Fair Value Measurements (Assets and Liabilities Measured at Fair Value) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Nov. 30, 2009
1 7/8 percent Convertible Senior Subordinated Notes [Member]
Derivative [Line Items]
Stated interest rate	1.875%
4 percent Convertible Senior Notes [Member]
Derivative [Line Items]
Stated interest rate	4.00%	4.00%	4.00%
Effective interest rate	6.90%
Capital Leases [Member]
Derivative [Line Items]
Effective interest rate	7.00%
Swap [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount (in gallons)	7,900,000
Derivative, notional amount (in dollars per gallon)	3.88
Average forward price (in dollars per gallon)	3.89
Accrued Expenses And Other Liabilities [Member] | Swap [Member]
Derivative [Line Items]
Derivative liability, fair value, gross liability		1
Accrued Expenses And Other Liabilities [Member] | Maximum [Member] | Swap [Member]
Derivative [Line Items]
Derivative liability, fair value, gross liability	1
Prepaid Expenses And Other Assets [Member]
Derivative [Line Items]
Derivative asset, fair value, gross asset	1
Prepaid Expenses And Other Assets [Member] | Swap [Member]
Derivative [Line Items]
Derivative asset, fair value, gross asset		0
Prepaid Expenses And Other Assets [Member] | Maximum [Member] | Swap [Member]
Derivative [Line Items]
Derivative asset, fair value, gross asset	1