Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Reconciliation of Company's Financial Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level 3) (Detail)

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Fair Value Measurements - Reconciliation of Company's Financial Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level 3) (Detail) - Warrant Liabilities [Member] - USD ($)
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Balance at beginning of period $ 44,349,846 $ 4,345,902 $ 6,068,978 $ 20,781,663
Issuance of 2020 Warrants     31,391,369  
Increase (decrease) in fair value [1] (10,689,855) (2,186,710) (3,800,356) (18,622,471)
Balance at end of period $ 33,659,991 $ 2,159,192 $ 33,659,991 $ 2,159,192
[1] The change in fair values of the warrant liabilities is recorded in other income (expense) in the consolidated statement of operations.