Warranty (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
	Oct. 30, 2011	Oct. 30, 2011
Movement in Standard Product Warranty Accrual [Roll Forward]
Beginning balance at April 30, 2011		$ 4,469
Additions during the period based on product sold	1,452
Additions during ther period due to acquisition of controlling interest in subsidiary	313
Change in estimates		(557)
Settlement and expirations	(2,238)
Ending balance at October 30, 2011	$ 3,439	$ 3,439