Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning balance at Dec. 31, 2018	$ (122,588)		$ 2	$ 4,275		$ (126,865)
Temporary equity, Beginning balance, Shares at Dec. 31, 2018		18,670,328
Temporary equity, Beginning balance at Dec. 31, 2018		$ 152,806
Beginning balance, Shares at Dec. 31, 2018			1,824,852
Exercise of common stock warrants for cash	110			110
Exercise of common stock warrants for cash, Shares			50,331
Issuance of common stock upon net exercise of warrants	133			133
Issuance of common stock upon net exercise of warrants, Shares			101,744
Conversion of preferred stock to common stock upon initial public offering	152,806		$ 18	152,788
Temporary equity, Conversion of preferred stock to common stock upon initial public offering, Shares		(18,670,328)
Temporary equity, Conversion of preferred stock to common stock upon initial public offering		$ (152,806)
Conversion of preferred stock to common stock upon initial public offering, Shares			18,670,328
Conversion of Series A-1 warrants to common stock warrants upon initial public offering	789			789
Issuance of common stock in connection with initial/public offering	100,139		$ 7	100,132
Issuance of common stock in connection with initial/public offering, Shares			6,555,000
Issuance of common stock in connection with private placement	10,000		$ 1	9,999
Issuance of common stock in connection with private placement, Shares			588,235
Exercise of stock options	169			169
Exercise of stock options, Shares			80,515
Vesting of early exercised options	18			18
Offering cost related to the initial/public offering	(11,300)
Stock-based compensation	412			412
Settlement of fractional shares resulting from reverse stock split	(3)			(3)
Settlement of fractional shares resulting from reverse stock split, Shares			(114)
Net loss	(12,799)					(12,799)
Ending balance at Mar. 31, 2019	129,186		$ 28	268,822		(139,664)
Ending balance, shares at Mar. 31, 2019			27,870,891
Beginning balance at Dec. 31, 2018	(122,588)		$ 2	4,275		(126,865)
Temporary equity, Beginning balance, Shares at Dec. 31, 2018		18,670,328
Temporary equity, Beginning balance at Dec. 31, 2018		$ 152,806
Beginning balance, Shares at Dec. 31, 2018			1,824,852
Net loss	(36,364)
Ending balance at Sep. 30, 2019	108,250		$ 28	271,394	$ 57	(163,229)
Ending balance, shares at Sep. 30, 2019			28,255,893
Beginning balance at Mar. 31, 2019	129,186		$ 28	268,822		(139,664)
Beginning balance, Shares at Mar. 31, 2019			27,870,891
Issuance of common stock upon net exercise of warrants, Shares			79,208
Exercise of stock options	148			148
Exercise of stock options, Shares			73,608
Vesting of early exercised options	9			9
Offering cost related to the initial/public offering	(215)			(215)
Unrealized gain (loss) on available-for- sale securities	75				75
Stock-based compensation	818			818
Net loss	(10,608)					(10,608)
Ending balance at Jun. 30, 2019	119,413		$ 28	269,582	75	(150,272)
Ending balance, shares at Jun. 30, 2019			28,023,707
Exercise of stock options	706			706
Exercise of stock options, Shares			232,186
Unrealized gain (loss) on available-for- sale securities	(18)				(18)
Stock-based compensation	1,106			1,106
Net loss	(12,957)					(12,957)
Ending balance at Sep. 30, 2019	108,250		$ 28	271,394	57	(163,229)
Ending balance, shares at Sep. 30, 2019			28,255,893
Beginning balance at Dec. 31, 2019	192,653		$ 31	370,561	35	(177,974)
Beginning balance, Shares at Dec. 31, 2019			31,446,787
Exercise of stock options	1,113		$ 1	1,112
Exercise of stock options, Shares			356,128
Issuance of common stock under employee stock purchase plan	842			842
Issuance of common stock under employee stock purchase plan, Share			24,691
Unrealized gain (loss) on available-for- sale securities	68				68
Stock-based compensation	1,871			1,871
Net loss	(18,775)					(18,775)
Ending balance at Mar. 31, 2020	177,772		$ 32	374,386	103	(196,749)
Ending balance, shares at Mar. 31, 2020			31,827,606
Beginning balance at Dec. 31, 2019	$ 192,653		$ 31	370,561	35	(177,974)
Beginning balance, Shares at Dec. 31, 2019			31,446,787
Exercise of stock options, Shares	747,829
Net gain reclassified from accumulated other comprehensive income	$ (21)
Net loss	(49,825)
Ending balance at Sep. 30, 2020	237,047		$ 34	464,812		(227,799)
Ending balance, shares at Sep. 30, 2020			34,236,165
Beginning balance at Mar. 31, 2020	177,772		$ 32	374,386	103	(196,749)
Beginning balance, Shares at Mar. 31, 2020			31,827,606
Issuance of common stock in connection with initial/public offering	83,382		$ 2	83,380
Issuance of common stock in connection with initial/public offering, Shares			1,955,000
Exercise of stock options	480			480
Exercise of stock options, Shares			137,178
Offering cost related to the initial/public offering	(6,100)
Issuance of common stock in connection with vesting of restricted stock units, Shares			41,229
Restricted stock units withheld in net settlement for tax	(616)			(616)
Restricted stock units withheld in net settlement for tax, Shares			(15,456)
Unrealized gain (loss) on available-for- sale securities	(82)				(82)
Stock-based compensation	2,605			2,605
Net loss	(18,118)					(18,118)
Ending balance at Jun. 30, 2020	245,423		$ 34	460,235	21	(214,867)
Ending balance, shares at Jun. 30, 2020			33,945,557
Exercise of stock options	993			993
Exercise of stock options, Shares			254,523
Issuance of common stock under employee stock purchase plan	953			953
Issuance of common stock under employee stock purchase plan, Share			27,921
Offering cost related to the initial/public offering	(14)			(14)
Issuance of common stock in connection with vesting of restricted stock units, Shares			12,775
Restricted stock units withheld in net settlement for tax	(246)			(246)
Restricted stock units withheld in net settlement for tax, Shares			(4,611)
Stock-based compensation	2,891			2,891
Net gain reclassified from accumulated other comprehensive income	(21)				$ (21)
Net loss	(12,932)					(12,932)
Ending balance at Sep. 30, 2020	$ 237,047		$ 34	$ 464,812		$ (227,799)
Ending balance, shares at Sep. 30, 2020			34,236,165