Debt (Schedule Of Debt Issuance Costs Associated With Long-Term Obligations) (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term Obligations	$ 433,984,664	$ 458,997,331
Less unamortized debt issuance costs	2,546,476	2,669,485
2011 Series A Bonds [Member] | Term Loan Facility [Member]
Debt Instrument [Line Items]
Long-term Obligations	189,666,664	200,333,331
Less unamortized debt issuance costs	1,157,389	1,218,687
2012 Series A Bonds [Member] | Term Loan Facility [Member]
Debt Instrument [Line Items]
Long-term Obligations	172,750,000	183,500,000
Less unamortized debt issuance costs	978,270	1,019,582
2017 Series A Bonds [Member] | Term Loan Facility [Member]
Debt Instrument [Line Items]
Long-term Obligations	36,000,000	38,000,000
Less unamortized debt issuance costs	194,152	199,399
2016 CoBank Note [Member]
Debt Instrument [Line Items]
Long-term Obligations	38,800,000
2016 CoBank Note [Member] | Term Loan Facility [Member]
Debt Instrument [Line Items]
Long-term Obligations	35,568,000	37,164,000
Less unamortized debt issuance costs	$ 216,665	$ 231,817