Derivatives (Narrative) (Details) (Swap [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Derivative [Line Items]
Fixed price swap contract (in gallons)	7,700,000
Accrued Expenses And Other Liabilities [Member]
Derivative [Line Items]
Derivative liability	$ 2	$ 1
Accumulated Other Comprehensive Income [Member]
Derivative [Line Items]
Derivative accumulated other comprehensive income	1
Maximum [Member] | Accumulated Other Comprehensive Income [Member]
Derivative [Line Items]
Derivative accumulated other comprehensive income		$ 1