Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	At market equity offering program (2018 ATM)	Public Stock Offering	At Market Equity Offering Program (2020 ATM)	Common Stock	Common Stock At market equity offering program (2018 ATM)	Common Stock Public Stock Offering	Additional Paid-in Capital	Additional Paid-in Capital Public Stock Offering	Additional Paid-in Capital At Market Equity Offering Program (2020 ATM)	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balance at beginning of period (in shares) at Dec. 31, 2018					23,234,472
Balance at beginning of period at Dec. 31, 2018	$ 8,795				$ 3			$ 172,966			$ (8)	$ (164,166)
Increase (Decrease) in Stockholders' Equity
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
Purchase of common stock under ESPP (in shares)					140,073
Purchase of common stock under ESPP	489							489
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
Stock-based compensation expense	4,872							4,872
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
Issuance of stock (in shares)						10,900,599	9,200,000
Issuance of stock		$ 62,977	$ 163,991			$ 1	$ 1		$ 163,990
Purchase of common stock under ESPP (in shares)					80,267
Purchase of common stock under ESPP	561							561
Exercise of common stock warrant in exchange for common stock (in shares)					2,574,971
Exercise of stock options (in shares)					697,428
Exercise of stock options	3,138							3,138
Stock-based compensation expense	7,172							7,172
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
Issuance of stock				$ 43,087						$ 43,087
Purchase of common stock under ESPP (in shares)					78,253
Purchase of common stock under ESPP	$ 640							640
Exercise of stock options (in shares)	421,381				421,381
Exercise of stock options	$ 1,837							1,837
Stock-based compensation expense	18,409							18,409
Vesting of restricted stock units, net of employee tax obligation (in shares)					407,060
Vesting of restricted stock units, net of employee tax obligation	(259)							(259)
Net loss	(170,060)											(170,060)
Balance at end of period (in shares) at Dec. 31, 2021					73,709,056
Balance at end of period at Dec. 31, 2021	$ 121,741				$ 7			$ 572,213			$ 0	$ (450,479)