Fair Value Measurements (Narrative) (Details) (Fixed price swap contracts, USD $)	3 Months Ended
	Mar. 31, 2014 gal	Mar. 31, 2014 Prepaid Expenses and Other Assets	Dec. 31, 2013 Prepaid Expenses and Other Assets	Mar. 31, 2014 Accrued Expenses and Other Liabilities	Dec. 31, 2013 Accrued Expenses and Other Liabilities
Derivative [Line Items]
Derivative asset (Less than $1 as of March 31, 2014 and December 31, 2013)		$ 1,000,000	$ 1,000,000
Derivative liability (Less than $1 as of March 31, 2014 and December 31, 2013)				$ 1,000,000	$ 1,000,000
Fixed price swap contract (in gallons)	6,400,000
Average contract price (in dollars per gallon)	3.89
Average forward price (in dollars per gallon)	3.88