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Asset Retirement Obligations - Asset Retirement Obligations (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2014
Dec. 31, 2013
Asset Retirement Obligation [Abstract]    
Beginning of period $ 230,077  
Liabilities incurred 2,128  
Liabilities settled (384)  
Disposition of wells (122)  
Accretion expense 3,707  
Change in estimate 1,089  
End of period 236,495  
Less current portion (5,037) (5,037)
Long-term asset retirement obligations $ 231,458