Fair Value Measurements - Information about Company's Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 36,379,938	$ 39,858,864
Warrant liabilities	(25,823,996)	(13,549,437)
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	3,094,855	5,949,477
Marketable securities	36,379,938	39,858,864
Total assets (liabilities)	39,474,793	45,808,341
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liabilities	25,823,996	13,549,437
Total assets (liabilities)	$ 25,823,996	$ 13,549,437