Capital Stock - Additional Information (Detail) - USD ($)		1 Months Ended	9 Months Ended
	Sep. 29, 2016	Jan. 31, 2018	Sep. 30, 2018
Class Of Stock [Line Items]
Proceeds from issuance of common stock			$ 8,164,000
Minimum threshold percentage of beneficial common stock interest	4.99%
Maximum threshold percentage of beneficial common stock interest on holder's discretion	9.99%
Convertible preferred stock, terms of conversion			The Series A Preferred Stock shall not be converted if, after giving effect to the conversion, the holder and its affiliated persons would own beneficially more than 4.99% of our common stock (subject to adjustment up to 9.99% solely at the holder’s discretion upon 61 days’ prior notice to us or, solely as to a holder, if such limitation is waived by such holder upon execution of the private placement agreement).
Private Placement [Member]
Class Of Stock [Line Items]
Common stock price per share	$ 2.25
Gross proceeds from issuance of common stock, preferred stock and warrants	$ 30,000,000
Conversion of preferred stock in to common stock, preferred stock converted	10,737,275		444.44
Class of Warrants or right to purchase common stock	13,333,334
Class of Warrants or right to purchase common stock, exercise price	$ 2.25		$ 2.25
Warrants granted to placement agent	133,333
Proceeds from issuance of common stock, preferred stock and warrants, net of issuance costs	$ 27,600,000
Warrants granted to placement agent, exercise price	$ 2.25
Minimum percentage of outstanding common stock			50.00%
Warrants expiry period			5 years
Warrants exercisable period			6 months
Fair value of warrants			$ 30,700,000
Excess fair value of warrant liability			$ 400,000
Convertible preferred stock, par value			$ 0.01
Private Placement [Member] | Members of Board of Directors [Member]
Class Of Stock [Line Items]
Class of Warrants or right to purchase common stock			1,422,221
Class of Warrants or right to purchase common stock, exercise price			$ 2.25
Private Placement [Member] | Series A Preferred Stock [Member]
Class Of Stock [Line Items]
Number of shares issued	24,158.8693
Convertible preferred stock, shares outstanding			400.4910
Private Placement [Member] | Series A Preferred Stock [Member] | Members of Board of Directors [Member]
Class Of Stock [Line Items]
Number of shares issued			2,563.1439
Common Stock [Member]
Class Of Stock [Line Items]
Number of shares issued		2,691,494
Proceeds from issuance of common stock		$ 5,700,000
Common stock price per share		$ 2.35
Common Stock [Member] | At-The-Market Sales Agreement [Member]
Class Of Stock [Line Items]
Number of shares issued			5,766,247
Proceeds from issuance of common stock			$ 4,000,000
Common Stock [Member] | Private Placement [Member]
Class Of Stock [Line Items]
Number of shares issued	2,596,059
Common Stock [Member] | Private Placement [Member] | Members of Board of Directors [Member]
Class Of Stock [Line Items]
Number of shares issued			283,046
Common Stock [Member] | Private Placement [Member] | Series A Preferred Stock [Member]
Class Of Stock [Line Items]
Conversion of preferred stock in to common stock, preferred stock converted			177,996
Common Stock [Member] | Maximum [Member] | At-The-Market Sales Agreement [Member]
Class Of Stock [Line Items]
Aggregate offering price of shares			$ 10,000,000