Summary of Impairment Charges (Detail) (USD $) In Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Impaired Long-Lived Assets Held and Used [Line Items]
Oil and gas properties	$ 32,627	$ 71,071	$ 32,627
Other	2,500		3,624
Asset Impairment Charges, Total	$ 35,127	$ 71,071	$ 36,251

The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

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+ Details