Stockholders' Equity - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Aug. 08, 2017
Class of Stock [Line Items]
Number of common stock issued upon conversion of convertible instrument	0	0
Common Stock [Member] | Lincoln Park Capital Fund, LLC [Member]
Class of Stock [Line Items]
Common stock, shares issued	270,000
Net proceeds from the issuance of common stock	$ 932,000
Common Stock [Member] | Lincoln Park Capital Fund, LLC [Member] | Maximum [Member]
Class of Stock [Line Items]
Potential consideration under purchase agreement			15,000,000