Related Party - Gilead Sciences, Inc. (Details) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2025 USD ($) $ / shares	Mar. 31, 2025 USD ($) shares	Sep. 30, 2024 USD ($)	Mar. 31, 2024 USD ($) shares	Sep. 30, 2025 USD ($) member $ / shares	Sep. 30, 2024 USD ($)	Dec. 31, 2023 USD ($) program	Dec. 31, 2021 USD ($) program	Dec. 31, 2020 USD ($)	Dec. 31, 2024 USD ($)
Related Party Transaction [Line Items]
Sale of stock, consideration received on transaction		$ 150.0
Number of programs, eligible to receive regulatory and commercial milestone payments | program							4
Revenue recognized from amounts in deferred revenue at the beginning of the period	$ 26.0		$ 33.0		$ 214.0	$ 212.0
Accounts payable, current	42.0				42.0					$ 18.0
Receivable from collaboration partners, current	$ 11.0				$ 11.0					20.0
Gilead
Related Party Transaction [Line Items]
Sale of stock, consideration received on transaction		$ 15.0
Gilead
Related Party Transaction [Line Items]
Sale of stock, number of shares acquired in transaction (in shares) | shares		1.4
Related Party
Related Party Transaction [Line Items]
Percentage of outstanding common stock held	29.30%				29.30%
Accounts payable, current	$ 29.0				$ 29.0					0.0
Receivable from collaboration partners, current	0.0				0.0					$ 6.0
Related Party | Research and Development
Related Party Transaction [Line Items]
Reimbursement from related party for shared costs	$ 16.0		(2.0)		$ 24.0	(32.0)
Purchase Agreement | Related Party
Related Party Transaction [Line Items]
Common stock shares issued (in shares) | shares				15.2
Funds received for stock purchase agreement				$ 320.0
Purchase price of common stock allocation to performance obligation				87.0
Percentage of premium purchase price of common stock					20.00%
Trailing days average closing price					5 days
Weighted average closing price of our common stock on grant date (in dollars per share) | $ / shares	$ 33.54				$ 33.54
Number of board members | member					3
Purchase Agreement | Related Party | Maximum
Related Party Transaction [Line Items]
Right to purchase additional outstanding voting common stock percentage	35.00%				35.00%
Gilead Collaboration Agreement
Related Party Transaction [Line Items]
Option payment upon completion of certain IND-enabling activities								$ 60.0
Option payment upon achievement of certain development milestones								150.0
Gilead Collaboration Agreement | Related Party
Related Party Transaction [Line Items]
Collaboration term for current and future clinical programs									10 years
Option continuation payment due upon second anniversary of agreement									$ 100.0
Option continuation payment due upon fourth anniversary of agreement				$ 100.0					100.0
Option continuation payment due upon sixth anniversary of agreement									100.0
Option continuation payment due upon eighth anniversary of agreement									100.0
Upfront cash payment									$ 175.0
Option fee per program for all other programs entering clinical development to exercise option								$ 150.0
Number of research programs | program								2
Revenue recognized from amounts in deferred revenue at the beginning of the period	$ 26.0		$ 30.0		$ 214.0	$ 207.0
Gilead Collaboration Agreement | Related Party | Maximum
Related Party Transaction [Line Items]
Potential regulatory approval milestones payment receivable related to domvanalimab								$ 500.0
Amended Gilead Collaboration Agreement
Related Party Transaction [Line Items]
Number of exercise option to programs | program								3
Option payments received								$ 725.0
Removal of option continuation payment under agreement								$ 100.0
Option payment upon achievement of certain development milestones							$ 150.0
Number of programs, eligible to receive regulatory and commercial milestone payments | program							2
Amended Gilead Collaboration Agreement | Related Party
Related Party Transaction [Line Items]
Upfront cash payment							$ 17.5
Number of research programs | program							2
Option payment upon completion of certain IND-enabling activities							$ 45.0
Total upfront cash payment							35.0
Amended Gilead Collaboration Agreement | Related Party | Maximum
Related Party Transaction [Line Items]
Regulatory and commercial milestone payments received							$ 375.0