Segment Information - Financial Data by Segment (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Net sales	$ 164,003,040	$ 142,457,342
Operating income	11,412,664	8,429,348
Assets	129,867,736	110,748,853
Additions to property, plant and equipment	2,569,000	1,680,000
Depreciation and amortization	3,841,000	3,433,000
United States Segment
Net sales	140,191,000	125,717,000
Operating income	8,872,000	7,199,000
Assets	113,831,000	98,577,000
Additions to property, plant and equipment	2,386,000	1,646,000
Depreciation and amortization	3,668,000	3,347,000
Canada Segment
Net sales	10,986,000	6,678,000
Operating income	1,332,000	771,000
Assets	7,432,000	6,168,000
Additions to property, plant and equipment	34,000	2,000
Depreciation and amortization	95,000	16,000
Europe Segment
Net sales	12,826,000	10,062,000
Operating income	1,209,000	459,000
Assets	8,605,000	6,003,000
Additions to property, plant and equipment	149,000	32,000
Depreciation and amortization	$ 78,000	$ 70,000