Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2023	Jul. 31, 2022	Apr. 30, 2023
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 585,855		$ 573,589
Less accumulated amortization and depreciation	(362,045)		(354,174)
Property, Plant and Equipment, Net, Total	223,810		219,415
Amortization and depreciation expense on property, plant and equipment	9,600	$ 9,700
Finance lease, right-of-use asset, accumulated amortization	31,900		31,900
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	4,475		4,475
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	123,186		121,903
Buildings and improvements - finance leases
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	11,164		11,164
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	334,553		331,146
Machinery and equipment - finance leases
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	29,680		29,869
Software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	29,510		29,322
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 53,287		$ 45,710