Supplemental Oil And Gas Disclosures (Schedule Of Principal Sources Of Changes In Standardized Measure Of Discounted Future Net Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reserve Quantities [Line Items]
Sales and transfers of oil and natural gas produced, net of production costs	$ (470,970)	$ (425,626)	$ (389,339)
Net changes in prices and production costs	188,826	(321,099)	115,852
Revisions in quantity estimates and changes in production timing	(10,650)	(148,648)	(38,336)
Extensions, discoveries and improved recovery, less related costs	426,377	432,058	401,134
Changes in estimated future development costs	26,629	51,587	37,742
Previously estimated cost incurred during the period	96,457	104,377	45,327
Purchases of minerals in place	9	283,774	58,567
Sales of minerals in place	(43,435)	(112,359)	(29)
Accretion of discount	147,579	157,842	128,492
Net change in income taxes	(170,091)	94,678	(60,675)
Other-net	(44,711)	(124,537)	(65,912)
Net change	146,020	(7,953)	232,823
Beginning of year	1,079,956	1,087,909	855,086
End of year	$ 1,225,976	$ 1,079,956	$ 1,087,909