Annual report pursuant to Section 13 and 15(d)

Fair Value - Carrying and Fair Value Amounts (Details)

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Fair Value - Carrying and Fair Value Amounts (Details) - USD ($)
Dec. 31, 2019
Aug. 15, 2019
Aug. 12, 2019
Dec. 31, 2018
Jun. 29, 2015
Carrying Amount | Level 1          
Financial Assets:          
Cash and cash equivalents $ 120,863,643     $ 69,287,177  
Carrying Amount | Level 2          
Financial Liabilities:          
Secured credit facilities 33,785,930     37,261,109  
Carrying Amount | Level 3          
Financial Assets:          
Financing notes receivable 1,235,000     1,300,000  
Fair Value | Level 1          
Financial Assets:          
Cash and cash equivalents 120,863,643     69,287,177  
Fair Value | Level 2          
Financial Liabilities:          
Secured credit facilities 33,785,930     37,261,109  
Fair Value | Level 3          
Financial Assets:          
Financing notes receivable 1,235,000     1,300,000  
7.00% Unsecured Convertible Senior Notes | Carrying Amount | Level 1          
Financial Liabilities:          
Unsecured convertible senior notes 2,084,178     112,777,271  
7.00% Unsecured Convertible Senior Notes | Fair Value | Level 1          
Financial Liabilities:          
Unsecured convertible senior notes 2,820,832     119,378,982  
5.875% Unsecured Convertible Senior Notes | Carrying Amount | Level 2          
Financial Liabilities:          
Unsecured convertible senior notes 116,239,318     0  
5.875% Unsecured Convertible Senior Notes | Fair Value | Level 2          
Financial Liabilities:          
Unsecured convertible senior notes $ 122,508,000     $ 0  
Convertible Debt | 7.00% Unsecured Convertible Senior Notes          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Effective interest rate 7.00%     7.00% 7.00%
Convertible Debt | 5.875% Unsecured Convertible Senior Notes          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Effective interest rate 5.875% 5.875% 5.875% 0.00%