Condensed Consolidated Statements of Income - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Net sales	$ 10,806,600	$ 9,873,800	$ 18,234,600	$ 20,316,400
Operating costs and expenses:
Cost of sales	5,429,000	5,606,800	9,836,500	11,229,000
Advertising	344,700	138,700	881,900	421,300
Selling	1,841,400	1,679,300	3,473,100	3,295,200
General and administrative	1,431,200	1,023,300	2,524,500	2,103,600
Total operating costs and expenses	9,046,300	8,448,100	16,716,000	17,049,100
Income from operations	1,760,300	1,425,700	1,518,600	3,267,300
Interest expense	(47,700)	(33,200)	(71,800)	(75,100)
Income before income taxes	1,712,600	1,392,500	1,446,800	3,192,200
Income tax expense	(428,700)	(517,200)	(359,300)	(1,235,800)
Net income	$ 1,283,900	$ 875,300	$ 1,087,500	$ 1,956,400
Net income per common share
Basic	$ 0.11	$ 0.07	$ 0.09	$ 0.17
Diluted	$ 0.10	$ 0.07	$ 0.09	$ 0.16
Weighted average shares outstanding
Basic	12,023,935	11,859,927	11,976,761	11,818,143
Diluted	12,548,947	12,286,256	12,577,916	12,158,117