Segment Information - Financial Data by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Sales to external customers	$ 38,849	$ 40,997	$ 66,595	$ 66,285
Operating income (loss)	3,889	4,640	5,081	5,595
Interest expense, net	321	211	583	395
Other (income) expense, net	(51)	11	(60)	(27)
Consolidated income before income taxes	3,619	4,418	4,558	5,227
Assets	109,362		109,362		$ 92,066
United States
Sales to external customers	34,140	36,296	58,615	58,821
Operating income (loss)	3,267	4,246	4,375	5,191
Assets	99,945		99,945		84,104
Canada
Sales to external customers	2,503	2,646	3,895	4,039
Operating income (loss)	503	377	535	410
Assets	4,806		4,806		3,882
Europe
Sales to external customers	2,206	2,055	4,085	3,425
Operating income (loss)	119	$ 17	171	$ (6)
Assets	$ 4,611		$ 4,611		$ 4,080