Income Taxes - Schedule of Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Current tax expense
Federal	$ 58,273	$ 49,593	$ 44,078
State	8,959	7,093	5,657
Current income tax expense (benefit)	67,232	56,686	49,735
Deferred tax expense	55,492	44,711	17,089
Total income tax expense	$ 122,724	$ 101,397	$ 66,824