Debt and Fair Value of Financial Instruments - Aggregate Fair Value and Carrying Value of Warrant Liability and Short and Long-term Debt (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Mar. 06, 2018	Dec. 31, 2017
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrant liability	$ 3,000	$ 2,900
Carrying Amount [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrant liability	3,047
Short-term debt, related party			$ 1,000
Long-term debt, related party	1,200		1,200
Long-term debt	1,623		1,558
Total liabilities	5,870		3,758
Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrant liability	3,047
Short-term debt, related party			1,000
Long-term debt, related party	1,200		1,200
Long-term debt	1,623		1,558
Total liabilities	$ 5,870		$ 3,758