Preferred Stock, Common Stock and Stockholders' Equity - Common Stock - Additional Information (Detail) - USD ($)	2 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Feb. 28, 2019	Nov. 30, 2017
Sale Of Stock [Line Items]
Common stock, shares outstanding		17,427,533	15,413,610
Shareholders voting power description		Each share of common stock is entitled to one vote. The holders of the common stock are also entitled to receive dividends whenever funds are legally available and when declared by the board of directors of the Company.
Dividends declared on common stock		$ 0
Shares of common stock subject to Registration Rights		1,509,789
Proceeds from issuance of common stock, net		$ 4,618,297	$ 7,389,101
Common stock, shares issued		17,427,533	15,413,610
Underwritten Public Offering [Member]
Sale Of Stock [Line Items]
Common stock shares issues	2,775,861
Purchase price of common stock	$ 2.90
Gross proceeds from public offering of common stock	$ 8,000,000
Proceeds from issuance of common stock, net	$ 7,300,000
FBR Sales Agreement [Member]
Sale Of Stock [Line Items]
Proceeds from issuance of common stock, net		$ 4,600,000
Common stock, shares issued		1,985,054
Common stock , weighted average price per share		$ 2.38
FBR Sales Agreement [Member] | Maximum [Member]
Sale Of Stock [Line Items]
Common stock, value of shares issuable					$ 16,000,000
FBR Sales Agreement [Member] | Subsequent Event [Member]
Sale Of Stock [Line Items]
Common stock, shares issued				0