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Divestiture and Discontinued Operations - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified | 3 Months Ended | 9 Months Ended
--- | --- | ---
Jul. 31, 2013 | Jan. 31, 2013 | Jul. 31, 2012 | Jan. 31, 2014 | Jan. 31, 2013
Divestitures [Line Items] |  |  |  |  |
Undiscounted purchase consideration paid in installments | 5 years |  | 21 years |  |
Loss on disposal of discontinued operations, net of tax | $ (378) |  |  | $ (378) |
Loss on divestiture |  | 353 |  |  | 353
Bio Fuels Assets [Member] |  |  |  |  |
Divestitures [Line Items] |  |  |  |  |
Undiscounted purchase consideration | 2,000 |  |  |  |
Maine Energy Facility [Member] |  |  |  |  |
Divestitures [Line Items] |  |  |  |  |
Undiscounted purchase consideration |  |  | $ 6,650 |  |

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- Definition Amount of gain (loss), after tax expense or benefit and not previously recognized, resulting from the sale of a business component. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e957-107759 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760 + Details
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- Definition Gain (loss) from sale or disposal of an organization or integrated set of activities (for example, but not limited to, a partnership or corporation) engaged in providing a product or service in a commercial, industrial, or professional environment. + References No definition available. + Details
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