Note 11 - Employee Benefit Plan (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	30.00%	30.00%	25.00%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount	$ 2,100	$ 2,100	$ 1,800
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 300,000	$ 300,000	$ 200,000