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Special Purpose Entities - Additional Information (Detail) (USD $)	3 Months Ended
	Apr. 30, 2014 Project JointVenture	Apr. 30, 2013
Variable Interest Entity [Line Items]
Number of natural gas-fired power plant projects under development	2
Gains on the deconsolidation of variable interest entities		$ 1,120,000
Income attributable to the noncontrolling interest	1,325,000	530,000
Number of joint ventures	2
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Gains on the deconsolidation of variable interest entities		1,120,000
Investment income interest		162,000
Income attributable to the noncontrolling interest		$ 261,000

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- Definition

Number of joint venture under contract with company.

+ References

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- Definition

Variable interest entity deconsolidation gain loss.

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- Definition

Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Article 5



Reference 2: 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=26872669&loc=d3e20235-122688

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- Definition

Amount of Net Income (Loss) attributable to noncontrolling interest.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 1A

-URI http://asc.fasb.org/extlink&oid=18733093&loc=SL4573702-111684



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 55

-Paragraph 4J

-URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591551-111686

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Number of Variable Interest Entities (VIE) or potential VIEs for which the necessary information is unable to be obtained to: (1) determine whether the legal entity is a VIE, (2) determine whether it (the reporting entity) is the VIE's primary beneficiary, or (3) perform the accounting required to consolidate the VIE for which it is determined that it (the reporting entity) is the primary beneficiary.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 6

-Subparagraph a

-URI http://asc.fasb.org/extlink&oid=28200181&loc=d3e5747-111685

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