Purchase Price Allocation for Hereford Facility Based on Estimated Fair Value of Assets Acquired (Detail) (Ethanol Plant in Hereford, Texas, USD $)	Dec. 31, 2010
Business Acquisition [Line Items]
Total purchase price	$ 40,000,000
Land and Land Improvements
Business Acquisition [Line Items]
Business acquisition, purchase price allocation	2,379,000
Buildings and Improvements
Business Acquisition [Line Items]
Business acquisition, purchase price allocation	639,000
Machinery and Transportation Equipment
Business Acquisition [Line Items]
Business acquisition, purchase price allocation	$ 36,982,000

The amount of acquisition cost of a business combination allocated to property, plant and equipment to be used in ongoing operations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph e

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 37

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationPropertyPlantAndEquipment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant