Note 6 - Leases (Details Textual) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Oct. 31, 2020	Oct. 26, 2019	Oct. 31, 2020	Oct. 26, 2019	Oct. 21, 2020	May 02, 2020
Operating Lease, Cost	$ 3.5	$ 3.4	$ 7.3	$ 6.7
Operating Lease, Weighted Average Remaining Lease Term (Year)	4 years 1 month 6 days		4 years 1 month 6 days			4 years 3 months 18 days
Operating Lease, Weighted Average Discount Rate, Percent					3.10%	3.38%
Operating Lease, Payments	$ 3.5	$ 3.7	$ 7.0	$ 7.5