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Collaboration Agreements and Revenues - Deferred Revenue - Additional Information (Detail) - USD ($)
$ in Thousands
Sep. 30, 2020
Dec. 31, 2019
Contract with Customer, Liability [Abstract]    
Deferred revenue $ 0 $ 54,790
AstraZeneca Agreements [Member] | China [Member]    
Contract with Customer, Liability [Abstract]    
Deferred revenue $ 3,200