Note 8 - Stock-based Compensation - Summary of Stock Option Activity (Details) - $ / shares		12 Months Ended
		Apr. 28, 2018	Apr. 29, 2017	Apr. 30, 2016
Options outstanding, beginning of year (in shares)		383,595
Options outstanding, beginning of year (in dollars per share)	[1]	$ 11.47
Granted (in shares)		500	0	3,500
Granted (in dollars per share)	[1]	$ 29.61
Exercised (in shares)		(34,650)
Exercised (in dollars per share)	[1]	$ 16.15
Cancelled (in shares)		(4,500)
Cancelled (in dollars per share)	[1]	$ 17.59
Options outstanding, end of year (in shares)		344,945	383,595
Options outstanding, end of year (in dollars per share)	[1]	$ 10.84	$ 11.47
Options exercisable, end of year (in shares)		209,579
Options exercisable, end of year (in dollars per share)	[1]	$ 8.49

[1] Weighted average exercise price.