Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue:
Product and service	$ 21,453	$ 16,915	$ 59,882	$ 50,990
Collaboration	7,163	10,101	16,818	28,682
Total revenue	28,616	27,016	76,700	79,672
Costs and expenses:
Cost of product and service revenue	9,291	7,305	25,538	22,692
Research and development	16,651	11,374	45,068	33,213
Selling, general and administrative	17,810	18,380	57,897	54,590
Total costs and expenses	43,752	37,059	128,503	110,495
Loss from operations	(15,136)	(10,043)	(51,803)	(30,823)
Other income (expense):
Interest income	384	252	826	549
Interest expense	(1,631)	(1,556)	(4,798)	(4,585)
Other income (expense), net	(46)	(12)	(330)	185
Total other income (expense), net	(1,293)	(1,316)	(4,302)	(3,851)
Net loss before provision for income tax	(16,429)	(11,359)	(56,105)	(34,674)
Provision for income tax	(57)	(45)	(185)	(137)
Net loss	$ (16,486)	$ (11,404)	$ (56,290)	$ (34,811)
Net loss per share - basic and diluted (in dollars per share)	$ (0.56)	$ (0.45)	$ (2.09)	$ (1.50)
Weighted average shares used in computing basic and diluted net loss per share (in shares)	29,366	25,240	26,882	23,172