Fair Value Measurements - Summary of Reconciliation of Warrant Liability Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Detail) - Fair Value Measurement, Recurring [Member] - Warrant Liability [Member] - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 4,095,019
Issuance of warrants		$ 4,899,459
Change in fair value upon re-measurement	1,005,349	(597,615)
Reclassification to Additional Paid-in Capital due to warrant amendment		(206,825)
Reclassification to Additional Paid-in Capital due to warrant exercise	(1,399,091)
Ending balance	$ 3,701,277	$ 4,095,019