Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Assumption Used to Determine Fair Value of Warrant Liability (Detail)

v3.10.0.1
Fair Value Measurements - Assumption Used to Determine Fair Value of Warrant Liability (Detail)
Sep. 30, 2018
yr
Dec. 31, 2017
yr
Representative's Warrant [Member] | Expected Volatility [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 64.0 88.1
Representative's Warrant [Member] | Remaining Contractual term (in years) [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 0.92 1.67
Representative's Warrant [Member] | Risk-free Interest Rate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 2.59 1.89
2016 Warrants [Member] | Expected Volatility [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 82.6 80.3
2016 Warrants [Member] | Remaining Contractual term (in years) [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 2.83 3.58
2016 Warrants [Member] | Risk-free Interest Rate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 2.88 2.09
2017 Warrants [Member] | Expected Volatility [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 87.0 81.5
2017 Warrants [Member] | Remaining Contractual term (in years) [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 3.83 4.58
2017 Warrants [Member] | Risk-free Interest Rate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 2.91 2.20