Acquisitions - Additional Information (Detail) (USD $)	12 Months Ended	3 Months Ended
	Dec. 31, 2010 Ethanol Plant in Hereford, Texas	Dec. 31, 2009 Ethanol Plant in Hankinson, North Dakota gal
Schedule of Business Acquisitions, Cost of Acquired Entity [Line Items]
Date of acquisition of business	2010-08-31	2009-10-01
Plant capacity		110,000,000
Total purchase price	$ 40,000,000	$ 92,000,000
Nonrecourse loan		$ 82,000,000
Nonrecourse loan, Interest rate		5.00%
Nonrecourse loan maturity period		2014
Date of loan repaid		Sep. 30, 2010