Oil And Gas Properties (Changes In Asset Retirement Obligations) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Asset retirement obligations at December 31, 2011	$ 254,391
Liability incurred during the period	1,110
Liability settled during the period	(108,729)
Other revision in estimated cash flows	47,080	[1]
Accretion expense (included in depreciation and amortization)	9,743
Asset retirement obligations at September 30, 2012	203,595
Non-Producing Oil And Gas Properties [Member]
Other revision in estimated cash flows	$ 24,900

[1] The increased amount of these liabilities includes revisions to both non-producing and producing oil and gas properties. Increases to liabilities associated with non-producing properties ($24.9 million) include a corresponding charge to cost of sales within our condensed consolidated statements of operations and comprehensive income while changes in estimates for producing properties are recorded as an increase to property and equipment carrying costs of the related oil and gas properties within our condensed consolidated balance sheets.