Quarterly report pursuant to Section 13 or 15(d)

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

v3.20.1
Fair Value Measurements - Assumption Used to Determine Fair Value of Warrant Liability (Detail)
Mar. 31, 2020
yr
Dec. 31, 2019
yr
2016 Warrants [Member] | Expected Volatility [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 137.2 121.4
2016 Warrants [Member] | Remaining Contractual term (in years) [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 1.33 1.58
2016 Warrants [Member] | Risk-free Interest Rate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 0.19 1.59
2017 Warrants [Member] | Expected Volatility [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 113.3 104.2
2017 Warrants [Member] | Remaining Contractual term (in years) [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 2.33 2.58
2017 Warrants [Member] | Risk-free Interest Rate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 0.25 1.60