Note 8 - 401(k) Retirement Plan (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Contribution Plan, Eligibility Service Period (Month)	90 days
Defined Contribution Plan, Eligibility Age of Employee (Year)	18 years
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	60.00%
Defined Contribution Plan, Employer Matching Contribution Rate	25.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	6.00%
Defined Contribution Plan, Cost	$ 267	$ 152