Sales of Equity Securities - Additional Information (Detail) - USD ($)								1 Months Ended		9 Months Ended
	Sep. 20, 2018	Aug. 13, 2018	Jan. 31, 2018	Jan. 30, 2018	Dec. 08, 2017	Aug. 09, 2017	Mar. 31, 2017	May 31, 2018	May 31, 2015	Sep. 30, 2018	Sep. 30, 2017
Class Of Stock [Line Items]
Shelf registration statement expiration period									May 21, 2018
Shares issued in offering	642,438
Issuance of unregistered warrants to purchase shares of common stock	762,438	2,549,140		1,095,153			72,000
Proceeds from exercise of common stock warrants		$ 0								$ 0	$ 7,498,535
Stock price	$ 3.285			$ 13.50
Issuance of warrants to purchase shares of common stock, grant date fair value	$ 2,000,000	$ 8,400,000		$ 9,700,000			$ 2,800,000
Exercise price of warrants		$ 4.53		$ 4.53			$ 75.00
Net cash proceeds from sale of securities	2,200,000
Class of warrant or rights, term		5 years		5 years
Proceeds from issuance of common stock	2,500,000	$ 11,600,000
Net proceeds from issuance of units, net of issuance expenses	$ 2,200,000	$ 10,200,000
Aggregate units sold under right offering		11,587
Warrant exercisable for share of common stock		1
Series A Preferred Stock convertible to common stock, conversion price		$ 4.53
Prefunded Warrants [Member]
Class Of Stock [Line Items]
Exercise price of warrants	$ 3.275
Issuance of warrants to purchase shares of common stock	120,000
Change in exercise price of warrants	$ 0.01
Series A Preferred Stock [Member]
Class Of Stock [Line Items]
Shares issued in offering		11,587
Ally Bridge [Member]
Class Of Stock [Line Items]
Proceeds from exercise of common stock warrants						$ 0
Stock price						$ 45.00
Issuance of warrants to purchase shares of common stock, grant date fair value						$ 1,500,000
Exercise price of warrants						$ 45.00
Net cash proceeds from sale of securities						$ 2,000,000
Class of warrant or rights, term						5 years
Private offering, number of common stock and warrants issued						48,888
Issuance of warrants to purchase shares of common stock						47,821
Proceeds from issuance of common stock						$ 2,200,000
Common stock issuance costs						$ 200,000
Warrants [Member]
Class Of Stock [Line Items]
Aggregate warrants sold under right offering		2,549,140
Roth Capital Partners, LLC, WestPark Capital and Chardan Capital [Member]
Class Of Stock [Line Items]
Placement agent agreement, effective date							Mar. 28, 2017
Shares issued in offering							144,000
Issuance of unregistered warrants to purchase shares of common stock							72,000
Proceeds from exercise of common stock warrants							$ 0
Stock price							$ 64.50
Issuance of warrants to purchase shares of common stock, grant date fair value							$ 2,800,000
Exercise price of warrants							$ 75.00
Class of warrant or rights, expiration date							Oct. 01, 2022
Cost directly associated with offering							$ 700,000
Net cash proceeds from sale of securities							$ 8,600,000
Roth Capital Partners, LLC, WestPark Capital and Chardan Capital [Member] | Second Offering [Member]
Class Of Stock [Line Items]
Placement agent agreement, effective date							Mar. 28, 2017
Shares issued in offering							144,000
Issuance of unregistered warrants to purchase shares of common stock							72,000
Stock price							$ 64.50
Issuance of warrants to purchase shares of common stock, grant date fair value							$ 2,800,000
Exercise price of warrants							$ 75.00
Cost directly associated with offering							$ 700,000
Net cash proceeds from sale of securities							$ 8,600,000
Class of warrant or rights, term							5 years
Dawson James Securities, Inc and WestPark Capital [Member]
Class Of Stock [Line Items]
Placement agent agreement, effective date					Dec. 05, 2017
Shares issued in offering					164,166
Issuance of unregistered warrants to purchase shares of common stock					8,208
Stock price					$ 20.40
Issuance of warrants to purchase shares of common stock, grant date fair value					$ 100,000
Exercise price of warrants					$ 25.50
Class of warrant or rights, expiration date					Dec. 05, 2022
Cost directly associated with offering					$ 400,000
Net cash proceeds from sale of securities					$ 2,900,000
Maximum [Member]
Class Of Stock [Line Items]
Issuance of warrants to purchase shares of common stock				1,095,153
Maximum [Member] | Prefunded Warrants [Member]
Class Of Stock [Line Items]
Issuance of warrants to purchase shares of common stock	120,000
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
Follow-on Public Offering [Member]
Class Of Stock [Line Items]
Proceeds from exercise of common stock warrants			$ 0	$ 0
Stock price				$ 13.50
Issuance of warrants to purchase shares of common stock, grant date fair value				$ 9,700,000
Exercise price of warrants	$ 3.16	$ 4.53		$ 4.53
Cost directly associated with offering				$ 1,400,000
Net cash proceeds from sale of securities				$ 13,300,000
Class of warrant or rights, term	5 years	5 years		5 years
Private offering, number of common stock and warrants issued				1,095,153
Follow-on Public Offering [Member] | Maximum [Member]
Class Of Stock [Line Items]
Issuance of warrants to purchase shares of common stock				1,095,153
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