Segment Reporting (Detail) - Schedule of Segment Reporting Information, Profit Loss And Revenue Percentage (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2012	Jul. 31, 2011
Net sales and revenues	$ 153,164	$ 73,796	$ 304,178	$ 154,959
Gross profit (loss)	6,794	(219)	12,260	4,511
Income from continuing operations before income taxes and noncontrolling interests	1,518	3,157	3,387	10,933
Interest expense	(1,173)	(638)	(2,527)	(1,301)
Income from synthetic fuel partnerships		2,883		2,883
Interest income	41	101	90	271
Ethanol [Member] \| Alternative Energy Segment [Member]
Sale of products	76.00%	81.00%	77.00%	81.00%
Distillers Grains [Member] \| Alternative Energy Segment [Member]
Sale of products	21.00%	19.00%	20.00%	19.00%
Other Products [Member] \| Alternative Energy Segment [Member]
Sale of products	3.00%		3.00%
Alternative Energy Segment [Member]
Net sales and revenues	152,778	73,531	303,442	154,413
Gross profit (loss)	7,027	952	12,537	5,730
Income from continuing operations before income taxes and noncontrolling interests	2,432	2,061	4,901	10,459
Sale of products	100.00%	100.00%	100.00%	100.00%
Real Estate Segment [Member]
Net sales and revenues	386	265	736	546
Gross profit (loss)	(233)	(1,171)	(277)	(1,219)
Income from continuing operations before income taxes and noncontrolling interests	(289)	(1,218)	(382)	(1,331)
Lease revenue	100.00%	100.00%	100.00%	100.00%
Corporate [Member]
Income from continuing operations before income taxes and noncontrolling interests	(623)	(615)	(1,136)	(1,232)
Interest expense	(21)	(27)	(45)	(61)
Income from synthetic fuel partnerships		2,883		2,883
Interest income	$ 19	$ 73	$ 49	$ 215

The percentage of net lease revenue to total net revenue from the lease as of year end.

No definition available.

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- Definition

The percentage of net product revenue to total net revenue from the sale of goods as of year end.

+ References

No definition available.

+ Details

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- Definition

This item represents the amount of gain (loss) arising from the disposal of an equity method investment.

+ References

No definition available.

+ Details

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- Definition

Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

+ References

+ Details

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- Definition

This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 10

-Article 5

+ Details

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- Definition

The cost of borrowed funds accounted for as interest that was charged against earnings during the period.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 9

-Article 9

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

-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

-Section 563c.102

-Paragraph 9

-Chapter V

-Subsection II

-LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 34

-Paragraph 21

-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 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.9)

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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- Definition

Income derived from investments in debt securities and on cash and cash equivalents the earnings of which reflect the time value of money or transactions in which the payments are for the use or forbearance of money.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 14

-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 SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.7(b))

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

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- Definition

Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

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