Inventories (Details) (USD $)	3 Months Ended			6 Months Ended
	Oct. 30, 2011	Oct. 31, 2010	Aug. 01, 2010	Oct. 30, 2011	Oct. 31, 2010	Apr. 30, 2011
Inventory, Net [Abstract]
Raw materials	$ 47,993,000			$ 47,993,000		$ 64,997,000
Work-in-process	97,020,000			97,020,000		66,073,000
Finished goods	69,927,000			69,927,000		56,547,000
Total inventories	214,940,000			214,940,000		187,617,000
Inventory write-down	5,700,000	2,800,000		11,400,000	6,600,000
Inventory recovery	(3,000,000)		(2,800,000)	(7,000,000)	(6,400,000)
Inventory write down, net of recovery	2,700,000			4,400,000	200,000
Purchase Commitments [Abstract]
Purchase commitment	$ 2,100,000			$ 2,100,000		$ 3,200,000