Derivatives (Amount Of Gain Or (Loss) Recognized In Accumulated OCI On Derivative) (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) Recognized in Accumulated OCI on Derivative (Effective Portion)	$ (13,503)	[1]	$ (20,704)	[1]
Commodity Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Accumulated OCI on Derivative (Effective Portion)	(13,503)	[1]	(19,864)	[1]
Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Accumulated OCI on Derivative (Effective Portion)	$ 0	[1]	$ (840)	[1]

[1] Net of taxes.