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Common Stock - Additional Information (Detail) - USD ($)
9 Months Ended
Sep. 30, 2021
Dec. 31, 2020
Common Class A [Member]    
Class of Stock [Line Items]    
Common stock shares authorized 500,000,000 273,986,920
Common stock par or stated value per share $ 0.001 $ 0.001
Common stock conversion basis one  
Cash dividends $ 0  
Common Class B [Member]    
Class of Stock [Line Items]    
Common stock shares authorized 14,600,000 21,593,607
Common stock par or stated value per share $ 0.001 $ 0.001
Cash dividends $ 0