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Key Assumptions Used to Value the Warrants (Detail)
Mar. 31, 2020
$ / shares
Dec. 31, 2019
$ / shares
May 31, 2016
$ / shares
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]      
Stock price $ 3.62    
PIPE Warrants      
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]      
Stock price $ 3.62 $ 6.20 $ 8.90
PIPE Warrants | Measurement Input, Price Volatility      
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]      
Expected price volatility 153.57 133.07 76.25
PIPE Warrants | Measurement Input, Expected Term      
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]      
Expected term (in years) 1 year 3 months 1 year 6 months 5 years
PIPE Warrants | Measurement Input, Risk Free Interest Rate      
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]      
Expected price volatility 0.17 1.59 1.22
PIPE Warrants | Measurement Input, Expected Dividend Rate      
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]      
Expected price volatility 0 0 0