CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Net sales	$ 2,125,000	$ 1,806,000	$ 4,468,000	$ 3,557,000
Cost of sales	1,171,000	907,000	2,459,000	1,823,000
Gross profit	954,000	899,000	2,009,000	1,734,000
Costs and expenses:
Research and development	5,347,000	6,149,000	11,189,000	13,083,000
Sales, general and administrative	11,332,000	12,837,000	24,275,000	25,559,000
Total costs and expenses	16,679,000	18,986,000	35,464,000	38,642,000
Loss from operations	(15,725,000)	(18,087,000)	(33,455,000)	(36,908,000)
Other income (expense):
Interest expense	(3,835,000)	(3,528,000)	(7,584,000)	(6,987,000)
Foreign currency exchange gain (loss)	91,000	6,000	(37,000)	(53,000)
Interest income	224,000	812,000	604,000	1,653,000
Other income (expense), net	15,000	(1,000)	(67,000)	(3,000)
Total other expense, net	(3,505,000)	(2,711,000)	(7,084,000)	(5,390,000)
Net loss before income taxes	(19,230,000)	(20,798,000)	(40,539,000)	(42,298,000)
Provision for income taxes	0	(17,000)	0	(238,000)
Net loss	$ (19,230,000)	$ (20,815,000)	$ (40,539,000)	$ (42,536,000)
Basic and diluted net loss per share (usd per share)	$ (0.35)	$ (0.38)	$ (0.74)	$ (0.78)
Weighted average shares outstanding (shares)	55,445	54,476	55,139	54,407
Other comprehensive loss:
Net loss	$ (19,230,000)	$ (20,815,000)	$ (40,539,000)	$ (42,536,000)
Net unrealized gain (loss) on debt securities available-for-sale	(44,000)	98,000	179,000	219,000
Foreign currency translation adjustment	34,000	50,000	19,000	(26,000)
Comprehensive loss	$ (19,240,000)	$ (20,667,000)	$ (40,341,000)	$ (42,343,000)