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ASSET RETIREMENT OBLIGATIONS (Reconciliations Of Asset Retirement Obligations) (Details) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Asset Retirement Obligations      
Balance at beginning of period $ 228,234us-gaap_AssetRetirementObligation $ 150,072us-gaap_AssetRetirementObligation  
Liabilities incurred 9,130us-gaap_AssetRetirementObligationLiabilitiesIncurred 69,111us-gaap_AssetRetirementObligationLiabilitiesIncurred  
Liabilities settled (26,547)us-gaap_AssetRetirementObligationLiabilitiesSettled (16,203)us-gaap_AssetRetirementObligationLiabilitiesSettled  
Accretion expense 11,601us-gaap_AssetRetirementObligationAccretionExpense 10,685us-gaap_AssetRetirementObligationAccretionExpense 7,956us-gaap_AssetRetirementObligationAccretionExpense
Revisions up (down), net 4,147us-gaap_AssetRetirementObligationRevisionOfEstimate 14,569us-gaap_AssetRetirementObligationRevisionOfEstimate  
Balance at end of period $ 226,565us-gaap_AssetRetirementObligation $ 228,234us-gaap_AssetRetirementObligation $ 150,072us-gaap_AssetRetirementObligation