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ASSET RETIREMENT OBLIGATIONS Asset Retirement Obligations (Details) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]      
Balance beginning of year, January 1 $ 62,563 $ 46,566  
Obligations incurred with development activities and assumed with acquisitions 2,389 14,169  
Accretion of asset retirement obligation 4,747 4,060 1,897
Obligations discharged with disposal of properties and asset retirements (29,281) (2,232)  
Revisions in estimated cash flows 612 0  
Balance end of year, December 31 41,030 62,563 46,566
Less: Liabilities held for sale (2,061) [1] 0 [1]  
Less: Current portion (1,158) (1,000)  
Long-term portion $ 37,811 $ 61,563  
[1] Represents asset retirement obligations related to assets sold and assets held for sale. See Note 14, Assets Held for Sale, Divestitures and Discontinued Operations, for additional information.