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License and Collaboration Agreements - Additional Information (Details) |  |  | 1 Months Ended | 12 Months Ended
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Jul. 13, 2020 USD ($) $ / shares shares | Apr. 30, 2019 USD ($) shares | Dec. 31, 2020 USD ($) shares | Oct. 31, 2017 USD ($) | Sep. 30, 2017 USD ($) Program | Aug. 31, 2017 USD ($) | Dec. 31, 2020 USD ($) shares | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Upfront cash payment |  |  |  |  |  |  | $ 175,000,000 |  |  |
Issuance of common stock |  |  |  |  |  |  | 326,246,000 |  | $ 124,735,000 |
Cost sharing receivable, current |  |  | $ 1,049,000 |  |  |  | 1,049,000 | $ 132,000 |  |
Total collaboration and license revenues |  |  |  |  |  |  | 77,517,000 | 15,000,000 | 8,353,000 |
Deferred revenue recognized |  |  |  |  |  |  | 7,000,000 | 7,000,000 | 5,353,000 |
Deferred revenue, current |  |  | 74,571,000 |  |  |  | 74,571,000 | 7,000,000 |  |
Deferred revenue, noncurrent |  |  | $ 122,830,000 |  |  |  | 122,830,000 | 12,022,000 |  |
Development expense |  |  |  |  |  |  | $ 159,348,000 | 78,481,000 | 49,646,000 |
Shares probable of vesting | shares |  |  | 9,892,697 |  |  |  | 9,892,697 |  |  |
Stock Purchase Agreement |  |  |  |  |  |  |  |  |  |
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Direct offering cost | $ 1,900,000 |  |  |  |  |  |  |  |  |
Gilead | Gilead Collaboration Agreement |  |  |  |  |  |  |  |  |  |
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Upfront cash payment | 175,000,000.0 |  |  |  |  |  | $ 175,000,000 |  |  |
Unconstrained consideration to be received |  |  | $ 100,000,000 |  |  |  | 100,000,000 |  |  |
Premium on stock purchased | $ 90,600,000 |  |  |  |  |  |  |  |  |
Collaboration term for current and future clinical programs | 10 years |  |  |  |  |  |  |  |  |
Contingent milestone payments receivable | $ 400,000,000 |  |  |  |  |  |  |  |  |
Additional collaboration term for programs entering clinical development prior to end of collaboration term | 3 years |  |  |  |  |  |  |  |  |
Option fee per program for all other programs entering clinical development to exercise option | $ 150,000,000 |  |  |  |  |  |  |  |  |
Ongoing research and development support | 400,000,000 |  |  |  |  |  |  |  |  |
Research and development information access rights payment related to year 2022 | 100,000,000.0 |  |  |  |  |  |  |  |  |
Initial transaction price | 365,600,000 |  |  |  |  |  |  |  |  |
Option payment upon achievement of certain development milestones | 250,000,000.0 |  |  |  |  |  |  |  |  |
Deferred revenue related to etrumadenant option |  |  | 127,000,000.0 |  |  |  | $ 127,000,000.0 |  |  |
Etrumadenant option initial term of agreement |  |  |  |  |  |  | 4 years |  |  |
Option payment upon achievement of certain development milestones | $ 275,000,000.0 |  |  |  |  |  |  |  |  |
Deferred revenue related to domvanalimab option |  |  | 36,700,000 |  |  |  | $ 36,700,000 |  |  |
Domvanalimab option recognized term |  |  |  |  |  |  | 1 year |  |  |
Current and future programs exclusive access period | 10 years |  |  |  |  |  |  |  |  |
Additional payment due at each of the fourth, sixth, and eighth anniversaries of the agreement | $ 100,000,000.0 |  |  |  |  |  |  |  |  |
Contingent milestone payment start period | 2022 |  |  |  |  |  |  |  |  |
Contractual obligation for first payment | $ 100,000,000.0 |  |  |  |  |  |  |  |  |
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 |  |  | 121,700,000 |  |  |  | $ 121,700,000 |  |  |
Future development and promotion costs contract liability |  |  | 9,700,000 |  |  |  | 9,700,000 |  |  |
Consultant and legal fees | 7,300,000 |  |  |  |  |  |  |  |  |
Amortization expense |  |  |  |  |  |  | 200,000 |  |  |
Cost sharing receivable |  |  | 4,200,000 |  |  |  | 4,200,000 |  |  |
Gilead | Gilead Collaboration Agreement | Prepaid Expenses and Other Current Assets |  |  |  |  |  |  |  |  |  |
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Cost sharing receivable, current |  |  | 1,000,000.0 |  |  |  | 1,000,000.0 |  |  |
Gilead | Gilead Collaboration Agreement | Other Noncurrent Assets |  |  |  |  |  |  |  |  |  |
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Cost sharing receivable, noncurrent |  |  | 3,200,000 |  |  |  | 3,200,000 |  |  |
Gilead | Gilead Collaboration Agreement | Maximum |  |  |  |  |  |  |  |  |  |
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Contingent milestone payments receivable | 400,000,000 |  |  |  |  |  |  |  |  |
Option fee per program for current clinical programs to exercise option | 275,000,000 |  |  |  |  |  |  |  |  |
Gilead | Gilead Collaboration Agreement | Minimum |  |  |  |  |  |  |  |  |  |
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Option fee per program for current clinical programs to exercise option | 200,000,000 |  |  |  |  |  |  |  |  |
