Summary of Significant Accounting Policies - Schedule of Anti-Dilutive Securities Excluded from Diluted Loss Per Share (Detail) - shares	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Anti-dilutive securities excluded from diluted loss per share:
Anti-dilutive securities excluded from diluted loss per share	14,092,315	14,391,115
Stock Options [Member]
Anti-dilutive securities excluded from diluted loss per share:
Anti-dilutive securities excluded from diluted loss per share	5,275,543	5,186,927
Warrants [Member]
Anti-dilutive securities excluded from diluted loss per share:
Anti-dilutive securities excluded from diluted loss per share		1,676,747
Shares Issuable Upon Conversion of Convertible Promissory Notes Including Accrued Interest [Member]
Anti-dilutive securities excluded from diluted loss per share:
Anti-dilutive securities excluded from diluted loss per share	8,816,772	7,527,441