Note 11 - Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Apr. 29, 2017	Jan. 28, 2017	Oct. 29, 2016	Jul. 30, 2016	Apr. 30, 2016	Jan. 30, 2016	Nov. 01, 2015	Aug. 02, 2015	Apr. 29, 2017	Apr. 30, 2016	May 02, 2015
Earnings per common share – basic (in dollars per share)	$ 0.63	$ 0.52	$ 0.53	$ 0.62	$ 0.37	$ 0.24	$ 0.33	$ 0.37	$ 2.30	$ 1.31	$ 1.06
Earnings per common share – diluted (in dollars per share)	$ 0.62	$ 0.52	$ 0.53	$ 0.62	$ 0.37	$ 0.24	$ 0.33	$ 0.37	$ 2.29	$ 1.31	$ 1.05
Net sales	$ 212,066	$ 194,564	$ 203,180	$ 217,108	$ 179,034	$ 161,687	$ 178,678	$ 185,386	$ 826,918	$ 704,785	$ 645,825
Gross profit	85,946	75,920	78,717	85,494	65,365	52,552	60,621	62,899	326,077	241,437	219,140
Net income	$ 29,161	$ 24,285	$ 24,604	$ 28,995	$ 17,537	$ 11,236	$ 15,312	$ 17,113	$ 107,045	$ 61,198	$ 49,311
Earnings per common share – basic (in dollars per share)	$ 0.63	$ 0.52	$ 0.53	$ 0.62	$ 0.37	$ 0.24	$ 0.33	$ 0.37	$ 2.30	$ 1.31	$ 1.06
Earnings per common share – diluted (in dollars per share)	$ 0.62	$ 0.52	$ 0.53	$ 0.62	$ 0.37	$ 0.24	$ 0.33	$ 0.37	$ 2.29	$ 1.31	$ 1.05