Debt (Schedule Of Long-Term Debt Obligations) (Details) (USD $)			12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended			12 Months Ended			12 Months Ended			12 Months Ended			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 CoBank 3 And 4 Variable Rate Notes Maturing In 2022 [Member]	Dec. 31, 2011 CoBank 3 And 4 Variable Rate Notes Maturing In 2022 [Member]	Dec. 31, 2012 CoBank 5 Variable Rate Notes Maturing In 2012 [Member]	Dec. 31, 2011 CoBank 5 Variable Rate Notes Maturing In 2012 [Member]	Dec. 31, 2012 2002 Series A Bond Of 6.2% Maturing 2012 [Member]	Dec. 31, 2011 2002 Series A Bond Of 6.2% Maturing 2012 [Member]	Dec. 31, 2012 2011 Series A Bond Of 4.2% Maturing 2031 [Member]	Dec. 31, 2011 2011 Series A Bond Of 4.2% Maturing 2031 [Member]	Jan. 21, 2011 2011 Series A Bond Of 4.2% Maturing 2031 [Member]	Dec. 31, 2012 2011 Series A Bond Of 4.75% Maturing 2041 [Member]	Dec. 31, 2011 2011 Series A Bond Of 4.75% Maturing 2041 [Member]	Jan. 21, 2011 2011 Series A Bond Of 4.75% Maturing 2041 [Member]	Dec. 31, 2012 2012 Series A Bond Of 4.01% Maturing 2032 [Member]	Jan. 11, 2012 2012 Series A Bond Of 4.01% Maturing 2032 [Member]	Dec. 31, 2011 2012 Series A Bond Of 4.01% Maturing 2032 [Member]	Dec. 31, 2012 2012 Series A Bond Of 4.41% Maturing 2042 [Member]	Jan. 11, 2012 2012 Series A Bond Of 4.41% Maturing 2042 [Member]	Dec. 31, 2011 2012 Series A Bond Of 4.41% Maturing 2042 [Member]	Dec. 31, 2012 2012 Series A Bond Of 4.78% Maturing 2042 [Member]	Jan. 11, 2012 2012 Series A Bond Of 4.78% Maturing 2042 [Member]	Dec. 31, 2011 2012 Series A Bond Of 4.78% Maturing 2042 [Member]
Debt Instrument [Line Items]
Long-term obligations, including current installments	$ 546,090,108	$ 429,450,318	$ 31,756,775	$ 33,659,141	$ 0	$ 791,177	$ 0	$ 120,000,000	$ 85,500,000	$ 90,000,000		$ 178,833,333	$ 185,000,000		$ 75,000,000		$ 0	$ 125,000,000		$ 0	$ 50,000,000		$ 0
Current installments of long-term obligations	24,493,022	133,360,210
Total long-term obligations, excluding current installments	$ 521,597,086	$ 296,090,108
Variable interest rate			2.55%		2.55%
Bonds, interest rate							6.20%				4.20%			4.75%		4.01%			4.41%			4.78%
Maturity date			2022		2012		2012
Maturity date									Mar. 15, 2031			Mar. 15, 2041			Mar. 15, 2032			Mar. 15, 2042			Mar. 15, 2042
Frequency of payment			interest payable monthly and principal due annually beginning in 2003		interest and principal payable monthly		interest payable semi-annually February 1 and August 1		interest payable semi-annually March 15 and September 15 and principal due annually beginning in 2012			interest payable semi-annually March 15 and September 15 and principal due annually beginning in 2012			interest payable semi-annually March 15 and September 15 and principal due annually beginning in 2013			interest payable semi-annually March 15 and September 15 and principal due annually between 2013 and 2020 and between 2032 and 2042			interest payable semi-annually March 15 and September 15 and principal due annually beginning in 2023