Derivatives (Narrative) (Details) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2012 CAD	Sep. 30, 2012 CAD	Sep. 30, 2012 Swap [Member] gal	Dec. 31, 2011 Swap [Member] Accrued Expenses And Other Liabilities [Member] USD ($)	Sep. 30, 2012 Maximum [Member] Swap [Member] Prepaid Expenses And Other Assets [Member] USD ($)	Sep. 30, 2012 Maximum [Member] Swap [Member] Accumulated Other Comprehensive Income [Member] USD ($)	Dec. 31, 2011 Maximum [Member] Swap [Member] Accumulated Other Comprehensive Income [Member] USD ($)
Derivative [Line Items]
Fixed price swap contract (in gallons)			7,100,000
Amount of forward contracts sold	25	55
Derivative asset					1
Derivative liability				1
Derivative accumulated other comprehensive income						$ 1	$ 1