Income Taxes - Deferred Income Taxes (Details) - USD ($) $ in Thousands	Apr. 30, 2019	Apr. 30, 2018
Deferred income tax assets:
Allowances on accounts and notes receivable	$ 2,306	$ 3,540
Accrued payroll and related costs	1,577	1,138
Insurance reserves	1,746	1,734
Inventory costs	2,066	2,013
Deferred compensation	6,854	6,662
Equity compensation	2,944	2,361
Derivative instrument	1,358	561
Acquisition related costs	1,779	1,955
Net operating loss carry-forwards	1,745	1,965
Disallowed interest expense	2,507
Investment in partnerships	4,676
Deferred rent	604	488
Noncompete agreements	133	681
Other deferred tax assets, net	1,394	946
Total deferred income tax assets	31,689	24,044
Less: Valuation allowance	(1,112)	(448)
Total deferred income tax assets, net of valuation allowance	30,577	23,596
Deferred income tax liabilities:
Amortization of intangible assets	(22,950)	(28,641)
Rebates	(72)	(253)
Depreciation	(10,495)	(3,596)
Deferred financing costs	(2,075)	(1,848)
Other deferred tax liabilities, net	(535)
Total deferred income tax liabilities	(36,127)	(34,338)
Deferred income tax liabilities, net	$ (5,550)	$ (10,742)