Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Financial Liabilities Subject to Fair Value Measurements (Detail)

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Stockholders' Equity - Financial Liabilities Subject to Fair Value Measurements (Detail) - Warrants - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
2017 Warrants    
Fair Value Inputs Liabilities Quantitative Information [Line Items]    
Financial liabilities subject to fair value measurements $ 954  
2017 Warrants | Basis of Fair Value Measurements, Level 1    
Fair Value Inputs Liabilities Quantitative Information [Line Items]    
Financial liabilities subject to fair value measurements 0  
2017 Warrants | Basis of Fair Value Measurements, Level 2    
Fair Value Inputs Liabilities Quantitative Information [Line Items]    
Financial liabilities subject to fair value measurements 0  
2017 Warrants | Basis of Fair Value Measurements, Level 3    
Fair Value Inputs Liabilities Quantitative Information [Line Items]    
Financial liabilities subject to fair value measurements $ 954  
2014 Warrants    
Fair Value Inputs Liabilities Quantitative Information [Line Items]    
Financial liabilities subject to fair value measurements   $ 49
2014 Warrants | Basis of Fair Value Measurements, Level 1    
Fair Value Inputs Liabilities Quantitative Information [Line Items]    
Financial liabilities subject to fair value measurements   0
2014 Warrants | Basis of Fair Value Measurements, Level 2    
Fair Value Inputs Liabilities Quantitative Information [Line Items]    
Financial liabilities subject to fair value measurements   0
2014 Warrants | Basis of Fair Value Measurements, Level 3    
Fair Value Inputs Liabilities Quantitative Information [Line Items]    
Financial liabilities subject to fair value measurements   $ 49