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Stock-Based Compensation - Summary of Warrant Activity (Detail) - Outstanding Warrants - shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Class Of Warrant Or Right [Line Items]    
Number of shares Warrants, Beginning Balance 1,638,000 21,302,049
Number of shares Warrants exercised 0 (19,664,049)
Number of shares Warrants, Ending Balance 1,638,000 1,638,000