Segment Information - Financial Data by Segment (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
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
Operating income									7,796,053	8,442,056
Assets	114,729,806				92,066,092				114,729,806	92,066,092
Additions to property, plant and equipment									7,146,000	1,789,000
Depreciation and amortization									2,895,000	2,393,000
United States
Net sales									115,407,000	110,793,000
Operating income									6,701,000	7,769,000
Assets	104,431,000				84,104,000				104,431,000	84,104,000
Additions to property, plant and equipment									7,014,000	1,737,000
Depreciation and amortization									2,845,000	2,362,000
Canada
Net sales									6,935,000	6,824,000
Operating income									775,000	568,000
Assets	4,926,000				3,882,000				4,926,000	3,882,000
Additions to property, plant and equipment									19,000	7,000
Depreciation and amortization									8,000	8,000
Europe
Net sales									8,208,000	6,957,000
Operating income									320,000	105,000
Assets	$ 5,373,000				$ 4,080,000				5,373,000	4,080,000
Additions to property, plant and equipment									113,000	44,000
Depreciation and amortization									$ 42,000	$ 23,000