STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total		Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income/(Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2019	$ 51,113		$ 1	$ 468,285	$ 57	$ (417,230)
Beginning balance, shares at Dec. 31, 2019			45,523,088
Exercise of stock options	2,157			2,157
Exercise of stock options, shares			395,528
Stock-based compensation	4,013			4,013
Other comprehensive income (loss)	279				279
Net income (loss)	12,205					12,205
Ending balance at Mar. 31, 2020	69,767		$ 1	474,455	336	(405,025)
Ending balance, shares at Mar. 31, 2020			45,918,616
Beginning balance at Dec. 31, 2019	51,113		$ 1	468,285	57	(417,230)
Beginning balance, shares at Dec. 31, 2019			45,523,088
Other comprehensive income (loss)	(41)
Net income (loss)	(3,474)
Ending balance at Jun. 30, 2020	58,829		$ 1	479,516	16	(420,704)
Ending balance, shares at Jun. 30, 2020			46,190,070
Beginning balance at Mar. 31, 2020	69,767		$ 1	474,455	336	(405,025)
Beginning balance, shares at Mar. 31, 2020			45,918,616
Exercise of stock options	1,179			1,179
Exercise of stock options, shares			199,139
Issuance of common stock under the ESPP	369			369
Issuance of common stock under the ESPP, shares			72,315
Stock-based compensation	3,513			3,513
Other comprehensive income (loss)	(320)				(320)
Net income (loss)	(15,679)					(15,679)
Ending balance at Jun. 30, 2020	58,829		$ 1	479,516	16	(420,704)
Ending balance, shares at Jun. 30, 2020			46,190,070
Beginning balance at Dec. 31, 2020	49,803	[1]	$ 1	499,964	(47)	(450,115)
Beginning balance, shares at Dec. 31, 2020			48,251,819
Issuance of common stock in follow-on offering, net of issuance costs	107,712			107,712
Issuance of common stock in follow-on offering, net of issuance costs, shares			16,428,571
Exercise of stock options	1,023			1,023
Exercise of stock options, shares			322,507
Stock-based compensation	3,034			3,034
Other comprehensive income (loss)	4				4
Net income (loss)	(15,554)					(15,554)
Ending balance at Mar. 31, 2021	146,022		$ 1	611,733	(43)	(465,669)
Ending balance, shares at Mar. 31, 2021			65,002,897
Beginning balance at Dec. 31, 2020	$ 49,803	[1]	$ 1	499,964	(47)	(450,115)
Beginning balance, shares at Dec. 31, 2020			48,251,819
Exercise of stock options, shares	391,478
Other comprehensive income (loss)	$ 62
Net income (loss)	(34,797)
Ending balance at Jun. 30, 2021	130,953		$ 1	615,849	15	(484,912)
Ending balance, shares at Jun. 30, 2021			65,157,003
Beginning balance at Mar. 31, 2021	146,022		$ 1	611,733	(43)	(465,669)
Beginning balance, shares at Mar. 31, 2021			65,002,897
Exercise of stock options	173			173
Exercise of stock options, shares			68,971
Issuance of common stock under the ESPP	518			518
Issuance of common stock under the ESPP, shares			85,135
Stock-based compensation	3,425			3,425
Other comprehensive income (loss)	58				58
Net income (loss)	(19,243)					(19,243)
Ending balance at Jun. 30, 2021	$ 130,953		$ 1	$ 615,849	$ 15	$ (484,912)
Ending balance, shares at Jun. 30, 2021			65,157,003

[1] The condensed balance sheet as of December 31, 2020 was derived from the audited financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2020.