Revenue - Revenue from External Customers by Geographic Areas (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Total	$ 93,056	$ 138,684	$ 198,153	$ 254,471
North America
Disaggregation of Revenue [Line Items]
Total	81,979	119,943	176,499	217,622
Pacific Rim
Disaggregation of Revenue [Line Items]
Total	6,295	10,804	12,749	23,429
Europe
Disaggregation of Revenue [Line Items]
Total	2,578	5,006	5,235	8,383
Other
Disaggregation of Revenue [Line Items]
Total	2,204	2,931	3,670	5,037
Energy
Disaggregation of Revenue [Line Items]
Total	29,649	52,245	79,733	97,893
Industrial
Disaggregation of Revenue [Line Items]
Total	30,463	54,660	67,594	105,247
Transportation
Disaggregation of Revenue [Line Items]
Total	$ 32,944	$ 31,779	$ 50,826	$ 51,331