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, 2012	Dec. 31, 2011	Dec. 31, 2010
Supplemental Oil and Gas Disclosures [Abstract]
Standardized measure, beginning of year	$ 1,063,132	$ 991,067	$ 991,060
Sales, net of production costs	(379,910)	(516,895)	(294,212)
Net change in prices and production costs	(242,037)	414,426	577,687
Changes in future development costs	(65,854)	(108,007)	84,907
Development costs incurred	149,702	168,005	55,646
Accretion of Discount	147,157	131,464	129,083
Net change in income taxes	101,720	(54,613)	(41,115)
Extensions and discoveries	110,655	29,479
Sales of reserves in place	(6,096)	(14,324)
Net change due to revision in quantity estimates	28,627	(186,197)	(422,987)
Changes in production rates (timing) and other	(68,783)	208,727	(89,002)
Total	(224,819)	72,065	7
Standardized measure, end of year	$ 838,313	$ 1,063,132	$ 991,067