Derivatives (Gain Or Loss Of Reclassified Accumulated Other Comprehensive Income And Recognized Income) (Details) (USD $) In Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income	$ (4,951)	[1]	$ 15,812	[1]	$ (4,619)	[1]	$ 21,078	[1]
Amount of Gain or (Loss) Recognized in Income	3,731	[2]	(662)	[2]	1,822	[2]	429	[2]
Interest Rate Swaps [Member] | Interest [Member]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income	(1,431)	[1]	(302)	[1]	(1,734)	[1]	(609)	[1]
Amount of Gain or (Loss) Recognized in Income	0	[2]	0	[2]	0	[2]	0	[2]
Oil And Natural Gas Revenue [Member] | Commodity Derivatives [Member]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income	(3,520)	[1]	16,114	[1]	(2,885)	[1]	21,687	[1]
Amount of Gain or (Loss) Recognized in Income	$ 3,731	[2]	$ (662)	[2]	$ 1,822	[2]	$ 429	[2]

[1] Effective portion of gain (loss).

[2] Ineffective portion of gain (loss).