Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2013
Income Tax Disclosure [Line Items]
Federal statutory income tax rate	35.00%	35.00%	35.00%
Effective income tax rate	22.00%	35.00%	33.00%
Tax benefits realized from the recognition of stock option deductions	$ 420,000	$ 361,000	$ 160,000
Unrecognized tax benefits that, if recognized, would impact effective tax rate	115,000	1,200,000	$ 1,200,000
Income tax benefit due to reversal of FIN 48 Reverse	973,000
Liability for potential penalties and interest	54,000	$ 160,000
State and Local Jurisdiction
Income Tax Disclosure [Line Items]
Operating loss carryforwards	$ 10,600,000
Operating loss carryforwards expiration year	2034