Derivative Instruments And Hedging Activities (Derivatives Designated As Hedging Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Asset derivatives designated as hedging instruments	$ 22,708
Liability derivatives designated as hedging instruments	2,800
Other Current Assets [Member] | Oil Contract [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
Other Assets, Net [Member] | Natural Gas Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives designated as hedging instruments	857
Other Assets, Net [Member] | Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives designated as hedging instruments	327
Other Liabilities [Member] | Oil Contract [Member]
Derivatives, Fair Value [Line Items]
Liability derivatives designated as hedging instruments	1,712
Accrued Liabilities [Member] | Oil Contract [Member]
Derivatives, Fair Value [Line Items]
Liability derivatives designated as hedging instruments	886
Accrued Liabilities [Member] | Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Liability derivatives designated as hedging instruments	$ 202