.05)	$ (0.14)	$ 0.09	$ (0.16)
Diluted loss per share (in USD per share)	$ (0.22)	$ (0.21)	$ (0.14)	$ 0.08	$ (0.05)	$ (0.14)	$ 0.09	$ (0.16)