Segment Information - Financial Data by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Sales to external customers	$ 36,995	$ 34,731	$ 108,585	$ 106,191
Operating income	1,726	1,373	7,029	6,363
Interest expense, net	469	496	1,463	1,346
Other income, net	40	23	52	84
Consolidated income before income taxes	1,217	854	5,514	4,933
Assets	114,224		114,224		$ 109,478
United States
Sales to external customers	32,780	30,913	95,178	93,468
Operating income	1,381	1,182	5,942	5,209
Assets	103,944		103,944		99,721
Canada
Sales to external customers	1,775	1,691	5,402	5,715
Operating income	280	193	746	876
Assets	4,241		4,241		3,839
Europe
Sales to external customers	2,440	2,127	8,005	7,008
Operating income	65	$ (2)	341	$ 278
Assets	$ 6,039		$ 6,039		$ 5,918