Note 14 - Quarterly Financial Data (Unaudited) - Quarterly Financial Data (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net sales	$ 24,502,272	$ 18,388,381	$ 19,280,770	$ 20,149,845	$ 24,100,498	$ 18,628,362	$ 19,552,905	$ 20,672,227	$ 82,321,268	$ 82,923,992	$ 84,161,200
Gross Profit	15,296,919	11,635,331	12,895,534	12,286,045	14,519,835	11,644,871	12,895,790	12,652,746	52,113,829	51,713,242	52,071,060
Net income	$ 1,671,340	$ 521,414	$ 1,027,732	$ 1,231,265	$ 2,059,997	$ 1,000,350	$ 1,820,915	$ 1,520,997	$ 4,451,751	$ 6,402,259	$ 6,402,405
NET INCOME PER COMMON SHARE:
Earnings per share – basic (in dollars per share)	$ 0.18	$ 0.06	$ 0.11	$ 0.13	$ 0.23	$ 0.11	$ 0.19	$ 0.16	$ 0.48	$ 0.69	$ 0.64
Earnings per share - diluted (in dollars per share)	$ 0.18	$ 0.06	$ 0.11	$ 0.13	$ 0.23	$ 0.11	$ 0.19	$ 0.16	$ 0.48	$ 0.69	$ 0.63
Weighted average number of common shares outstanding:
Weighted average common shares outstanding (in shares)	9,270,862	9,270,862	9,225,960	9,308,726	9,188,483	9,188,483	9,209,446	9,698,951	9,242,092	9,301,867	10,077,506
Diluted (in shares)	9,272,330	9,273,950	9,229,129	9,330,919	9,301,867	9,206,382	9,227,941	9,718,453	9,256,810	9,321,558	10,102,760
Net sales	$ 24,502,272	$ 18,388,381	$ 19,280,770	$ 20,149,845	$ 24,100,498	$ 18,628,362	$ 19,552,905	$ 20,672,227	$ 82,321,268	$ 82,923,992	$ 84,161,200
Gross Profit	15,296,919	11,635,331	12,895,534	12,286,045	14,519,835	11,644,871	12,895,790	12,652,746	52,113,829	51,713,242	52,071,060
Net income	$ 1,671,340	$ 521,414	$ 1,027,732	$ 1,231,265	$ 2,059,997	$ 1,000,350	$ 1,820,915	$ 1,520,997	$ 4,451,751	$ 6,402,259	$ 6,402,405