Total Expenditures and Amortization of Capitalized Computer Software (Detail) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2013
Capitalized Software [Line Items]
Total capitalized computer software development costs	$ 2,747	$ 2,949	$ 3,418
Total research and development expense	11,088	9,074	8,882
Total research and development expense and capitalized computer software-development costs	13,835	12,023	12,300
Total amortization of capitalized computer software development costs	$ 3,663	$ 925	$ 2,501