Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2024	Jan. 31, 2023	Jan. 31, 2024	Jan. 31, 2023	Apr. 30, 2023
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 628,137		$ 628,137		$ 573,589
Less accumulated amortization and depreciation	(375,969)		(375,969)		(354,174)
Property, Plant and Equipment, Net, Total	252,168		252,168		219,415
Amortization and depreciation expense on property, plant and equipment	10,600	$ 9,300	30,000	$ 28,700
Finance lease, right-of-use asset, accumulated amortization	31,600		31,600		31,900
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	4,475		4,475		4,475
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	126,128		126,128		121,903
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	351,059		351,059		331,146
Machinery and equipment - finance leases
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	31,149		31,149		29,869
Software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	34,096		34,096		29,322
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 70,066		$ 70,066		$ 45,710