Derivative Instruments (Location And Amounts Of Derivative Fair Values In Condensed Consolidated Balance Sheets) (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Liability Derivatives, Total	$ 18,181	$ 11,458
Interest Rate Contracts [Member] | Accrued Expenses [Member] | Derivatives Designated as Hedging Instruments [Member]
Liability Derivatives, Total	361	581
Commodity Contracts [Member] | Fuel Price Derivatives, At Fair value [Member] | Derivatives Not Designated As Hedging Instruments [Member]
Liability Derivatives, Total	$ 17,820	$ 10,877