Derivatives (Gain Or Loss Of Reclassified Accumulated Other Comprehensive Income And Recognized In Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income	$ 8,176	[1]	$ 332	[1]
Amount of Gain or (Loss) Recognized in Income	(1,993)	[2]	(1,909)	[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	8,176	[1]	635	[1]
Amount of Gain or (Loss) Recognized in Income	(1,993)	[2]	(1,909)	[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]	(303)	[1]
Amount of Gain or (Loss) Recognized in Income	$ 0	[2]	$ 0	[2]

[1] Effective portion of gain (loss).

[2] Ineffective portion of gain (loss).