Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net sales	$ 4,177	$ 246	$ 147
Cost of sales	1,002	0	0
Gross profit	3,175	246	147
Costs and expenses:
Research and development	22,301	29,564	27,142
Sales, general and administrative	45,058	37,183	18,554
Total costs and expenses	67,359	66,747	45,696
Loss from operations	(64,184)	(66,501)	(45,549)
Other income (expense):
Interest expense	0	0	(4)
Foreign currency exchange loss	(75)	(77)	(19)
Interest and dividend income	908	494	74
Interest expense	(184)	(23)	0
Total other income, net	649	394	51
Net loss before income taxes	(63,535)	(66,107)	(45,498)
Provision for income taxes	(493)	(267)	0
Net loss	$ (64,028)	$ (66,374)	$ (45,498)
Basic and diluted net loss per share (dollars per share)	$ (1.18)	$ (1.29)	$ (1.01)
Weighted average shares outstanding (shares)	54,073	51,276	44,998
Other comprehensive loss:
Net loss	$ (64,028)	$ (66,374)	$ (45,498)
Net unrealized loss on available-for-sale investments	(117)	(64)	(20)
Foreign currency translation adjustment	321	(128)	1
Comprehensive loss	$ (63,824)	$ (66,566)	$ (45,517)