Revenue - Disaggregated Revenue by Geography (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Total Revenues	$ 8,948	$ 11,847	$ 19,103	$ 24,638
United States
Disaggregation of Revenue [Line Items]
Total Revenues	7,562	8,830	16,377	19,072
South America
Disaggregation of Revenue [Line Items]
Total Revenues	17	354	192	626
Europe
Disaggregation of Revenue [Line Items]
Total Revenues	668	1,562	1,285	3,028
Asia
Disaggregation of Revenue [Line Items]
Total Revenues	701	1,101	1,249	1,912
Total Foreign Revenues
Disaggregation of Revenue [Line Items]
Total Revenues	$ 1,386	$ 3,017	$ 2,726	$ 5,566

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

Name:	us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration