Statements of Changes in Redeemable Convertible Preferred Stock and Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Series Seed Preferred Stock	Series A Preferred Stock	Series B Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2018	$ (18,417)				$ 1	$ 2,496	$ (20,914)
Balance, temporary equity, shares at Dec. 31, 2018		6,480,000	8,997,085
Balance, temporary equity at Dec. 31, 2018		$ 3,524	$ 76,186
Balance, shares at Dec. 31, 2018					7,209,000
Issuance of Preferred Stock				$ 49,834
Issuance of Preferred Stock, shares				3,958,046
Stock-based compensation	3,017					3,017
Conversion of convertible preferred stock into common stock upon the closing of initial public offering	129,543	$ (3,524)	$ (76,186)	$ (49,834)	$ 1	129,542
Conversion of convertible preferred stock into common stock upon the closing of initial public offering, shares		(6,480,000)	(8,997,085)	(3,958,046)	19,435,131
Issuance of common stock upon closing of initial public offering, net of issuance costs	113,215				$ 1	113,214
Issuance of common stock upon closing of initial public offering, net of issuance costs, shares					7,353,000
Exercise of stock options	17					17
Exercise of stock options, shares					101,688
Net loss	(45,347)						(45,347)
Balance at Sep. 30, 2019	182,028				$ 3	248,286	(66,261)
Balance, shares at Sep. 30, 2019					34,098,819
Balance at Jun. 30, 2019	201,039				$ 3	246,998	(45,962)
Balance, shares at Jun. 30, 2019					34,021,194
Stock-based compensation	1,276					1,276
Exercise of stock options	12					12
Exercise of stock options, shares					77,625
Net loss	(20,299)						(20,299)
Balance at Sep. 30, 2019	182,028				$ 3	248,286	(66,261)
Balance, shares at Sep. 30, 2019					34,098,819
Balance at Dec. 31, 2019	$ 165,342				$ 3	249,441	(84,102)
Balance, shares at Dec. 31, 2019	34,138,750				34,138,750
Stock-based compensation	$ 6,358					6,358
Conversion of convertible preferred stock into common stock upon the closing of initial public offering, shares					19,435,131
Exercise of stock options	138					138
Exercise of stock options, shares					106,683
Net loss	(59,262)						(59,262)
Net unrealized gain on investments	4							$ 4
Balance at Sep. 30, 2020	$ 112,580				$ 3	255,937	(143,364)	4
Balance, shares at Sep. 30, 2020	34,245,433				34,245,433
Balance at Jun. 30, 2020	$ 128,656				$ 3	253,430	(124,777)	(1)
Balance, shares at Jun. 30, 2020					34,214,851
Stock-based compensation	2,477					2,477
Exercise of stock options	30					30
Exercise of stock options, shares					30,582
Net loss	(18,587)						(18,587)
Net unrealized gain on investments	5							5
Balance at Sep. 30, 2020	$ 112,580				$ 3	$ 255,937	$ (143,364)	$ 4
Balance, shares at Sep. 30, 2020	34,245,433				34,245,433