Note 10 - Stock-based Compensation (Details Textual) - USD ($)	12 Months Ended
	May 02, 2020	Apr. 27, 2019	Apr. 28, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)	0	9,000	500
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term (Year)		8 years	8 years
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate		21.70%	23.80%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate		2.60%	2.40%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate		1.60%	1.60%
Share-based Payment Arrangement, Expense	$ 126,000	$ 251,000	$ 161,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value	768,000	127,000	140,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	4,900,000	2,200,000	3,000,000.0
Proceeds from Stock Options Exercised	740,000	456,000	560,000
Share-based Payment Arrangement, Expense, Tax Benefit	974,000	$ 443,000	$ 886,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)		$ 63.71
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total	$ 465,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	4 years 6 months
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term (Year)	3 years 8 months 12 days	3 years 3 months 18 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value	$ 7,000,000.0	$ 14,900,000
Omnibus Plan [Member]
Share Based Compensation Arrangement by Share Based Payment Award Number of Shares Authorized Per Individual (in shares)	1,680,000
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)	5 years
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)	10 years
Omnibus Plan [Member] | Stock Options or Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)	4,800,000
Omnibus Plan [Member] | SARS Dividend Equivalents and Other Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)	4,800,000
Special Stock Option Plan [Member] | Determined by Board of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)	1,800,000
Special Stock Option Plan [Member] | Determined By Chairman Member
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)	50,000
KEEP Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)	240,000
Share Based Compensation Arrangement by Share Based Payment Award Number of Shares Authorized Per Individual (in shares)	6,000
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)	6 years
Share Based Compensation Arrangement by Share Based Payment Award Percentage of Purchased Shares Matched	50.00%
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants, Period (Year)	2 years
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent	60.00%