Annual report pursuant to Section 13 and 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 ($)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Balance at beginning of period $ 20,781,663 $ 13,549,437 $ 12,698,980
Issuance of warrants     12,383,435
Change in fair value (14,712,685) 7,232,226 (11,532,978)
Balance at end of period $ 6,068,978 $ 20,781,663 $ 13,549,437