Note 9 - Stock-based Employee Compensation (Details Textual)	3 Months Ended
	Mar. 31, 2022
Restricted Stock Units (RSUs) [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period (Year)	1 year
The 2020 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period (Year)	3 years
Non-plan Stock Options [Member] | Executive Officers and Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period (Year)	3 years