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Derivative Financial Instruments - Schedule of Fair Value of Warrants (Details)
Jun. 30, 2019
Dec. 31, 2018
Dec. 31, 2017
Contractual Term [Member]      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Warrants expiration period 4 years 6 months    
Expected Volatility [Member]      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Warrants measurement input 1.636    
Risk-free Interest Rates [Member]      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Warrants measurement input 0.018    
Minimum [Member] | Contractual Term [Member]      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Warrants expiration period   1 year 1 month 17 days 9 months 25 days
Minimum [Member] | Expected Volatility [Member]      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Warrants measurement input   1.457 1.309
Minimum [Member] | Risk-free Interest Rates [Member]      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Warrants measurement input   0.025 0.017
Maximum [Member] | Contractual Term [Member]      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Warrants expiration period   5 years 1 month 9 days 4 years 10 months 17 days
Maximum [Member] | Expected Volatility [Member]      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Warrants measurement input   2.653 2.669
Maximum [Member] | Risk-free Interest Rates [Member]      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]      
Warrants measurement input   0.026 0.021