Stock Options and Warrants - Summary of Outstanding Warrants Related to Warrant Transactions (Detail) - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Class of Warrant or Right [Line Items]
Number of Shares, Outstanding, Beginning balance	4,001,469	7,321,468
Warrants, Forfeited/Cancelled	(50,417)	(3,319,999)
Number of Shares, Outstanding, Ending balance	3,951,052	4,001,469
Weighted Average Exercise Price, Forfeited/Cancelled	$ 30.00	$ 1.75
Weighted Average Exercise Price, Outstanding, Ending balance	1.75
Maximum [Member]
Class of Warrant or Right [Line Items]
Weighted Average Exercise Price, Outstanding, Beginning balance	30.00	30.00
Weighted Average Exercise Price, Outstanding, Ending balance		30.00
Minimum [Member]
Class of Warrant or Right [Line Items]
Weighted Average Exercise Price, Outstanding, Beginning balance	1.75	1.75
Weighted Average Exercise Price, Outstanding, Ending balance		1.75
Weighted Average
Class of Warrant or Right [Line Items]
Weighted Average Exercise Price, Outstanding, Beginning balance	2.94	2.40
Weighted Average Exercise Price, Forfeited/Cancelled	30.00	1.75
Weighted Average Exercise Price, Outstanding, Ending balance	$ 1.75	$ 2.94
Jan 2013 Financing [Member]
Class of Warrant or Right [Line Items]
Number of Shares, Outstanding, Beginning balance	33,750	33,750
Warrants, Forfeited/Cancelled	(33,750)
Number of Shares, Outstanding, Ending balance		33,750
Mar 2013 Financing [Member]
Class of Warrant or Right [Line Items]
Number of Shares, Outstanding, Beginning balance	16,667	16,667
Warrants, Forfeited/Cancelled	(16,667)
Number of Shares, Outstanding, Ending balance		16,667
March 2016 Financing [Member] | Series A Common Stock [Member]
Class of Warrant or Right [Line Items]
Number of Shares, Outstanding, Beginning balance	3,605,713	3,605,713
Number of Shares, Outstanding, Ending balance	3,605,713	3,605,713
March 2016 Financing [Member] | Series C Common Stock [Member]
Class of Warrant or Right [Line Items]
Number of Shares, Outstanding, Beginning balance		3,319,999
Warrants, Forfeited/Cancelled		(3,319,999)
March 2016 Financing [Member] | Placement Agent [Member]
Class of Warrant or Right [Line Items]
Number of Shares, Outstanding, Beginning balance	342,856	342,856
Number of Shares, Outstanding, Ending balance	342,856	342,856
October 2014 Financing [Member] | Placement Agent [Member]
Class of Warrant or Right [Line Items]
Number of Shares, Outstanding, Beginning balance	2,483	2,483
Number of Shares, Outstanding, Ending balance	2,483	2,483