Segments - Reconciliation of Revenues from Reportable Segments to Consolidated Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting, Asset Reconciling Item [Line Items]
Revenues	$ 35,986	$ 45,275	$ 59,321	$ 84,941
Other revenues, including from other operating segments
Segment Reporting, Asset Reconciling Item [Line Items]
Revenues	8,743	9,726	14,108	20,581
Elimination of intersegment revenues
Segment Reporting, Asset Reconciling Item [Line Items]
Revenues	(4,571)	(1,866)	(9,159)	(4,295)
Total revenues from reportable segments
Segment Reporting, Asset Reconciling Item [Line Items]
Revenues	$ 31,814	$ 37,415	$ 54,372	$ 68,655