Product Warranty (Schedule Of Warranty Liability) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2015	Jul. 31, 2014
Movement in Standard and Extended Product Warranty, Increase (Decrease) [Roll Forward]
Beginning balance at May 1	$ 2,643	$ 1,910
Accrual	3,756	3,938
Settlements	(3,522)	(3,362)
Ending balance at July 31	$ 2,877	$ 2,486