Quarterly Data - Quarterly 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
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 30,171,000	$ 33,785,000	$ 38,849,000	$ 27,745,000	$ 26,377,000	$ 31,913,000	$ 40,997,000	$ 25,288,000	$ 130,550,349	$ 124,574,371
Cost of goods sold	19,545,000	21,559,000	24,366,000	17,181,000	16,564,000	20,050,000	26,302,000	16,103,000	82,651,076	79,019,315
Gross profit	10,626,000	12,226,000	14,483,000	10,564,000	9,813,000	11,863,000	14,695,000	9,185,000	47,899,273	45,555,056
Net income	$ (655,000)	$ 1,202,000	$ 2,846,000	$ 659,000	$ 545,000	$ 1,473,000	$ 3,267,000	$ 565,000	$ 4,052,479	$ 5,850,998
Basic earnings per share	$ (.20)	$ .36	$ .85	$ .20	$ .16	$ .44	$ .98	$ .17	$ 1.21	$ 1.76
Diluted earnings per share	(.16)	.32	.75	.18	.15	.40	.91	.16	1.09	1.64
Dividends per share	$ .11	$ .11	$ .11	$ .10	$ .1	$ .10	$ .10	$ .10	$ .43	$ .40