Pension Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Oct. 27, 2012	Oct. 29, 2011	Oct. 27, 2012	Oct. 29, 2011
Net periodic pension costs [Line Items]
Service cost	$ 277	$ 277	$ 585	$ 555
Interest cost	1,331	1,391	2,662	2,782
Expected return on plan assets	(1,714)	(1,705)	(3,428)	(3,410)
Net amortization	756	409	1,512	818
Net periodic pension cost	$ 650	$ 372	$ 1,331	$ 745