Annual report pursuant to Section 13 and 15(d)

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

v3.21.1
Fair Value Measurements - Assumption Used to Determine Fair Value of Warrant Liability (Detail)
Dec. 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 59.7 121.4
2016 Warrants [Member] | Remaining Contractual term (in years) [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 0.58 1.58
2016 Warrants [Member] | Risk-free Interest Rate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 0.09 1.59
2017 Warrants [Member] | Expected Volatility [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 100.1 104.2
2017 Warrants [Member] | Remaining Contractual term (in years) [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 1.58 2.58
2017 Warrants [Member] | Risk-free Interest Rate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 0.12 1.60
2020 Warrants [Member] | Expected Volatility [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 111.9 106.4
2020 Warrants [Member] | Remaining Contractual term (in years) [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 2.42 3.00
2020 Warrants [Member] | Risk-free Interest Rate [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair value of warrant liability 0.15 0.22