Related Party - Gilead Sciences, Inc. - Additional Information (Details) $ / shares in Units, shares in Millions	1 Months Ended			3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2023 USD ($) Program shares	May 31, 2023 USD ($) Program	Oct. 31, 2022	Sep. 30, 2023 USD ($) $ / shares	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) $ / shares	Sep. 30, 2022 USD ($)	Dec. 31, 2021 USD ($) Program shares	Dec. 31, 2020 USD ($) shares
Related Party Transaction [Line Items]
Common stock share value				$ 5,000,000
Amended Investor Rights Agreement
Related Party Transaction [Line Items]
Lockup period			2 years
Extended lockup period			3 years
Gilead Collaboration Agreement
Related Party Transaction [Line Items]
Option payment upon completion of certain IND-enabling activities								$ 60,000,000
Option payment upon achievement of certain development milestones								$ 150,000,000
Amended Gilead Collaboration Agreement
Related Party Transaction [Line Items]
Number of exercise option to programs | Program								3
Option payments received								$ 725,000,000
Removal of option continuation payment under agreement								$ 100,000,000
Option payment upon achievement of certain development milestones		$ 150,000,000
Number of programs, eligible to receive regulatory and commercial milestone payments | Program		2
Related Party
Related Party Transaction [Line Items]
Percentage of outstanding common stock held				19.80%		19.80%
Related Party | Research and Development
Related Party Transaction [Line Items]
Reimbursement from related party for shared costs				$ 22,000,000	$ 27,000,000	$ 89,000,000	$ 93,000,000
Related Party | Purchase Agreement
Related Party Transaction [Line Items]
Issuance of common stock (in shares) | shares	1.0							5.7	6.0
Funds received for stock purchase agreement									$ 200,000,000
Purchase price of common stock allocation to performance obligation									$ 91,000,000
Common stock share value	$ 20,000,000							$ 220,000,000
Percentage of premium purchase price of common stock						20.00%
Weighted average closing price of our common stock on grant date (in dollars per share) | $ / shares				$ 33.54		$ 33.54
Trailing days average closing price						5 days
Related Party | Purchase Agreement | Maximum
Related Party Transaction [Line Items]
Right to purchase additional outstanding voting common stock percentage				35.00%		35.00%
Related Party | Gilead Collaboration Agreement
Related Party Transaction [Line Items]
Collaboration term for current and future clinical programs									10 years
Option continuation payment due upon sixth anniversary of agreement									$ 100,000,000
Upfront cash payment									$ 175,000,000
Option fee per program for all other programs entering clinical development to exercise option								$ 150,000,000
Number of research programs								2
Revenue recognized				$ 28,000,000	$ 31,000,000	$ 82,000,000	$ 73,000,000
Related Party | Gilead Collaboration Agreement | Maximum
Related Party Transaction [Line Items]
Potential regulatory approval milestones payment receivable related to domvanalimab								$ 500,000,000
Related Party | Amended Gilead Collaboration Agreement
Related Party Transaction [Line Items]
Upfront cash payment	$ 35,000,000	$ 17,500,000
Number of research programs | Program	2
Option payment upon completion of certain IND-enabling activities		45,000,000
Related Party | Amended Gilead Collaboration Agreement | Maximum
Related Party Transaction [Line Items]
Regulatory and commercial milestone payments received		$ 375,000,000