Product Warranty (Schedule Of Warranty Liability) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jul. 31, 2014	Jul. 31, 2013
Movement in Standard and Extended Product Warranty, Increase (Decrease) [Roll Forward]
Beginning balance at May 1	$ 1,910	$ 1,795
Accrual	3,938	2,546
Settlements	(3,362)	(2,596)
Ending balance at July 31	$ 2,486	$ 1,745