Consolidated Statements of Shareholders' Deficit - USD ($) $ in Thousands	Total	Preferred Stock Series C-1 Convertible Preferred Stock	Preferred Stock Series F Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Additional Paid-in Capital Cumulative Effect, Period of Adoption, Adjustment	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment
Beginning Balance at Dec. 31, 2018	$ 35,921	$ 3,906	$ 2,737	$ 3	$ 950,258		$ (920,983)
Beginning Balance (in shares) at Dec. 31, 2018		4	3	26,259
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	23,733				23,733
Issuance of common stock under 2013 Equity Plan	31				31
Issuance of common stock under 2013 Equity Plan (in shares)				5
Issuance of common stock under ESPP	833				833
Issuance of common stock under ESPP (in shares)				149
Issuance of common stock for conversion of Series F Preferred Stock			$ (2,737)		2,737
Issuance of common stock for conversion of Series F Preferred Stock (in shares)			(3)	782
Net loss	(116,508)						(116,508)
Ending Balance at Dec. 31, 2019	(55,990)	$ 3,906		$ 3	977,432	$ (160)	(1,037,331)	$ 160
Ending Balance (in shares) at Dec. 31, 2019		4		27,195
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	6,207				6,207
Issuance of common stock under 2013 Equity Plan	$ 605				605
Issuance of common stock under 2013 Equity Plan (in shares)	94,219			94
Issuance of common stock under ESPP	$ 512				512
Issuance of common stock under ESPP (in shares)				114
Net loss	(39,421)						(39,421)
Ending Balance at Dec. 31, 2020	$ (88,087)	$ 3,906		$ 3	$ 984,756		$ (1,076,752)
Ending Balance (in shares) at Dec. 31, 2020		4		27,403