Derivatives (Gain Or Loss Of Reclassified Accumulated Other Comprehensive Income And Recognized Income) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income	$ 2,965	[1]	$ 52,255	[1]
Amount of Gain or (Loss) Recognized in Income	2,749	[2]	700	[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	4,699	[1]	53,473	[1]
Amount of Gain or (Loss) Recognized in Income	2,749	[2]	700	[2]
Interest Rate Swaps [Member] | Interest [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income	(1,734)	[1]	(1,218)	[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).