XML 48 R35.htm IDEA: XBRL DOCUMENT v3.8.0.1
Summary of Significant Accounting Policies (Restricted Cash and Cash Equivalents) (Details) - USD ($)
Jun. 30, 2018
Dec. 31, 2017
Dec. 31, 2016
Restricted Cash and Cash Equivalents Items [Line Items]      
Restricted cash and cash equivalents   $ 17,200,000  
Restricted cash, short-term   $ 10,701,305 $ 10,138,890
Secured Debt | Scenario, Forecast | Loan Agreement      
Restricted Cash and Cash Equivalents Items [Line Items]      
Additional borrowing capacity $ 5,000,000