Income Taxes - 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, 2018	Apr. 30, 2017	Apr. 30, 2016
Income Tax Disclosure [Abstract]
Deferred tax expense/(benefit)	$ 1,823	$ 968	$ (310)
Deferred tax benefit related to tax reform	(1,206)
Increase (decrease) in the valuation allowance for deferred tax assets	4	(293)	(2)
Deferred income tax expense/(benefit)	$ 621	$ 675	$ (312)