Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		12 Months Ended
	Jul. 13, 2020	Feb. 28, 2021	Jun. 30, 2020	Dec. 31, 2021	Dec. 31, 2020
Class Of Stock [Line Items]
Capital stock shares authorized				410,000,000
Common stock, shares authorized				400,000,000	400,000,000
Preferred stock, shares authorized				10,000,000	10,000,000
Common stock, par value				$ 0.0001	$ 0.0001
Preferred stock, par value				$ 0.0001	$ 0.0001
Net proceeds from public offering after deducting underwriting discounts, commissions and other offering expenses				$ 220,235	$ 433,776
Common stock share value					$ 326,246
Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock, shares outstanding				0	0
Stock Purchase Agreement | Gilead
Class Of Stock [Line Items]
Common stock shares issued	5,963,029	5,650,000			5,963,029
Shares issued, price per share	$ 33.54	$ 39.00			$ 33.54
Net proceeds from public offering after deducting underwriting discounts, commissions and other offering expenses	$ 107,500
Common stock share value	200,000	$ 220,400		$ 220,296	$ 107,468
Purchase price of common stock allocation to performance obligation	90,600				$ 90,600
Deferred offering expenses	$ 1,900
May 2020 Public Offering
Class Of Stock [Line Items]
Common stock shares issued			12,650,000
Shares issued, price per share			$ 27.50
Net proceeds from public offering after deducting underwriting discounts, commissions and other offering expenses			$ 326,200
Base Shares
Class Of Stock [Line Items]
Common stock shares issued			11,000,000
Underwriters Option Exercise
Class Of Stock [Line Items]
Common stock shares issued			1,650,000