Note 12 - Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Apr. 27, 2019	Jan. 26, 2019	Oct. 27, 2018	Jul. 28, 2018	Apr. 28, 2018	Jan. 27, 2018	Oct. 28, 2017	Jul. 29, 2017	Apr. 27, 2019	Apr. 28, 2018	Apr. 29, 2017
Net sales	$ 239,914	$ 220,892	$ 260,709	$ 292,590	$ 244,306	$ 227,477	$ 244,119	$ 259,832	$ 1,014,105	$ 975,734	$ 826,918
Gross profit	84,578	80,554	103,524	115,694	99,359	91,193	96,080	104,503	384,350	391,135	326,077
Net income	$ 26,135	$ 24,811	$ 41,077	$ 48,830	$ 36,442	$ 41,080	$ 33,980	$ 38,272	$ 140,853	$ 149,774	$ 107,045
Earnings per common share – basic (in dollars per share)	$ 0.56	$ 0.53	$ 0.88	$ 1.05	$ 0.78	$ 0.88	$ 0.73	$ 0.82	$ 3.02	$ 3.21	$ 2.30
Earnings per common share – diluted (in dollars per share)	$ 0.56	$ 0.53	$ 0.88	$ 1.04	$ 0.78	$ 0.88	$ 0.72	$ 0.82	$ 3	$ 3.19	$ 2.29