Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Income Tax Disclosure [Abstract]
Income taxes at the statutory rates	21.00%	21.00%	30.40%
Impact of Tax Reform Act	0.00%	0.40%	(80.50%)
Federal tax credits	(1.90%)	(2.30%)	(2.20%)
State income taxes, net of federal tax benefit	4.00%	4.30%	3.70%
Impact of phased-in state law changes, net of federal benefit	(0.20%)	(1.80%)	0.80%
ASU 2016-09 benefit (share based compensation)	(0.50%)	(0.60%)	(0.80%)
Other	0.50%	1.60%	0.30%
Effective income tax rate	22.90%	22.60%	(48.30%)