Income Taxes - Significant Components of Deferred Income Tax (Benefit) Expense Attributable to Income from Continuing Operations before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
Income Tax Disclosure [Abstract]
Deferred tax expense	$ 330	$ 1,823	$ 968
Deferred tax benefit related to tax reform	0	(1,206)	0
(Decrease) increase in the valuation allowance for deferred tax assets	(10)	4	(293)
Deferred income tax expense/(benefit)	$ 320	$ 621	$ 675