Income Taxes - Deferred Income Taxes (Details) - USD ($) $ in Thousands	Apr. 30, 2021	Apr. 30, 2020
Deferred income tax assets:
Allowances on accounts and notes receivable	$ 2,617	$ 2,016
Accrued payroll and related costs	5,093	1,859
Insurance reserves	4,086	2,501
Inventory costs	3,252	2,630
Deferred compensation	7,892	7,426
Equity compensation	2,612	2,695
Derivative instrument	5,083	7,850
Acquisition related costs	1,202	1,311
Net operating loss carry-forwards	1,591	1,595
Disallowed interest expense	974	736
Investment in partnerships	24,316	16,535
Deferred rent	829	1,112
Noncompete agreements	95	120
Other deferred tax assets, net	1,147	1,424
Total deferred income tax assets	60,789	49,810
Less: Valuation allowance	(11,768)	(10,183)
Total deferred income tax assets, net of valuation allowance	49,021	39,627
Deferred income tax liabilities:
Amortization of intangible assets	(19,583)	(18,917)
Rebates	(151)	(400)
Depreciation	(25,668)	(21,508)
Deferred financing costs	(463)	(1,582)
Other deferred tax liabilities, net	(169)	(334)
Total deferred income tax liabilities	(46,034)	(42,741)
Deferred income tax liabilities, net	$ 2,987
Deferred income tax liabilities, net		$ (3,114)