Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating results:
Total revenues	$ 53,765	$ 56,656	$ 53,617	$ 46,901	$ 49,299	$ 53,889	$ 51,984	$ 61,902	$ 210,939	$ 217,074	$ 190,355
Cost of product revenues	35,153	33,558	33,709	33,088	37,420	33,761	30,973	32,340	135,508	134,494	112,845
Cost of licensing and other revenues	1,572	1,054	850	612	580	500			4,088	1,080
Gross profit	17,040	22,044	19,058	13,201	11,299	19,628	21,011	29,562
Other expenses	61,956	47,087	46,095	50,232	49,012	46,283	43,526	39,167
Interest expense and other income (expense), net	(405)	(1,914)	(631)	1,117	(155)	741	(641)	920
Income tax expense	(181)	(162)	(64)	(47)	(39)	(103)			(454)	(142)
Net loss	$ (45,502)	$ (27,119)	$ (27,732)	$ (35,961)	$ (37,907)	$ (26,017)	$ (23,156)	$ (8,685)	$ (136,314)	$ (95,765)	$ (70,275)
Per share data:
Net loss - basic (in dollars per share)	$ (0.84)	$ (0.51)	$ (0.52)	$ (0.68)	$ (0.72)	$ (0.50)	$ (0.46)	$ (0.17)	$ (2.56)	$ (1.86)	$ (2.68)
Net loss - diluted (in dollars per share)	$ (0.87)	$ (0.51)	$ (0.52)	$ (0.70)	$ (0.72)	$ (0.50)	$ (0.46)	$ (0.17)	$ (2.56)	$ (1.86)	$ (2.68)