Derivative Financial Instruments (Derivatives And Hedging-Nondesignated) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Not Designated As Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives	$ 3,414	$ 6,431
Liability Derivatives	8,237	1,548
NYMEX Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives	16,400
NYMEX Commodity Contracts [Member] | Not Designated As Hedging Instruments [Member] | Energy Commodity Derivatives Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives	3,414	6,403
Liability Derivatives	8,230	1,514
Butane Swap Agreements [Member] | Not Designated As Hedging Instruments [Member] | Energy Commodity Derivatives Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives		28
Liability Derivatives	$ 7	$ 34