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Collaboration Agreements and Revenues - Accounting for the Astellas Agreements - Additional Information 2 (Detail) - Astellas Agreement [Member] | 12 Months Ended
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Dec. 31, 2020 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] |
Co-development services, currently estimated continuation year | 2024
Minimum [Member] | Measurement Input Discount Rate [Member] | Discounted Cash Flow [Member] |
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] |
Discount rate applied | 17.5
Maximum [Member] | Measurement Input Discount Rate [Member] | Discounted Cash Flow [Member] |
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] |
Discount rate applied | 20.0
Japan [Member] |
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] |
Non-contingent upfront payments received | $ 40,100,000
Variable consideration related to payments for milestones considered probable of being achieved | 65,000,000.0
Variable consideration related to co-development billings | 11,700,000
Provision for co-development services | 0
Europe [Member] |
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] |
Non-contingent upfront payments received | 320,000,000.0
Variable consideration related to payments for milestones considered probable of being achieved | 220,000,000.0
Variable consideration related to co-development billings | $ 225,900,000

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