Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Series A Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]
Stockholders Equity, Beginning Balance at Dec. 31, 2017	$ 94,726		$ 52	$ 718,751	$ (624,077)
Stockholders Equity, Beginning Balance, Shares at Dec. 31, 2017			1,309,856
Issuance of common stock for exercise of stock options	180			180
Issuance of common stock for exercise of stock options, Shares			3,014
Stock-based compensation	6,796			6,796
Issuance of common stock	45,996		$ 22	45,974
Issuance of common stock, Shares			546,250
Issuance of common stock warrant	116			116
Net loss	(53,335)				(53,335)
Stockholders Equity, Ending Balance at Dec. 31, 2018	94,479		$ 74	771,817	(677,412)
Stockholders Equity, Ending Balance, Shares at Dec. 31, 2018			1,859,120
Issuance of common stock for exercise of stock options	445			445
Issuance of common stock for exercise of stock options, Shares			8,056
Stock-based compensation	5,695			5,695
Issuance of convertible voting preferredstock, net of offering costs	74,001	$ 1		74,000
Issuance of convertible voting preferredstock, net of offering costs, Share		103,000
Net loss	(88,275)				(88,275)
Stockholders Equity, Ending Balance at Dec. 31, 2019	86,345	$ 1	$ 74	851,957	(765,687)
Stockholders Equity, Ending Balance, Shares at Dec. 31, 2019		103,000	1,867,176
Conversion of Series A convertible voting preferred stock to common stock		$ (1)	$ 8	(7)
Conversion of Series A convertible voting preferred stock to common stock, Shares		(103,000)	7,803,273
Reclassification of warrant liabilities to equity	62,175			62,175
Issuance of common stock in connection with an amendment to the asset purchase agreement	8,782		$ 1	8,781
Number of shares issued in connection with an amendment to asset purchase agreement			725,283
Reverse stock split adjustment			$ (73)	73
Stock-based compensation	9,470			9,470
Issuance of common stock	8,901		$ 1	8,900
Issuance of common stock, Shares			732,752
Issuance of common stock warrant	3,188			3,188
Net loss	(80,902)				(80,902)
Stockholders Equity, Ending Balance at Dec. 31, 2020	$ 97,959		$ 11	$ 944,537	$ (846,589)
Stockholders Equity, Ending Balance, Shares at Dec. 31, 2020			11,128,484