Fair Value Measurements (Narrative) (Details) (Swap [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Derivative [Line Items]
Fixed price swap contract (in gallons)	3,000,000
Average contract price (in dollars per gallon)	3.97
Average forward price (in dollars per gallon)	4.15
Prepaid Expenses And Other Assets [Member]
Derivative [Line Items]
Derivative asset	$ 1	$ 0
Accrued Expenses And Other Liabilities [Member]
Derivative [Line Items]
Derivative liability	$ 0	$ 1