CONDENSED CONSOLIDATEDSTATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Net sales	$ 801	$ 530
Cost of sales	492	26
Gross profit	309	504
Costs and expenses:
Research and development	6,782	4,288
Sales, general and administrative	14,353	10,526
Total costs and expenses	21,135	14,814
Loss from operations	(20,826)	(14,310)
Other income (expense):
Interest expense	(158)	0
Foreign currency exchange gain (loss)	55	(26)
Interest income	301	136
Total other income, net	198	110
Net loss before income taxes	(20,628)	(14,200)
Provision for income taxes	(184)	0
Net loss	$ (20,812)	$ (14,200)
Basic and diluted net loss per share (usd per share)	$ (0.37)	$ (0.27)
Weighted average shares outstanding (shares)	55,640	51,887
Other comprehensive loss:
Net loss	$ (20,812)	$ (14,200)
Net unrealized (loss) gain on available-for-sale investments	(53)	11
Foreign currency translation adjustment	112	56
Comprehensive loss	$ (20,753)	$ (14,133)