Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2023	Jan. 31, 2022	Jan. 31, 2023	Jan. 31, 2022	Apr. 30, 2022
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 552,570		$ 552,570		$ 541,328
Less accumulated amortization and depreciation	(349,061)		(349,061)		(327,520)
Property, Plant and Equipment, Net, Total	203,509		203,509		213,808
Amortization and depreciation expense on property, plant and equipment	9,300	$ 9,200	28,700	$ 28,300
Finance lease, right-of-use asset, accumulated amortization	32,800		32,800		32,800
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	4,475		4,475		4,431
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	120,492		120,492		119,066
Buildings and improvements - finance leases
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	11,164		11,164		11,164
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	328,639		328,639		324,417
Machinery and equipment - finance leases
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	30,930		30,930		31,341
Software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	29,229		29,229		28,115
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 27,641		$ 27,641		$ 22,794