Allowance for Credit Losses (Details) (USD $)	3 Months Ended		9 Months Ended
	Jan. 25, 2014	Jan. 26, 2013	Jan. 25, 2014	Jan. 26, 2013
Allowance for Credit Losses [Abstract]
Notes receivable, gross	$ 4,500,000		$ 4,500,000
Notes receivable written off during the period			2,700,000
Number of customers with notes receivable balance	5		5
Notes receivable, current	600,000		600,000
Allowance for Credit Losses [Member]
Analysis of allowance for credit losses [Roll Forward]
Beginning balance	158,000	1,481,000	1,986,000	1,537,000
Recoveries	0	(17,000)	0	(73,000)
Write-offs	0	0	(1,888,000)	0
Provision for credit losses	0	0	60,000	0
Ending balance	$ 158,000	$ 1,464,000	$ 158,000	$ 1,464,000