Note 10 - Employee Benefit Plan (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	30.00%	30.00%	30.00%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount	$ 2,400	$ 2,100	$ 2,100
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 400,000	$ 300,000	$ 300,000