Material Customers (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Apr. 27, 2013 customer	Apr. 28, 2012 customer	Apr. 30, 2011 customer
Minimum
Revenue, Major Customer [Line Items]
Accounts receivable - collection terms	30 days
Maximum
Revenue, Major Customer [Line Items]
Accounts receivable - collection terms	60 days
Automotive
Revenue, Major Customer [Line Items]
Number of significant customers	2	2	2
Accounts receivable	$ 40,744	$ 31,850
Automotive | Maltese subsidiary
Revenue, Major Customer [Line Items]
Accounts receivable	$ 16,090	$ 8,260
Automotive | Customer 1
Revenue, Major Customer [Line Items]
Percentage of consolidated net sales	19.90%	18.70%	17.90%
Automotive | Customer 2
Revenue, Major Customer [Line Items]
Percentage of consolidated net sales	16.70%	18.50%	17.60%