Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2022	Oct. 31, 2021	Oct. 31, 2022	Oct. 31, 2021	Apr. 30, 2022
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 548,351		$ 548,351		$ 541,328
Less accumulated amortization and depreciation	(344,701)		(344,701)		(327,520)
Property, Plant and Equipment, Net, Total	203,650		203,650		213,808
Amortization and depreciation expense on property, plant and equipment	9,700	$ 9,400	19,400	$ 19,100
Finance lease, right-of-use asset, accumulated amortization	32,500		32,500		32,800
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	4,431		4,431		4,431
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	120,037		120,037		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	331,523		331,523		324,417
Machinery and equipment - finance leases
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	30,546		30,546		31,341
Software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	27,817		27,817		28,115
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 22,833		$ 22,833		$ 22,794