Significant Components of Deferred Income Tax (Benefit) Expense Attributable to Income from Continuing Operations before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Income Tax Disclosure [Abstract]
Deferred tax expense/(benefit)	$ 968	$ (310)	$ (728)
Decrease in the valuation allowance for deferred tax assets	(293)	(2)	(5)
Deferred Income Tax Expense (Benefit), Net of Valuation Allowance, Total	$ 675	$ (312)	$ (733)