Industry Segment and Geographic Areas (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) segment	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Revenues from External Customers and Long-Lived Assets
Number of segments | segment									1
Revenues:	$ 95,770	$ 99,388	$ 98,896	$ 83,644	$ 89,339	$ 96,271	$ 95,662	$ 83,496	$ 377,698	$ 364,768	$ 334,122
Long-lived assets (net property, plant and equipment):	90,920				81,806				90,920	81,806
Total assets:	355,480				341,158				355,480	341,158
United States
Revenues from External Customers and Long-Lived Assets
Revenues:									322,535	309,651	290,019
Long-lived assets (net property, plant and equipment):	53,615				46,521				53,615	46,521
Total assets:	289,447				278,094				289,447	278,094
Asia
Revenues from External Customers and Long-Lived Assets
Revenues:									8,299	10,647	8,085
Canada
Revenues from External Customers and Long-Lived Assets
Revenues:									9,095	12,092	8,514
Europe
Revenues from External Customers and Long-Lived Assets
Revenues:									17,036	19,448	15,677
Long-lived assets (net property, plant and equipment):	15,676				13,873				15,676	13,873
Total assets:	40,813				38,453				40,813	38,453
Mexico
Revenues from External Customers and Long-Lived Assets
Revenues:									8,889	3,941	4,226
Long-lived assets (net property, plant and equipment):	21,629				21,412				21,629	21,412
Total assets:	$ 25,220				$ 24,611				25,220	24,611
Middle East
Revenues from External Customers and Long-Lived Assets
Revenues:									9,672	6,221	1,604
Other
Revenues from External Customers and Long-Lived Assets
Revenues:									$ 2,172	$ 2,768	$ 5,997