Significant Accounting Policies (Reconciliation Of Cash, Cash Equivalents, And Restricted Cash Equivalents) (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Significant Accounting Policies [Abstract]
Cash and cash equivalents	$ 4,689,826	$ 5,485,631
Restricted cash equivalents	556,783	687,370
Restricted cash equivalents included in other property and investments	748,953	1,028,758
Total cash, cash equivalents and restricted cash equivalents shown in the consolidated statements of cash flows	$ 5,995,562	$ 7,201,759	$ 4,596,657	$ 6,383,217