Stockholders' Equity - Additional Information (Detail) - USD ($)			9 Months Ended
	Apr. 10, 2018	Jun. 15, 2017	Sep. 30, 2018	Dec. 31, 2017
Class Of Stock [Line Items]
Common stock, capital shares reserved for future issuance			16,049,273
Shares of common stock issued	3,450,000
Purchase price per share	$ 8.60
Net proceeds received after deducting underwriters' discounts and commissions and offering costs	$ 28,000,000
Private Placement [Member]
Class Of Stock [Line Items]
Shares of common stock issued		1,552,795
Purchase price per share		$ 9.66
Aggregate purchase price		$ 15,000
Volume-weighted average trading price of common stock trading days		30 days
Percentage of volume-weighted average trading price of common stock		95.00%
Volume-weighted average trading price of common stock trading days ending on		Jun. 14, 2017
Underwriters' Option [Member]
Class Of Stock [Line Items]
Shares of common stock issued	450,000
Series A Convertible Preferred Stock [Member]
Class Of Stock [Line Items]
Preferred Stock, shares authorized			1,000,000	1,000,000
Preferred stock dividends issued			1,128
Dividends in arrears			$ 8,000
Preferred Stock [Member]
Class Of Stock [Line Items]
Preferred Stock, shares authorized			50,000,000