Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue:
Total revenue	$ 8,335	$ 10,500	$ 4,666
Costs and expenses:
Research and development	16,326	14,489	23,733
Selling, general and administrative	27,304	25,697	22,757
Total costs and expenses	60,393	55,590	58,518
Loss from operations	(52,058)	(45,090)	(53,852)
Interest expense, net	(7,348)	(6,682)	(8,907)
Other income, net	400	619	331
Net loss and comprehensive loss	$ (59,006)	$ (51,153)	$ (62,428)
Net loss per share — basic and diluted	$ (1.30)	$ (1.26)	$ (1.94)
Weighted-average number of common shares used in computing net loss per share — basic and diluted	45,507,754	40,558,826	32,131,512
Product [Member]
Revenue:
Total revenue	$ 5,327	$ 4,805	$ 3,440
Costs and expenses:
Cost of product revenue	16,763	15,404	12,028
Research [Member]
Revenue:
Total revenue	563	$ 5,695	$ 1,226
Contribution [Member]
Revenue:
Total revenue	$ 2,445