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Inventories - Additional Information (Detail) - USD ($)	Jan. 31, 2017	Apr. 30, 2016
Inventory Disclosure [Abstract]
LIFO inventory amount	$ 14,272,000	$ 13,373,000

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- References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	na
Period Type:	duration

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- Definition

The amount of LIFO (last in first out) inventory present at the reporting date when inventory is also valued using different valuation methods.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6361739&loc=d3e7789-107766

+ Details

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Balance Type:	debit
Period Type:	instant