Sales of Equity Securities - Additional Information (Detail) - USD ($)									1 Months Ended	3 Months Ended
	Mar. 19, 2019	Mar. 11, 2019	Feb. 12, 2019	Jan. 18, 2019	Sep. 20, 2018	Aug. 13, 2018	Jan. 31, 2018	Jan. 30, 2018	May 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	May 24, 2018
Class Of Stock [Line Items]
Net cash proceeds from sale of securities	$ 7,500,000			$ 2,000,000
Stock price	$ 1.37			$ 2.25	$ 3.285
Exercise price of warrants	$ 1.25		$ 1.20			$ 4.53		$ 1.20
Class of warrant or rights, term	5 years 6 months							5 years
Issuance of warrants to purchase shares of common stock, grant date fair value	$ 6,000,000		$ 6,800,000					$ 9,700,000
Proceeds from exercise of common stock warrants										$ 4,748	$ 0
Aggregate units sold under right offering						11,587
Public offering, number of shares issued	5,950,000			990,000
Warrant exercisable for share of common stock	1					1
Series A Preferred Stock convertible to common stock, conversion price						$ 4.53
Net proceeds from issuance of units, net of issuance expenses					$ 2,200,000	$ 10,100,000
Common stock, par value						$ 0.0001				$ 0.0001		$ 0.0001
Public offering, number of common stock and warrants issued					642,438
Prefunded Warrants [Member]
Class Of Stock [Line Items]
Exercise price of warrants					$ 3.275
Change in exercise price of warrants					$ 0.01
Warrant [Member]
Class Of Stock [Line Items]
Aggregate warrants sold under right offering						2,549,140
Common Stock [Member]
Class Of Stock [Line Items]
Net cash proceeds from sale of securities				$ 2,000,000
Stock price				$ 2.25
Public offering, number of shares issued				990,000
Series A Preferred Stock [Member]
Class Of Stock [Line Items]
Public offering, number of shares issued						11,587
Preferred stock stated value per share						$ 1,000
Maximum [Member] | Prefunded Warrants [Member]
Class Of Stock [Line Items]
Issuance of warrants to purchase shares of common stock					120,000
Follow-on Public Offering [Member]
Class Of Stock [Line Items]
Net cash proceeds from sale of securities		$ 592,000	$ 6,600,000					$ 13,300,000
Private offering, number of common stock and warrants issued								1,095,153
Stock price		$ 1.20	$ 1.20					$ 13.50
Cost directly associated with offering								$ 1,400,000
Exercise price of warrants	$ 1.25		$ 1.20					$ 1.20
Class of warrant or rights, term	5 years 6 months		5 years					5 years
Issuance of warrants to purchase shares of common stock, grant date fair value								$ 9,700,000
Proceeds from exercise of common stock warrants			$ 0				$ 0	$ 0
Public offering, number of shares issued			6,250,000
Public offering, number of common stock and warrants issued								1,095,153
Purchase of common stock by underwriters to cover overallotments, number of shares		538,867
Follow-on Public Offering [Member] | Maximum [Member]
Class Of Stock [Line Items]
Issuance of warrants to purchase shares of common stock			6,250,000					1,095,153
Shelf Registration Statement [Member]
Class Of Stock [Line Items]
Shelf registration statement expiration period									May 31, 2021
Minimum public float limit for offering									$ 75,000,000				$ 75,000,000
Shelf Registration Statement [Member] | Maximum [Member]
Class Of Stock [Line Items]
Aggregate offering price									$ 50,000,000				$ 50,000,000
Private Placement [Member]
Class Of Stock [Line Items]
Exercise price of warrants					$ 3.16
Class of warrant or rights, term					5 years
Warrant exercisable for share of common stock					1
Over-allotment Option [Member] | Warrant [Member]
Class Of Stock [Line Items]
Public offering, number of shares issued			915,000
Over-allotment Option [Member] | Maximum [Member]
Class Of Stock [Line Items]
Issuance of warrants to purchase shares of common stock			937,500