Warrants - Summary of Initial Fair Value of Warrants Estimated using Black - Scholes Option Pricing Model (Details)	Dec. 31, 2020	Oct. 29, 2013
2020 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrant term	7 years
2019 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrant term	7 years
2018 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrant term	7 years
2017 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrant term	1 year
2016 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrant term	7 years
2014 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrant term	5 years
2013 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrant term	5 years	5 years
Risk Free Interest Rate | 2020 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input	0.005
Risk Free Interest Rate | 2019 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input	0.028
Risk Free Interest Rate | 2018 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input	0.030
Risk Free Interest Rate | 2017 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input	0.017
Risk Free Interest Rate | 2016 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input	0.018
Risk Free Interest Rate | 2014 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input	0.016
Risk Free Interest Rate | 2013 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input	0.014
Volatility | 2020 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input	0.88
Volatility | 2019 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input	0.97
Volatility | 2018 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input	0.85
Volatility | 2017 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input	0.61
Volatility | 2016 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input	0.73
Volatility | 2014 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input	0.70
Volatility | 2013 Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants and Rights Outstanding, Measurement Input	0.64