Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2015 Forecast	Apr. 30, 2014 State and Local Jurisdiction [Member]
Income Tax Disclosure [Line Items]
Federal statutory income tax rate	35.00%	35.00%	35.00%
Effective income tax rate	35.00%	32.90%	34.30%
Tax benefits realized from the recognition of stock option deductions	$ 361,000	$ 160,000	$ 881,000
Operating loss carryforwards					11,800,000
Operating loss carryforwards expiration year					2034
Unrecognized tax benefits that, if recognized, would impact effective tax rate	1,200,000	1,200,000	1,100,000
Liability for potential penalties and interest	160,000	191,000
Change in total unrecognized tax benefits in tax				899,000
Change in total unrecognized tax benefits in interest				$ 54,000