Derivative Instruments And Hedging Activities (Impact Of Derivative Instruments On Accumulated Comprehensive Income (Loss)) (Details) (USD $) In Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	$ 33,888	[1]	$ (3,795)	[1]	$ 44,291	[1]	$ 12,308	[1]
Oil And Natural Gas Commodity Contracts [Member]
Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	33,432	[1]	(3,405)	[1]	43,373	[1]	13,799	[1]
Interest Rate Swaps [Member]
Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	$ 456	[1]	$ (390)	[1]	$ 918	[1]	$ (1,491)	[1]

[1] All unrealized gains (losses) related to our oil and natural gas commodity contracts are expected to be reclassified into earnings by no later than December 31, 2013. The last of our interest swaps will mature in January 2014 and we have foreign exchange forwards that have maturities through June 2012.