Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Net sales	$ 9,297	$ 5,670	$ 4,177
Cost of sales	4,897	3,187	1,002
Gross profit	4,400	2,483	3,175
Costs and expenses:
Research and development	25,345	27,638	22,301
Sales, general and administrative	51,886	55,214	45,058
Total costs and expenses	77,231	82,852	67,359
Loss from operations	(72,831)	(80,369)	(64,184)
Other income (expense):
Interest expense	(14,256)	(10,113)	0
Foreign currency exchange loss	(124)	(450)	(75)
Interest and dividend income	2,809	2,845	908
Other expense, net	(14)	(28)	(184)
Total other income (expense), net	(11,585)	(7,746)	649
Net loss before income taxes	(84,416)	(88,115)	(63,535)
Benefit (provision) for income taxes	111	(211)	(493)
Net loss	$ (84,305)	$ (88,326)	$ (64,028)
Basic and diluted net loss per share (dollars per share)	$ (1.55)	$ (1.62)	$ (1.18)
Weighted average shares outstanding (shares)	54,506	54,494	54,073
Other comprehensive loss:
Net loss	$ (84,305)	$ (88,326)	$ (64,028)
Net unrealized gain (loss) on available-for-sale investments	193	23	(117)
Foreign currency translation adjustment	(102)	(172)	321
Comprehensive loss	$ (84,214)	$ (88,475)	$ (63,824)