Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue:
Revenue, Product and Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember
Total revenue, net	$ 2,609	$ 492
Costs and operating expenses:
Cost, Product and Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember
Cost of product revenue	$ 819	$ 128
Research and development	6,098	11,317
Selling and marketing	7,130	3,347
General and administrative	5,176	5,358
Total costs and operating expenses	19,223	20,150
Loss from operations	(16,614)	(19,658)
Other income (expense):
Interest income	139	329
Interest expense	(1,633)	(1,018)
Change in fair value of derivative liability	(3,404)	3,223
Total other income (expense), net	(4,898)	2,534
Net loss and comprehensive loss	$ (21,512)	$ (17,124)
Net loss per share, basic	$ (0.41)	$ (0.41)
Weighted average common shares outstanding, basic	51,900,882	42,251,292
Net loss per share, diluted	$ (0.41)	$ (0.45)
Weighted average common shares outstanding, diluted	51,900,882	44,174,369