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Asset Retirement Obligations (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2014
Asset Retirement Obligations  
Asset retirement obligations at December 31, 2013 $ 94,830
Change in the asset retirement obligations  
Liabilities added from drilling 1,412
Current year accretion expense 1,316
Settlements (1,566)
Asset retirement obligations at March 31, 2014 $ 95,992