Stockholders' Equity (Details) - USD ($) $ in Thousands			1 Months Ended	9 Months Ended		12 Months Ended
	May 03, 2021	Apr. 05, 2021	Mar. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Sep. 11, 2020
Class of Stock [Line Items]
Reverse stock split				1-for-5
Common Stock, shares authorized upon the completion of the IPO				225,000,000		225,000,000	225,000,000
Total proceeds				$ 134,140	$ 139,760
Common stock, shares outstanding				60,017,333		51,626,508
Controlled Equity Offering SM Sales Agreement [Member]
Class of Stock [Line Items]
Total proceeds				$ 24,500
Company issued shares				3,818,300
Aggregate offering price of additional shares issued				$ 33,500
Controlled Equity Offering SM Sales Agreement [Member] | Cantor Fitzgerald & Co. [Member]
Class of Stock [Line Items]
Total proceeds				$ 40,000		$ 100,000
Company issued shares				2,397,791
Aggregate offering price of additional shares issued				$ 58,700
2021 Underwritten Public Offering [Member]
Class of Stock [Line Items]
Sale of additional shares of common stock	427,017
2021 Underwritten Public Offering [Member] | J.P. Morgan Securities LLC and Jefferies LLC [Member]
Class of Stock [Line Items]
Shares issued in public offering		5,000,000	5,000,000
Warrants to purchase common stock			750,000
Proceeds from sale of shares after offering costs			$ 94,200
2020 Equity Plan [Member]
Class of Stock [Line Items]
Shares available for future grant							7,000,000
Maximum [Member]
Class of Stock [Line Items]
Common stock, shares outstanding							210,900,000
Minimum [Member]
Class of Stock [Line Items]
Common stock, shares outstanding							42,200,000