Supplemental Oil And Gas Disclosures (Changes In Standardized Measure Of Discounted Future Net Cash Flows) (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]
Standardized measure, beginning of year	$ 991,067	$ 991,060	$ 1,312,155
Sales, net of production costs	(516,895)	(294,212)	(265,501)
Net change in prices and production costs	414,426	577,687	(245,883)
Changes in future development costs	(108,007)	84,907	(16,905)
Development costs incurred	168,005	55,646	74,133
Accretion of discount	131,464	129,083	161,254
Net change in income taxes	(54,613)	(41,115)	257,919
Purchases of reserves in place
Extensions and discoveries	29,479		10,457
Sales of reserves in place	(14,324)		(30,124)
Net change due to revision in quantity estimates	(186,197)	(422,987)	(85,450)
Changes in production rates (timing) and other	208,727	(89,002)	(180,995)
Total	72,065	7	(321,095)
Standardized measure, end of year	$ 1,063,132	$ 991,067	$ 991,060