Note 6 - Employee Benefit and Savings Plans (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Contribution Plan, Cost	$ 361,338	$ 326,612	$ 277,753
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0	$ 0	$ 0
100% Matching [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	100.00%	100.00%	100.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	3.00%	3.00%	3.00%
50% Matching [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	50.00%	50.00%	50.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	2.00%	2.00%	2.00%