Income Taxes - Reconciliation to Federal Statutory Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Reconciliation of income tax expense (benefit)
Federal statutory rate (as a percent)	35.00%	35.00%	35.00%
Income tax expense (benefit) differences to amount computed by applying federal statutory rate
Federal income taxes at statutory rate	$ 25,039	$ 8,802	$ (6,413)
State income taxes, net of federal income tax benefit	2,236	2,336	(51)
Net change in valuation allowance	214	(60)	(1,134)
Nondeductible meals & entertainment	761	627	462
338(h)(10) election	(6,936)
Redeemable noncontrolling interests	1,053	291	550
Nondeductible transaction costs	109	253
Other	178	335	(40)
Total provision for (benefit from) income taxes	22,654	$ 12,584	$ (6,626)
Decrease in deferred tax liabilities and tax expense for election to change tax treatment of acquisition from stock to asset transaction	$ 6,936