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Fixed Assets And Asset Retirement Obligations (Schedule Of Reconciliation Of Liability For Asset Retirement Obligations) (Details) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Fixed Assets And Asset Retirement Obligations [Abstract]    
Asset retirement obligations, beginning balance $ 5,179 $ 4,838
Liabilities incurred and assumed in the current period 349  
Accretion expense 372 341
Asset retirement obligations, ending balance $ 5,900 $ 5,179