Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Cumulative Effect, Period of Adoption, Adjustment [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Balance (Accounting Standards Update 2014-09 [Member]) at Dec. 31, 2018	$ 238	$ 238
Balance at Dec. 31, 2018			$ 1,101	$ 780,400	$ (297)	$ (731,969)	$ 49,235
Net loss						(108,897)	(108,897)
Other comprehensive income (loss)					336		336
Exercise of stock options, net			3	832			835
Employee stock purchase plan			1	403			404
Issuance of common stock, net			436	58,064			58,500
Issuance of pre-funded warrants				19,882			19,882
Stock-based compensation expense				17,719			17,719
Balance at Dec. 31, 2019			1,541	877,300	39	(840,628)	38,252
Net loss						(182,814)	(182,814)
Other comprehensive income (loss)					(36)		(36)
Exercise of stock options, net			5	1,809			1,814
Employee stock purchase plan			3	629			632
Issuance of common stock, net			220	93,059			93,279
Issuance of pre-funded warrants				14,817			14,817
Stock-based compensation expense				14,794			14,794
Balance at Dec. 31, 2020			1,769	1,002,408	3	(1,023,442)	(19,262)
Net loss						(184,062)	(184,062)
Other comprehensive income (loss)					174		174
Exercise of stock options, net			33	13,772			13,805
Employee stock purchase plan			3	1,986			1,989
Issuance of common stock, net			38	45,692			45,730
Stock-based compensation expense				34,640			34,640
Balance at Dec. 31, 2021			$ 1,843	$ 1,098,498	$ 177	$ (1,207,504)	$ (106,986)