Income Taxes - Schedule of Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Current tax (benefit) expense:
Federal	$ (7,057)	$ 41,300	$ 58,273
State	1,769	5,693	8,959
Current income tax expense (benefit)	(5,288)	46,993	67,232
Deferred tax (benefit) expense	(98,178)	45,190	55,492
Total income tax (benefit) expense	$ (103,466)	$ 92,183	$ 122,724