Subsequent Event - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended						12 Months Ended
	Mar. 12, 2019	Jan. 14, 2019	Jan. 31, 2019	Jan. 18, 2019	Jan. 17, 2019	Sep. 20, 2018	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2018	Dec. 31, 2017
Subsequent Event [Line Items]
Stock Issued During Period, Shares, New Issues							29,412
Stock Issued During Period, Value, New Issues									$ 1,180	$ 3,567
Proceeds from Issuance of Common Stock	$ 17,000								$ 1,180	$ 3,567
Warrant [Member]
Subsequent Event [Line Items]
Stock Issued During Period, Shares, New Issues							14,706
Stock Issued During Period, Value, New Issues							$ 10,000	$ 25,000
Proceeds from Issuance of Common Stock						$ 1,200
Subsequent Event [Member]
Subsequent Event [Line Items]
Stockholders' Equity, Reverse Stock Split				1-for-20	common stock at a ratio of 1-for-20, and our common stock began trading on the split-adjusted basis on the Nasdaq Capital Market at the commencement of trading on January 18, 2019. All common stock share and per share amounts in our consolidated financial statements have been adjusted to give effect to the 1-for-20 reverse stock split.
Stock Issued During Period, Shares, New Issues				648,233
Stock Issued During Period, Value, New Issues				$ 1,700
Proceeds from Issuance of Common Stock	$ 17,000	$ 900	$ 900	$ 1,500
Subsequent Event [Member] | Two Thousand Nineteen Underwritten Offering [Member]
Subsequent Event [Line Items]
Stock Issued During Period, Shares, New Issues		429,616
Stock Issued During Period, Value, New Issues		$ 1,100
Proceeds from Issuance Initial Public Offering		$ 900
Revised Share Offering Price		$ 2.418
Stock Issued During Period, Shares, Issued for Services		25,777
Share Offering Price		$ 2.60
Subsequent Event [Member] | Two Thousand Nineteen Registered Direct Offering [Member]
Subsequent Event [Line Items]
Stock Issued During Period, Shares, New Issues				648,233
Stock Issued During Period, Value, New Issues				$ 1,700
Proceeds from Issuance Initial Public Offering				$ 1,500
Subsequent Event [Member] | Two Thousand Nineteen Registered Direct Offering [Member] | HC Wainwright Co [Member]
Subsequent Event [Line Items]
Stock Issued During Period, Shares, New Issues				38,894
Subsequent Event [Member] | Series A Warrant [Member] | Private Placement [Member]
Subsequent Event [Line Items]
Stock Issued During Period, Shares, New Issues				324,117
Subsequent Event [Member] | Warrant [Member]
Subsequent Event [Line Items]
Stock Issued During Period, Shares, New Issues	712,910
Stock Issued During Period, Value, New Issues	$ 18,500
Warrants issued	42,775