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Fair Value Of Financial Instruments (Tables)
6 Months Ended
Jun. 30, 2012
Fair Value Of Financial Instruments [Abstract]  
Schedule Of Carrying Amounts And Estimated Fair Values Of Long-Term Debt
    June 30,   December 31,
    2012   2011
Carrying Amount $ 1,613,747 $ 1,516,548
Estimated Fair Value   1,717,833   1,592,411