Note 10 - Commitments and Contingencies (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Apr. 28, 2018	Apr. 29, 2017	Apr. 30, 2016
Operating Leases, Rent Expense, Total	$ 13.3	$ 12.0	$ 9.2
Raw Material [Member]
Purchase Obligation, Due in Next Twelve Months	11.2
Commitments for Plant and Equipment [Member]
Purchase Obligation, Due in Next Twelve Months	$ 4.7