Note 7 - 401(k) Retirement Plan (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Plan, Eligibility Service Period	90 days
Defined Contribution Plan, Eligibility Age of Employee	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	$ 152	$ 286