Organization and Basis of Presentation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands				17 Months Ended
	May 21, 2020	Feb. 12, 2019	Jan. 04, 2018	Feb. 28, 2019	Dec. 31, 2020	Dec. 31, 2019
Organization and Basis of Presentation [Line Items]
Sale of shares of common stock (in shares)	9,433,963
Offering price (in dollars per share)	$ 13.25
Retained earnings (accumulated deficit)					$ (577,530)	$ (334,170)
Funds raised through Series A and Series B Convertible Preferred Stock, convertible note financings and completed IPO				$ 942,000
2027 Notes
Organization and Basis of Presentation [Line Items]
Interest rate	5.00%
AA Biopharma Inc.
Organization and Basis of Presentation [Line Items]
Cash received in connection with acquisition			$ 12,800
Initial Public Offering ("IPO")
Organization and Basis of Presentation [Line Items]
Sale of shares of common stock (in shares)		19,837,500
Offering price (in dollars per share)		$ 16.00
Net proceeds, after deducting underwriting discounts, commissions, and offering expenses		$ 291,300