SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Allowance for doubtful accounts
Movement in valuation and qualifying accounts and reserves
Balance at Beginning of Period	$ 1,041	$ 1,080	$ 104
Charged to Cost and Expenses	219	198	976
Deductions	(70)	(237)
Balance at End of Period	1,190	1,041	1,080
Warranty reserve
Movement in valuation and qualifying accounts and reserves
Balance at Beginning of Period	1,704	2,090	1,947
Charged to Cost and Expenses	2,069	702	1,884
Deductions	(1,758)	(1,088)	(1,741)
Balance at End of Period	2,015	1,704	2,090
Reserve for inventory excess and obsolescence
Movement in valuation and qualifying accounts and reserves
Balance at Beginning of Period	7,824	3,953	2,756
Charged to Cost and Expenses	5,377	5,054	2,758
Deductions	(2,969)	(1,183)	(1,561)
Balance at End of Period	10,232	7,824	3,953
Reserve for self-insured medical claims
Movement in valuation and qualifying accounts and reserves
Balance at Beginning of Period	944	1,003	1,133
Charged to Cost and Expenses	13,031	10,808	9,100
Deductions	(13,222)	(10,867)	(9,230)
Balance at End of Period	$ 753	$ 944	$ 1,003