Derivative Instruments And Hedging Activities (Derivatives Designated As Hedging Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Asset derivatives designated as hedging instruments	$ 7,350	$ 22,708
Liability derivatives designated as hedging instruments	23,708	2,799
Other Current Assets [Member] | Oil Contract [Member]
Asset derivatives designated as hedging instruments	3,184	8,567
Other Current Assets [Member] | Natural Gas Contracts [Member]
Asset derivatives designated as hedging instruments	2,824	12,957
Other Assets, Net [Member] | Oil Contract [Member]
Asset derivatives designated as hedging instruments	1,227
Other Assets, Net [Member] | Natural Gas Contracts [Member]
Asset derivatives designated as hedging instruments	115	857
Other Assets, Net [Member] | Interest Rate Swaps [Member]
Asset derivatives designated as hedging instruments		327
Other Liabilities [Member] | Oil Contract [Member]
Liability derivatives designated as hedging instruments	3,234	1,711
Other Liabilities [Member] | Interest Rate Swaps [Member]
Liability derivatives designated as hedging instruments	141
Accrued Liabilities [Member] | Oil Contract [Member]
Liability derivatives designated as hedging instruments	19,840	886
Accrued Liabilities [Member] | Interest Rate Swaps [Member]
Liability derivatives designated as hedging instruments	$ 493	$ 202