Supplemental Oil And Gas Disclosures (Results Of Operations For Producing Activities) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Supplemental Oil And Gas Disclosures [Abstract]
Revenues	$ 504,739	$ 392,229	$ 352,572
Production costs	(115,400)	(91,143)	(75,214)
Depreciation, depletion, amortization and impairment	(181,960)	(117,793)	(394,942)
Results of operations, income before income taxes	207,379	183,293	(117,584)
Income tax (expense) benefit	(80,048)	(70,110)	43,153
Results of operations for producing activities (excluding corporate overhead and financing costs)	$ 127,331	$ 113,183	$ (74,431)