The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement.

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Gross amount of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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- Definition

Amount, net of accumulated depreciation, depletion and amortization, of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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Summary of Significant Accounting Policies - Schedule of Property Plant and Equipment (Detail) (USD $) In Thousands, unless otherwise specified							12 Months Ended				12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2013 Land [Member]	Apr. 30, 2012 Land [Member]	Apr. 30, 2013 Building and improvements [Member]	Apr. 30, 2012 Building and improvements [Member]	Apr. 30, 2013 Building and improvements [Member] Minimum [Member]	Apr. 30, 2013 Building and improvements [Member] Maximum [Member]	Apr. 30, 2013 Machinery and equipment [Member]	Apr. 30, 2012 Machinery and equipment [Member]	Apr. 30, 2013 Machinery and equipment [Member] Minimum [Member]	Apr. 30, 2013 Machinery and equipment [Member] Maximum [Member]
Depreciation Amortization Impairment [Line Items]
Useful Life							10 years	40 years			5 years	10 years
Property plant and equipment gross	$ 45,109	$ 43,556	$ 41	$ 41	$ 14,921	$ 14,626			$ 30,147	$ 28,889
Less accumulated depreciation	(30,011)	(28,210)
Net property, plant and equipment	$ 15,098	$ 15,346