Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Income Tax Disclosure [Abstract]
Income taxes at the statutory rates	35.00%	35.00%	35.00%
Federal tax credits	(1.80%)	(1.70%)	(1.70%)
State income taxes, net of federal tax benefit	2.80%	2.70%	3.10%
ASU 2016-09 Benefit (share based compensation)	(1.30%)	0.00%	0.00%
Other	(0.50%)	(0.80%)	(0.40%)
Effective income tax rate	34.20%	35.20%	36.00%