Quarterly report pursuant to Section 13 or 15(d)

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

v3.20.2
Fair Value Measurements - Assumption Used to Determine Fair Value of Warrant Liability (Detail)
Jun. 30, 2020
yr
May 27, 2020
yr
Dec. 31, 2019
yr
2020 Warrants [Member] | Expected Volatility [Member]      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Fair value of warrant liability 107.5 106.4  
2020 Warrants [Member] | Remaining Contractual term (in years) [Member]      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Fair value of warrant liability 2.92 3.00  
2020 Warrants [Member] | Risk-free Interest Rate [Member]      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Fair value of warrant liability 0.18 0.22  
2016 Warrants [Member] | Expected Volatility [Member]      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Fair value of warrant liability 115.9   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 1.08   1.58
2016 Warrants [Member] | Risk-free Interest Rate [Member]      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Fair value of warrant liability 0.16   1.59
2017 Warrants [Member] | Expected Volatility [Member]      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Fair value of warrant liability 120.0   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 2.08   2.58
2017 Warrants [Member] | Risk-free Interest Rate [Member]      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Fair value of warrant liability 0.16   1.60