Note 18 - Quarterly Data (Unaudited) - Summary of Quarterly Data (Unaudited) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Sales	$ 21,103,124	$ 22,244,681	$ 24,514,636	$ 21,836,087	$ 21,135,277	$ 19,771,137	$ 13,593,192	$ 11,878,700	$ 89,698,527	$ 66,378,306
Gross Profit	4,530,251	4,987,563	5,226,933	4,829,888	4,348,726	4,450,389	3,486,578	3,018,441	19,574,635	15,303,967
Operating Income	2,589,263	2,558,779	2,791,553	2,571,071	2,383,150	2,471,279	1,816,945	643,085	10,510,666	7,314,459
Net Income	$ 1,708,058	$ 1,694,868	$ 1,831,479	$ 1,745,458	$ 1,348,254	$ 1,497,079	$ 394,625	$ 373,752	$ 6,979,863	$ 3,613,710
Net Income Per Common Share - Basic (in dollars per share)	$ 0.58	$ 0.59	$ 0.66	$ 0.63	$ 0.50	$ 0.55	$ 0.14	$ 0.13	$ 2.45	$ 1.29
Net Income Per Common Share - Diluted (in dollars per share)	$ 0.51	$ 0.52	$ 0.57	$ 0.55	$ 0.43	$ 0.48	$ 0.13	$ 0.11	$ 2.13	$ 1.14