SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Allowance for doubtful accounts
Movement in valuation and qualifying accounts and reserves
Balance at Beginning of Period	$ 606	$ 791	$ 936
Charged to Cost and Expenses	178	106	(6)
Deductions	(522)	(291)	(139)
Balance at End of Period	262	606	791
Warranty reserve
Movement in valuation and qualifying accounts and reserves
Balance at Beginning of Period	2,653	1,280	1,515
Charged to Cost and Expenses	4,516	2,919	1,436
Charged to Other Accounts	(424)
Deductions	(2,611)	(1,546)	(1,671)
Balance at End of Period	4,134	2,653	1,280
Reserve for inventory excess and obsolescence
Movement in valuation and qualifying accounts and reserves
Balance at Beginning of Period	4,588	3,234	3,871
Charged to Cost and Expenses	2,767	2,035	2,187
Deductions	(2,900)	(681)	(2,824)
Balance at End of Period	4,455	4,588	3,234
Reserve for self-insured medical claims
Movement in valuation and qualifying accounts and reserves
Balance at Beginning of Period	1,293	1,281	1,543
Charged to Cost and Expenses	9,213	8,953	8,908
Deductions	(9,330)	(8,941)	(9,170)
Balance at End of Period	$ 1,176	$ 1,293	$ 1,281