Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue:
Revenue, Product and Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Total revenue, net	$ 1,569	$ 650	$ 4,178	$ 1,142
Costs and operating expenses:
Cost, Product and Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Cost of product revenue	$ 134	$ 552	$ 953	$ 680
Research and development	8,021	9,414	14,119	20,731
Selling and marketing	6,153	7,225	13,283	10,572
General and administrative	5,145	5,058	10,321	10,416
Total costs and operating expenses	19,453	22,249	38,676	42,399
Loss from operations	(17,884)	(21,599)	(34,498)	(41,257)
Other income (expense):
Interest income	17	379	156	708
Interest expense	(1,694)	(1,627)	(3,327)	(2,645)
Change in fair value of derivative liability	(17,007)	(1,606)	(20,411)	1,617
Total other income (expense), net	(18,684)	(2,854)	(23,582)	(320)
Net loss and comprehensive loss	$ (36,568)	$ (24,453)	$ (58,080)	$ (41,577)
Net loss per share, basic and diluted	$ (0.64)	$ (0.57)	$ (1.06)	$ (0.98)
Weighted average common shares outstanding, basic and diluted	57,368,292	42,910,084	54,634,572	42,582,501