Annual report pursuant to Section 13 and 15(d)

Fair Value - Carrying and Fair Value Amounts (Details)

v3.8.0.1
Fair Value - Carrying and Fair Value Amounts (Details) - USD ($)
Dec. 31, 2017
Dec. 31, 2016
Carrying Amount [Member] | Level 1 [Member]    
Financial Assets:    
Cash and cash equivalents $ 15,787,069 $ 7,895,084
Financial Liabilities:    
Unsecured convertible senior notes 112,032,083 111,244,895
Carrying Amount [Member] | Level 2 [Member]    
Financial Assets:    
Derivative asset 0 19,950
Financial Liabilities:    
Long-term debt 40,745,354 89,387,985
Carrying Amount [Member] | Level 3 [Member]    
Financial Assets:    
Financing notes receivable 1,500,000 1,500,000
Fair Value [Member] | Level 1 [Member]    
Financial Assets:    
Cash and cash equivalents 15,787,069 7,895,084
Financial Liabilities:    
Unsecured convertible senior notes 139,101,660 129,527,940
Fair Value [Member] | Level 2 [Member]    
Financial Assets:    
Derivative asset 0 19,950
Financial Liabilities:    
Long-term debt 40,745,354 89,387,985
Fair Value [Member] | Level 3 [Member]    
Financial Assets:    
Financing notes receivable $ 1,500,000 $ 1,500,000