Property, Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2023	Apr. 30, 2022	Apr. 30, 2021
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 573,589	$ 541,328
Less accumulated amortization and depreciation	(354,174)	(327,520)
Property, Plant and Equipment, Net, Total	219,415	213,808
Amortization and depreciation expense on property, plant and equipment	37,900	38,000	$ 38,300
Finance Lease, Right-of-Use Asset, Accumulated Amortization	31,900	32,800
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	4,475	4,431
Buildings And Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	121,903	119,066
Building And Improvements - Capital Leases [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	11,164	11,164
Machinery And Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	331,146	324,417
Machinery And Equipment - Capital Leases [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	29,869	31,341
Construction In Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	45,710	22,794
Property, Plant and Equipment, Net, Total	219,415	213,808
Software and Software Development Costs
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 29,322	$ 28,115