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, 2012		Dec. 31, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income	$ 51,853		$ 2,965
Amount of Gain or (Loss) Recognized in Income	(2,616)		2,749
Commodity Contract [Member] | Oil And Natural Gas Revenue [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income	51,853	[1]	4,699	[1]
Commodity Contract [Member] | Gain (Loss) on Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income	(2,616)	[2]	2,749	[2]
Interest Rate Swaps [Member] | Interest [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income	0		(1,734)
Amount of Gain or (Loss) Recognized in Income	$ 0		$ 0

[1] Effective portion of gain (loss).

[2] Ineffective portion of gain (loss).