Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Income Tax Disclosure [Line Items]
Federal statutory income tax rate	35.00%	35.00%	34.00%
Effective income tax rate	32.90%	34.30%	33.90%
Tax benefits realized from the recognition of stock option deductions	$ 160,000	$ 881,000	$ 383,000
Unrecognized tax benefits that, if recognized, would impact effective tax rate	1,200,000	1,100,000	1,200,000
Liability for potential penalties and interest	191,000	161,000
State and Local Jurisdiction
Income Tax Disclosure [Line Items]
Operating loss carryforwards	$ 10,900,000
Operating loss carryforwards expiration year	2033

A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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The domestic federal statutory tax rate applicable under enacted tax laws to the Company's pretax income from continuing operations for the period. The "statutory" tax rate is the regular tax rate if there are alternative tax systems.

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- Definition

This element represents the total of accruals as of the date of the statement of financial position for interest recognized for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity and the amount of statutory penalties for a tax position claimed or expected to be claimed by the entity, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties.

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