Revenue - Revenue from External Customers by Geographic Areas (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Total	$ 114,450	$ 138,512	$ 312,603	$ 392,983
North America
Disaggregation of Revenue [Line Items]
Total	104,840	125,971	281,339	343,593
Pacific Rim
Disaggregation of Revenue [Line Items]
Total	5,466	6,744	18,215	30,173
Europe
Disaggregation of Revenue [Line Items]
Total	2,395	4,329	7,630	12,712
Other
Disaggregation of Revenue [Line Items]
Total	1,749	1,468	5,419	6,505
Energy
Disaggregation of Revenue [Line Items]
Total	33,813	64,331	113,546	162,224
Industrial
Disaggregation of Revenue [Line Items]
Total	29,843	37,020	97,437	142,267
Transportation
Disaggregation of Revenue [Line Items]
Total	$ 50,794	$ 37,161	$ 101,620	$ 88,492