Restructuring (Details) (USD $)	3 Months Ended	6 Months Ended
	Oct. 25, 2014 facility	Oct. 25, 2014	Oct. 26, 2013
Restructuring
Number of facilities sold	1
Number of facilities sold or being marketed for sale	2
Restructuring charges
Pre-tax restructuring charges since inception of plan	$ 7,700,000	$ 7,700,000
Restructuring charges since inception of plan, net of tax	5,000,000	5,000,000
Pre-tax restructuring charges (income)		(332,000)	(55,000)
Restructuring charges (income), net of tax		(200,000)
Restructuring liability	400,000	400,000
Maximum
Restructuring charges
Pre-tax restructuring charges (income)	100,000
Restructuring charges (income), net of tax	100,000
Continuing Operations
Restructuring charges
Pre-tax restructuring charges since inception of plan	4,500,000	4,500,000
Restructuring charges since inception of plan, net of tax	2,900,000	2,900,000
Discontinued Operations
Restructuring charges
Pre-tax restructuring charges since inception of plan	3,200,000	3,200,000
Restructuring charges since inception of plan, net of tax	$ 2,100,000	$ 2,100,000