CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Net sales	$ 2,342,000	$ 1,750,000
Cost of sales	1,287,000	916,000
Gross profit	1,055,000	834,000
Costs and expenses:
Research and development	5,842,000	6,933,000
Sales, general and administrative	12,943,000	12,723,000
Total costs and expenses	18,785,000	19,656,000
Loss from operations	(17,730,000)	(18,822,000)
Other income (expense):
Interest expense	(3,749,000)	(3,459,000)
Foreign currency exchange loss	(128,000)	(59,000)
Interest income	380,000	842,000
Other expense, net	(82,000)	(2,000)
Total other expense, net	(3,579,000)	(2,678,000)
Net loss before income taxes	(21,309,000)	(21,500,000)
Provision for income taxes	0	(221,000)
Net loss	$ (21,309,000)	$ (21,721,000)
Basic and diluted net loss per share (usd per share)	$ (0.39)	$ (0.40)
Weighted average shares outstanding (shares)	54,837	54,337
Other comprehensive loss:
Net loss	$ (21,309,000)	$ (21,721,000)
Net unrealized gain on debt securities available-for-sale	223,000	121,000
Foreign currency translation adjustment	(15,000)	(76,000)
Comprehensive loss	$ (21,101,000)	$ (21,676,000)