CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	ATM	Common Stock	Common Stock ATM	Additional Paid-in Capital	Additional Paid-in Capital ATM	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2019	$ 258,507		$ 4		$ 457,994		$ 183	$ (199,674)
Beginning balance, Shares at Dec. 31, 2019			45,116,742
Vesting of common stock from option exercises	12				12
Vesting of common stock from option exercises, Shares			15,542
Issuance of common stock from option exercises	135				135
Issuance of common stock from option exercises, Shares			34,311
Issuance of common stock pursuant to employee stock purchase plan	537				537
Issuance of common stock pursuant to employee stock purchase plan, Shares			39,471
Stock-based compensation	2,883				2,883
Other comprehensive loss	(202)						(202)
Net loss	(35,331)							(35,331)
Ending balance at Mar. 31, 2020	226,541		$ 4		461,561		(19)	(235,005)
Ending balance, Shares at Mar. 31, 2020			45,206,066
Beginning balance at Dec. 31, 2020	195,995		$ 5		524,358			(328,368)
Beginning balance, Shares at Dec. 31, 2020			50,265,575
Vesting of common stock from option exercises	4				4
Vesting of common stock from option exercises, Shares			1,011
Issuance of common stock from option exercises	$ 143				143
Issuance of common stock from option exercises, Shares	55,277		55,277
Issuance of common stock pursuant to employee stock purchase plan	$ 446				446
Issuance of common stock pursuant to employee stock purchase plan, Shares			48,792
Issuance of common stock, net of discounts and issuance costs		$ 1,454				$ 1,454
Issuance of common stock, net of discounts and issuance costs, Shares		114,914		114,914
Stock-based compensation	3,883				3,883
Other comprehensive loss	(23)						(23)
Net loss	(1,073)							(1,073)
Ending balance at Mar. 31, 2021	$ 200,829		$ 5		$ 530,288		$ (23)	$ (329,441)
Ending balance, Shares at Mar. 31, 2021			50,485,569