License and Collaboration Agreements - Additional Information (Details)		1 Months Ended							3 Months Ended			9 Months Ended		12 Months Ended			61 Months Ended	62 Months Ended
	Jul. 13, 2020 USD ($) Program $ / shares shares	Oct. 31, 2022	Jan. 31, 2022 USD ($)	Nov. 30, 2021 USD ($) Program	Jan. 31, 2021 USD ($) $ / shares shares	Nov. 30, 2019 USD ($)	Sep. 30, 2017 USD ($)	Aug. 31, 2017 USD ($)	Sep. 30, 2022 USD ($) $ / shares	Sep. 30, 2021 USD ($) $ / shares	Mar. 31, 2021 USD ($)	Sep. 30, 2022 USD ($) $ / shares	Sep. 30, 2021 USD ($) $ / shares	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2017 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2022 USD ($)	Dec. 30, 2021 USD ($)
License And Collaboration Agreements [Line Items]
Total collaboration and license revenues									$ 33,581,000	$ 9,461,000		$ 78,345,000	$ 28,383,000
Net loss per share, basic | $ / shares									$ (0.90)	$ (1.11)		$ (2.78)	$ (3.28)
Net loss per share, diluted | $ / shares									$ (0.90)	$ (1.11)		$ (2.78)	$ (3.28)
Option continuation payment due upon second anniversary of agreement														$ 100,000,000.0
Deferred revenue recognized									$ 33,581,000	$ 9,461,000		$ 78,345,000	$ 28,383,000
Remaining capitalized fees at closing														3,800,000
Fees allocated among performance obligations														8,300,000
Contract with customer liability, noncurrent									382,584,000			382,584,000		462,217,000			$ 382,584,000	$ 382,584,000
Gilead
License And Collaboration Agreements [Line Items]
Fee incurred to third party upon receipt of option exercise payments														4,500,000
WuXi Biologics License Agreement
License And Collaboration Agreements [Line Items]
Clinical and regulatory milestones achieved												$ 16,500,000
Range of tiered royalty payments on net sales												high single-digits to low teens
WuXi Biologics License Agreement | Research and Development
License And Collaboration Agreements [Line Items]
Upfront cash payment																		500,000
Sub-license fees incurred																		11,300,000
Upfront and milestone payments																		41,000,000.0
Development milestone payments																		1,500,000
WuXi Biologics License Agreement | WuXi PD-1
License And Collaboration Agreements [Line Items]
Development milestone expense									0	0		$ 0	10,000,000.0
WuXi Biologics License Agreement | WuXi CD39
License And Collaboration Agreements [Line Items]
Development milestone expense									0	0		1,500,000	0
WuXi Biologics License Agreement | Maximum
License And Collaboration Agreements [Line Items]
Clinical, regulatory and commercialization milestone payments								$ 375,000,000.0
Abmuno License Agreement
License And Collaboration Agreements [Line Items]
Upfront and milestone payments												14,600,000
Clinical, regulatory and commercialization remaining milestone payments												93,000,000.0
Development milestone expense									0	0		0	5,000,000.0
Gilead Collaboration Agreement
License And Collaboration Agreements [Line Items]
Option payment upon completion of certain IND-enabling activities	$ 60,000,000.0
Option payment upon achievement of certain development milestones	150,000,000.0
Total collaboration and license revenues									8,900,000			13,100,000
Deferred revenue									$ 485,900,000			$ 485,900,000		559,200,000			485,900,000	485,900,000
Net loss per share, basic | $ / shares									$ 0.12			$ 0.18
Net loss per share, diluted | $ / shares									$ 0.12			$ 0.18
Revenue recognized									$ 32,100,000	7,700,000		$ 73,300,000	23,100,000
Increase (Decrease) in Operating expenses									(27,100,000)	(800,000)		(93,400,000)	(6,900,000)
Gilead Collaboration Agreement | Gilead
License And Collaboration Agreements [Line Items]
Upfront cash payment	$ 175,000,000.0
Collaboration term for current and future clinical programs	10 years
Contingent milestone payments receivable	$ 300,000,000.0
Additional collaboration term for programs entering clinical development prior to end of collaboration term	3 years
Option continuation payment receivable upon eighth anniversary of agreement	$ 100,000,000.0
Option continuation payment receivable upon fourth anniversary of agreement	100,000,000.0
Option continuation payment receivable upon sixth anniversary of agreement	100,000,000.0
Option fee per program for all other programs entering clinical development to exercise option	$ 150,000,000.0
Number of research programs | Program	2
Option payment upon achievement of certain development milestones	$ 250,000,000.0
Total collaboration and license revenues									2,300,000			20,500,000
Deferred revenue									198,200,000			198,200,000					198,200,000	198,200,000
Deferred revenue related to domvanalimab option																			$ 36,700,000
Deferred revenue recognized														328,800,000
Deferred revenue related to etrumadenant option																			127,000,000.0
Option payment upon achievement of certain development milestones	$ 275,000,000.0
Current and future programs exclusive access period	10 years
Performance obligation period	4 years
Contractual obligation remaining amount not obligated to pay	$ 300,000,000.0
Deferred revenue related to research and development pipeline																			$ 91,700,000
Consultant and legal fees	7,300,000
Capitalized costs									200,000	100,000		600,000	300,000
Cost sharing receivable									4,300,000			4,300,000					4,300,000	4,300,000
Gilead Collaboration Agreement | Gilead | Prepaid Expenses and Other Current Assets
License And Collaboration Agreements [Line Items]
Capitalized costs to obtain the contract, current									900,000			900,000					900,000	900,000
Gilead Collaboration Agreement | Gilead | Other Noncurrent Assets
License And Collaboration Agreements [Line Items]
Receivable from collaboration partners- noncurrent									1,900,000			1,900,000					1,900,000	1,900,000
