Quarterly report pursuant to Section 13 or 15(d)

Asset Retirement Obligations (Reconciliation of Asset Retirement Obligations Liability) (Detail)

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Asset Retirement Obligations (Reconciliation of Asset Retirement Obligations Liability) (Detail) (USD $)
In Thousands, unless otherwise specified
 6 Months Ended
Jun. 30, 2012
Dec. 31, 2011
Asset Retirement Obligations [Line Items]    
Balance, December 31, 2011 $ $ 393,880  
Liabilities settled (29,228)  
Accretion of discount 10,347  
Disposition of properties (3,993)  
Liabilities incurred 362  
Balance 349,001  
Less current portion 99,211 138,185
Long-term $ 249,790 255,695
Hurricane Ike
    
Asset Retirement Obligations [Line Items]    
Revisions of estimated liabilities (30,360) [1]  
All other
    
Asset Retirement Obligations [Line Items]    
Revisions of estimated liabilities $ 7,993  
[1] During the six months ended June 30, 2012, our recommended remediation plan for one of the hurricane damaged platforms and its associated wells was approved by all required parties. The approved plan, which included remediating the damaged platform as a reef in place, was responsible for most of the reduction of the estimated costs.