Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue:
Revenue	$ 106,732	$ 114,905	$ 86,489
Total revenue	106,732	114,905	86,489
Costs and expenses:
Cost of product and service revenue	36,331	31,880	30,245
Research and development	61,599	46,888	34,720
Selling, general and administrative	78,195	74,334	62,700
Total costs and expenses	176,125	153,102	127,665
Loss from operations	(69,393)	(38,197)	(41,176)
Other income (expense):
Interest income	1,331	809	390
Interest expense	(7,431)	(6,153)	(5,672)
Other income (expense)	(1,658)	183	(515)
Total other income (expense)	(7,758)	(5,161)	(5,797)
Net loss before provision for income taxes	(77,151)	(43,358)	(46,973)
Provision for income taxes	(249)	(204)	(116)
Net loss	$ (77,400)	$ (43,562)	$ (47,089)
Net loss per share-basic and diluted (in dollars per share)	$ (2.78)	$ (1.84)	$ (2.34)
Weighted average shares used in computing basic and diluted net loss per share (in shares)	27,883	23,731	20,116