CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	ATM	Private Placement	Follow On Offering	Common Stock	Common Stock ATM	Common Stock Private Placement	Common Stock Follow On Offering	Additional Paid-in Capital	Additional Paid-in Capital ATM	Additional Paid-in Capital Private Placement	Additional Paid-in Capital Follow On Offering	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2018	$ 196,355				$ 3				$ 292,187				$ (77)	$ (95,758)
Beginning balance, Shares at Dec. 31, 2018					37,358,526
Issuance of common stock, net of discounts and issuance costs		$ 22,409		$ 134,524				$ 1		$ 22,409		$ 134,523
Issuance of common stock, net of discounts and issuance costs, Shares						1,105,000		6,388,889
Issuance of common stock pursuant to employee stock purchase plan	829								829
Issuance of common stock pursuant to employee stock purchase plan, Shares					55,234
Vesting of common stock from option exercises	60								60
Vesting of common stock from option exercises, Shares					94,816
Issuance of common stock from option exercises	351								351
Issuance of common stock from option exercises, Shares					114,277
Stock-based compensation	7,635								7,635
Other comprehensive gain (loss)	260												260
Net loss	(103,916)													(103,916)
Ending balance at Dec. 31, 2019	258,507				$ 4				457,994				183	(199,674)
Ending balance, Shares at Dec. 31, 2019					45,116,742
Issuance of common stock, net of discounts and issuance costs			$ 51,979				$ 1				$ 51,978
Issuance of common stock, net of discounts and issuance costs, Shares						0	5,000,000
Issuance of common stock pursuant to employee stock purchase plan	938								938
Issuance of common stock pursuant to employee stock purchase plan, Shares					83,848
Vesting of common stock from option exercises	24								24
Vesting of common stock from option exercises, Shares					18,575
Issuance of common stock from option exercises	$ 176								176
Issuance of common stock from option exercises, Shares	46,410				46,410
Stock-based compensation	$ 13,248								13,248
Other comprehensive gain (loss)	(183)												$ (183)
Net loss	(128,694)													(128,694)
Ending balance at Dec. 31, 2020	$ 195,995				$ 5				$ 524,358					$ (328,368)
Ending balance, Shares at Dec. 31, 2020					50,265,575