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, 2020	Apr. 30, 2019	Apr. 30, 2018
Income Tax Disclosure [Abstract]
Deferred tax (benefit) expense	$ (639)	$ 330	$ 1,823
Deferred tax benefit related to tax reform	0	0	(1,206)
Increase (decrease) in the valuation allowance for deferred tax assets	30	(10)	4
Deferred income tax expense/(benefit)	$ (609)	$ 320	$ 621