Gilead | Stock Purchase Agreement |  |  |  |  |  |  |  |  |  |
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Funds received for purchase of common stock |  |  |  |  |  |  | 200,000,000 |  |  |
Fair value of stock purchased |  |  |  |  |  |  | 109,400,000 |  |  |
Premium on stock purchased |  |  |  |  |  |  | 90,600,000 |  |  |
Issuance of common stock | $ 200,000,000 |  |  |  |  |  | $ 107,468,000 |  |  |
Issuance of common stock, shares | shares | 5,963,029 |  |  |  |  |  |  |  |  |
Shares issued, price per share | $ / shares | $ 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 |  |  |  |  |  |  |  |  |
Taiho Pharmaceutical Co., Ltd | Taiho Agreement |  |  |  |  |  |  |  |  |  |
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Upfront cash payment |  |  |  |  | $ 20,000,000.0 |  |  |  |  |
Option period |  |  |  |  | 5 years |  |  |  |  |
Non refundable and non creditable cash payments |  |  |  |  |  |  |  |  |  | $ 35,000,000.0
Payment received for license agreement |  |  |  | $ 5,000,000.0 |  |  |  | 5,000,000.0 | 5,000,000.0 | $ 25,000,000.0
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 |  |  |
Payment for first option exercise |  |  |  |  |  |  |  | 8,000,000.0 | 3,000,000.0 |
Licensing revenue recognized |  |  |  |  |  |  |  | 8,000,000.0 |  |
Clinical and regulatory milestones achieved |  |  |  |  |  |  | $ 0 |  |  |
Sales milestone or royalty revenue recognized |  |  |  |  |  |  | 0 |  |  |
Total collaboration and license revenues |  |  |  |  |  |  | 7,000,000.0 | 15,000,000.0 |  |
Deferred revenue recognized |  |  |  |  |  |  |  |  | 8,300,000 |
Deferred revenue, current |  |  | 7,000,000.0 |  |  |  | 7,000,000.0 | 7,000,000.0 |  |
Deferred revenue, noncurrent |  |  | 5,000,000.0 |  |  |  | $ 5,000,000.0 | 12,000,000.0 |  |
Taiho Pharmaceutical Co., Ltd | Taiho Agreement | Maximum |  |  |  |  |  |  |  |  |  |
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Contingent milestone payments receivable |  |  |  |  | $ 145,000,000.0 |  |  |  |  |
Extended option agreement period |  |  |  |  | 7 years |  |  |  |  |
Payment for option exercise |  |  |  |  | $ 15,000,000.0 |  |  |  |  |
Additional clinical and regulatory milestone payments receivable |  |  |  |  | $ 130,000,000.0 |  |  |  |  |
Taiho Pharmaceutical Co., Ltd | Taiho Agreement | Minimum |  |  |  |  |  |  |  |  |  |
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Number of programs, IND enabling studies not initiated | Program |  |  |  |  | 5 |  |  |  |  |
Payment for option exercise |  |  |  |  | $ 3,000,000.0 |  |  |  |  |
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 |  |  |  |  |  |  |
Milestone payments |  |  |  |  |  |  | $ 5,000,000.0 | 7,500,000 | 0 |
Sub-license fees incurred |  |  |  |  |  |  | 10,100,000 | 1,200,000 | 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] |  |  |  |  |  |  |  |  |  |
Development expense |  |  |  |  |  |  |  | 0 |  |
Abmuno License Agreement | Research and Development |  |  |  |  |  |  |  |  |  |
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Milestone payments |  |  |  |  |  |  | 3.0 |  | $ 2,800,000 |
Abmuno License Agreement | Maximum |  |  |  |  |  |  |  |  |  |
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Clinical, regulatory and commercialization remaining milestone payments |  |  |  |  |  |  | 98,000,000.0 |  |  |
Genentech |  |  |  |  |  |  |  |  |  |
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Development expense |  |  |  |  |  |  | 500,000 | 0 |  |
Strata Oncology Inc | Co-Development and Collaboration Agreement |  |  |  |  |  |  |  |  |  |
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Development milestone payable |  | $ 2,500,000 |  |  |  |  |  |  |  |
Development cost recorded within research and development expenses |  |  |  |  |  |  | 1,700,000 | 1,000,000.0 |  |
Development cost reimbursed |  |  |  |  |  |  | $ 300,000 | 200,000 |  |
Number of restricted shares of common stock issued | shares |  | 1,257,651 |  |  |  |  |  |  |  |
Fair value of restricted shares of common stock issued |  | $ 15,000,000.0 |  |  |  |  |  |  |  |
Strata Oncology Inc | Co-Development and Collaboration Agreement | Non-vested Restricted Stock |  |  |  |  |  |  |  |  |  |
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Shares probable of vesting | shares |  |  | 0 |  |  |  | 0 |  |  |
Compensation expense recognized |  |  |  |  |  |  | $ 0 |  |  |
Strata Oncology Inc | Co-Development and Collaboration Agreement | Research and Development |  |  |  |  |  |  |  |  |  |
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Milestone payments |  |  |  |  |  |  | $ 0 | $ 2,500,000 |  |
Strata Oncology Inc | Co-Development and Collaboration Agreement | Maximum |  |  |  |  |  |  |  |  |  |
License And Collaboration Agreements [Line Items] |  |  |  |  |  |  |  |  |  |
Regulatory and commercial milestone payable |  | $ 125,000,000.0 |  |  |  |  |  |  |  |

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