Note 7 - Employee Stock Plans (Details Textual) - shares	May 12, 2021	Mar. 05, 2020	Apr. 26, 2017	Apr. 23, 2015	Oct. 03, 2021	Apr. 24, 2019
Stock Plan 2019 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)					642,899	357,143
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized (in shares)	600,000	550,000
Stock Plan 2009 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)						241,203
The 2009 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)					281,859
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized (in shares)		300,000	107,143	71,429