Restructuring Charges (Narrative) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Jan. 31, 2021	Apr. 30, 2022	Apr. 30, 2021	Apr. 30, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net		$ 183,000	$ 5,848,000	$ (18,000)
Manufacturing Plant Closure
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net		300,000	4,400,000
Nationwide Reductions In Force | Employee Severance and Separation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net		$ (100,000)	$ 1,400,000	$ 200,000
Discontinued Operations, Disposed of by Sale | Humboldt Facility | Facility Closing
Restructuring Cost and Reserve [Line Items]
Gain (Loss) on Disposition of Business	$ 2,300,000