Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
Income Tax Disclosure [Abstract]
Income taxes at the statutory rates	21.00%	30.40%	35.00%
Impact of Tax Reform Act	0.40%	(80.50%)	0.00%
Federal tax credits	(2.30%)	(2.20%)	(1.80%)
State income taxes, net of federal tax benefit	4.30%	3.70%	2.80%
Impact of phased-in state law changes, net of federal benefit	(1.80%)	0.80%	0.00%
ASU 2016-09 Benefit (share based compensation)	(0.60%)	(0.80%)	(1.30%)
Other	1.60%	0.30%	(0.50%)
Effective income tax rate	22.60%	(48.30%)	34.20%