Segment and Related Information - Schedule of identifiable assets by geographic area (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	$ 94,681	$ 114,624
United States | Reportable Geographical Components
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	84,652	99,284
Other Countries | Reportable Geographical Components
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	$ 10,029	$ 15,340