Derivative Instruments And Hedging Activities (Derivatives Designated As Hedging Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Derivatives, Fair Value [Line Items]
Asset derivatives designated as hedging instruments	$ 22,708	$ 5,324
Liability derivatives designated as hedging instruments	2,799	31,634
Other Current Assets [Member] | Oil Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives designated as hedging instruments	8,567
Other Current Assets [Member] | Natural Gas Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives designated as hedging instruments	12,957	5,324
Other Assets [Member] | Natural Gas Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives designated as hedging instruments	857
Other Assets [Member] | Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives designated as hedging instruments	327
Other Long-Term Liabilities [Member] | Oil Contracts [Member]
Derivatives, Fair Value [Line Items]
Liability derivatives designated as hedging instruments	1,711
Other Long-Term Liabilities [Member] | Natural Gas Contracts [Member]
Derivatives, Fair Value [Line Items]
Liability derivatives designated as hedging instruments		913
Other Long-Term Liabilities [Member] | Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Liability derivatives designated as hedging instruments		115
Accrued Liabilities [Member] | Oil Contracts [Member]
Derivatives, Fair Value [Line Items]
Liability derivatives designated as hedging instruments	886	28,855
Accrued Liabilities [Member] | Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Liability derivatives designated as hedging instruments	$ 202	$ 1,751