Derivatives (Gain Or Loss Of Reclassified Accumulated Other Comprehensive Income And Recognized Income) (Details) (USD $) In Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income	$ 2,003	[1]	$ 14,462	[1]	$ (2,616)	[1]	$ 35,540	[1]
Amount of Gain or (Loss) Recognized in Income	2,336	[2]	176	[2]	4,158	[2]	605	[2]
Interest Rate Swaps [Member] | Interest [Member]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income	0	[1]	(298)	[1]	(1,734)	[1]	(907)	[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	2,003	[1]	14,760	[1]	(882)	[1]	36,447	[1]
Amount of Gain or (Loss) Recognized in Income	$ 2,336	[2]	$ 176	[2]	$ 4,158	[2]	$ 605	[2]

[1] Effective portion of gain (loss).

[2] Ineffective portion of gain (loss).