Derivatives (Gain Or Loss Of Reclassified Accumulated Other Comprehensive Income And Recognized In Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income	$ 14,243	[1]	$ 2,003	[1]	$ 38,088	[1]	$ (2,616)	[1]
Amount of Gain or (Loss) Recognized in Income	(4,015)	[2]	2,336	[2]	(4,621)	[2]	4,158	[2]
Oil And Natural Gas Revenue [Member] | Commodity Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income	14,243	[1]	2,003	[1]	38,088	[1]	(882)	[1]
Amount of Gain or (Loss) Recognized in Income	(4,015)	[2]	2,336	[2]	(4,621)	[2]	4,158	[2]
Interest Rate Swaps [Member] | Interest, Net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income	0	[1]	0	[1]	0	[1]	(1,734)	[1]
Amount of Gain or (Loss) Recognized in Income	$ 0	[2]	$ 0	[2]	$ 0	[2]	$ 0	[2]

[1] Effective portion of gain (loss).

[2] Ineffective portion of gain (loss).