Income Taxes - Deferred Income Taxes (Details) - USD ($) $ in Thousands	Apr. 30, 2020	Apr. 30, 2019
Deferred income tax assets:
Allowances on accounts and notes receivable	$ 2,016	$ 2,306
Accrued payroll and related costs	1,859	1,577
Insurance reserves	2,501	1,746
Inventory costs	2,630	2,066
Deferred compensation	7,426	6,854
Equity compensation	2,695	2,944
Derivative instrument	7,850	1,358
Acquisition related costs	1,311	1,779
Net operating loss carry-forwards	1,595	1,745
Disallowed interest expense	736	2,507
Investment in partnerships	16,535	4,676
Deferred rent	1,112	604
Noncompete agreements	120	133
Other deferred tax assets, net	1,424	1,394
Total deferred income tax assets	49,810	31,689
Less: Valuation allowance	(10,183)	(1,112)
Total deferred income tax assets, net of valuation allowance	39,627	30,577
Deferred income tax liabilities:
Amortization of intangible assets	(18,917)	(22,950)
Rebates	(400)	(72)
Depreciation	(21,508)	(10,495)
Deferred financing costs	(1,582)	(2,075)
Other deferred tax liabilities, net	(334)	(535)
Total deferred income tax liabilities	(42,741)	(36,127)
Deferred income tax liabilities, net	$ (3,114)	$ (5,550)