Income Taxes AFMC for CBPC exchange (Details) (USD $)	3 Months Ended			6 Months Ended		3 Months Ended		12 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Mar. 31, 2013 Exchange of Alternative Fuel Tax Benefit [Member]	Jun. 30, 2012 Exchange of Alternative Fuel Tax Benefit [Member]	Dec. 31, 2009 Cellulosic Biofuel Producer Credit [Member]	Dec. 31, 2009 Alternative Fuel Mixture Credit [Member]
AFMC for CBPC Exchange [Line Items]
Tax Credit Amount per Gallon								$ 1.01	$ 0.50
Gallons Exchanged		120000000	60000000
Income Tax Benefit						19,000,000	9,100,000
Interest Expense	$ 10,019,000		$ 16,056,000	$ 17,736,000	$ 27,880,000		$ 3,400,000