Derivative Instruments And Hedging Activities (Derivatives Designated As Hedging Instruments) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Asset derivatives designated as hedging instruments	$ 42,522	$ 5,324
Liability derivatives designated as hedging instruments	692	31,634
Other Current Assets [Member] | Oil Contract [Member]
Asset derivatives designated as hedging instruments	28,020
Other Current Assets [Member] | Natural Gas Contracts [Member]
Asset derivatives designated as hedging instruments	5,074	5,324
Other Assets, Net [Member] | Oil Contract [Member]
Asset derivatives designated as hedging instruments	8,868
Other Assets, Net [Member] | Natural Gas Contracts [Member]
Asset derivatives designated as hedging instruments	322
Other Assets, Net [Member] | Interest Rate Swaps [Member]
Asset derivatives designated as hedging instruments	238
Other Liabilities [Member] | Natural Gas Contracts [Member]
Liability derivatives designated as hedging instruments		913
Other Liabilities [Member] | Interest Rate Swaps [Member]
Liability derivatives designated as hedging instruments		115
Accrued Liabilities [Member] | Oil Contract [Member]
Liability derivatives designated as hedging instruments		28,855
Accrued Liabilities [Member] | Interest Rate Swaps [Member]
Liability derivatives designated as hedging instruments	$ 692	$ 1,751