Note 16 - Benefit Plan (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	3.00%
Defined Contribution Plan, Cost	$ 96,000	$ 140,000	$ 124,000
Defined Contribution Plan, Administrative Expense	$ 10,000	$ 14,000	$ 9,000