Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 104,881	$ 105,041
Revenue recognized over time
Disaggregation of Revenue [Line Items]
Revenues	3,753	2,687
Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Revenues	101,128	102,354
United States
Disaggregation of Revenue [Line Items]
Revenues	91,499	91,153
Asia
Disaggregation of Revenue [Line Items]
Revenues	1,452	1,700
Canada
Disaggregation of Revenue [Line Items]
Revenues	3,497	3,260
Europe
Disaggregation of Revenue [Line Items]
Revenues	5,352	5,047
Mexico
Disaggregation of Revenue [Line Items]
Revenues	834	623
Middle East
Disaggregation of Revenue [Line Items]
Revenues	1,584	2,152
Other
Disaggregation of Revenue [Line Items]
Revenues	$ 663	$ 1,106