Stockholders' Equity - Common Stock - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended
	Apr. 30, 2019	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Nov. 30, 2017
Sale Of Stock [Line Items]
Common stock, shares issued		17,877,533		17,427,533
Proceeds from issuance of common stock, net		$ 636,432	$ 544,643
FBR Sales Agreement [Member]
Sale Of Stock [Line Items]
Common stock, shares issued		450,000	268,870
Common stock , weighted average price per share		$ 1.44	$ 2.10
Proceeds from issuance of common stock, net		$ 636,000	$ 545,000
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	5,384,117
Common stock , weighted average price per share	$ 0.86
Proceeds from issuance of common stock, net	$ 4,500,000