CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Net sales	$ 2,271,000	$ 1,355,000	$ 5,827,000	$ 3,848,000
Cost of sales	1,117,000	680,000	2,940,000	1,889,000
Gross profit	1,154,000	675,000	2,887,000	1,959,000
Costs and expenses:
Research and development	6,064,000	7,891,000	19,145,000	20,734,000
Sales, general and administrative	12,743,000	12,153,000	38,302,000	41,835,000
Total costs and expenses	18,807,000	20,044,000	57,447,000	62,569,000
Loss from operations	(17,653,000)	(19,369,000)	(54,560,000)	(60,610,000)
Other income (expense):
Interest expense	(3,598,000)	(3,357,000)	(10,585,000)	(6,720,000)
Foreign currency exchange loss	(89,000)	(133,000)	(142,000)	(331,000)
Interest income	676,000	908,000	2,329,000	1,983,000
Other expense, net	(9,000)	0	(12,000)	(25,000)
Total other expense, net	(3,020,000)	(2,582,000)	(8,410,000)	(5,093,000)
Net loss before income taxes	(20,673,000)	(21,951,000)	(62,970,000)	(65,703,000)
Benefit (provision) for income taxes	239,000	(147,000)	0	(432,000)
Net loss	$ (20,434,000)	$ (22,098,000)	$ (62,970,000)	$ (66,135,000)
Basic and diluted net loss per share (usd per share)	$ (0.37)	$ (0.41)	$ (1.16)	$ (1.21)
Weighted average shares outstanding (shares)	54,553	54,145	54,456	54,591
Other comprehensive loss:
Net loss	$ (20,434,000)	$ (22,098,000)	$ (62,970,000)	$ (66,135,000)
Net unrealized gain (loss) on available-for-sale investments	10,000	1,000	229,000	(54,000)
Foreign currency translation adjustment	(113,000)	(26,000)	(139,000)	(105,000)
Comprehensive loss	$ (20,537,000)	$ (22,123,000)	$ (62,880,000)	$ (66,294,000)