CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Net sales	$ 1,750	$ 801
Cost of sales	916	492
Gross profit	834	309
Costs and expenses:
Research and development	6,933	6,782
Sales, general and administrative	12,723	14,353
Total costs and expenses	19,656	21,135
Loss from operations	(18,822)	(20,826)
Other income (expense):
Interest expense	(3,459)	(158)
Foreign currency exchange (loss) gain	(59)	55
Interest income	842	301
Other expense (net)	(2)	0
Total other (expense) income, net	(2,678)	198
Net loss before income taxes	(21,500)	(20,628)
Provision for income taxes	(221)	(184)
Net loss	$ (21,721)	$ (20,812)
Basic and diluted net loss per share (usd per share)	$ (0.40)	$ (0.37)
Weighted average shares outstanding (shares)	54,337	55,640
Other comprehensive loss:
Net loss	$ (21,721)	$ (20,812)
Net unrealized gain (loss) on available-for-sale investments	121	(53)
Foreign currency translation adjustment	(76)	112
Comprehensive loss	$ (21,676)	$ (20,753)