Commitments and Contingencies - Schedule of Total Expected Environmental Remediation Payments for Succeeding Year (Detail) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2014
Accrual for Environmental Loss Contingencies, Fiscal Year Maturity [Abstract]
2015	$ 45
2016	3,399
2017	1,029
2018	27
2019	42
Thereafter	750
Total	$ 5,292

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Undiscounted amount of the accrual for environmental loss contingencies.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 5.Y.Q1)

-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section Y

-Paragraph Question 1

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 30

-Section 50

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859

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Undiscounted amount of the accrual for environmental loss contingencies maturing after the fifth fiscal year following the latest fiscal year.

+ References

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Undiscounted amount of the accrual for environmental loss contingencies maturing in the fifth fiscal year following the latest fiscal year.

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Undiscounted amount of the accrual for environmental loss contingencies maturing in the fourth fiscal year following the latest fiscal year.

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Undiscounted amount of the accrual for environmental loss contingencies maturing in the second fiscal year following the latest fiscal year.

+ References

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Undiscounted amount of the accrual for environmental loss contingencies maturing in the third fiscal year following the latest fiscal year.

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Undiscounted amount of the accrual for environmental loss contingencies maturing in the next fiscal year following the latest fiscal year.

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