Note 11 - Segment Information - Summary of Reportable Operating Segments (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net sales	$ 24,744,403	$ 18,887,099	$ 19,177,767	$ 20,288,918	$ 24,502,272	$ 18,388,381	$ 19,280,770	$ 20,149,845	$ 83,098,187	$ 82,321,268	$ 82,923,992
Gross Profit	12,771,954	$ 11,846,833	$ 13,118,442	$ 12,842,962	15,296,919	$ 11,635,331	$ 12,895,534	$ 12,286,045	50,580,191	52,113,829	51,713,242
Operating earnings									3,828,463	7,241,822	10,300,731
Interest expense									304,957	205,555	155,189
Other (income) expense, net									(180,191)	(126,857)	(57,287)
Income before income taxes									3,703,697	7,163,124	10,202,829
Depreciation and amortization									1,797,281	1,875,102	1,719,154
Fixed asset additions									1,091,433	1,689,645	1,697,704
Total assets	76,140,134				74,914,596				76,140,134	74,914,596	70,652,720
North America Segment [Member]
Net sales									79,553,353	78,568,219	79,041,920
Gross Profit									48,375,877	49,889,888	49,315,003
Operating earnings									4,182,969	7,498,817	10,224,773
Interest expense									304,957	205,555	155,189
Other (income) expense, net									(150,067)	(135,011)	(35,290)
Income before income taxes									4,028,079	7,428,370	10,104,873
Depreciation and amortization									1,696,656	1,790,421	1,631,534
Fixed asset additions									1,000,263	1,666,171	1,609,829
Total assets	71,578,634				70,302,116				71,578,634	70,302,116	66,502,432
International [Member]
Net sales									3,544,834	3,753,049	3,882,072
Gross Profit									2,204,314	2,223,941	2,398,239
Operating earnings									(354,506)	(256,995)	75,958
Interest expense
Other (income) expense, net									(30,124)	8,154	(21,997)
Income before income taxes									(324,382)	(265,246)	97,956
Depreciation and amortization									100,625	84,681	87,620
Fixed asset additions									91,170	23,474	87,875
Total assets	$ 4,561,500				$ 4,612,480				$ 4,561,500	$ 4,612,480	$ 4,150,288