Contractual interest rate for funds borrowed, under the debt agreement.

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Fair Value Measurements - Derivative Liabilities (Details)	Sep. 30, 2021 $ / shares	Dec. 31, 2020 $ / shares	May 31, 2013
Stock Price Volatility \| Compound embedded derivative with the 2013 8.00% Notes \| Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	1.25	0.40
Stock Price Volatility \| Compound embedded derivative with the 2013 8.00% Notes \| Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	1.46	0.85
Risk-Free Interest Rate \| Compound embedded derivative with the 2013 8.00% Notes
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative liability, measurement input	0.002	0.001
Note Conversion Price \| Compound embedded derivative with the 2013 8.00% Notes
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative liability, measurement input	0.69	0.69
Discount Rate \| Compound embedded derivative with the 2013 8.00% Notes
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative liability, measurement input	0.17	0.19
Market Price of Common Stock \| Compound embedded derivative with the 2013 8.00% Notes
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative liability, measurement input	1.67	0.34
8.00% Convertible Senior Notes Issued in 2013
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loan interest rate	8.00%		8.00%