Significant Customers and Geographic Data Property and Equipment by Region (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, net of depreciation	$ 545	$ 911
Geography Concentration Risk [Member] | Property, Plant and Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, net of depreciation	545	911
Geography Concentration Risk [Member] | Property, Plant and Equipment | North America
Property, Plant and Equipment [Line Items]
Property and equipment, net of depreciation	515	855
Geography Concentration Risk [Member] | Property, Plant and Equipment | Europe
Property, Plant and Equipment [Line Items]
Property and equipment, net of depreciation	$ 30	$ 56