Income Taxes - Deferred Income Taxes (Details) - USD ($) $ in Thousands	Apr. 30, 2017	Apr. 30, 2016
Deferred income tax assets:
Allowances on accounts and notes receivable	$ 5,792	$ 4,924
Accrued payroll and related costs	1,651	2,013
Insurance reserves	1,139	1,920
Inventory costs	2,430	1,725
Deferred compensation	9,293	9,080
Equity compensation	3,424	2,593
Derivative instrument	1,488	1,589
Deferred financing costs		143
Acquisition related costs	1,732	895
Net operating loss carry-forwards	2,949	855
Deferred rent	996	791
Noncompete agreements	819	573
Other	2,576	2,149
Total deferred income tax assets	34,289	29,250
Less: Valuation allowance	(297)	(83)
Total deferred income tax assets, net of valuation allowance	33,992	29,167
Deferred income tax liabilities, net
Amortization on intangible assets	(53,345)	(62,599)
Rebates	(1,007)	(1,270)
Depreciation	(3,808)	(6,501)
Deferred financing costs	(2,652)
Total deferred income tax liabilities	60,812	70,370
Deferred income tax liabilities, net	$ 26,820	$ 41,203