Income Taxes - Schedule of Income Tax Reconciliation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Income Tax Disclosure [Abstract]
Income tax expense at statutory rate	$ 1,952	$ 1,831	$ 2,035
State and local taxes, net of federal income tax benefit (expense)	102	97	165
Tax credits (state, net of federal benefit)	(407)	(157)	(134)
Effects of differing US and foreign tax rates	173	47	(30)
Decrease in valuation allowance	(10)	(40)	(9)
Other items, net	52	(33)	(44)
Net income tax expense	$ 1,862	$ 1,745	$ 1,983