The cash outflow associated with extending a long-term loan to a related party. Alternate caption: Payments for Advances to Affiliates.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
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-Section 50
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
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-Section 45
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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

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Number of shares issued in lieu of cash for services contributed to the entity. Number of shares includes, but is not limited to, shares issued for services contributed by vendors and founders.

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Additional loans committed.

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Represents the amount of cash resources in hand for future use.

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Related party transaction expenses from transactions with related party advisory fees.

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Research and development service agreement aggregate payment.

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Related Party Transactions - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2015
Related Party Transaction [Line Items]
Research and development expense	$ 13,336,000	$ 12,706,000
MD Anderson License and the Research and Development Agreement [Member]
Related Party Transaction [Line Items]
Cash resources on hand	5,100,000
License Agreement \| M.D. Anderson Cancer Center
Related Party Transaction [Line Items]
Issuance of common stock in licensing agreement (in shares)				11,722,163
Research and development expense				$ 67,300,000
Cooperative Research and Development Agreement \| M.D. Anderson Cancer Center
Related Party Transaction [Line Items]
Research and development service agreement aggregate payments	41,900,000		$ 41,900,000
Vineti Inc [Member] \| Collaborative Arrangement [Member]
Related Party Transaction [Line Items]
Expenses From Transactions With Related Party	200,000
Eden Biocell [Member]
Related Party Transaction [Line Items]
Payments to Fund Long-term Loans to Related Parties	10,000,000.0
Additional Loans Committed	$ 25,000,000.0