Income Taxes - Components of Net Deferred Tax Amounts Recognized in Accompanying Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Apr. 30, 2015	Apr. 30, 2014
Deferred tax asset:
Bad debts	$ 1,493	$ 743
Other accruals	1,317	2,165
Charitable contributions	352	274
Stock options	5,412	4,829
State tax credit	496	554
Net operating losses	58,822	58,536
Research and development credit	6,485	3,497
Deferred rent	273	671
Deferred revenue	1,816	1,175
Total deferred tax asset	76,466	72,444
Less valuation allowance	(66,448)	(52,734)
Net deferred tax assets	10,018	19,710
Deferred tax liability:
Amortization of intangible assets	(4,300)	(15,190)
Depreciation	(4,374)	(4,517)
Total deferred tax liability	(8,674)	(19,707)
Total net deferred tax assets	$ 1,344	$ 3