SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Allowance for doubtful accounts
Movement in valuation and qualifying accounts and reserves
Balance at Beginning of Period	$ 262	$ 606	$ 791
Charged to Cost and Expenses	56	178	106
Deductions	(27)	(522)	(291)
Balance at End of Period	291	262	606
Warranty reserve
Movement in valuation and qualifying accounts and reserves
Balance at Beginning of Period	4,134	2,653	1,280
Charged to Cost and Expenses	3,079	4,516	2,919
Charged to Other Accounts		(424)
Deductions	(3,982)	(2,611)	(1,546)
Balance at End of Period	3,231	4,134	2,653
Reserve for inventory excess and obsolescence
Movement in valuation and qualifying accounts and reserves
Balance at Beginning of Period	4,455	4,588	3,234
Charged to Cost and Expenses	2,040	2,767	2,035
Deductions	(1,245)	(2,900)	(681)
Balance at End of Period	5,250	4,455	4,588
Reserve for self-insured medical claims
Movement in valuation and qualifying accounts and reserves
Balance at Beginning of Period	1,176	1,293	1,281
Charged to Cost and Expenses	8,251	9,213	8,953
Deductions	(8,098)	(9,330)	(8,941)
Balance at End of Period	$ 1,329	$ 1,176	$ 1,293