Product Warranty (Schedule Of Warranty Liability) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Oct. 31, 2012	Oct. 31, 2011
Product Warranty [Abstract]
Beginning balance at May 1	$ 1,885	$ 1,738
Accrual	4,953	4,432
Settlements	(4,747)	(4,392)
Ending balance at October 31	$ 2,091	$ 1,778