Income Taxes - Schedule of Income Tax Reconciliation (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Income Tax Disclosure [Abstract]
Income tax expense at statutory rate	$ 1,775	$ 863	$ 1,007
State and local taxes, net of federal income tax benefit (expense)	128	3	96
Tax credits (state, net of federal benefit)	(118)	(76)	(122)
Effects of differing US and foreign tax rates	(106)	(61)	(155)
(Decrease) increase in valuation allowance	(14)	73
Other items, net	(125)	(63)	38
Net income tax expense	$ 1,540	$ 739	$ 864

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The sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to continuing operations.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to changes in the valuation allowance for deferred tax assets in the period.

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The portion of the difference, between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations, that is attributable to total foreign income tax expense or benefit. The foreign income tax expense or benefit difference represents the income tax expense or benefit at applicable domestic statutory income tax rates applied to foreign earnings or loss for the period versus the foreign income tax expense or benefit calculated by applying the appropriate foreign tax rates.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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The sum of other amounts reflected in the reconciliation of the statutory tax provision (benefit) to the actual tax provision (benefit).

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The sum of the differences between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to tax credits.

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