Organization - Additional Information (Details) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended	9 Months Ended
	Feb. 28, 2021 USD ($) $ / shares shares	Jan. 31, 2021	Mar. 31, 2021 shares	Sep. 30, 2021 USD ($) shares	Dec. 31, 2020 USD ($) shares	Sep. 30, 2020 shares	Jun. 30, 2020 shares	Mar. 31, 2020 shares	Dec. 31, 2019 shares
Description Of Organization [Line Items]
Entity incorporation, date of Incorporation				Jul. 13, 2018
Reverse stock split, conversion ratio		0.25
Reverse stock split, description				In January 2021, the Company’s board of directors approved an amendment to the Company’s amended and restated certificate of incorporation to effect a 1-for-4 reverse stock split of shares of the Company’s common and convertible preferred stock, which was effected on January 27, 2021.
Proceeds from public offering of common stock, net of offering costs				$ 626,405
Convertible preferred stock, shares outstanding | shares				0	134,113,000
Accumulated deficit				$ 674,629	$ 429,432
Cash, cash equivalents and marketable securities				866,100
Success payment liabilities				131,800
Contingent consideration				$ 80,700
Convertible Preferred Stock
Description Of Organization [Line Items]
Convertible preferred stock, shares outstanding | shares				0	134,113,000	134,113,000	134,113,000	106,890,000	106,890,000
Common Stock
Description Of Organization [Line Items]
Conversion of preferred stock into common stock (in shares) | shares			134,113,000
IPO
Description Of Organization [Line Items]
Convertible preferred stock, shares outstanding | shares	134,100,000
IPO | Convertible Preferred Stock
Description Of Organization [Line Items]
Conversion of preferred stock into common stock (in shares) | shares	134,100,000
Carrying value of converted preferred stock	$ 852,900
IPO | Common Stock
Description Of Organization [Line Items]
Issuance of common stock in initial public offering, net of offering costs (in shares) | shares	27,000,000.0		27,025,000
Common stock price per share | $ / shares	$ 25.00
Proceeds from public offering of common stock, net of offering costs	$ 626,400
Payments of underwriting discounts and commissions	45,200
Offering expenses	$ 4,000
Underwriters' Option To Purchase Additional Shares | Common Stock
Description Of Organization [Line Items]
Issuance of common stock in initial public offering, net of offering costs (in shares) | shares	3,500,000