Organization and Business - Additional Information (Detail) $ / shares in Units, $ in Thousands			1 Months Ended				3 Months Ended	9 Months Ended
	Mar. 12, 2019 USD ($) shares	Jan. 14, 2019 USD ($) $ / shares shares	Jan. 18, 2019 USD ($) shares	Jan. 17, 2019	Sep. 20, 2018 USD ($) shares	Jun. 30, 2015 USD ($)	Sep. 30, 2018 USD ($) shares	Sep. 30, 2019 USD ($) shares	Sep. 30, 2018 USD ($) shares	Dec. 31, 2018 shares
Organization and Nature of Operations [Line Items]
Stock issued during period, shares, new issues			648,233
Stock issued during period, value, new issues | $			$ 1,700				$ 1,179	$ 19,411	$ 1,179
Proceeds from Issuance of Common Stock | $	$ 17,000	$ 900	$ 1,500					$ 19,411	$ 1,179
Class of Warrant or Right, Number of Securities Called by Warrants or Rights			324,117
Stockholders' Equity Note, Stock Split, Conversion Ratio				0.05
Stockholders Equity Note Adjusted Stock Split Conversation Ratio			0.05
Common Stock, Shares, Issued								2,884,000		680,000
Warrant [Member]
Organization and Nature of Operations [Line Items]
Stock issued during period, value, new issues | $						$ 25,000
Warrants issued	42,775
HC Wainwright LLC [Member]
Organization and Nature of Operations [Line Items]
Shares Issued, Price Per Share | $ / shares		$ 2.418
Common Stock [Member]
Organization and Nature of Operations [Line Items]
Stock issued during period, shares, new issues			38,894				98,000	1,794,000	98,000
Stock issued during period, value, new issues | $								$ 2
Warrants 2016 [Member]
Organization and Nature of Operations [Line Items]
Proceeds from Issuance of Common Stock | $					$ 1,200
2018 Registered Direct Offering [Member]
Organization and Nature of Operations [Line Items]
Stock issued during period, shares, new issues					98,454
Stock issued during period, value, new issues | $					$ 1,500
2018 Registered Direct Offering [Member] | Warrant [Member]
Organization and Nature of Operations [Line Items]
Stock issued during period, shares, new issues					14,624
Private Placement [Member]
Organization and Nature of Operations [Line Items]
Common Stock, Shares, Issued		25,777
Private Placement [Member] | Series A Warrants [Member]
Organization and Nature of Operations [Line Items]
Stock issued during period, shares, new issues					113,077
IPO [Member]
Organization and Nature of Operations [Line Items]
Stock issued during period, shares, new issues	712,910	429,616
Stock issued during period, value, new issues | $	$ 18,500
Proceeds from Issuance of Common Stock | $		$ 1,100
Shares Issued, Price Per Share | $ / shares		$ 2.60
HC Wainwright Co [Member] | 2018 Registered Direct Offering [Member]
Organization and Nature of Operations [Line Items]
Stock issued during period, shares, new issues					6,785