Fair Value Measurements (Schedule Of Assets And Liabilities Measured At Fair Value) (Details) (Level 2 [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 26, 2011
Commodity Contracts - Fuel [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Category, Assets	$ 790		$ 4,511
Fair Value Measurement Category, Liabilities		251
Foreign Exchange Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Category, Assets	341	341	633
Fair Value Measurement Category, Liabilities	$ 435	$ 92	$ 331