Supplemental Oil And Gas Disclosures (Capitalized Costs) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Supplemental Oil and Gas Disclosures [Abstract]
Unproved oil and gas properties	$ 50,389	$ 56,093
Proved oil and gas properties	2,524,304	2,691,802
Total oil and gas properties	2,574,693	2,747,895
Accumulated depletion, depreciation and amortization	(1,703,046)	(1,673,740)
Net capitalized costs	871,647	1,074,155
Oil and gas asset retirement obligations	$ 254,391	$ 234,936	$ 248,128

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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Capitalized costs of proved properties incurred for any combination mineral interests acquisitions; wells and related equipment; support equipment and facilities; and uncompleted wells and equipment and other costs not previously disclosed within this table.

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- Definition

Capitalized costs of unproved properties incurred for any combination mineral interests acquisitions and other costs not previously disclosed within this table.

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