Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		12 Months Ended
	Feb. 28, 2021	May 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2022
Class Of Stock [Line Items]
Common stock, shares authorized			400,000,000.0		400,000,000.0
Preferred stock, shares authorized			10,000,000.0		10,000,000.0
Net proceeds from public offering after deducting underwriting discounts, commissions and other offering expenses			$ 220	$ 434
Common stock share value				$ 326
Preferred stock, shares outstanding			0		0
Stock Purchase Agreement | Gilead
Class Of Stock [Line Items]
Common stock shares issued	5,700,000			6,000,000.0
Shares issued, price per share	$ 39.00			$ 33.54
Net proceeds from public offering after deducting underwriting discounts, commissions and other offering expenses				$ 108
Common stock share value	$ 220		$ 220	107
Funds received for purchase of common stock				200
Purchase price of common stock allocation to performance obligation				91
Deferred offering expenses				$ 2
May 2020 Public Offering
Class Of Stock [Line Items]
Common stock shares issued		12,700,000
Shares issued, price per share		$ 27.50
Net proceeds from public offering after deducting underwriting discounts, commissions and other offering expenses		$ 326
Base Shares
Class Of Stock [Line Items]
Common stock shares issued		11,000,000.0
Underwriters Option Exercise
Class Of Stock [Line Items]
Common stock shares issued		1,700,000