Material Customers - Narrative (Details) $ in Millions	12 Months Ended
	Apr. 29, 2017 USD ($) customer	Apr. 30, 2016 USD ($) customer	May 02, 2015 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 | customer	2	2	2
Accounts receivable	$ 90.6	$ 90.0
Automotive | Maltese subsidiary
Revenue, Major Customer [Line Items]
Accounts receivable	$ 55.3	$ 51.4
Automotive | Customer 1
Revenue, Major Customer [Line Items]
Percentage of consolidated net sales	49.60%	49.50%	44.80%
Automotive | Customer 2
Revenue, Major Customer [Line Items]
Percentage of consolidated net sales	9.30%	11.50%	12.80%