Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue:
Revenue, Product and Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Total revenue, net	$ 4,227	$ 1,990	$ 1,923
Costs and operating expenses:
Cost, Product and Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Cost of product revenue	$ 2,325	$ 465	$ 457
Research and development	41,091	36,915	30,880
Selling and marketing	24,491	4,942	17,000
General and administrative	22,122	18,786	15,509
Total costs and operating expenses	90,029	61,108	63,846
Loss from operations	(85,802)	(59,118)	(61,923)
Other income (expense):
Interest income	1,229	879	424
Interest expense	(6,101)	(1,739)	(1,892)
Change in fair value of derivative liability	4,310
Other income (expense), net	(8)		5
Total other income (expense), net	(570)	(860)	(1,463)
Net loss and comprehensive loss	$ (86,372)	$ (59,978)	$ (63,386)
Net loss per share, basic and diluted	$ (1.91)	$ (1.57)	$ (2.20)
Weighted average common shares outstanding, basic and diluted	45,273,231	38,115,142	28,818,196
Comprehensive loss:
Net loss	$ (86,372)	$ (59,978)	$ (63,386)
Other comprehensive loss:
Unrealized gain on marketable securities			5
Total other comprehensive income			5
Total comprehensive loss	$ (86,372)	$ (59,978)	$ (63,381)