Significant Customers and Geographic Data Revenues and Accounts Receivable by Customers (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue, Major Customer [Line Items]
Property and equipment, net of depreciation	$ 545	$ 911
Revenues	25,013
Customer Concentration Risk | Revenues | Customer A [Member]
Revenue, Major Customer [Line Items]
Revenues		4,945	$ 4,402
Customer Concentration Risk | Current Receivables | Customer A [Member]
Revenue, Major Customer [Line Items]
Accounts Receivable	841
Customer Concentration Risk | Current Receivables | Customer B
Revenue, Major Customer [Line Items]
Accounts Receivable	782	$ 814
Customer Concentration Risk | Current Receivables | Customer C
Revenue, Major Customer [Line Items]
Accounts Receivable	$ 692