Restructuring - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net	$ (847)	$ 0	$ 5,404	$ (207)
Manufacturing Plant Closure
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net	(700)		3,900
Facility Closing | Discontinued Operations, Disposed of by Sale | Humboldt Facility
Restructuring Cost and Reserve [Line Items]
Gain (Loss) on Disposition of Business	2,300
Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net	1,746
Employee Severance | Nationwide Reductions In Force
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net	$ (100)		1,500
Employee Severance | Manufacturing Plant Closure
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net			900
Other Restructuring | Manufacturing Plant Closure
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net			$ 3,000