Preferred Stock, Common Stock and Stockholders' Equity - Summary of Warrants Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Warrants And Rights Note Disclosure [Abstract]
Warrants, Outstanding beginning balance	2,797,561
Warrants, Expired/Forfeited	(84,000)
Warrants, Outstanding ending balance	2,713,561	2,797,561
Weighted Average Exercise Price, Outstanding beginning balance	$ 3.46
Weighted Average Exercise Price, Expired/Forfeited	21.00
Weighted Average Exercise Price, Outstanding ending balance	$ 2.91	$ 3.46
Weighted Average Remaining Contractual Term (Years), Outstanding	3 years 14 days	3 years 11 months 8 days