Pension Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 30, 2016	Jul. 25, 2015
Net periodic pension costs
Service cost	$ 319	$ 333
Interest cost	1,170	1,211
Expected return on plan assets	(1,245)	(1,226)
Net amortization	764	736
Net periodic pension cost	$ 1,008	$ 1,054