Related party - Gilead Sciences, Inc. - Additional Information (Details) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended		3 Months Ended		12 Months Ended
	Oct. 31, 2022	Jan. 31, 2022 USD ($)	Mar. 31, 2023 USD ($) Program $ / shares	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($) Program shares	Dec. 31, 2020 USD ($) shares
Research and Development
Related Party Transaction [Line Items]
Reimbursed under cost-sharing provisions of arrangement			$ 33	$ 30
Gilead Collaboration Agreement
Related Party Transaction [Line Items]
Option payment upon completion of certain IND-enabling activities			60
Option payment upon achievement of certain development milestones			$ 150
Amended Investor Rights Agreement
Related Party Transaction [Line Items]
Lockup period	2 years
Extended lockup period	3 years
Amended Gilead Collaboration Agreement
Related Party Transaction [Line Items]
Number of exercise option to programs | Program					3
Option payments received		$ 725
Removal of option continuation payment under agreement					$ 100
Gilead
Related Party Transaction [Line Items]
Percentage of outstanding common stock held			18.90%
Gilead | Research and Development
Related Party Transaction [Line Items]
Reimbursed under cost-sharing provisions of arrangement			$ 33	30
Gilead | Gilead Collaboration Agreement
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
Option continuation payment due upon fourth anniversary of agreement						100
Option continuation payment due upon sixth anniversary of agreement						100
Option Continuation Payment Due Upon Eighth Anniversary of Agreement						100
Upfront cash payment						175
Option fee per program for all other programs entering clinical development to exercise option						150
Number of research programs | Program			2
Revenue recognized			$ 25	$ 16
Gilead | Gilead Collaboration Agreement | Maximum
Related Party Transaction [Line Items]
Potential regulatory approval milestones payment receivable related to domvanalimab						$ 500
Gilead | Stock Purchase Agreement
Related Party Transaction [Line Items]
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 | $ / shares			$ 33.54
Issuance of common stock, shares | shares					5.7	6.0
Issuance of common stock					$ 220
Funds received for purchase of common stock						$ 200
Purchase price of common stock allocation to performance obligation						$ 91
Gilead | Stock Purchase Agreement | Maximum
Related Party Transaction [Line Items]
Right to purchase additional outstanding voting common stock percentage			35.00%