Fair Value Measurements (Assets and Liabilities Measured at Fair Value) (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010
1 7/8 percent Convertible Senior Subordinated Notes
Derivative [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.875%
Swap [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount (in gallons)	4,200,000
Derivative, Nonmonetary Notional Amount, Price Per Gallon	3.98
Derivative, Average Forward Price	3.79
Prepaid Expenses And Other Assets [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 0
Prepaid Expenses And Other Assets [Member] | Maximum [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		1,000,000
Prepaid Expenses And Other Assets [Member] | Maximum [Member] | Swap [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	1,000,000
Accrued Expenses And Other Liabilities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability		0
Accrued Expenses And Other Liabilities [Member] | Swap [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	1,000,000
Accrued Expenses And Other Liabilities [Member] | Maximum [Member] | Swap [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ 1,000,000