Segment Information - Financial Data by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Sales to external customers	$ 34,731	$ 33,785	$ 106,191	$ 100,380
Operating income (loss)	1,373	1,970	6,363	7,095
Interest expense, net	496	365	1,346	949
Other expense, net	23	37	84	21
Consolidated income before income taxes	854	1,568	4,933	6,125
Assets	115,183		115,183		$ 114,730
United States
Sales to external customers	30,913	30,038	93,468	88,653
Operating income (loss)	1,182	1,730	5,209	6,149
Assets	105,071		105,071		104,431
Canada
Sales to external customers	1,691	1,661	5,715	5,556
Operating income (loss)	193	209	876	744
Assets	4,367		4,367		4,926
Europe
Sales to external customers	2,127	2,086	7,008	6,171
Operating income (loss)	(2)	$ 31	278	$ 202
Assets	$ 5,745		$ 5,745		$ 5,373