Environmnetal Matters - Narrative (Details) $ in Thousands	12 Months Ended
	Apr. 30, 2016 USD ($) site	May 02, 2015 USD ($)	May 03, 2014 USD ($)
Site Contingency [Line Items]
Number of plant sites subject to environmental investigation and/or remediation | site	2
Accruals for environmental matters	$ 1,700	$ 2,800
Spent on remediation clean-ups and related studies	1,000	500	$ 400
Other accrued expenses
Site Contingency [Line Items]
Accruals for environmental matters	$ 800	$ 800