Revenue From Contracts With Customers - Revenue by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Net revenues	$ 47,200	$ 61,095	$ 105,451	$ 139,652
Latin America
Disaggregation of Revenue [Line Items]
Net revenues	19,910	34,561	37,356	53,318
North America
Disaggregation of Revenue [Line Items]
Net revenues	13,095	9,374	25,452	30,639
Europe
Disaggregation of Revenue [Line Items]
Net revenues	8,202	11,137	19,811	28,201
Asia Pacific
Disaggregation of Revenue [Line Items]
Net revenues	3,718	3,733	11,581	15,318
Africa
Disaggregation of Revenue [Line Items]
Net revenues	1,121	1,187	8,362	2,660
Middle East
Disaggregation of Revenue [Line Items]
Net revenues	717	632	1,907	1,713
Commonwealth of Independent States
Disaggregation of Revenue [Line Items]
Net revenues	$ 437	$ 471	$ 982	$ 7,803