Product Warranty (Schedule Of Warranty Liability) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Oct. 31, 2014	Oct. 31, 2013
Movement in Standard and Extended Product Warranty, Increase (Decrease) [Roll Forward]
Beginning balance at May 1	$ 1,910	$ 1,795
Accrual	7,777	5,950
Settlements	(7,084)	(5,820)
Ending balance at October 31	$ 2,603	$ 1,925