Quarterly report pursuant to Section 13 or 15(d)

Reconciliation of Asset Retirement Obligations Liability (Detail)

v2.4.0.6
Reconciliation of Asset Retirement Obligations Liability (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2013
Dec. 31, 2012
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Asset retirement obligations, beginning of period $ 384,053  
Liabilities settled (23,464)  
Accretion of discount 5,515  
Liabilities incurred 131  
Asset retirement obligations, end of period 378,225  
Less current portion 69,964 92,630
Long-term 308,261 291,423
Hurricane Ike
   
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Revisions of estimated liabilities 3,951  
All Other
   
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Revisions of estimated liabilities $ 8,039 [1]  
[1] Revisions are primarily due to increases in the scope of work at several offshore locations required by the Bureau of Safety and Environmental Enforcement.