Allowance for Credit Losses (Details) (USD $)	3 Months Ended		9 Months Ended
	Jan. 26, 2013	Jan. 28, 2012	Jan. 26, 2013	Jan. 28, 2012
Allowance for Credit Losses [Abstract]
Notes receivable, gross	$ 8,600,000		$ 8,600,000
Number of customers with notes receivable balance	9		9
Notes receivable, current	1,200,000		1,200,000
Allowance for Credit Losses [Member]
Allowance for Credit Losses [Roll Forward]
Beginning balance	1,481,000	2,283,000	1,537,000	2,067,000
Recoveries	(17,000)	0	(73,000)	(18,000)
Write-offs	0	0	0	(15,000)
Provision for credit losses	0	0	0	283,000
Currency effect	0	(52,000)	0	(86,000)
Ending balance	$ 1,464,000	$ 2,231,000	$ 1,464,000	$ 2,231,000