Capitalized costs to obtain the contract, noncurrent									3,400,000			3,400,000					3,400,000	3,400,000
Gilead Collaboration Agreement | Gilead | Maximum
License And Collaboration Agreements [Line Items]
Contingent milestone payments receivable	300,000,000.0
Potential regulatory approval milestones payment receivable related to domvanalimab	500,000,000.0
Gilead Collaboration Agreement | Taiho Pharmaceutical Co., Ltd
License And Collaboration Agreements [Line Items]
Option period							5 years
Option ending period							2022-09
Non refundable and non creditable cash payments																$ 35,000,000.0
Payment for first option exercise				$ 15,000,000.0
Purchase Agreement
License And Collaboration Agreements [Line Items]
Direct offering cost	1,900,000
Purchase Agreement | Gilead
License And Collaboration Agreements [Line Items]
Issuance of common stock	$ 200,000,000.0										$ 220,296,000
Issuance of common stock, shares | shares	5,963,029														5,963,029
Shares issued, price per share | $ / shares	$ 33.54														$ 33.54
Percentage of option to purchase maximum shares of common stock	35.00%
Period over common stock to be purchased	5 years
Percentage of premium purchase price of common stock	20.00%
Trailing days average closing price	5 days
Share Price | $ / shares	$ 33.54
Funds received for purchase of common stock															$ 200,000,000.0
Purchase price of common stock allocation to performance obligation															$ 90,600,000
Purchase Agreement | Gilead | May 2020 Public Offering
License And Collaboration Agreements [Line Items]
Shares issued, price per share | $ / shares															$ 27.50
Additional equity investment net of offering costs															$ 56,700,000
Additional equity investment shares issued | shares															2,200,000
Amended Gilead Collaboration Agreement
License And Collaboration Agreements [Line Items]
Upfront cash payment														725,000,000.0
Issuance of common stock					$ 220,300,000
Issuance of common stock, shares | shares					5,650,000
Shares issued, price per share | $ / shares					$ 39.00
Option payments received			$ 725,000,000.0
Number of exercise option to programs | Program				3
Removal of option continuation payment under agreement				$ 100,000,000.0
Deferred revenue														165,100,000
Initial transaction price														890,100,000
Maximum ownership percentage of outstanding common stock remain unchanged					35.00%
Amended Investor Rights Agreement | Subsequent Event
License And Collaboration Agreements [Line Items]
Lockup period		2 years
Extended lockup period		3 years
Quemliclustat Option, and R&D Activities Agreement
License And Collaboration Agreements [Line Items]
Option payment upon achievement of certain development milestones												200,000,000.0
Total collaboration and license revenues									12,700,000			16,400,000
Deferred revenue									159,200,000			159,200,000					159,200,000	159,200,000
R&D activities for Domvanalimab
License And Collaboration Agreements [Line Items]
Total collaboration and license revenues									200,000			2,400,000
Deferred revenue									32,200,000			32,200,000					32,200,000	32,200,000
R&D and Commercialization Activities for Zimberelimab Monotherapy
License And Collaboration Agreements [Line Items]
Deferred revenue related to development and commercialization services									9,700,000			9,700,000					9,700,000	9,700,000
Total collaboration and license revenues									8,500,000			9,100,000
Deferred revenue									1,000,000.0			1,000,000.0					1,000,000.0	1,000,000.0
Access Rights related to Research and Development Pipeline
License And Collaboration Agreements [Line Items]
Total collaboration and license revenues									8,300,000	7,700,000		24,900,000	23,100,000
Deferred revenue									95,300,000			$ 95,300,000					95,300,000	95,300,000
Taiho Agreement | Taiho Pharmaceutical Co., Ltd
License And Collaboration Agreements [Line Items]
Payment for option exercise						$ 8,000,000.0											26,000,000.0
Range of royalties receivable on net sales												high single-digits to mid-teens
Royalties payable description												Royalties will be payable on a licensed product-by-licensed product and country-by-country basis during the period of time commencing on the first commercial sale of a licensed product in a country and ending upon the later of: (a) ten (10) years from the date of first commercial sale of such licensed product in such country; and (b) expiration of the last-to-expire valid claim of the Company’s patents covering the manufacture, use or sale or exploitation of such licensed product in such country (the Royalty Term).
Non-refundable, non-creditable upfront cash payments												$ 35,000,000.0
Estimated performance period												5 years
Clinical and regulatory milestones achieved												$ 0
Sales milestone or royalty revenue recognized												0
Deferred revenue, current									0			0		$ 5,000,000.0			0	0
Taiho Agreement | Taiho Pharmaceutical Co., Ltd | Minimum
License And Collaboration Agreements [Line Items]
Payment for option exercise							$ 3,000,000.0
Taiho Agreement | Taiho Pharmaceutical Co., Ltd | Maximum
License And Collaboration Agreements [Line Items]
Contingent milestone payments receivable							145,000,000.0
Payment for option exercise							15,000,000.0
Additional clinical and regulatory milestone payments receivable							$ 130,000,000.0
AstraZeneca Agreement
License And Collaboration Agreements [Line Items]
Development cost recorded within research and development expenses									1,100,000	$ 300,000		2,700,000	$ 600,000
AstraZeneca Agreement | Other Long-term Liabilities
License And Collaboration Agreements [Line Items]
Contract with customer liability, noncurrent									$ 3,700,000			$ 3,700,000					$ 3,700,000	$ 3,700,000