Segment Information - Financial Data by Segment (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Net sales	$ 33,872,000	$ 36,995,000	$ 40,220,000	$ 31,370,000	$ 31,130,000	$ 34,731,000	$ 39,751,000	$ 31,709,000	$ 142,457,342	$ 137,321,395
Operating income									8,429,348	7,456,906
Assets	110,748,853				109,477,786				110,748,853	109,477,786
Additions to property, plant and equipment									1,680,000	2,851,000
Depreciation and amortization									3,433,000	3,229,000
United States Segment
Net sales									125,717,000	120,993,000
Operating income									7,199,000	6,103,000
Assets	98,577,000				99,721,000				98,577,000	99,721,000
Additions to property, plant and equipment									1,646,000	2,705,000
Depreciation and amortization									3,347,000	3,153,000
Canada Segment
Net sales									6,678,000	7,040,000
Operating income									771,000	884,000
Assets	6,168,000				3,839,000				6,168,000	3,839,000
Additions to property, plant and equipment									2,000	83,000
Depreciation and amortization									16,000	9,000
Europe Segment
Net sales									10,062,000	9,288,000
Operating income									459,000	470,000
Assets	$ 6,003,000				$ 5,918,000				6,003,000	5,918,000
Additions to property, plant and equipment									32,000	63,000
Depreciation and amortization									$ 70,000	$ 67,000