Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative effect adjustment for adoption of ASC 606	At market equity offering program (2018 ATM)	Public Stock Offering	Common Stock	Common Stock At market equity offering program (2018 ATM)	Common Stock Public Stock Offering	Additional Paid-in Capital	Additional Paid-in Capital At market equity offering program (2018 ATM)	Additional Paid-in Capital Public Stock Offering	Accumulated Other Comprehensive Loss	Accumulated Deficit	Accumulated Deficit Cumulative effect adjustment for adoption of ASC 606
Balance at beginning of period (in shares) at Dec. 31, 2017					22,765,017
Balance at beginning of period at Dec. 31, 2017	$ 69,994	$ (2,031)			$ 3			$ 168,018			$ (149)	$ (97,878)	$ (2,031)
Increase (Decrease) in Stockholders' Equity
Exercise of stock options (in shares)					427,269
Exercise of stock options	918							918
Purchase of common stock under ESPP (in shares)					42,186
Purchase of common stock under ESPP	146							146
Stock-based compensation expense	3,884							3,884
Other comprehensive income (loss)	141										141
Net loss	(64,257)											(64,257)
Balance at end of period (in shares) at Dec. 31, 2018					23,234,472
Balance at end of period at Dec. 31, 2018	$ 8,795				$ 3			172,966			(8)	(164,166)
Increase (Decrease) in Stockholders' Equity
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201409Member
Purchase of common stock under ESPP (in shares)					140,073
Purchase of common stock under ESPP	$ 489							489
Stock-based compensation expense	4,872							4,872
Issuance of stock (in shares)					24,437,500
Issuance of stock	92,162				$ 2			92,160
Exercise of stock options and warrants (in shares)					150,978
Exercise of stock options and warrants	175							175
Retirement of common stock in exchange for common stock warrant (in shares)					(2,575,000)
Retirement of common stock in exchange for common stock warrant	(8,986)							(8,986)
Issuance of common stock warrant in exchange for retirement of common stock	8,986							8,986
Other comprehensive income (loss)	33										33
Net loss	(28,208)											(28,208)
Balance at end of period (in shares) at Dec. 31, 2019					45,388,023
Balance at end of period at Dec. 31, 2019	78,318				$ 5			270,662			25	(192,374)
Increase (Decrease) in Stockholders' Equity
Stock issuance, Discounts And Commissions On Transaction	$ 5,587
Exercise of stock options (in shares)	697,428				697,428
Exercise of stock options	$ 3,138							3,138
Purchase of common stock under ESPP (in shares)					80,267
Purchase of common stock under ESPP	561							561
Stock-based compensation expense	7,172							7,172
Issuance of stock (in shares)						10,900,599	9,200,000
Issuance of stock			$ 62,977	$ 163,991		$ 1	$ 1		$ 62,976	$ 163,990
Exercise of common stock warrant in exchange for common stock (in shares)					2,574,971
Other comprehensive income (loss)	(25)										(25)
Net loss	(88,045)											(88,045)
Balance at end of period (in shares) at Dec. 31, 2020					68,841,288
Balance at end of period at Dec. 31, 2020	$ 228,087				$ 7			$ 508,499			$ 0	$ (280,419)
Increase (Decrease) in Stockholders' Equity
Stock issuance, Discounts And Commissions On Transaction			$ 2,176	$ 10,809