Derivative Instruments And Hedging Activities (Impact Of Derivative Instruments On Accumulated Comprehensive Income (Loss)) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	$ (7,238)	$ (13,802)
Oil And Natural Gas Commodity Contracts [Member]
Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)		(13,555)
Interest Rate Swaps [Member]
Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)		(247)
Foreign Exchange Forward [Member]
Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	$ (7,238)