Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 113,648	$ 218,689
United States
Disaggregation of Revenue [Line Items]
Revenues	97,910	189,063
Asia
Disaggregation of Revenue [Line Items]
Revenues	3,161	4,861
Canada
Disaggregation of Revenue [Line Items]
Revenues	3,529	6,789
Europe
Disaggregation of Revenue [Line Items]
Revenues	5,101	10,148
Mexico
Disaggregation of Revenue [Line Items]
Revenues	483	1,106
Middle East
Disaggregation of Revenue [Line Items]
Revenues	3,204	5,356
Other
Disaggregation of Revenue [Line Items]
Revenues	260	1,366
Revenue recognized over time
Disaggregation of Revenue [Line Items]
Revenues	3,061	5,748
Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Revenues	$ 110,587	$ 212,941