Income Taxes - Reconciliation of Provision for Income Taxes from Continuing Operations (Detail) - USD ($) $ in Thousands		12 Months Ended
		Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Income Tax Disclosure [Abstract]
Federal income taxes expected at the statutory rate	[1]	$ 66,773	$ 8,233	$ 7,183
State income taxes, less federal income tax benefit		7,685	1,628	1,737
Stock compensation		(578)	1,077	646
Business meals and entertainment		115	257	144
Research and development tax credit		(297)	(496)	(460)
Non-deductible Separation expenses		195	688
Other		501	135	105
Federal tax rate change on deferred taxes				(71)
Total income tax expense/(benefit)		$ 74,394	$ 11,522	$ 9,284

[1] We had a statutory rate of 21% in fiscal 2021, 2020 and 2019.