Quarterly report pursuant to Section 13 or 15(d)

Purchase Price Allocation for Acquisition of Properties (Detail)

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Purchase Price Allocation for Acquisition of Properties (Detail) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2013
Dec. 31, 2012
Oct. 05, 2012
Newfield Properties
Business Acquisition [Line Items]      
Oil and natural gas properties and equipment     $ 237,278
Asset retirement obligations - current (69,964) (92,630) (7,250)
Asset retirement obligations - non-current (308,261) (291,423) (24,414)
Total cash paid     $ 205,614