Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Net sales	$ 5,670	$ 4,177	$ 246
Cost of sales	3,187	1,002	0
Gross profit	2,483	3,175	246
Costs and expenses:
Research and development	27,638	22,301	29,564
Sales, general and administrative	55,214	45,058	37,183
Total costs and expenses	82,852	67,359	66,747
Loss from operations	(80,369)	(64,184)	(66,501)
Other income (expense):
Interest expense	(10,113)	0	0
Foreign currency exchange loss	(450)	(75)	(77)
Interest and dividend income	2,845	908	494
Interest expense	(28)	(184)	(23)
Total other income (expense), net	(7,746)	649	394
Net loss before income taxes	(88,115)	(63,535)	(66,107)
Provision for income taxes	(211)	(493)	(267)
Net loss	$ (88,326)	$ (64,028)	$ (66,374)
Basic and diluted net loss per share (dollars per share)	$ (1.62)	$ (1.18)	$ (1.29)
Weighted average shares outstanding (shares)	54,494	54,073	51,276
Other comprehensive loss:
Net loss	$ (88,326)	$ (64,028)	$ (66,374)
Net unrealized gain (loss) on available-for-sale investments	23	(117)	(64)
Foreign currency translation adjustment	(172)	321	(128)
Comprehensive loss	$ (88,475)	$ (63,824)	$ (66,566)