CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Net sales	$ 3,588,000	$ 2,271,000	$ 8,056,000	$ 5,827,000
Cost of sales	2,287,000	1,117,000	4,745,000	2,940,000
Gross profit	1,301,000	1,154,000	3,311,000	2,887,000
Costs and expenses:
Research and development	5,001,000	6,064,000	16,191,000	19,145,000
Sales, general and administrative	11,465,000	12,743,000	35,738,000	38,302,000
Total costs and expenses	16,466,000	18,807,000	51,929,000	57,447,000
Loss from operations	(15,165,000)	(17,653,000)	(48,618,000)	(54,560,000)
Other income (expense):
Interest expense	(3,955,000)	(3,598,000)	(11,540,000)	(10,585,000)
Foreign currency exchange gain (loss)	229,000	(89,000)	191,000	(142,000)
Interest income	149,000	676,000	753,000	2,329,000
Other expense, net	(15,000)	(9,000)	(82,000)	(12,000)
Total other expense, net	(3,592,000)	(3,020,000)	(10,678,000)	(8,410,000)
Net loss before income taxes	(18,757,000)	(20,673,000)	(59,296,000)	(62,970,000)
Provision for income taxes	0	239,000	0	0
Net loss	$ (18,757,000)	$ (20,434,000)	$ (59,296,000)	$ (62,970,000)
Basic and diluted net loss per share (usd per share)	$ (0.33)	$ (0.37)	$ (1.07)	$ (1.16)
Weighted average shares outstanding (shares)	56,560	54,553	55,617	54,456
Other comprehensive loss:
Net loss	$ (18,757,000)	$ (20,434,000)	$ (59,296,000)	$ (62,970,000)
Net unrealized gain (loss) on debt securities available-for-sale	(117,000)	10,000	62,000	229,000
Foreign currency translation adjustment	71,000	(113,000)	90,000	(139,000)
Comprehensive loss	$ (18,803,000)	$ (20,537,000)	$ (59,144,000)	$ (62,880,000)