Property and Equipment - Property and Equipment (Detail) - USD ($) $ in Thousands	Apr. 30, 2018	Apr. 30, 2017
Property, Plant and Equipment [Line Items]
Gross property plant and equipment	$ 31,678	$ 30,208
Accumulated depreciation and amortization	(28,644)	(28,153)
Net property plant and equipment	3,034	2,055
Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Gross property plant and equipment	15,325	14,704
Computer equipment and purchased software
Property, Plant and Equipment [Line Items]
Gross property plant and equipment	11,692	10,886
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Gross property plant and equipment	$ 4,661	$ 4,618